UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Brainstem and spinal cord pathways involved in the control of avian locomotion Weinstein, Gerald Norman 1984

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1985_A6_7 W44.pdf [ 11.68MB ]
Metadata
JSON: 831-1.0096213.json
JSON-LD: 831-1.0096213-ld.json
RDF/XML (Pretty): 831-1.0096213-rdf.xml
RDF/JSON: 831-1.0096213-rdf.json
Turtle: 831-1.0096213-turtle.txt
N-Triples: 831-1.0096213-rdf-ntriples.txt
Original Record: 831-1.0096213-source.json
Full Text
831-1.0096213-fulltext.txt
Citation
831-1.0096213.ris

Full Text

BRAINSTEM AND SPINAL CORD PATHWAYS INVOLVED IN THE CONTROL OF AVIAN LOCOMOTION By GERALD NORMAN WEINSTEIN B . S c , The U n i v e r s i t y o-f B r i t i s h Columbia,, 1974 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department o-f Zoology) We accept t h i s t h e s i s as con-forming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA November 1984 ^ G e r a l d Norman Weinstein, 1984 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library 'shall make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 3E-6 (3/81) T h i s study examined s e v e r a l a s p e c t s o-f the neural c o n t r o l o-f locomotion i n b i r d s . I n i t i a l l y , i t was necessary to d e f i n e an index of normal locomotor f u n c t i o n s . T h i s was accomplished f o r both -flyi n g and walking using electromyographic a n a l y s i s of -forelimb and hindlimb musculature to determine which muscles best de-fine the f l i g h t and walking p a t t e r n s r e s p e c t i v e l y . Secondly, i n c h r o n i c s u r v i v i n g b i r d s , a s e r i e s of s u b t o t a l s p i n a l l e s i o n i n g experiments were performed t o determine which descending pathways were r e s p o n s i b l e -for the i n i t i a t i o n of hindlimb locomotion. T h i r d l y , r e s u l t s were recorded from brainstem e l e c t r i c a l s t i m u l a t i o n s t u d i e s designed t o determine the l o c a t i o n of locomotor areas i n the avian brainstem which e f f e c t e d the i n i t i a t i o n and descending c o n t r o l o-f locomotion i n these animals. R e s u l t s i n d i c a t e d the i l i o t i b i a l i s c r a n i a l i s (ITC) and f l e x o r c r u r i s l a t e r a l i s (FCL) muscles best de-fine the swing and stance phases o-f hindlimb locomotion, r e s p e c t i v e l y . Muscles which best de-fined the e l e v a t o r and depressor phases of f l y i n g were d e l t o i d e u s major (DM) and p e c t o r a l i s ( P e c t ) , r e s p e c t i v e l y . R e s u l t s of the low t h o r a c i c s e l e c t i v e l e s i o n i n g experiments support the h y p o t h e s i s t h a t the medullary r e t i c u l o s p i n a l pathway i s necessary to the i n i t i a t i o n and c o n t r o l of v o l i t i o n a l hindlimb locomotion. F u r t h e r , descending input t o s p i n a l cord p a t t e r n g e n e r a t o r s v i a the v e s t i b u l o s p i n a l pathways may p l a y some a d j u n c t i v e r o l e or be necessary f o r the descending c o n t r o l of 1ocomoti on. E l e c t r i c a l s t i m u l a t i o n of the brainstem i n acute decerebrate b i r d s e l i c i t e d locomotor behaviours i n both h i n d l i m b s and •forelimbs. Four areas, i n c l u d i n g ; an area near the 1 a t e r a l /medi a l spiri-form nucleus; nucleus et t r a c t u s descendens t r i g e m i n i ; and c e n t r a l nucleus of the medulla, pars v e n t r a l i s and d o r s a l i s ; and the l a t e r a l r e t i c u l a r nucleus produced v a r y i n g locomotor behaviours when s t i m u l a t e d . Acute d o r s a l cord t r a n s e c t i o n d i d not 0 a-ffect the e l e c t r i c a l l y s t i m u l a t e d behaviour, i n d i c a t i n g t h a t descending pathways -from s u p r a s p i n a l c e n t r e s which t r a v e l i n the d o r s a l cord do not a-ffect the descending c o n t r o l o-f locomotion. A s t r o n g p a r a l l e l e x i s t s between the r e s u l t s of t h i s study i n two avian s p e c i e s and those -found i n the mammalian l i t e r a t u r e . i v IABLE OF CONTENTS Page General I n t r o d u c t i o n 1 Chapter I - F u n c t i o n a l C h a r a c t e r i z a t i o n of Limb Muscles 11 Involved i n Locomotion i n the Canada goose, S t i i Q t a canadensis I n t r o d u c t i o n 12 M a t e r i a l s and Methods 14 R e s u l t s 17 D i s c u s s i o n 22 Table I 25 Table II 29 F i g u r e s 1-11 33 Chapter II - C h a r a c t e r i z a t i o n o-f Descending S p i n a l Cord 55 Pathways Necessary -for Locomotion i n the Hindleg of the Canada goose, Branta canadensis I n t r o d u c t i o n 56 M a t e r i a l s and Methods 58 R e s u l t s 63 D i s c u s s i o n 70 F i g u r e s 12-34 80 Chapter I I I - The Pr o d u c t i o n of Locomotion R e s u l t i n g 126 •from E l e c t r i c a l S t i m u l a t i o n o-f the Brainstem i n the Acute Decerebrate B i r d I n t r o d u c t i o n 127 M a t e r i a l s and Methods 128 R e s u l t s 134 D i s c u s s i o n 141 Table III 150 F i g u r e s 35-53 154 C o n c l u s i o n s 192 References 195 V LISI OF TABLES Table I - Nomenclature -for hindlimb muscles i n the 25 Canada goose Table II - Nomenclature -for -forelimb muscles i n the 29 Canada goose Table III - L i s t o-f s t i m u l a t i o n s i t e , behaviour and 150 s t i m u l a t i o n parameters used i n brainstem s t i m u l a t i o n experiments v i LIST OF FIGURES 1 - L a t e r a l view o-f s u p e r f i c i a l hindlimb musculature. 33 2 - L a t e r a l view of second l a y e r of hindlimb muscles. 35 3 - Dorsal view of hindlimb musculature. 37 4 - Electromyographic r e c o r d s of goose walking (ITC, FCL). 39 5 - L a t e r a l view of t h i r d hindlimb muscle l a y e r . 41 6 - Electromyographic r e c o r d s (EMGs) of hindlimb. 43 muscles ITC and FCM. 7 - EMGs of hindlimb ITC and CFM muscles. 45 8 - EMGs of hindlimb ITC and IFB muscles. 47 9 - EMGs of f o r e l i m b Pect and DM muscles. 49 10 - L a t e r a l view of wing and a s s o c i a t e d trunk musculature. 51 11 - EMGs of f o r e l i m b LDCr, DM, TSC and Pect muscles. 53 12 - Diagram of attempted low t h o r a c i c s p i n a l cord l e s i o n s . 80 13 - EMGs from hindlimb ITC and FCL muscles i n a Sham 82 Operated b i r d . 14 - Cross s e c t i o n through low t h o r a c i c cord of Sham 84 Operated b i r d . 15 - Cross s e c t i o n through low t h o r a c i c s p i n a l cord 86 demonstrating complete t r a n s e c t i o n . 16 - EMGs of hindlimb ITC and FCL muscles during " s p i n a l 88 s t e p p i ng". 17 - Cross s e c t i o n of t h o r a c i c cord showing Hemisection. 90 18 - EMGs of hindlimb ITC and FCL f o l l o w i n g Hemisection. 92 19 - Cross s e c t i o n of Dorsal Cord T r a n s e c t i o n l e s i o n . 94 20 - P o s t o p e r a t i v e EMGs of ITC and FCL muscles (Dorsal 96 Cord T r a n s e c t i o n ) . 21 - P o s t o p e r a t i v e EMGs of ITC and FCL muscles (Ventral 98 Quadrant L e s i o n ) . 22 - Cross s e c t i o n through l e s i o n s i t e of V e n t r a l Quadrant 100 1esi on. 23 - Cross s e c t i o n through l e s i o n s i t e of L a t e r a l Margins 102 1esi on. 24 - EMGs of ITC and FCL muscles ( B i l a t e r a l Margins L e s i o n 104 25 - Cross s e c t i o n through l e s i o n s i t e of B i l a t e r a l 106 V e n t r o l a t e r a l L e s i o n . 26 - Cross s e c t i o n through l e s i o n s i t e of Ventromedial 108 L e s i on. 27 - EMGs of ITC and FCL muscles (Ventromedial Lesion) 110 28 - Cross s e c t i o n through l e s i o n s i t e of Ventromedial 112 In t a c t l e s i o n . 29 - EMGs of ITC and FCL muscles (Ventromedial I n t a c t ) 114 30 - Cross s e c t i o n through l e s i o n s i t e of V e n t r o l a t e r a l 116 In t a c t l e s i o n . 31 - EMGs of ITC and FCL muscles ( B i l a t e r a l V e n t r o l a t e r a l 118 In t a c t l e s i o n ) . 32 - Cross s e c t i o n through l e s i o n s i t e of V e n t r a l Quadrant 120 In t a c t l e s i o n . v i i 33 - EMGs of ITC and FCL muscles (Ventral Quadrant Int a c t 122 1esi on). 34 - Cross s e c t i o n through the avian b r a c h i a l s p i n a l cord 124 showing t r a j e c t o r i e s of s e v e r a l descending b u l b o s p i n a l pathways. 35 - Experimental apparatus used i n acute brainstem 154 s t i m u l a t i o n experiments. 36 - P a r a s a g g i t a l s e c t i o n of the brainstem of the Canada 156 goose. 37 - EMGs and potentiometer (PM) r e c o r d s of p r e s t i m u l a t i o n 158 spontaneous locomotion. 38 - Transverse s e c t i o n through medulla showing s t i m u l a t i o n 160 s i t e evoking locomotion. 39 - Transverse s e c t i o n through medulla showing s t i m u l a t i o n 162 s i t e evoking locomotion. 40 - EMGs and potentiometer r e c o r d s of s t i m u l u s induced 164 locomotion i n the acute decerebrate duck. 41 - Transverse s e c t i o n through mid-pons showing 166 s t i m u l a t i o n s i t e evoking locomotion. 42 - Transverse s e c t i o n through medulla showing s t i m u l a t i o n 168 s i t e evoking locomotion. 43 - EMG and potentiometer r e c o r d s showing stimulus-evoked 170 hindlirnb and wing movements i n the duck. 44 - EMG and potentiometer r e c o r d s of walking i n the 172 e l e c t r i c a l l y s t i m u l a t e d a v i a n . 45 - Transverse s e c t i o n through medulla o u t l i n i n g 174 s t i m u l a t i o n s i t e evoking locomotion. 46 - Transverse s e c t i o n through mesencephalon showing the 176 s t i m u l a t i o n s i t e evoking walking and wing movements i n the acute decerebrate duck. 47 - Transverse s e c t i o n through the medulla showing 178 s t i m u l a t i o n s i t e evoking t r e a d m i l l walking dur i n g e l e c t r i c a l s t i m u l a t i o n . 48 - EMG and potentiometer r e c o r d s showing hindlirnb (ITC) 180 a c t i v i t y d u r i n g e l e c t r i c a l l y evoked walking. 49 - The e f f e c t of i n c r e a s i n g t r e a d m i l l b e l t v e l o c i t y 182 during e l e c t r i c a l l y evoked locomotion. 50 - EMG and potentiometer r e c o r d s showing the 184 e f f e c t s of i n c r e a s i n g s t i m u l a t i o n c u r r e n t i n t e n s i t y during evoked locomotion. 51 - Cross s e c t i o n through low t h o r a c i c s p i n a l cord 186 f o l l o w i n g a c h r o n i c Dorsal Cord T r a n s e c t i o n . 52 - Transverse s e c t i o n through low t h o r a c i c s p i n a l 188 cord f o l l o w i n g an acute Dorsal Cord T r a n s e c t i o n . 53 - EMG and potentiometer r e c o r d s of hindlirnb muscles 190 (ITC) and l e g s f o l l o w i n g an acute Dorsal Cord T r a n s e c t i o n . v i i i ACKNOWLEDGEMENTS I thank Dr. John Steeves, without whose support t h i s r e s e a r c h c o u l d not have been undertaken. The help which Simon E l l i s p r o v ided i n t e a c h i n g me s u r g i c a l technique, the i n s and outs of the Department of Zoology, and how t o o b t a i n the necessary implements of d e s t r u c t i o n was i n v a l u a b l e . Carol Anderson provided the m a g n i f i c e n t i l l u s t r a t i o n s f o r Chapter I and gave a summer of v a l u a b l e t e c h n i c a l a s s i s t a n c e . Jones' crew, i n c l u d i n g Geoff Gabbott, Frank Smith, Mark Douse, and Mark H e i e i s a l l gave t e c h n i c a l e x p e r t i s e and much needed moral support, not t o mention many cups of c o f f e e , i n a i d of t h i s r e s e a r c h . Thanks a l s o t o John Steeves, P a u l i n e Weinstein and D i e r d r e Webster f o r re a d i n g and c o r r e c t i n g t h i s manuscript. L a s t l y , I would l i k e t o thank Stephanie f o r j u s t being t h e r e when I needed her. 1 GENERAL INTRODUCTION The neural c o n t r o l o-f locomotion i n v e r t e b r a t e s i s achieved by the i n t e g r a t i o n of s e v e r a l l e v e l s of o r g a n i z a t i o n . At i t s most simple l e v e l , the monosynaptic r e f l e x arc u t i l i z e s o n l y two neurons t o produce a r e l a t i v e l y simple motor behaviour i n response to ^a simple mechanical s t i m u l u s (eg. p a t e l l a r tendon r e f l e x ) at the s p i n a l cord l e v e l . More complex l e v e l s of o r g a n i z a t i o n a l s o occur w i t h i n the s p i n a l cord, where groups of i n t r i n s i c neurons i n t e r a c t t o produce l o c a l i z e d r h y thmical movements. H i s t o r i c a l l y , Freusberg (1874), Freusberg and G o l t z (1874,a,b) and S h e r r i n g t o n (1910) were the f i r s t t o study the performance of c a t s and dogs f o l l o w i n g removal of s u p r a s p i n a l i n f l u e n c e s . A f t e r s p i n a l t r a n s e c t i o n or s u r g i c a l d e c a p i t a t i o n , they found ,that the animals continued to step i n a rhythmic a l t e r n a t i n g f a s h i o n . T h i s " s p i n a l s t e p p i n g " provided the f i r s t d i r e c t evidence that higher b r a i n s t r u c t u r e s ( s u p r a s p i n a l ) were not necessary f o r the maintenance of the b a s i c p a t t e r n of locomotion. S h e r r i n g t o n (1910) a l s o suggested t h a t t h i s p o s t -t r a n s e c t i o n locomotion was dependent on a s e r i e s of r e f l e x a c t i o n s which were a c t i v a t e d by p e r i p h e r a l a f f e r e n t (sensory) i n p u t . Graham-Brown (1911) d i s p r o v e d t h i s h y p o t h e s i s by demonstrating t h a t p r e v i o u s l y d e a f f e r e n t e d animals c o u l d perform s t e p p i n g movements f a l l o w i n g s p i n a l cord t r a n s e c t i o n . Graham-Brown (1914) p o s t u l a t e d the H a l f - C e n t r e h y p o t h e s i s of s p i n a l cord p a t t e r n g e n e r a t o r s as the mechanism u n d e r l y i n g s p i n a l s t e p p i n g . The term p a t t e r n generator has been assigned t o these neuronal 2 networks and i m p l i e s t h a t the motor p a t t e r n o-f each limb may be i n t r i n s i c a l l y generated w i t h i n the i s o l a t e d s p i n a l c o r d . Each generator i s thought to i n t e r a c t with the p a t t e r n generators o-f other limbs to produce the rhythmic c o o r d i n a t e d movements of locomotor p r o g r e s s i o n ( G r i l i n e r , 1975). T h i s rhythm was p o s t u l a t e d t o be an i n t r i n s i c p r o p e r t y of the i n t e r c o n n e c t i o n s of a n t a g o n i s t i c nerve c e l l s <ie a c e n t r a l p a t t e r n g e n e r a t o r ) . G r i l l n e r and Zangger <1975), s u p p o r t i n g Graham-Brown's hypothesis, demonstrated t h a t s p i n a l - t r a n s e c t e d , p a r a l y s e d animals devoid of any r h y t h m i c a l p e r i p h e r a l feedback produce the p a t t e r n s of a l t e r n a t i n g motor a c t i v i t y , as recorded from p e r i p h e r a l nerve e f f e r e n t s . The electroneurograms (ENGs) recorded from t h i s procedure c o n s t i t u t e " f i c t i v e " locomotion. One d i f f i c u l t y with a p h y l o g e n e t i c theory of locomotor p a t t e r n g e n e r a t o r s o c c u r s at the l e v e l of the primates. I t has yet t o be demonstrated t h a t " s p i n a l s t e p p i n g " can occur i n any primate s p e c i e s . Several i n v e s t i g a t o r s have hypothesized that t h i s l a c k of " s p i n a l s t e p p i n g " i n humans and other primates r e s u l t s from an i n c r e a s e d dependency on s u p r a s p i n a l i n f l u e n c e s f o r the a c t i v a t i o n of s p i n a l s t e p p i n g mechanisms ( E i d e l b e r g , 1981a,b; G r i l l n e r , 1975). E i d e l b e r g (1981a) p o s t u l a t e s t h a t t o n i c descending f a c i l i t a t o r y i n f l u e n c e s are necessary f o r the p a t t e r n g e n e r a t o r s to access output motoneurons. The h i g h e s t l e v e l of motor i n t e g r a t i o n occurs w i t h i n s u p r a s p i n a l s t r u c t u r e s . These areas are r e s p o n s i b l e f o r the i n i t i a t i o n and c o n t r o l of v o l i t i o n a l locomotion. T e l e n c e p h a l i c s t r u c t u r e s are known t o be d i r e c t l y i n v o l v e d i n m o t i v a t i o n a l commands e l i c i t i n g locomotor responses (Wetzel and 3 S t u a r t , 1976; E c c l e s , 1980). In mammals, the premotor and motor cortex o-f the p r e c e n t r a l gyrus g i v e r i s e t o descending c o r t i c o s p i n a l neurons of the pyramidal system (Kuypers, 1982). S t i m u l a t i o n of v a r i o u s r e g i o n s of the motor cortex e l i c i t s d i s c h a r g e i n motorneurons i n n e r v a t i n g both d i s t a l and proximal e x t r e m i t y muscles (Marsden et a l . , 1981, Kuypers, 1964). However, these d i r e c t c o r t i c o s p i n a l c o n n e c t i o n s are thought t o be c o n s i d e r a b l y more important t o h i g h l y f r a c t i o n a t e d movements of the d i s t a l e x t r e m i t y muscles than t o the p r o d u c t i o n of b a s i c locomotor p a t t e r n s (eg. walking) (Kuypers, 1982). Indeed, a major component of the c o r t i c o s p i n a l (pyramidal) t r a c t a r i s e s from the somatosensory cortex and not from motor cortex (Kuypers, 1982). S t i m u l a t i o n of pyramidal t r a c t neurons has onl y been shown t o d i s r u p t locomotion when high c u r r e n t s t r e n g t h s are used. S t i m u l a t i o n at lower s t i m u l u s s t r e n g t h s o n l y i n c r e a s e s f l e x o r or extensor a c t i v i t y d u r i n g the a p p r o p r i a t e p o r t i o n of the step c y c l e (Shik et a l . , 1966; Orlovsky, 1972a). B i l a t e r a l pyramidotomy w i t h i n the caudal brainstem does not i n h i b i t the i n i t i a t i o n of locomotion by s t i m u l a t i o n of extrapyramidal motor areas such as the mesencephalic locomotor r e g i o n (MLR) (Shik et a l . , 1968). T h i s would tend t o i n d i c a t e t hat c o r t i c o f u g a l i n i t i a t i o n and c o n t r o l of v o l u n t a r y locomotion, even i n primates, may be mediated v i a the p h y l o g e n e t i c a l l y a l d e r brainstem s t r u c t u r e s of the extrapyramidal motor system. In f a c t , d e c e r e b r a t e f i s h e s , amphibians, b i r d s , and a l l sub-primate mammals e x h i b i t l i t t l e locomotor d i f f e r e n c e from i n t a c t animals (Wetzel and S t u a r t , 1976; G r i l l n e r , 1975; Gabbott and Jones, personal communication). 4 One predominant extrapyramidal motor area i s the basal g a n g l i a (caudate nucleus, putamen, globus p a l l i d u s , and amygdaloid n u c l e a r complex) which has been shown t o be s e v e r e l y compromised i n movement d i s o r d e r s such as Parkinsonianism, hemibal1ismus, and Huntingtons chorea (Carpenter 1978). Although these d i s o r d e r s c o n s t i t u t e severe impairments to motor performance, t h e i r major e f f e c t appears t o be of a p o s t u r a l nature (Wetzel and S t u a r t , 1976). S t i m u l a t i o n of the globus p a l l i d u s produces i n c o n s i s t e n t locomotor responses i n a l i g h t l y a n a e s t h e t i z e d c a t (Waller, 1940). Monkeys, dogs and c a t s with b i l a t e r a l a b l a t i o n of v a r i o u s p o r t i o n s of the basal g a n g l i a do not show severe impairment of c o o r d i n a t e d p r o g r e s s i o n (Waller, 1940; Denny-Brown, 1966; Hinsey et a l . , 1930). D i e n c e p h a l i c s t r u c t u r e s such as the epithalamus, thalamus, and hypothalamus ( v e n t r a l thalamus) a l s o e f f e c t c o n t r o l of locomotion. Hinsey et a l . (1930) r e p o r t e d t h a t thalamic and hypothalamic c a t s and dogs walk f o l l o w i n g s u r gery. If the r o s t r a l p o r t i o n of the thalamus i s l e f t i n t a c t , the animals w i l l then walk spontaneously and d i s p l a y behaviours which resemble motivated a c t i v i t i e s . Brainstem t r a n s e c t i o n l e a v i n g only the caudal t h i r d of the thalamus i n t a c t produces animals which w i l l locomote o n l y under s t r o n g e x t e r o c e p t i v e s t i m u l a t i o n (Laughton, 1924). Thalamic c a t s with m i d l i n e r o s t r o c a u d a l d i v i s i o n of the brainstem, however, l o s e the a b i l i t y of c o o r d i n a t e d p r o g r e s s i o n i n d i c a t i n g the p o s s i b i l i t y t h a t thalamic locomotor neurons r e q u i r e b i l a t e r a l c o n n e c t i o n s to more caudal b r a i n s t r u c t u r e s (Laughton, 1924). The subthalamus and subthalamic nucleus ( i n c l u d i n g the p o s t e r i o r and l a t e r a l hypothalamus) a l s o appear t o be i n v o l v e d i n 5 motor c o n t r o l . Although d e s t r u c t i o n o-f the subthalamus i n an i n t a c t c a t does not prevent locomotion (H a e r t i g and Masserman, 1940), e l e c t r i c a l s t i m u l a t i o n o-f t h i s r e g i o n i s known t o e l i c i t a l t e r n a t i n g s t e p p i n g movements i n l i g h t l y a n a e s t h e t i z e d animals (Waller, 1940; H a e r t i g and Masserman, 1940). F u r t h e r , Orlovsky (1969), -found t h a t s t i m u l a t i o n of the subthalamic r e g i o n i n an acute thalamic cat evoked locomotion on a t r e a d m i l l . N e v e r t h e l e s s , c a t s with b i l a t e r a l d e s t r u c t i o n of t h i s Subthalamic Locomotor Region (SLR) are a b l e t o run and walk d u r i n g e l e c t r i c a l s t i m u l a t i o n of a more caudal brainstem motor area, the mesencephalic locomotor r e g i o n (MLR) ( S i r o t a and Shik, 1973). Shik and Orlovsky (1976) p o s t u l a t e d t h a t the SLR e f f e c t s the i n i t i a t i o n of locomotion i n goal d i r e c t e d behaviours and t h e r e f o r e cannot be d e s c r i b e d i n s t r i c t l y motor terms. Shik, S e v e r i n , and Orlovsky (1966), d i s c o v e r e d t h a t e l e c t r i c a l s t i m u l a t i o n of an area i n the midbrain, which they termed the Mesencephalic Locomotor Region (MLR), c o u l d e l i c i t what appeared t o be normal locomotion i n a d e c e r e b r a t e cat walking on a t r e a d m i l l . These f i n d i n g s have allowed an i n i t i a l c h a r a c t e r i z a t i o n of some of the brainstem areas which form the presumptive r e l a y pathways between higher b r a i n s t r u c t u r e s r e s p o n s i b l e f o r v o l i t i o n a l c o n t r o l and the f i n a l common pathways of the s p i n a l c e n t r a l p a t t e r n g e n e r a t o r s . S i n c e the d i s c o v e r y of the MLR, s e v e r a l i n v e s t i g a t o r s have enlarged the i n f o r m a t i o n a v a i l a b l e by d e l i n e a t i n g other areas which w i l l evoke locomotion using e l e c t r i c a l s t i m u l a t i o n . These i n c l u d e the l a t e r a l p a r a b r a c h i a l nucleus ( B a r c i a - R i l l et a l . , 1983a), the p e r i a q u a d u c t a l gray ( G a r c i a - R i l l et a l . , 1983a), the 6 nucleus tegmenti pedunculopontis (Garcia-Ri11 et a l . , 1983a), the ponto-medullary locomotor s t r i p (PLS) (Budakova and Shik, 1980), P r o b s t ' s t r a c t (Garcia-Ri11 et a l . , 1983d), and the ventro-medial g i g a n t o c e l l u l a r and magnocel1ular r e t i c u l a r formations (Shik and Yagodnitsyn, 1977; Mori et a l . , 1978; Steeves and Jordan, 1984). P r e s e n t l y , the f u n c t i o n a l pathways u n d e r l y i n g these e l e c t r i c a l l y s t i m u l a t e d responses are not well understood. It i s p r e s e n t l y unknown whether locomotion was evoked by s t i m u l a t i o n of some of these proposed locomotor r e g i o n s are simply the result, of a c t i v a t i n g axonal f i b r e s of passage from higher b r a i n areas or, a l t e r n a t i v e l y , t h a t the s t i m u l a t e d areas e l i c i t locomotion i n d i r e c t l y v i a other brainstem areas which a l s o descend t o s p i n a l cord c e n t r a l p a t t e r n g e n e r a t o r s . Areas i n the h i n d b r a i n which are a l s o thought t o p l a y a r o l e i n locomotion i n c l u d e the v e s t i b u l a r and red n u c l e i , both of which have d i r e c t s p i n a l cord c o n n e c t i o n s v i a the v e s t i b u l o s p i n a l and r u b r o s p i n a l t r a c t s (Kuypers, 1982). Orlovsky (1972b) found t h a t v e s t i b u l o s p i n a l neurons a r i s i n g predominantly from D i e t e r s nucleus e x e r t s a f a c i l i t a t o r y e f f e c t on extensor muscles. The r u b r o s p i n a l neurons p r i m a r i l y e x e r t t h e i r e f f e c t s on f l e x o r muscles, f a c i l i t a t i n g f l e x o r a c t i v i t y d u r i n g the swing phase of locomotion (Orlovsky, 1972c). S t i m u l a t i o n of e i t h e r of these n u c l e i or t h e i r descending pathways y e i l d e d the same f a c i l i t a t o r y r e s u l t s d u r i n g both r e s t and locomotion (Orlovsky, 1972a). However, d e s t r u c t i o n of these pathways and t h e i r n u c l e i i n c h r o n i c animals does not s e v e r e l y impair rhythmic locomotor movements (Yu and E i d e l b e r g , 1981; Shik et a l . , 1968; Ingram and Ranson, 1932). R e t i c u l a r f o r m a t i o n neurons descending d i r e c t l y t o the s p i n a l 7 cord a re thought t o p l a y an important r o l e i n the c o n t r o l of s p i n a l cord p a t t e r n g e n e r a t o r s ( E i d e l b e r g , 1981b; Steeves and Jordan, 1980; A f e l t , 1974). L e s i o n s t u d i e s i n c a t s and monkeys i n both acute d e c e r e b r a t e brainstem s t i m u l a t e d and c h r o n i c s p i n a l p r e p a r a t i o n s , have demonstrated t h a t i n t a c t v e n t r o l a t e r a l quadrants of the s p i n a l cord are r e q u i r e d f o r locomotion ( E i d e l b e r g , 1981b; Steeves and Jordan, 1980; A f e l t , 1974). T h i s p o r t i o n of the cord i s known t o c a r r y r e t i c u l o s p i n a l neurons descending from the mid and h i n d b r a i n i n mammals (Kuypers, 1982). To date, the i n i t i a t i o n and c o n t r o l of s p i n a l locomotor mechanisms by s u p r a s p i n a l brainstem c e n t e r s has been s t u d i e d i n many v e r t e b r a t e s p e c i e s ( f o r review see G r i l i n e r , 1975; E i d e l b e r g , 1981). " S p i n a l s t e p p i n g " or i t s e q u i v a l e n t has been shown t o occur i n lower chordates such as lamprey ( G r i l i n e r , 1975; G r i l i n e r , M c C l e l l a n and S i g v a r d t , 1982); f i s h ( G r i l l n e r and Wallen, 1977; Wi l l i a m s et a l . , 1984); r e p t i l e s (Ten Cate, 1965); b i r d s (Tarchanoff, 1895; Ten Cate, I960); and mammals e x c l u d i n g primates ( Freusberg, 1874; S h e r r i n g t o n , 1910; P h i l l i p p s o n , 1905; E i d e l b e r g , 1981b). The predominant experimental animal f o r locomotion s t u d i e s has been the c a t . I t s easy a q u i s i t i o n , well d e f i n e d quadrapedal g a i t p a t t e r n s and mammalian c h a r a c t e r has made i t a good experimental animal f o r s t u d i e s of locomotion. N e v e r t h e l e s s , the c o m p l e x i t i e s of the mammalian system have made i t d i f f i c u l t t o d e f i n e the c e n t r a l l y programmed "step g e n e r a t o r s " i n t h i s animal. The quadrapedal g a i t and i t s ' r e q u i s i t e neuronal i n t e r c o n n e c t i o n s between hindlimb and f o r e l i m b i n t r o d u c e s a l e v e l of complexity which makes c h a r a c t e r i z a t i o n of the p a t t e r n 8 g e n e r a t o r s c o n s i d e r a b l y more d i f f i c u l t than i n an animal with a l e s s complex nervous system. The b i r d appears t o be an i n t e r e s t i n g animal f o r the study of locomotion. I t s two completely d i f f e r e n t forms of locomotion r e q u i r e in-phase c e n t r a l p a t t e r n g e n e r a t i o n f o r f l y i n g , d uring which the wings beat synchronously, and out of phase g e n e r a t i o n f o r walking and swimming, where the l e g s a l t e r n a t e a c t i v i t y . B e h a v i o u r a l l y , the i n t e r c o n n e c t i o n of these two s e t s of g e n e r a t o r s appears t o occur o n l y d u r i n g t a k e - o f f and l a n d i n g , when the modes of locomotion o v e r l a p . Jacobson and Hollyday (1982b) have suggested t h a t two d i f f e r e n t s u p r a s p i n a l pathways might mediate the i n i t i a t i o n of walking and f l y i n g i n b i r d s . Except f o r a few s t u d i e s (Ten Cate 1960,1962; Tarchanoff, 1895), i n which the phenomenon of s p i n a l s t e p p i n g was documented, very l i t t l e r e s e a r c h has been attempted to i s o l a t e and study the c e n t r a l c o n t r o l of movements i n b i r d s . S u p r a s p i n a l mechanisms r e s p o n s i b l e f o r the i n i t i a t i o n and descending c o n t r o l of avian locomotion have not been examined. The p r e v i o u s f i n d i n g s i n other v e r t e b r a t e s has l e d t h i s experimenter t o examine descending c o n t r o l systems i n the avian c e n t r a l nervous system. While the cat and monkey have a well developed c e r e b r a l c o r t e x , the b i r d does not possess a h i g h l y organized c o r t i c o s p i n a l (pyramidal) system (Cabot et a l . , 1982;) and no avian e q u i v a l e n t of motor cortex has been d e s c r i b e d i n b i r d s (Reiner e t a l . , 1982). T h i s d e f i c i e n c y s t r o n g l y i m p l i c a t e s more caudal brainstem s t r u c t u r e s i n the c o n t r o l of locomotion and a l l o w s one t o study a complex motor system t h a t i s devoid of c o r t i c o m o t o r i n f l u e n c e s , even i n the i n t a c t s t a t e . 9 The review of the l i t e r a t u r e i n d i c a t e s t h a t very l i t t l e i s known about the p h y s i o l o g y and anatomy of s t r u c t u r e s c o n t r o l l i n g locomotion i n b i r d s ( E i d e l b e r g , 1981b). P h y l o g e n e t i c a l 1 y , b i r d s occupy a "middle" p o s i t i o n i n v e r t e b r a t e e v o l u t i o n yet d i s p l a y "advanced" q u a l i t i e s such as b i p e d a l walking s i m i l a r t o human locomotion. A l l of which makes them very i n t e r e s t i n g from the sta n d p o i n t of comparative p h y s i o l o g y . The Canada goose, Branta canadensis, was chosen as the experimental animal, as i t d i s p l a y e d the q u a l i t i e s of being an e x c e l l e n t walking b i r d as well as a remarkable long d i s t a n c e f l y e r . F u r t h e r , i t i s r e a d i l y a v a i l a b l e f o r study, i s easy t o handle i n c a p t i v i t y , and i s not an endangered s p e c i e s . The domesticated n o n - f l y i n g , Pekin duck, Anas pL^tyrhynchos and the Pekin/Mal1ard c r o s s duck Anas pla^yrhynchgs w a s a l s o u t i l i s e d i n some of the acute brainstem s t i m u l a t i o n experiments t o determine the a p p l i c a b i l i t y of the experimental f i n d i n g s with the goose t o other avian s p e c i e s . I n i t i a l l y , i t was necessary t o d e f i n e an index of normal locomotor f u n c t i o n s . T h i s was accomplished f o r both f l y i n g and walking u s i n g electromyographic a n a l y s i s of f o r e l i m b and hindlimb musculature t o determine which muscles best d e f i n e the f l i g h t and walking p a t t e r n s r e s p e c t i v e l y . Secondly, i n c h r o n i c b i r d s , a s e r i e s of s u b t o t a l s p i n a l l e s i o n i n g experiments were performed t o determine which descending pathways were r e s p o n s i b l e f o r the i n i t i a t i o n of hindlimb locomotion. T h i r d l y , p r e l i m i n a r y r e s u l t s were recorded from brainstem e l e c t r i c a l s t i m u l a t i o n s t u d i e s designed t o determine the l o c a t i o n of locomotor areas i n the avian 10 brainstem which e f f e c t e d the i n i t i a t i o n and descending c o n t r o l of locomotion i n these animals. / EUNQIIQNAL QHARAQIERIZAIIQN OF LIMB MUSCLES INVOLVED IN LQCOMQIION IN THE CANADA GOOSE, l§!C.§Qt§. canadensis -12 INIRODUCIION The u t i l i z a t i o n o-f the Canada Goose as an experimental animal •for i t s q u a l i t i e s o-f being both a good b i p e d a l walker and an e x c e l l e n t -flyer r e q u i r e s t h a t the musculature be examined t o determine which muscles c o u l d be r e a d i l y u t i l i z e d as i n d i c a t o r s o-f normal locomotor patterns.- Consequently, i t i s necessary t o -find wing (forelimb) muscles which are both a c t i v e e i t h e r d u r i n g the e l e v a t o r or depressor phases of f l i g h t . Hindlirnb (leg) muscles which are a c t i v e and necessary f o r d e f i n i n g normal walking ( a toe extensor may be a c t i v e during walking, but i s not e s s e n t i a l f o r "normal" appearing locomotion) are most u s e f u l i f they are only a c t i v e during e i t h e r the swing or stance phases of locomotion. The bimodal or b i f u n c t i o n a l c h a r a c t e r of many muscles ( i e . a c t i v e d u r i n g both swing and stance phases or a c t i v e a c r o s s two j o i n t s ) makes i t necessary t o d e f i n e a l l muscles p h y s i o l o g i c a l l y . Each muscle with p o t e n t i a l v alue f o r f u n c t i o n a l l y d e f i n i n g the step c y c l e was s t u d i e d with electromyographic (EMG) r e c o r d i n g techniques. The anatomical approach used by many experimenters i n naming muscle groups does not always take i n t o account the f u n c t i o n a l aspects of muscle a c t i v i t y . For example, the f l e x o r c r u r i s l a t e r a l i s muscle of the l e g i s both a h i p extensor and knee f l e x o r (Nickel et a l . , 1977; Vanden Eerge, 1975), yet, on the b a s i s of anatomical examination, i t i s not p o s s i b l e t o determine whether i t i s a c t i v e d u r i n g the swing phase or stance phase of walki ng. As yet, no anatomical or p h y s i o l o g i c a l examination has been 13 undertaken on the musculature o-f the Canada Goose. There-fore, t h i s •formed the - f i r s t p a r t of t h i s i n v e s t i g a t i o n i n t o the neural c o n t r o l of avian locomotion. 14 M a t e r i a l s and Methods Wild a d u l t Canada geese were obtained under l i c e n s e and maintained i n a l a r g e outdoor e n c l o s u r e with adequate -food and water. A l l f e a t h e r s o v e r l y i n g the muscle groups of i n t e r e s t were removed t o f a c i l i t a t e the c o r r e c t i d e n t i f i c a t i o n of each muscle and the proper placement of EMG e l e c t r o d e s . I n i t i a l l y , EMG / e l e c t r o d e s were implanted a f t e r i n j e c t i o n of l o c a l a n a e s t h e t i c ( x y l o c a i n e h y d r o c h l o r i d e 27.) and r e f l e c t i o n of the o v e r l y i n g s k i n . In subsequent t r i a l s , EMG e l e c t r o d e s were implanted percutaneously using a 22 gauge needle (Basmajian, 1962). Each e l e c t r o d e was made from laquer coated 28 gauge copper wire which was bared at the t i p (approximately 3 mm). Two EMG e l e c t r o d e wires were p o s i t i o n e d i n each muscle examined (see Table 1) f o r d i f f e r e n t i a l r e c o r d s . A common ground e l e c t r o d e was implanted subcutaneously i n the back. A l l e l e c t r o d e s wires were gathered together and supported by a f l e x i b l e s h i e l d e d c a b l e harness sutured t o the s k i n of the back. Loca l a n a e s t h e t i c i n f i l t r a t i o n at a l l s k i n p e n e t r a t i o n p o i n t s was used throughout each t r i a l t o minimize i r r i t a t i o n . None of the animals showed any s i g n s of di s c o m f o r t from the r e c o r d i n g e l e c t r o d e s . To r e c o r d hindlimb muscle a c t i v i t y during walking, each animal was placed on a t r e a d m i l l enclosed by a box with a c l e a r p l e x i g l a s f r o n t . The b i r d s were permitted t o walk u n r e s t r a i n e d on the moving t r e a d m i l l b e l t . Normal locomotion was d e f i n e d by the animal walking with i t s head i n a normal u p r i g h t posture. T h i s 15 u s u a l l y occurred -following a short t r a i n i n g p e r i o d (5-15 min). There were no observable d i f f e r e n c e s between b i r d s walking on a t r e a d m i l l and those walking u n r e s t r a i n e d i n an open environment. EMG r e c o r d i n g s were made at t r e a d m i l l speeds up t o 2.0 m/sec with an average speed being 0.4 m/sec. F l i g h t muscle EMGs were recorded by p l a c i n g the animal i n a r e l a t i v e l y normal f l y i n g p o s i t i o n while s u p p o r t i n g the body and f e e t . Support of the f e e t was then removed and the b i r d was allowed t o beat i t s wings i n an u n r e s t r a i n e d manner while t e t h e r e d i n m i d a i r . A l l EMG s i g n a l s were a m p l i f i e d and f i l t e r e d p r i o r t o monitoring on a 4 channel o s c i l l o s c o p e and r e c o r d i n g on magnetic tape. Permanent r e c o r d s were obtained on tape playback i n t o a 4 channel s t r i p c h a r t r e c o r d e r . Hindlirnb and f o r e l i m b anatomy was determined i n both perfused (10% f o r m a l i n ) and unperfused s a c r i f i c e d animals. Each EMG r e c o r d i n g s i t e was confirmed by int r a m u s c u l a r examination of the e l e c t r o d e placement. S u p e r f i c i a l muscle groups and tendons were diagrammed, then removed t o f a c i l i t a t e o b s e r v a t i o n and documentation of inner muscle groups. To i n s u r e c o r r e c t anatomical d e f i n i t i o n , the o r i g i n and i n s e r t i o n p o i n t s f o r each muscle were a l s o examined. The o b s e r v a t i o n s were compared with p r e v i o u s s t u d i e s (eg. C r a c r a f t , 1971; George and Berger, 1966; Kaupp, 1918; Vanden Berge, 1975,1979; see Table 1). The nomenclature I have employed i s t h a t of Vanden Berge (1979) as approved by the I n t e r n a t i o n a l Committee on Avian Anatomical Nomenclature. In cases where no anatomical c o r r e l a t e s were found i n Vanden Berge (1979), a muscle 16 was named on the b a s i s of a consensus -from other sources. 17 RESULTS Hindlimb and -forelimb muscles, documented i n t h i s study, with a l t e r n a t e names i n common use, are l i s t e d i n Tables 1 and 2, r e s p e c t i v e l y . HINDLIMB: S u p e r f i c i a l hindlimb muscles that were examined f o r EMG a c t i v i t y i n c l u d e d : Muscle (M. ) i l i o t i b i a l i s c r a n i a l i s (ITC), M. f l e x o r c r u r i s l a t e r a l i s (FCL), M. f l e x o r c r u r i s m e d i a l i s (FCM), M. c a u d o - i 1 i o - f e m o r a l i s (CFM), M. i l i o t i b i a l i s l a t e r a l i s (ITL) and M. i l i o f i b u l a r i s (IFB). ITC (commonly named the s a r t o r i u s muscle or extensor i l i o t i b i a l i s a n t e r i o r , see Table 1), a muscle t h a t l i e s a n t e r i o r to the femur, a t t a c h e s p r o x i m a l l y on the a n t e r i o r i l i a c c r e s t and d i s t a l l y on the p a t e l l a , ( F i g s . 1,2,3). E l e c t r i c a l a c t i v i t y of t h i s muscle ( F i g . 4) i n d i c a t e s a p e r i o d i c monophasic EMG b u r s t d u r i n g the swing phase of the step c y c l e . C o n t r a c t i o n s of i p s i l a t e r a l ITC a l t e r n a t e out of phase with a c t i v i t y i n the c o n t r a l a t e r a l ITC. FCL (commonly named the semi tendinosus muscle, see Table 1), forms a t h i n band of muscle o v e r l y i n g M. f l e x o r c r u r i s m e d i a l i s (FCM). FCL a r i s e s p r o x i m a l l y from the c r i s t a i l i a c a d o r s a l i s p o s t e r i o r ( p o s t e r i o r d o r s a l i l i a c c r e s t ) and i n s e r t s on the femur ( F i g s . 1,3). Percutaneous i m p l a n t a t i o n of FCL y i e l d e d EMG r e c o r d i n g s (Fig.4) that demonstrate prolonged a c t i v i t y during the 18 stance phase of walking. The r e c i p r o c a l r e l a t i o n s h i p between FCL and i t s c o n t r a l a t e r a l homolog r e v e a l s a s t r i c t a l t e r n a t i n g , though o v e r l a p p i n g p a t t e r n of a c t i v i t y at slow speeds. The temporal r e l a t i o n s h i p of FCL with i t s i p s i l a t e r a l a n t a g o n i s t , ITC, i s a l s o one of s t r i c t a l t e r n a t i o n . Even though ITC c o n t r a c t i o n on one s i d e i s almost simultaneous with t h a t of the c o n t r a l a t e r a l FCL, the d u r a t i o n of ITC a c t i v i t y i s much s h o r t e r ( F i g . 4 ) . The f o l l o w i n g muscles of the hindlirnb provided l e s s r e l i a b l e or t o t a l l y e q u i v o c a l EMG r e c o r d i n g s during walking. In a d d i t i o n , some of the muscles were very d i f f i c u l t to p e n e t r a t e percutaneously with EMG e l e c t r o d e s (eg.ITL and CFM, F i g s . 1,2). FCM (or semimembranosus) l i e s medial to FCL i n the secondary l a y e r of hindlirnb muscles ( F i g s . 2 , 5 ) . FCM a r i s e s more m e d i a l l y than FCL from the ischium and i n s e r t s on the t i b i o t a r s u s . P h y s i o l o g i c a l l y , FCM has the same a c t i o n as FCL (hip e x t e n s i o n , weak knee f l e x i o n ) . F u n c t i o n a l l y , however, EMG r e c o r d i n g s i n d i c a t e t h a t FCM i s only a c t i v e d u r i n g the l a t t e r p a r t of the stance phase m a i n t a i n i n g i t s a c t i v i t y i n t o the e a r l y stages of f l e x i o n ( F i g . 6 ) . T h e r e f o r e , i t i s not an a p p r o p r i a t e marker to demonstrate the t r a n s i t i o n between ext e n s i o n and f l e x i o n phases of the step c y c l e . CFM (or c a u d o - i 1 i o - f e m o r a l i s , p i r i f o r m i s , or femorocaudal, Table 1) l i e s medial to FCL and FCM and i s p a r t i a l l y exposed to the s u p e r f i c i a l l a y e r ( F i g . l ) . However, i t i s more p r o p e r l y c l a s s i f i e d as a muscle of the secondary l a y e r ( F i g . 2 ) . It a r i s e s p r o x i m a l l y from the p o s t e r i o r d o r s a l i l i a c c r e s t and d i s t a l l y t e r m i n a t e s on the femur. EMG r e s u l t s ( F i g 7) i n d i c a t e t h a t t h i s muscle i s p r i m a r i l y a hip extensor, a c t i v e during the stance phase of the step c y c l e . It i s p o s s i b l e that CFM was i n c l u d e d 19 p e r i o d i c a l l y i n r e s u l t s from FCL; however, s i n c e both CFM and FCL are hip extensor muscles a c t i v e d u r i n g the same phase of the step c y c l e , i t should not s i g n i f i c a n t l y d i s t o r t FCL r e c o r d i n g s during walking. S u r g i c a l l y , CFM was a d i f f i c u l t muscle t o implant without r e f l e c t i o n of the o v e r l y i n g dermis and was t h e r e f o r e abandoned as a u s e f u l marker f o r the stance phase of locomotion. ITL ( i l i o t i b i a l i s or g l u t e u s primus, Table 1), i s a l a r g e muscle t h a t a t t a c h e s p r o x i m a l l y t o the d o r s a l i l i a c c r e s t and d i s t a l l y t o the p a t e l l a ( F i g . l ) . I t s p e r i o d of a c t i v i t y i s simultaneous, but of s h o r t e r d u r a t i o n than that of ITC. Although e a s i l y a c c e s s i b l e however, i n the goose, ITL produced e q u i v o c a l EMGs du r i n g locomotion ( i e . a c t i v e throughout a l l phases of the step c y c l e , with major a c t i v i t y corresponding t o that of ITC) ( F i g . 8 ) . T h e r e f o r e , i t was not e f f e c t i v e as an i n d i c a t o r of the a l t e r n a t i n g phases of s t e p p i n g . IFB (biceps femoris, Table 1) l i e s p o s t e r i o r to the femur ( F i g s . 1 and 2). It a t t a c h e s p r o x i m a l l y t o the d o r s a l i l i a c c r e s t , l o o ps i t s tendon through the Ansa M. i I i o f i b u l a r i s (Fig.5) and i n s e r t s on the f i b u l a ( F i g . 3 ) . In the goose i t appears to be a c t i v e d u r i n g both stance and swing phases of hindlimb s t e p p i n g ( F i g . 8 ) . FORELIMB: Muscles of the f o r e l i m b (wing) that were implanted f o r EMGs in c l u d e d : M. p e c t o r a l i s , M. d e l t o i d e u s major (DM), M. l a t i s s i m u s d o r s i , pars c r a n i a l i s (LDCr) and pars caudal i s (LDCa), and M. 20 s c a p u l o t r i c e p s (TSC) . The depressor and e l e v a t o r phases o-f the • f l i g h t c y c l e are best i l l u s t r a t e d by the p e c t o r a l i s and d e l t o i d e u s musceles r e s p e c t i v e l y ( F i g . 9). LDCa, LDCr and TSC were e i t h e r d i f f i c u l t t o access by percutaneous i m p l a n t a t i o n of EMG e l e c t r o d e s or were c o n t i n u o u s l y a c t i v e throughout the e n t i r e f l i g h t c y c l e . P e c t o r a l i s i s a n a t o m i c a l l y the l a r g e s t muscle found i n the goose ( F i g . 1 0 ) . T h i s muscle a r i s e s from the sternum and i n s e r t s on the humerus. It i s the primary depressor of the wing, as i n d i c a t e d by EMG r e c o r d i n g s d u r i n g t e t h e r e d '(Fig.lO) and u n r e s t r a i n e d f l i g h t . ( B u t l e r et a l . , 1977). Tethered f l i g h t i n the p r e p a r a t i o n s of t h i s study appeared to be comparable t o a c t u a l f l i g h t , at l e a s t with regards t o the a c t i v i t y p a t t e r n of p e c t o r a l i s . D e l t o i d e u s major a r i s e s from s e v e r a l bones of the shoulder j o i n t , i s anchored by means of the r e t i n a c u l u m and i n s e r t s v e n t r a l l y midway along the humerus ( F i g . l O ) . Recordings o n l y show a c t i v i t y d u r i n g the e l e v a t i o n phase of the f l i g h t c y c l e (Fig.9) LDCr a r i s e s from the neural s p i n e s of the most caudal c e r v i c a l and most r o s t r a l t h o r a c i c v e r t e b r a e and i n s e r t s on the humerus ( F i g . l O ) . LDCa a r i s e s from the d o r s a l i l i a c c r e s t caudal to and separated from LDCr. The p o i n t of i n s e r t i o n of LDCa i s s i m i l a r t o that of LDCr. Both LDCa and LDCr were found to be p h y s i o l o g i c a l l y weak e l e v a t o r s of the wing, a c t i v e throughout the e l e v a t o r phase of the f l i g h t c y c l e ( F i g . 1 1 ) . However, i t i s d i f f i c u l t t o d i s t i n g u i s h LDCa and LDCr from the rhomboideus s u p e r f i c i a l i s muscle on the b a s i s of t o p o g r a p h i c a l c r i t e r i a . T h i s makes i t very d i f f i c u l t t o a c c u r a t e l y implant percutaneously with EMG e l e c t r o d e s . TSC (or t r i c e p s s c a p u l a r i s , Table 1) a r i s e s from the proximal 21 humerus, passes c a u d a l l y along the humerus and i n s e r t s onto the ul n a ( F i g . 10) it Electromyographic r e s u l t s ( F i g . 11) show t o n i c muscle a c t i v i t y d u r i n g wing extension, demonstrating t h a t TSC i s a c t i v e throughout the e n t i r e - f l i g h t c y c l e . 22 DISCUSSION The c h a r a c t e r i z a t i o n o-f muscles d e f i n i n g normal hindlimb and f o r e l i m b locomotor behaviours i n the goose arose as a necessary p r e r e q u i s i t e to determining the locomotor c a p a b i l i t i e s of c h r o n i c s p i n a l cord l e s i o n e d and acute decerebrate animals. Due to the l a c k of i n f o r m a t i o n r e g a r d i n g the musculature of the Canada goose, i t was necessary t o a n a t o m i c a l l y c h a r a c t e r i z e the musculature to allow t o p o g r a p h i c a l i m p l a n t a t i o n of EMG e l e c t r o d e s which would d e f i n e the step c y c l e f l e x o r and extensor muscles necessary t o locomotion. It was a l s o necessary to p h y s i o l o g i c a l l y c h a r a c t e r i z e the musculature as t o i t s e f f i c a c y i n d e f i n i n g the avian step and f l i g h t c y c l e s , f o r an a n a t o m i c a l l y d e f i n e d muscle does not n e c e s s a r i l y r e f l e c t i t s p h y s i o l o g i c a l f u n c t i o n . Hindlimb and f o r e l i m b muscles d e f i n i n g rhythmic locomotor p a t t e r n s need t o meet s e v e r a l c r i t e r i a . These i n c l u d e : 1) the trauma to the animal must be minimized during e l e c t r o d e i m p l a n t a t i o n ; 2) the muscles must be e s s e n t i a l to the p r o d u c t i o n of normal locomotion; and 3) the muscle must produce an EMG t r a c e that i s c l e a r l y d i s t i n g u i s h a b l e , p h a s i c , and r e l i a b l y r e p l i c a b l e . The hindlimb muscles which met the above c r i t e r i a were the i l i o t i b i a l i s c r a n i a l i s (ITC) and the f l e x o r c r u r i s l a t e r a l i s (FCL). ITC i s a p h y s i o l o g i c a l f l e x o r which i s a c t i v e d u r i n g the m a j o r i t y of the swing phase of walking. It i s l o c a t e d s l i g h t l y a n t e r i o r t o the femur and i s the e a s i e s t hindlimb muscle to implant percutaneously ( F i g s . 1 , 2 , 3 ) . R e s u l t s show a p e r i o d i c 23 monophasic burst o-f a c t i v i t y •from t h i s muscle duri n g both swing ext e n s i o n and swing -flexion ( F i g . 4) which are i n agreement with p r e v i o u s f i n d i n g s of Jacobson and Hollyday (1982a) f o r the c h i c k . EMG r e s u l t s from FCL i n d i c a t e that i t i s a c t i v e during the e x t e n s i o n phase of the step c y c l e d e s p i t e i t s anatomical nomenclature ( F i g . 4 ) . A small component of t h i s muscle's a c t i v i t y begins i n the e a r l y swing extension phase of the step c y c l e . However, i t d e f i n e s the end of the extension phase of s t e p p i n g p r e c i s e l y and as such i s a good i n d i c a t o r of t h i s p o r t i o n of the c y c l e . T h i s f i n d i n g i s a l s o i n agreement with t h a t found f o r the c h i c k (Jacobson and Hollyday, 1982a). The p o s s i b i l i t y e x i s t s t h a t FCM and CFM were implanted percutaneously along with FCL, as FCL form only a t h i n f l a t l a y e r d i r e c t l y apposing the s k i n . The a c t i o n s of FCM and CFM are s i m i l a r t o t h a t of the o v e r l y i n g muscle (FCL) and t h e r e f o r e would not s i g n i f i c a n t l y a l t e r EMG r e c o r d i n g s from FCL. These muscles were not, however, e a s i l y penetrated with EMG e l e c t r o d e s , and as such co u l d not be r e l i a b l y used to d e f i n e avian walking. Regardless, care was taken t o implant o n l y FCL by i n t r o d u c t i o n of the r e c o r d i n g e l e c t r o d e s along a f l a t plane p a r a l l e l t o the o v e r l y i n g s k i n . T h i s p r e c a u t i o n provided r e l i a b l e EMG r e s u l t s i d e n t i f y i n g the e n t i r e e x t e n s i o n phase of the step c y c l e . Jacobson and H o l l y d a y (1982a) d e s c r i b e ITL as a p h y s i o l o g i c a l f l e x o r of the hindlirnb and IFB as a b i p h a s i c muscle with a c t i v i t y d uring the stance phase of locomotion. However, i n the goose, these two muscles d i d not prove to be usable i n d i c a t o r s of locomotion, as they were a c t i v e during both phases of the. step c y c l e . 24 The f o r e l i m b musculature which provided the most r e l i a b l e EMGs d e f i n i n g the f l i g h t c y c l e were the p e c t o r a l i s and d e l t o i d e u s major muscles. George and Berger (1966) used an anatomical b a s i s f o r d e s i g n a t i o n of the muscles c o n t r o l l i n g the e l e v a t o r and depressor phases of the f l i g h t c y c l e . They determined that p e c t o r a l i s and supracoracoideus were the major muscles r e s p o n s i b l e f o r the e l e v a t o r and depressor phases, r e s p e c t i v e l y . The r e s u l t s of t h i s study i n d i c a t e t hat the p e c t o r a l i s muscle i s the best muscle f o r d e f i n i n g the depressor phase of locomotion. However, the supracoracoideus muscle, which l i e s medial t o the p e c t o r a l i s muscle was not t e s t e d i n t h i s study, s i n c e i t i s very d i f f i c u l t to a c c u r a t e l y percutaneously implant with e l e c t r o d e s . D e l t o i d e u s major, however, produces EMGs which a l t e r n a t e out of phase with p e c t o r a l i s and i s t h e r e f o r e considered t o be a good i n d i c a t o r of the e l e v a t o r phase of f l i g h t ( F i g . 9 ) . LDCa, LDCr, and TSC were e i t h e r d i f f i c u l t t o implant percutaneouly or were t o n i c a l l y a c t i v e throughout wing e x t e n s i o n . T h e r e f o r e they could not be u t i l i z e d as i n d i c a t o r s of the avian f l i g h t c y c l e . The muscles which best exemplify the hindlirnb locomotion and f l y i n g locomotion i n the Canada goose f o r the purposes of f u t u r e experiments have been i d e n t i f i e d as being ITC/FCL and F'ec:t/DM r e s p e c t i v e l y . In an attempt t o c l a r i f y the avian muscle nomenclature, a l i s t of synonyms i s provided f o r the limb musculature i n Tables I and I I . 25 TABLE I Nomenclature f o r hindlimb muscles i n the Canada goose ABBREVIATION NAME 8< (SYNONYMS) FUNCTION caudofem. (CFM) -M. c a u d o - i 1 i o - f e m o r a l i s (D- caudofemoralis) ( I - p i r i f o r m i s ) (K- femorocaudal) L- hip extensor, t a i l depressor J- hip extensor, knee flexor (weak) Q- hip extensor ext. d ig, comm. -M. extensor d i g i t o r u m communis L,P- d i g i t extensor fern, t i b , ex t . -M. f e m o r o t i b i a l i s externus L,P- knee extensor (D,G,H- vastus l a t e r a l i s ) (F,I,R- f e m o r i t i b i a l i s externus) (L- quadriceps femoris) (M- vastus externus component of M. extensor femoris) fern. t i b . med. -M. f e m o r o t i b i a l i s medius (D,H- vastus m e d i a l i s ) (L- quadriceps femoris) (N- cruraeus component of extensor femoris) L,P- knee extensor J- knee extensor f i b . brev. -M. f i b u l a r i s (peroneus) b r e v i s L- i n t e r n a l r o t a t o r t arsometatarsus (ankle) P- i n t e r n a l ankle r o t a t i o n , ankle f1 ex or f i b . long -M. f i b u l a r i s (peroneus) longus P- ankle extensor J- ankle extensor 26 •flex, cru, l a t . (FCL) -M. -flexor c r u r i s l a t e r a l i s L,P- hip extensor, knee f l e x o r (I,K- semitendinosus) J,Q- h i p e x t e n s o r <B- caudi 1 i o f 1 e x o r i u s ) knee- flexor (weak) f l e x . c r u . med. (FCM) -M. f l e x o r c r u r i s m e d i a l i s P- hip extensor, knee f l e x o r (I,K- semimembranosus) ( F , J - i s c h i o f l e x o r i u s ) J,0t- hip extensor knee f1exori weak) f l e x . p. dig, IV -M. f l e x o r p e r f o r a n s d i g i t i IV (L- f l e x o r p e r f o r a t u s d i g . IV) P— ex t e n s i o n of t a r s o m e t a t a r s a l j o i n t (ankle) L,P- toe f l e x o r f1 ex. p. dig. I l l -M. f l e x o r p e r f o r a n s d i g i t i III L,P- toe f l e x o r P- ankle extensor (L- f l e x o r p e r f o r a t u s d i g . I l l ) f1 ex. p. et p. d i g . I l l -M. f l e x o r p e r f o r a n s et p e r f o r a t u s d i g i t i i III L.P- toe f l e x o r P- ankle extensor (K- f l e x o r p e r f o r a t u s medius secundus pedis) f 1 ex . p. et p. d i g . II -M. f l e x o r p e r f o r a n s et p e r f o r a t u s d i g i t i i II L,P- toe f1 exor P- ankle extensor <K- f l e x o r p e r f o r a t u s i n d i c i s secundus pedis) g a s t r o c . l a t . ' -M. gastrocnemius pars l a t e r a l i s (externa) L,P- ankle extensor J- ankle extensor g a s t r o c . med. -M. gastrocnemius pars m e d i a l i s ( i n t e r n a ) L,P- ankle extensor J- ankle extensor i 1 i o f i b . (IFB) —M. i 1 i o f i b u l a r i s (I,F,G- b i c e p s f e m o r i s or b i c e p s f e m o r a l i s ) (D,H- extensor i l i o -f i b u l a r i s ) (K,N- b i c e p s f l e x o r c r u r i s ) L- hip extensor, knee f l e x o r , l e g abductor P- knee f l e x o r J,Q- knee flexor hip extensor 27 i 1 i o t i b• (ITC) cran. —M. i l i o t i b i a l i s c r a n i a l i s (I,J,K- s a r t o r i u s ) (D,J- extensor i l i o -t i b i a l i s a n t e r i o r ) l _ - h i p -flexor P- hip -flexor, knee extensor J,<3- hip flexor, knee extensor i 1 i o t i b . (ITL) l a t . -M. i l i o t i b i a l i s l a t e r a l i s (K,N- g l u t e u s primus) (G- i l i o t i b i a l i s ) ( F , J - i ) i l i o t i b i a l i s a n t e r i o r i i ) i l i o t i b i a l i s med i us or tensor f a s c i a e i i i ) i l i o t i b i a l i s p o s t e r i or or g l u t e u s p o s t e r i o r ) L- hip extensor P- hip extensor or hip f1ex or, hip abductor J - iliotib. ant. -hip flexor iliotib. post. -hip extensor, knee extensor, external rotator of hip. i 1 i o t r o c h , caud. -M. i 1 i o t r o c h a n t e r i c u s c a u d a l i s (D- g l u t e u s profundus) l_,P- h i p extensor J - internal rotator of hip i 1 i otroch. c r a n . -M. i 1 i o t r o c h a n t e r i c u s c r a n i a l i s '(D- i l i a c u s ) L- hip f l e x o r P- i n t e r n a l r o t a t o r of hip J- hip flexor, internal rotator -. of hip i s c h i ofem. -M. i s c h i o f e m o r a l i s (D- f l e x o r i s c h i o f e m -o r a l i s externus) (N- o b t u r a t o r externus) L,P- e x t e r n a l hip r o t a t o r , hip extensor J- external rotator of hip l e v . caud. -M. l e v a t o r caudae (H,M) P- extends and r a i ses t a i 1 pubo-i s c h i o-f em. -M. p u b o - i s c h i o - f e m o r a l i s (C,D- adductor longus et b r e v i s ) (L- adductor femoris) L,P- hip extensor, hip adductor J- hip extensor 28 t i b . c r a n . -M. t i b i a l i s c r a n i a l i s t,P- ankle -flexor J- ankle flexor Note: I t a l i c s denotes f u n c t i o n i d e n t i f i e d on a p h y s i o l o g i c a l b a s i s. Source: A) Vanden Berge (1979)- A l l names given except where designated. B) B u t l e r et a l . (1977) C) C r a c a f t (1971) D) F i s h e r (1946) and F i s h e r and Goodman (1955) E) F u j i oka (1959) F) Gadow and Selenka (1891) G) George and Berger (1966) H) Howell (1938) I) Hudson (1937) J) Jacobson and Hol l y d a y (1982) K) Kaupp (1918) L) N i c k e l et a l . (1977) M) Romer (1927) N) S h u f e l d t (1890) 0) S u l 1 i v a n (1962) P) Vanden Berge (1975) Q) Weinstein et a l . , present study (see te x t ) R) Wilcox (1952) 29 TABLE II Nomenclature f o r f o r e l i m b muscles i n the Canada goose ABBREVIATION NAME & (SYNONYMS) FUNCTION add. a l u . -Muscle (M. ) adductor a l u l a e (P- adductor p o l l i c i s ) (P- adductor a l a e d i g i t i II) L,P- d i g i t adductor b i c . -M. b i c e p s b r a c h i i L,P~ elbow f l e x o r P- shoulder extensor d e l t . maj —M. d e l t o i d e u s major L- shoulder f l e x o r P- wing e l e v a t o r , wing f l e x o r Q- wing e l e v a t o r d e l t . min. —M. d e l t o i d e u s minor L,P- wing e l e v a t o r , wing adductor e c t e p i —M. e c t e p i c o n d y l o - u l n a r i s (S- anconeus) L- elbow extensor P- elbow f l e x o r , wing s u p i n a t o r ext. long, d i g . maj -M. extensor longus d i g i t i L- d i g i t extensor maj o r i s (D- extensor longus d i g i t i III) (G- extensor i n d i c i s longus) ( F , I - extensor medius longus) (D,G- extensor i n d i c i s longus and M. f l e x o r metacarpi b r e v i s) ext. meta. rad. -M. extensor metacarpi L,P- e x t e n s i o n of r a d i a l i s c a r p e l meta-c a r p a l j o i n t s (wrist) (L- extensor c a r p i r a d i a l i s ) P- elbow f l e x o r 30 ext. met a. - l i . extensor metacarpi L- w r i s t extensor u l n . u l n a r i s P- w r i s t -flexor, <L- extensor c a r p i u l n a r i s ) elbow -flexor -flex. d i g . - l i . -flexor d i g i t i m i n o r i s P- metacarpal min. -flexor (D,F- f l e x o r d i g i t i III or IV) (P- f l e x o r d i g i t i q u a r t i ) i n t e r o s s . - l i . i n t e r o s s e u s d o r s a l i s L,P- e x t e n s i o n of dor. second d i g i t i n t e r o s s . -M. i n t e r o s s e u s v e n t r a l i s L,P- f l e x i o n of v e n t r . - second d i g i t (D,F,G,L- i n t e r o s s e u s palmaris) (0- i n t e r o s s e u s v o l a r i s ) l a t . dors, caud. (LDCa) -M. l a t i s s i m u s d o r s i pars caudal i s L,P- draws wing c a u d a l l y , wing e l e v a t o r and f1 ex or Q- wing elevator (weak) l a t . dors, cran. (LDCr) - l i . l a t i s s i m u s d o r s i pars c r a n i a l i s L,P- draws wing c a u d a l l y , wing e l e v a t o r and f1 exor Q- ning elevator (weak) during wing extension pect. -M. p e c t o r a l i s G,P- wing depressor B,0- wing depressor pect. propatag, -M. p e c t o r a l i s pars p r o p a t a g i a l i s P- wing depressor rhom. p r o f . - l i . rhomboideus profundus L- e l e v a t e s c a p u l a P- s t a b i l i z e s s c a p u l a 31 rhom. s u p e r f . —M. rhomboideus superf i c i a l i s (E- t r a p e z i u s ) P-r e s p i r a t o r y expi r a t i on s t a b i l i z e s the s c a p u l a scap. hum. caud. —M. scapulohumeral i s !_-caudal i s P-(B- proscapulohumeralis) wing e l e v a t o r s t a b i 1 i z a t i o n of humerus during wing beat s e r r . s u p e r f . caud. —M. s e r r a t u s s u p e r f i c i a l i s pars caudal i s (G- s e r r a t u s p o s t e r i o r ) (N- t h o r a c o - s c a p u l a r i s ) L- wing depressor, r e s p i r a t o r y expi r a t i on P- s t a b i l i z e s scap-u l a , r e s p i r a t i o n s e r r . s u p e r f . metapatag. —M. s e r r a t u s s u p e r f i c i a l i s pars m e t a p a t a g i a l i s L— s t r e t c h e s the patagi urn P- s t a b i l i z e s the s c a p u l a sup. —M. s u p i n a t o r l_,P- s u p i n a t i o n of the wing T. of f l e x . -Tendon of f l e x o r d i g . pro. d i g i t o r u m profundus tens. -M. tensor p r o p a t a g i a l i s L- wing adductor propatag. P— d i g i t extensor, (G- tensor p a t a g i i longus) forearm f l e x o r ( F , I - p r o p a t a g i a l i s longus) t r i . scap. - l i . s c a p u l o t r i c e p s L- elbow extensor (TSC) P- elbow extensor, <G- t r i c e p s s c a p u l a r i s or shoulder f l e x o r anconaeus s c a p u l a r i s or anconaeus longus) (L- anconaeus) (P- t r i c e p s b r a c h i i pars s c a p u l a r i s ) 32 Note: I t a l i c s denotes -function i d e n t i f i e d on a p h y s i o l o g i c a l b a s i s . Source: as l i s t e d f o r Table I. o 33 FIGURE 1 L a t e r a l view of the s u p e r f i c i a l hindlirnb musculature. A b b r e v i a t i o n s : T= tendon, f o r muscles see Table 1. 34 lat. dors caud iliotroch. cran • iliotroch. caud. lev caud iliotib cran. iliotib. lat external condyle' of femur T.of fib. brev T. of gastroc med.& lat. tarsometatarsus 35 EIGURE 2 L a t e r a l view o-f the second l a y e r of hindlirnb muscles u n d e r l y i n g the s u p e r f i c i a l l a y e r . To show the second l a y e r , the f o l l o w i n g s u p e r f i c i a l muscles have been removed: f i b . long., f l e x . c r u . l a t . , g a s t r o c . l a t . , i l i o t i b . l a t . and l a t . dors. caud. A b b r e v i a t i o n s : T= tendon, f o r muscles see Table 1. 36 iliotroch cran. & caud. scap. hum. caud./ serr. superf. caud. iliotib. cran fern. tib. med.& ext gastroc. med.— flex. p. et p. dig III flex. p. et p. dig. II tib. c ran .^ T.of flex. T. of flex. p. et p.dig.Ill T. of gastroc. med brev IV-FIGURE 3 Dorsal view of hindlimb musculature. To r e v e a l the second l a y e r of muscle, the tendon of g a s t r o c . l a t . has been r e f l e c t e d . A b b r e v i a t i o n s : T= tendon, R= r o s t r a l , C= caudal, f o r muscles see Table 1. 38 iliotib. lat. gastroc. lat. flex. cru. lat flex p et p. dig II flex p et p. dig. Ill flex.perf. dig. IV caudofem gastroc. med. gastroc. inter flex. perf. dig. Ill tibiotarsus T.of gastroc. med. T. of flex. p. et p. dig II & III T. of gastroc. lat. 39 E1BLJRE 4 Electromyographic (EMG) r e c o r d s -from l e f t and r i g h t hindlimb ITC and FCL muscles during t r e a d m i l l walking ( b e l t speed= 0.3m/sec). ITC i s a -flexor a c t i v e throughout the stance phases ( i e . f o o t contact with the s u b s t r a t e ) are i n d i c a t e d by the bars beneath the EMG r e c o r d i n g s . A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , FCL= f l e x o r c r u r i s l a t e r a l i s . ITC LEFT FCL A ITC RIGHT FCL Left Right 41 FIGURE 5_ L a t e r a l view of the t h i r d l a y e r of hindlirnb musculature u n d e r l y i n g the second l a y e r . R e f l e c t i o n of the primary l a y e r of the f l e x . c r u . med., i n a d d i t i o n to c u t t i n g the f l e x . c r u . l a t . , and i l i o f i b . , r e v e a l s pubo-ishio-fem. and i s c h i o f e m . . F l e x . p. et p. d i g . II has been removed t o r e v e a l f l e x . p. et p. d i g . I l l 0 , and the ansa ( l o o p - l i k e s t r u c t u r e ) i l i o f i b . . A b b r e v i a t i o n s : T= tendon, f o r muscles see Table 1. 42 iliofib iliotroch cran. ischiofem. pubo-ischio-fem femorotib med.& ext. iliofib. flex. cru. lat. flex. cru. med. Ansa iliofib. flex. p. dig. Ill T. of 43 EI§yR§ 6 Electromyographic r e c o r d i n g o-f the hindlirnb ITC and FCM during t r e a d m i l l walking ( b e l t speed= 0.4 m/sec). ITC i s a -flexor a c t i v e throughout the swing phase. FCM i s a hip extensor and knee -flexor (weak) a c t i v e during the stance phase with a component ov e r l a p p i n g the swing phase during walking. A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , FCM= f l e x o r c r u r i s m e d i a l i s . ITC 45 FIGURE 7 Electromyographic r e c o r d i n g s of the hindlirnb ITC and CFM muscles during t r e a d m i l l walking. ITC i s a f l e x o r a c t i v e throughout the swing phase. CFM i s an hip extensor and knee f l e x o r (weak) a c t i v e throughout the stance phase of walking. A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , CFM= ca u d o - i 1 i o-f e m o r a l i s . 46 1 sec. 47 FIGURE 8 Electromyographic r e c o r d s -from l e f t and r i g h t ITC and l e f t IFB muscles of the hindlirnb during t r e a d m i l l walking <belt speed= 0.3m/sec). ITC i s a f l e x o r a c t i v e throughout the e n t i r e swing phase. IFB i s a c t i v e both during the stance phase and swing phase of walking. A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , IFB= i 1 i of i b u l a r i s. 48 RIGHT ITC IFB LEFT 49 E i s y R E 9 Electromyographic r e c o r d i n g s o-f the f o r e l i m b Pect and DM muscles during t e t h e r e d f l a p p i n g of the wings. Pect i s a wing depressor and DM i s a wing e l e v a t o r . A b b r e v i a t i o n s : Pect= P e c t o r a l i s , DM= d e l t o i d e u s major. 50 Pect LEFT RIGHT 1.0 s 51 FIGURE 10 L a t e r a l view o-f the wing and a s s o c i a t e d a x i a l trunk musculature. A b b r e v i a t i o n s : T= tendon, f o r muscles see Table 2. 52 rhom. superf iliotib. cran iliotroch. cran.-iliotroch. caud serr. superf.caud iliotib. lat scap hum.caud serr. superf.metapatag tri. scap ext. meta rad. rhom prof lat. dors. cran. rhom superf. scapula retinaculum delt. maj. delt. min. tens, propatag. flex dig. min. inteross dor inteross. ventr. T of flex. dig. pro. 53 EIGURE 11 Electromyographic r e c o r d s from the l e f t f o r e l i m b LDCr, DM, TSC, and Pect muscles. Pect i s a c t i v e during the depressor phase of wing f l a p p i n g . LDCr i s a c t i v e during the e l e v a t o r phase of wing movement c o i n c i d e n t with DM. DM a l t e r n a t e s out of phase with Pect.. TSC shows t o n i c a c t i v i t y during wing extension and i s a c t i v e throughout the e n t i r e f l i g h t c y c l e . A b b r e v i a t i o n s : DM= d e l t o i d e u s major, LDCa= l a t i s s i m u s d o r s i , pars c a u d a l i s , TSC= s c a p u l o t r i ceps. 54 55 CHAPTER II CHARACTERIZATION OF DESCENDING SPINAL CORD PATHWAYS NECESSARY EQR LOCOMOIIQN IN THE HINDLIMBS OF THE CANADA GOOSE, Branta canadensis 56 INTRODUCTION Motor c o n t r o l i s thought t o be the r e s u l t of descending input from c e n t r e s i n the hind, mid and f o r e b r a i n . The pathways c a r r y i n g t h i s i n f o r m a t i o n t r a v e l i n the s p i n a l cord white matter b e f o r e synapsing at the a p p r o p r i a t e s p i n a l l e v e l where they a c t i v a t e locomotor p a t t e r n g e n e r a t o r s (LPGs) ( B r i l l n e r , 1975). S e l e c t i v e l e s i o n i n g of descending s p i n a l cord pathways at both c e r v i c a l and t h o r a c i c l e v e l s has y i e l d e d i n f o r m a t i o n r e g a r d i n g the s p i n a l t r a j e c t o r i e s of these locomotor pathways and provided v a l u a b l e c l u e s as t o the s u p r a s p i n a l areas which e f f e c t the c o n t r o l of locomotion ( A f e l t , 1974; Steeves and Jordan, 1980; Yu and E i d e l b e r g , 1981; W i l l i a m s et a l . , 1984). The l i t e r a t u r e suggests t h a t descending r e t i c u l o s p i n a l pathways p l a y an important r o l e i n the i n i t i a t i o n and c o n t r o l of walking i n c a t s and monkeys. The maintenance of both v e n t r a l quadrants of the s p i n a l cord which have been shown t o c o n t a i n descending r e t i c u l o s p i n a l pathways (Kuypers, 1982), al l o w s b i l a t e r a l walking i n a c u t e l y s t i m u l a t e d (MLR) mesencephalic c a t s (Steeves and Jordan, 1980), non-decerebrate c h r o n i c l e s i o n e d c a t s ( A f e l t , 1974; E i d e l b e r g et a l . , 1981c) and non-decerebrate c h r o n i c l e s i o n e d monkeys ( E i d e l b e r g et a l . , 1981a). The s e l e c t i v e c h r o n i c l e s i o n i n g experiments i n t h i s study with the the goose extend the work which has been done i n mammals by d e l i m i t i n g the pathways i n the avian s p i n a l cord e f f e c t i n g descending c o n t r o l . A comparison between avian and mammalian s t u d i e s may determine whether p h y l o g e n e t i c u n i f o r m i t y e x i s t s 57 between t h e s e groups, t h e r e b y a l l o w i n g one t o c o r r e l a t e t h e r e s u l t s -from t h e a v i a n c e n t r a l nervous system <CNS) w i t h t h o s e o-f t h e mammalian system. I t i s a l s o a n e c e s s a r y p r e r e q u i s i t e i n d e t e r m i n i n g one or more o-f t h e e s s e n t i a l s u p r a s p i n a l c e n t r e s which c o n t r o l h i n d l i m b l o c o m o t i o n i n t h e a v i a n nervous system. F i n a l l y , i t i s p r e r e q u i s i t e t o d i s t i n g u i s h i n g any d i f f e r e n c e s which may e x i s t between s u p r a s p i n a l pathways c o n t r o l l i n g w a l k i n g from t h o s e i n f l u e n c i n g f l y i n g (Jacobson and H o l l y d a y , 1982). 58 dAIiB'IALS AND METHODS Adult Canada Geese from an outdoor e n c l o s u r e were placed i n a p r e o p e r a t i v e / p o s t o p e r a t i v e h o l d i n g room at l e a s t one day bef o r e electromyographic (EMG) c h a r a c t e r i z a t i o n of locomotion as d e s c r i b e d i n Chapter I. Food and water were s u p p l i e d ad l i b i d u m . No more than t h r e e animals were placed i n the pen at any one time. F o l l o w i n g p r e o p e r a t i v e c h a r a c t e r i z a t i o n of locomotion, the experimental animal was deprived of food f o r twenty f o u r hours p r i o r t o surgery. T h i s reduced or e l i m i n a t e d o p e r a t i v e and p o s t o p e r a t i v e r e g u r g i t a t i o n of food, thereby r e d u c i n g the r i s k of a s p h y x i a t i o n . The surgery was performed under F'entobarbi t o l (Somnitol) a n a e s t h e s i a which was i n j e c t e d v i a a cannula (PE100) i n s e r t e d i n t o the u l n a r or b a s i l i c a v e i n s of e i t h e r wing. A basal dose of 20 mg/kg was i n j e c t e d i n t h r e e a l i q u o t s with phosphate b u f f e r e d s a l i n e (PBS) (pH 7.4) administered between each a l i q u o t . A d d i t i o n a l p e n t o b a r b i t o l was i n j e c t e d as needed. T o t a l dosage depended on the i n d i v i d u a l animal and v a r i e d from approximately 20 mg/kg to 45 mg/kg. Xy l o c a i n e h y d r o c h l o r i d e (2%) was u t i l i z e d as a l o c a l a n a e s t h e t i c and i n j e c t e d l i b e r a l l y surrounding a l l i n c i s i o n s . The c r i t e r i a used f o r depth of a n a e s t h e s i a were the eye n i c t i t a t i n g membrane r e f l e x response t o touch (Fedde,1978) ( i t slows down as the l e v e l of a n a e s t h e s i a i n c r e a s e s ) and the r e f l e x withdrawal t o f o o t web pinch ( i t i s e l i m i n a t e d when the animal i s a n a e s t h e t i z e d ) . V e n t i l a t i o n was unnecessary as a s u f f i c i e n t l y deep l e v e l of a n a e s t h e s i a c o u l d be a t t a i n e d without a c e s s a t i o n of 59 b r e a t h i n g . A laminectomy was performed at the thoracolumbar l e v e l through the fused v e r t e b r a e o-f the C r i s t a i l i a c a d o r s a l i s (dorsal i l i a c c r e s t ) t a k i n g care t o remove and s t o r e the c r e s t bone as a s i n g l e u n i t . Trabeculae which j o i n the c r e s t and s p i n a l cord bony c o v e r i n g were removed as necessary t o all o w exposure of the cord u n d e r l y i n g the thoracolumbar v e r t e b r a e . The cord was exposed by removing the f i n a l t h i n l a y e r of bone which covers i t . As much bone as p o s s i b l e was l e f t i n t a c t t o l i m i t the amount of p o s t o p e r a t i v e movement-induced i n j u r y t o the cor d . L e s i o n s were made with e i t h e r f i n e d i s s e c t i n g m i c r o - s c i s s o r s , s c a l p e l or modified d e n t a l instruments with the a i d of a s t e r e o d i s s e c t i n g microscope. Ventromedial l e s i o n s were produced by i n s e r t i n g a modified dental t o o l through the m i d l i n e d o r s o v e n t r a l 1 y . L e s i o n extent at the time of su r g e r y was determined by v i s u a l o b s e r v a t i o n . The c a v i t y surrounding the l e s i o n was continuous with the a i r s a c s . To prevent blood from f l a w i n g i n t o the a i r sacs and l e s i o n s i t e , the c a v i t y was f i l l e d with s t e r i l e gauze impregnated with p h y s i o l o g i c a l s a l i n e . The i l i a c c r e s t bone was r e p l a c e d i n i t s o r i g i n a l p o s i t i o n i n an attempt to r e s t a b i l i z e the i l i a c c r e s t . The wing cannula was removed and the ve i n t i e d o f f with #000 s i l k . The s k i n was then sutur e d . Post-mortem examination of the wound s i t e r e v e a l e d : 1) f u n c t i o n a l r e c o v e r y of the sutured musculature; 2) adhesion of the r e p l a c e d i l i a c c r e s t bone to the surrounding c r e s t ; and 3) i n most cases complete absence of sca r t i s s u e i n the o v e r l y i n g s k i n . P o s t o p e r a t i v e c a r e r e q u i r e d t h a t the animal be kept warm 60 ( i n f r a r e d heat lamp) u n t i l such time as i t was capable of m a i n t a i n i n g i t s head i n an u p r i g h t p o s i t i o n thus i n d i c a t i n g r e c o v e r y from a n a e s t h e s i a ( mean time of r e c o v e r y from a n a e t h e s i a was 3.5 hours). Each animal r e c e i v e d Meperidine H y d r o c h l o r i d e (Demerol) a n a l g a e s i c i n t r a m u s c u l a r l y (1.8 mg/kg) every s i x hours f o r a p e r i o d of two t o t h r e e days, depending on i t s s t a t e of a r o u s a l . A m p i c i l l i n Sodium (Penbritin-250) a n t i b i o t i c (250 mg i n j e c t a b l e i n 2ml. PBS) was administered i n t r a m u s c u l a r l y d a i l y f o r seven days. The r e c o v e r y p e r i o d depended on the s e v e r i t y of the l e s i o n and each animal was assessed d a i l y as to i t s a b i l i t y t o stand, walk, respond to r e f l e x i n p u t s , d r i n k , and feed. Animals which d i d not eat w i t h i n t h r e e days p o s t o p e r a t i v e l y were f o r c e f e d with l i q u i d food (Bucker f i e l ds 167. Layer P e l l e t s i n water) twice d a i l y u n t i l s e l f - f e e d i n g resumed. T h i s amount was s u f f i c i e n t t o maintain the body mass f o r up t o 45 days (the animals weight was monitored on a r e g u l a r b a s i s ) . Animals capable of walking u s u a l l y began e a t i n g q u i t e q u i c k l y a f t e r surgery. Environmental c o n d i t i o n s were observed to have importance to the r e t u r n of locomotor f u n c t i o n i n l e s i o n e d animals. Maintenance of an animal i n an i s o l a t e d area appeared to be d e t r i m e n t a l t o r e t u r n of f u n c t i o n even though, i n some cases, the l e s i o n s e v e r i t y was minimal. C o n d i t i o n s conducive t o r e t u r n of e a t i n g and locomotion o c c u r r e d when the animal was placed i n the same area with another l e s i o n e d b i r d or i n the same room, but separated from, an i n t a c t animal. Placement of an operate i n the same e n c l o s u r e with an i n t a c t animal produced d e t r i m e n t a l e f f e c t s on 61 locomotor c a p a b i l i t y i n the operate perhaps due t o aggression on the p a r t o-f the i n t a c t animal. R e s t o r a t i o n o-f se l f - - f e e d i n g c o r r e l a t e d well with a r e t u r n o-f locomotor c a p a b i l i t y f o l l o w i n g the l e s i o n . Animals f o r c e f e d f o l l o w i n g a maximum of thr e e p o s t o p e r a t i v e days recovered f u n c t i o n more q u i c k l y than animals which were not f o r c e f e d f o r a l e n g t h i e r p o s t o p e r a t i v e p e r i o d . T h e r e f o r e , a l l animals l e s i o n e d subsequent t o these f i n d i n g s were f o r c e f e d w i t h i n t h r e e days a f t e r the surgery u n t i l such time as s e l f - f e e d i n g was apparent. Each p o s t o p e r a t i v e animal was hel d t h i r t y days or longer (maximum 49 days) t o allow f o r maximal recover y of f u n c t i o n . The s t a b i l i z a t i o n of locomotor a b i l i t y was determined by v i s u a l o b s e r v a t i o n , t e s t i n g of r e f l e x e s , and assessment of muscle tonus. P o s t o p e r a t i v e EMG r e c o r d i n g s were undertaken u t i l i z i n g the same procedures as f o r the p r e o p e r a t i v e EMB r e c o r d i n g s . In cases where the animal was i n c a p a b l e of s e l f — s u p p o r t i n g locomotion on the t r e a d m i l l apparatus, EMGs of hindlirnb s t e p p i n g were recorded by s u p p o r t i n g i t over the t r e a d m i l l b e l t so that the f e e t r e s t e d on the moving b e l t . Animals i n c a p a b l e of any v o l u n t a r y hindlirnb movement were t e s t e d f o r muscle a c t i v i t y both i n t h e i r normal r e s t i n g p o s t i o n and i n m i d - a i r . B i r d s were then s a c r i f i c e d under p e n t o b a r b i t o l a n a e s t h e s i a . The s u b - t o t a l or t o t a l l y l e s i o n e d p o r t i o n of the s p i n a l cord was e x c i s e d i n s i t u with the surrounding v e r t e b r a and f i x e d i n 107. f o r m a l i n PBS. A f t e r a few days f i x a t i o n , the bone surrounding the cord was removed. The cord was washed i n water, dehydrated i n a l c o h o l s , and embedded i n wax ( P a r a p l a s t or P a r a p l a s t +) f o r s e c t i o n i n g on a microtome. 62 S e r i a l l o n g i t u d i n a l or c r o s s s e c t i o n s of cord were cut at t h i c k n e s s e s o-f 8 t o 12 micrometers and -floated on a warm water bath be-fore mounting onto chrom-alum double subbed g l a s s microscope s l i d e s . The s e c t i o n s were d r i e d twenty f o u r hours b e f o r e s t a i n i n g f o r myelin (Luxol Fast Blue G) and c e l l bodies (Neutral Red). S t a i n e d s l i d e s were c o v e r s l i p p e d and examined t o determine the extent of the s p i n a l cord l e s i o n under a compound mi croscope. 63 RESULTS A t o t a l o-f ten d i f f e r e n t l e s i o n types were produced i n order t o d e l i m i t the areas of the s p i n a l cord which c a r r y pathways necessary f o r the c o n t r o l of hindlirnb locomotion ( F i g . 1 2 ) . The sham operated animals, with no s p i n a l cord l e s i o n (Fig.12a) (n=2>, showed no observable d e f i c i t s i n locomotor performance. P o s t o p e r a t i v e o b s e r v a t i o n and EMG r e s u l t s (Fig.13) i n d i c a t e d a performance l e v e l comparable t o p r e o p e r a t i v e l e v e l s with r e c o v e r y of f u n c t i o n w i t h i n the f i r s t day f o l l o w i n g surgery. H i s t o l o g i c a l examination v e r i f i e d that sham animals had i n t a c t s p i n a l cords ( F i g . 1 4 ) . Complete t r a n s e c t i o n of the cord (n=2) (Fig.15) produced locomotor d e f i c i t s which l e f t the animal t o t a l l y i n c a p a b l e of s e l f - s u p p o r t . In these b i r d s , r e c o v e r y p e r i o d s of up to t h i r t y days showed no i n d i c a t i o n f o r the r e t u r n of any normal locomotion. T y p i c a l immediate p o s t o p e r a t i v e posture was caudal extension of both l e g s and a l a c k of muscle tone ( a t o n i a ) . S p i n a l r e f l e x e s were depressed f o r a p e r i o d of 4 to 9 days. Reflex responsiveness to f o o t web pinch reappeared between 4 and 9 days f o l l o w i n g the l e s i o n . " S pinal s t e p p i n g " (supported a l t e r n a t i n g stepping movements) occurred nine to ten days p o s t o p e r a t i v e l y . EMGs of " s p i n a l s t e p p i n g " demonstrated a l t e r n a t i n g f l e x o r (ITC)(swing phase) and extensor (FCL)(extensor phase) a c t i v i t y i n both l e g s ( F i g . 16). Although a l t e r n a t e s t e p p i n g movements occurred i n most G a s e s , sometimes these completely s p i n a l b i r d s demonstrated a simultaneous b i l a t e r a l f1 exor/extensor a c t i o n r e s u l t i n g i n a 64 "hopping" or "pushing o f f " motion when the b i r d s were placed on t h e i r s i d e s . T h i s a c t i o n , as well as the b i l a t e r a l a l t e r n a t i n g s t e p p i n g occurred both spontaneously and as the r e s u l t of p e r i a n a l s t i m u l a t i o n or p i n c h i n g the webbing of the f e e t . E x t e n s i o n and f l e x i o n manipulation of one limb would a l s o o c c a s i o n a l l y r e s u l t i n a p e r i o d of " s p i n a l s t e p p i n g " . In no case d i d the stepping resemble a motivated behaviour. Animals f l o a t i n g on water demonstrated no a b i l i t y t o paddle with t h e i r h i n d l e g s . P l a c i n g the b i r d s i n water a l s o a l l e v i a t e d the d i f f i c u l t y a s s o c i a t e d with the maintenance of l a t e r a l s t a b i l i t y which i s important f o r overground locomotion. Transected animals which demonstrated " s p i n a l s t e p p i n g " d i d not even produce a moderate degree of f o r c e d u r i n g hindlimb e x t e n s i o n and at no time c o u l d the animals produce enough extensor f o r c e t o support themselves even when placed i n an u p r i g h t standing posture. Muscle wasting progressed with severe wasting apparent by the end of the experimental p e r i o d <30 days p o s t o p e r a t i v e ) . H i s t o l o g i c a l examination of the l e s i o n s demonstrated a complete t r a n s e c t i o n of the thoracolumbar s p i n a l cord. Hemisection of the s p i n a l cord (n=3) (Fig.17) produced t r a n s i e n t d e f i c i t s i n locomotor c a p a b i l i t y of the hindlimb. Reflex withdrawal to f o o t web pinch reappeared f i v e t o nine days p o s t o p e r a t i v e l y i n the l e g i p s i l a t e r a l t o the l e s i o n and i n but one day on the i n t a c t si.de. Caudal hyperex t e n s i on of the i p s i l a t e r a l l e g was e v e n t u a l l y r e p l a c e d (9 t o 26 days) by e x t e n s i o n of the l e g i n a more normal stance p o s i t i o n , p a r a l l e l with the i n t a c t c o n t r a l a t e r a l hindlimb. A l l animals were able to 65 stand (5-21 days p o s t o p e r a t i v e ) and walk (5-49 days), although locomotor c a p a b i l i t y (eg. -flexion) a c r o s s the d i s t a l j o i n t s i n the i p s i l a t e r a l l e g remained somewhat r e s t r i c t e d . The d e f i c i t s appeared t o r e s u l t from an i n a b i l i t y to f u l l y f l e x / e x t e n d muscles a c r o s s the d i s t a l ( t i b i o - m e t a t a r s a l ) j o i n t s and a c e r t a i n degree of extensor h y p e r t o n i c i t y ( r i g i d i t y ) was apparent. EMG (Fig.18) r e s u l t s r e v e a l the a b i l i t y to f l e x and extend the femur acr o s s the hip j o i n t i n a r e l a t i v e l y normal manner. H i s t o l o g i c a l v e r i f i c a t i o n p f a r e p r e s e n t a t i v e l e s i o n s i t e i n d i c a t e s a s l i g h t l y incomplete hemisection with some s p a r i n g of the d o r s a l columns (F i g . 1 7 ) . A l l hemisected b i r d s demonstrated s i m i l a r c h a r a c t e r i s t i c r e c o v e r y of f u n c t i o n i n t h e i r locomotor c a p a b i l i t i e s . T r a n s e c t i o n of the d o r s a l h a l f of the s p i n a l cord, l e a v i n g the v e n t r a l cord i n t a c t (Fig,12d) (n=3), produced an i n i t i a l d e f i c i t i n standing a b i l i t y c h a r a c t e r i z e d by an i n a b i l i t y of the animals to maintain l a t e r a l and r o s t r o c a u d a l s t a b i l i t y . Maintained, balanced standing occurred a f t e r t h r e e t o f o u r t e e n days, with s e l f - s u p p o r t e d walking reappearing between four and eighteen days p o s t o p e r a t i v e l y . T y p i c a l l y , the b i r d s d i s p l a y e d an i n a b i l i t y to step over uneven t e r r a i n without t r i p p i n g , although t h i s d e f i c i t disappeared r a p i d l y with time. Walking improved to the p o i n t where i t was i m p o s s i b l e to d i s c e r n any d i f f e r e n c e between normal unoperated animals and animals with the d o r s a l cord t r a n s e c t e d . EMG data demonstrate no d i f f e r e n c e between l e s i o n e d and normals ( F i g . 2 0 ) . V e r i f i c a t i o n of the l e s i o n s i t e shows d o r s a l cord s e c t i o n to the l e v e l of the c e n t r a l canal ( F i g . 1 9 ) . U n i l a t e r a l v e n t r a l cord l e s i o n s (n=3) ( F i g . l 2 e ) produced minor locomotor d e f i c i t s i n the hindlirnb i p s i l a t e r a l t o the 66 l e s i o n . Re-flex response t o -foot web pinch appeared w i t h i n one day p o s t o p e r a t i v e l y . Standing occurred between one and twelve days, with walking reappearing -from one to t h i r t e e n days. D e f i c i t s were r e s t r i c t e d t o a mild hyperextension ( r i g i d i t y ) of the hindlimb which produced a walking g a i t having a limp on the l e s i o n e d s i d e . EMG r e s u l t s i n d i c a t e a near normal p a t t e r n of a c t i v i t y during t r e a d m i l l locomotion (Fig.21) of f l e x o r and extensor muscles w i t h i n each hindlimb, with a l t e r n a t i n g a c t i v i t y of homologous muscles between limbs. Fig.22 i l l u s t r a t e s a r e p r e s e n t a t i v e l e s i o n f o r t h i s type of s u b t o t a l t r a n s e c t i o n . B i l a t e r a l s e c t i o n i n g of the l a t e r a l margins of the s p i n a l cord (Figs.12f,23) (n=3) produced l i t t l e i n the way of locomotor d e f i c i t s . Foot web pinch r e f l e x withdrawal reappeared w i t h i n four days p o s t o p e r a t i v e l y . Standing occurred w i t h i n one to two days and walking began w i t h i n f o u r t e e n days. No motor d e f i c i t s c ould be detected at the end of the t h i r t y day p o s t o p e r a t i v e p e r i o d , as e x e m p l i f i e d by the EMG r e s u l t s ( F i g . 2 4 ) . Normal i n t r a l i m b and i n t e r l i m b t i ming f o r FCL/ITC muscles was apparent during t r e a d m i l l 1ocomot i on. A b i l a t e r a l v e n t r o l a t e r a l l e s i o n (Fig.12g)(n=l) produced t r a n s i e n t d e f i c i t s i n locomotor a b i l i t y . I n i t i a l d e f i c i t s i n c l u d e d an i n a b i l i t y t o stand u p r i g h t . Reflex withdrawal t o . f o o t web pinch reappeared at eleven days. E v e n t u a l l y , ( a f t e r 20 days) the animal regained the a b i l i t y t o stand normally. Walking occurred at 22 days but the animal d i d not recover s u f f i c i e n t l y d u r i n g the experimental p e r i o d to walk without f a l l i n g . However, the locomotor p a t t e r n was near normal when the animal was t e t h e r e d 67 i n a s l i n g . H i s t o l o g i c a l v e r i f i c a t i o n of the l e s i o n s i t e (Fig.25) r e v e a l s t h at the damage i n c l u d e d the e n t i r e v e n t r a l quadrant on one s i d e , with o n l y p a r t i a l l e s i o n i n g of the c o n t r a l a t e r a l cord. A ventromedial l e s i o n (Figs.12h,26) (n=l) produced no locomotor d e f i c i t s . Recovery of f u n c t i o n o c c u r r e d w i t h i n one day f o r both standing and walking with no observable d e f i c i t s . EMG r e s u l t s show normal a c t i v i t y f o r both hindlimbs (Fig.27) i n FCL/ITC. Animals i n which on l y the ventromedial cord was l e f t i n t a c t (Fig.12i)(n=6) demonstrated v a r i a b l e locomotor r e c o v e r y depending on the extent of the l e s i o n e d area and the amount of ventromedial cord l e f t i n t a c t . Two of the animals e x h i b i t e d a h i s t o l o g i c a l l y v e r i f i e d l e s i o n (Figs.28a,b) which c l o s e l y resembled the attempted l e s i o n ( F i g . l 2 i ) . These b i r d s recovered the a b i l i t y t o stand w i t h i n f i v e days p o s t o p e r a t i v e l y , with walking o c c u r r i n g between seven and nineteen days. Observations i n d i c a t e d normal walking, with r e p r e s e n t i t i v e EMG r e s u l t s (Fig.29) demonstrating the r e l a t i v e l y normal p a t t e r n of a l t e r n a t i n g f l e x i o n and ext e n s i o n f o r the hindlimb musculature. L e s i o n s m a i n t a i n i n g the i n t e g r i t y of the v e n t r o l a t e r a l cord b i l a t e r a l l y ( F i g s . 12j , 30) (n=4) allowed the b i r d s t o stand between f i v e and f o u r t e e n days p o s t o p e r a t i v e l y . Walking began from seventeen to eighteen days. P o s t o p e r a t i v e EMGs of one experimental b i r d (Fig.31) c l e a r l y demonstrate a l t e r n a t i n g a c t i v i t y of FCL and ITC i n each l e g and rhythmic a l t e r n a t i o n of the two hindlimbs c h a r a c t e r i z i n g normal walking. No d e f i c i t s c o u l d be observed at the end of the t h i r t y day experimental p e r i o d with the exception of one animal which demonstrated s h o r t steps and some l a t e r a l 68 i n s t a b i 1 i t y . I-f a s i n g l e v e n t r a l quadrant ( F i g s . 12k,32) (n=3) of the s p i n a l cord remained i n t a c t , the b i r d was a b l e t o stand and take s e v e r a l s t e p s , but was not capable of normal, s e l f - s u p p o r t i n g locomotion. I n i t i a l p o s t o p e r a t i v e d e f i c i t s i n c l u d e d absence of r e f l e x r e s p o n s i v e n e s s t o f o o t web pinch b i l a t e r a l l y . T h i s r e f l e x reappeared between 10 and 12 days f o l l o w i n g the l e s i o n and was seen f i r s t i n the l e g i p s i l a t e r a l t o the i n t a c t p o r t i o n of cord. Animals p l a c e d i n water, a l l o w i n g them t o maintain l a t e r a l s t a b i l i t y , were capable of producing v o l u n t a r y swimming behaviour ( a l t e r n a t i n g l e g p a d d l i n g ) . P o s t o p e r a t i v e hyperextension and r i g i d i t y o c c u r r e d i n the hindlirnb c o n t r a l a t e r a l t o the i n t a c t p o r t i o n of s p i n a l c o r d . T h i s was e v e n t u a l l y r e p l a c e d by movement of t h i s limb i n t o a more n a t u r a l r e s t i n g p o s i t i o n under the animals body. Attempts t o stand and support the body with the l e g i p s i l a t e r a l t o the i n t a c t p o r t i o n of cord preceded standing movements with the c o n t r a l a t e r a l limb. The c o n t r a l a t e r a l limb maintained a degree of r i g i d i t y which d i d not t o t a l l y disappear d u r i n g the experimental p e r i o d , although a c e r t a i n degree of f l e x i b i l i t y was recovered i n a l l of the j o i n t s of that limb. A r e d u c t i o n from normal f o r c e p r o d u c t i o n was found i n both hindlimbs with the d e f i c i t being more apparent on the t r a n s e c t e d s i d e . D i s t a l e x t r e m i t i e s ( i e f o o t ) muscle tonus appeared to be s e v e r e l y reduced and c o n s e q e n t l y impeded normal locomotor a c t i v i t y . When the b i r d was s t a n d i n g unaided, however, the d i s t a l e x t r e m i t i e s were f o r c e d i n t o a more n a t u r a l p o s i t i o n with the f e e t placed f l a t l y on the ground. EMG data (Fig.33) supports the o b s e r v a t i o n 69 that a l t e r n a t i n g hindlirnb a c t i v i t y d i d occur. FCL/ITC a c t i v i t y w i t h i n a hindlirnb a l t e r n a t e d out o-f phase with the c o n t r a l a t e r a l hindlirnb. However, the animals were not capable o-f normal s e l f -s u p p o r t i n g locomotion. 70 D.ISCLJSSIQN Sup r a s p i n a l c e n t r e s which c o n t r o l locomotion e x e r t t h e i r i n f l u e n c e on s p i n a l cord p a t t e r n generators v i a descending pathways i n the s p i n a l cord (Steeves and Jordan, 1980) (Shik, Orlovsky, S e v e r i n , 1966) (Shik and Orlovsky, 1976) ( E i d e l b e r g , 1981). Evidence a v a i l a b l e at the present time i n d i c a t e s t h a t t h i s h o l d s t r u e f o r primates such as monkeys ( E i d e l b e r g et a l . , 1981a), c a t s ( E i d e l b e r g et a l . , 1981c) ( A f e l t , 1974) (Steeves and Jordan, 1980, 1984), and s t i n g r a y s (Williams et a l . , 1984). The experiments upon which t h i s i n f o r m a t i o n i s based i n c l u d e both acute and c h r o n i c l e s i o n s of the s p i n a l cord i n acute brainstem s t i m u l a t e d and i n t a c t c h r o n i c animals. D i s r u p t i o n of p a r t i c u l a r descending pathways by s e l e c t i v e l e s i o n i n g of the s p i n a l cord o f t e n l e a d s to s p e c i f i c d e f i c i t s i n locomotor c a p a b i l i t y . T h i s experimental procedure i s one approach f o r d e f i n i n g those descending pathways which are e s s e n t i a l t o the i n i t i a t i o n and modulation of s p i n a l locomotor mechanisms. The approach r e q u i r e s a knowledge of the f u n i c u l a r t r a j e c t o r i e s of descending s p i n a l pathways. Cabot et a l . (1982), u s i n g anterograde and r e t r o g r a d e anatomical t r a c i n g techniques, d e s c r i b e d the t r a j e c t o r i e s of some of the major descending pathways i n the pigeon ( F i g . 34) which w i l l be used i n t h i s study to d e f i n e the pathways necessary to 1ocomot i on. Complete t r a n s e c t i o n of the goose s p i n a l cord at the low t h o r a c i c l e v e l produces a p e r i o d of " s p i n a l shock" s i m i l a r to that found i n primates, c a t s , dogs, and lower v e r t e b r a t e s . T h i s 71 " s p i n a l shock" i s c h a r a c t e r i s e d by somatic muscle f l a c c i d i t y , absence o-f segmental r e f l e x responses (hyporef 1 ex i a) , and c l o a c a l f l a c c i d i t y . T h i s p e r i o d of " s p i n a l shock" i s s h o r t e r i n d u r a t i o n than t h a t f o r mammals and u s u a l l y d i s a p p e a r s w i t h i n f o u r days a f t e r the t r a n s e c t i o n . These r e s u l t s support r e s e a r c h f i n d i n g s t h a t the p e r i o d of " s p i n a l shock" tends t o shorten with a decrease i n c e n t r a l nervous system complexity ( E i d e l b e r g , 1981). The gradual r e t u r n of hindlimb muscle tone i n the geese allowed f o r the p r o d u c t i o n of " s p i n a l s t e p p i n g " s i m i l a r to t h a t found f o l l o w i n g t r a n s e c t i o n i n many v e r t e b r a t e s p e c i e s , e x c l u d i n g primates ( E i d e l b e r g et a l . , 1981a). T h i s o b s e r v a t i o n agrees with p r e v i o u s i n v e s t i g a t o r s of avian s p e c i e s (Tarchanoff, 1895) (Ten Cate, 1960), non-primate mammals (Phi 11ippson, 1905-dogs) ( G r i l l n e r , 1973-cats) ( S t e l z n e r et a l . , 1975-rats) (Graham Brown, 1911-guinea p i g ) , and lower v e r t e b r a t e s (Cohen and Wallen, 1980-lamprey) ( G r i l l n e r , 1974-dogfish) (Gray and Lissman, 1946-amphibians). Although some i n v e s t i g a t o r s have r e p o r t e d that completely t r a n s e c t e d animals were capable of s e l f - s u p p o r t (Phi 11ippson, 1905), no i n d i c a t i o n of t h i s a b i l i t y was found i n any of the b i r d s used i n t h i s study. "Spinal s t e p p i n g " was r e s t r i c t e d t o a l t e r n a t i n g or simultaneous movements of the hindlimbs with a degree of f o r c e i n s u f f i c i e n t t o support the body of these animals. One might p o s t u l a t e that t h i s lack of f o r c e could be a t t r i b u t e d to e x c e s s i v e muscle wasting which occurred p r i o r t o r e s t i t u t i o n of locomotor f u n c t i o n . However, i f on c o n s i d e r s the s h o r t time p e r i o d between the l e s i o n and the appearance of " s p i n a l s t e p p i n g " coupled with the apparent lack of 72 any d e t e c t a b l e muscle wasting i n that time, then the p o s t u l a t e i s h i g h l y u n l i k e l y . A l t e r n a t i v e l y , on might hypothesize that the g e n e r a t o r s are unable to, i n the absence of descending i n f l u e n c e , r e c r u i t a s u f f i c i e n t number of motor u n i t s f o r a n t i - g r a v i t y support. The r e s u l t s of t h i s study support the h y p o t h e s i s of Graham Brown (1911) that a mechanism i n t r i n s i c t o the s p i n a l cord i s r e s p o n s i b l e f o r the p r o d u c t i o n of s t e p p i n g (step generators) i n the absence of descending s u p r a s p i n a l i n f l u e n c e s . However, adequate p r o d u c t i o n of muscle f o r c e s u f f i c i e n t f o r s e l f - s u p p o r t i n g locomotion may r e q u i r e the i n t e g r i t y of some descending s u p r a s p i n a l i n p u t . S p i n a l cord hemisection f a i l e d t o produce major c h r o n i c d e f i c i t s i n locomotion i n the goose. The b i r d s d i s p l a y e d symptoms very s i m i l a r t o those d e s c r i b e d by Brown-Sequard (1870) i n humans. The Brown-Sequard syndrome i n humans i s c h a r a c t e r i z e d by l o s s of p o s t u r a l sense, t r a n s i t o r y i p s i l a t e r a l s p a s t i c p a r a l y s i s or severe p a r e s i s and c o n t r a l a t e r a l l o s s of pain as well as thermal sense caudal to the l e s i o n s i t e . L a t e r experimenters confirmed these r e s u l t s i n non—human primates such as monkeys (Lassek and Anderson, 1961) and non—primate mammals such as c a t s ( M a r s h a l l , 1895) and dogs (Weiss, 1879). L i t t l e r e s e a r c h e x i s t s with r e s p e c t t o hemisection i n lower v e r t e b r a t e s . The r e s u l t s of t h i s study i n d i c a t e t h a t t h i s type of l e s i o n i n the goose produces a s h o r t term d e f i c i t i n motor f u n c t i o n , with r e c o v e r y of f u n c t i o n i n a p e r i o d (5-21 days) that i s u s u a l l y more r a p i d than f o r mammalian s p e c i e s ( A f e l t , 1974; E i d e l b e r g , 1981c). Motor recove r y f o l l o w i n g hemisection was o r i g i n a l l y thought t o be subserved by the 73 c o r t i c o s p i n a l system which sends both crossed and uncrossed p r o j e c t i o n s to the s p i n a l cord i n mammals. It has r e c e n t l y been demonstrated however, t h a t l e s i o n i n g o-f the pyramids produces l i t t l e d i s r u p t i o n t o primary locomotor p a t t e r n s (eg. walking), o n l y d i s r u p t i n g d i s t a l musculature r e s p o n s i b l e f o r f i n e c o n t r o l of movement (eg.Kuypers, 1982). The absence of a l a r g e , well d e f i n e d c o r t i c o s p i n a l p r o j e c t i o n i n the goose (Cabot et a l . , 1982; Reiner et a l . , 1982) supports the h y p o t h e s i s t h a t lower s u p r a s p i n a l c e n t r e s are r e s p o n s i b l e f o r t h i s r e c o v e r y of f u n c t i o n i n the hemisected animal. However, due to the p o s s i b l e presence of crossed c o n n e c t i o n s caudal to the l e s i o n s i t e , i t i s d i f f i c u l t , on the b a s i s of hemisection locomotor d e f i c i t s , t o determine which pathways c o n t r o l and i n i t i a t e locomotion. S i m i l a r l y , the d o r s a l cord l e s i o n ( F i g . l 2 d ) d i d not produce any long l a s t i n g e f f e c t s on goose locomotor p a t t e r n s . The i n i t i a l i n a b i l i t y of p o s t o p e r a t i v e animals to navigate uneven t e r r a i n may r e f l e c t the l o s s of a f f e r e n t sensory input v i a the ascending d o r s a l columns pathways r e s p o n s i b l e f o r t a c t i l e and k i n e s t h e t i c i n f o r m a t i o n t o s u p r a s p i n a l areas ( F a s c i c u l u s g r a c i l i s , c f . Carpenter, 1978) . L e s i o n of the d o r s a l column pathways i n humans and monkeys r e s u l t s i n a l o s s of p o s i t i o n sense r e s u l t i n g i n d o r s a l column a t a x i a ( F e r r a r o and B a r r e r a , 1934; Gilman and Denny-Brown, 1966). However, E i d e l b e r g et a l . (1966) found t h a t these d e f i c i t s c o u l d be overcome by the p r o d u c t i o n of s p e c i f i c m o t i v a t i o n a l d r i v e i n p r e t r a i n e d animals. By comparing the extent of the s p i n a l cord l e s i o n s which do not s i g n i f i c a n t l y a l t e r avian locomotion with the f u n i c u l a r 74 t r a j e c t o r i e s of known avian descending s p i n a l pathways, i t i s p o s s i b l e t o e l i m i n a t e the r o l e of c e r t a i n neural pathways from the i n i t i a t i o n and c o n t r o l of locomotion. Dorsal cord i n t e r r u p t i o n of the descending hypothalamo-spinal, d o r s o l a t e r a l p o n t i n e - s p i n a l , d o r s a l column n u c l e i - s p i n a l , r u b r o s p i n a l , N. raphe magnus-spinal , N. raphe pal 1 i d u s - s p i n a l , and p o r t i o n s of the N. raphe pal 1 i d u s / o b s c u r u s - s p i n a l t r a c t s ( F i g . 34) does not appear to produce any long l a s t i n g d e f i c i t s i n motor f u n c t i o n . Of the above l e s i o n e d pathways, onl y the r u b r o s p i n a l t r a c t has been d e f i n i t e l y shown to be i n v o l v e d i n the c o n t r o l of f l e x o r motorneurons ( G r i l l n e r and Lund, 1968) and i n the i n i t i a t i o n of locomotion. However, Lawrence and Kuypers (1968b) showed t h a t b i l a t e r a l l e s i o n of the Red n u c l e i i n monkeys had l i t t l e e f f e c t on locomotion, only d i s r u p t i n g f i n e motor c o n t r o l . The o b s e r v a t i o n s obtained i n t h i s study tend to support the f i n d i n g s of Lawrence and Kuypers (1966) In that b i l a t e r a l l e s i o n of the r u b r o s p i n a l t r a c t s at the low t h o r a c i c l e v e l had l i t t l e e f f e c t on the walking a b i l i t y of the goose. B i l a t e r a l ventromedial l e s i o n ( F i g . 26) of the s p i n a l cord which d i s r u p t s the descending p e r i a q u a d u c t a l g r e y - s p i n a l , the i p s i l a t e r a l pontine r e t i c u l o s p i n a l , and p o r t i o n s of both v e s t i b u l o s p i n a l and r a p h e - s p i n a l pathways ( F i g . 34) was not e f f e c t i v e i n l i m i t i n g locomotion i n the goose. The r a p i d recovery and l a c k of any apparent d e f i c i t demonstrated t h a t the p e r i a q u a d u c t a l g r e y - s p i n a l and i p s i l a t e r a l pontine r e t i c u l o s p i n a l former pathways are not e s s e n t i a l f o r the p r o d u c t i o n of locomotion i n these animals, even though e l e c t r i c a l s t i m u l a t i o n of .these areas i n acute decerebrate c a t s evokes locomotion ( G a r c i a — R i l l et 75 a l . , 1983; Budakova and Shik, 1930). The p a r t i a l d e s t r u c t i o n of c o n t i n u i t y i n the avian v e s t i b u l o s p i n a l and r a p h e - s p i n a l pathways a l s o d i d not seem to a f f e c t hindlimb walking. P r e v i o u s l e s i o n s t u d i e s have hypothesized the p o s s i b i l i t y t h a t the v e s t i b u l o s p i n a l t r a c t has some r o l e i n the i n i t i a t i o n and c o n t r o l o-f locomotion i n the c a t (Yu and E i d e l b e r g , 1981). B i l a t e r a l l e s i o n of the v e s t i b u l a r n u c l e i produced severe d e f i c i t s i n posture and locomotion, which were manifested as r e d u c t i o n i n extensor d r i v e to the limbs and l o s s of e x i t a b i l i t y i n neck motorneurones. The d e f i c i t s diminished over time. E i d e l b e r g p o s t u l a t e d , however, t h a t the v e s t i b u l a r n u c l e i , and i n p a r t i c u l a r , the l a t e r a l v e s t i b u l a r nucleus ( D i e t e r s n u c l e u s ) , (Orlovsky, 1972b) p l a y s a major a d j u n c t i v e r o l e i n the i n i t i a t i o n and c o n t r o l of locomotion by enhancing the extensor elements of the step c y c l e . T h i s i s c o r r o b o r a t e d by acute experiments i n which an i n c r e a s e i n extensor a c t i v i t y r e s u l t e d from s t i m u l a t i o n of D i e t e r s nucleus. A l s o , i n c r e a s e d phasic a c t i v i t y of the v e s t i b u l a r neurons occurred d u r i n g acute s t i m u l a t i o n (MLR) i n decerebrate f r e e l y performing animals and " f i c t i v e " p r e p a r a t i o n s (Orlovsky, 1972a,b) . The r e t u r n of f u n c t i o n which oc c u r s a f t e r the i n i t i a l d e f i c i t s i n c h r o n i c animals has yet to be e x p l a i n e d . L e s i o n s which maintained the i n t e g r i t y of the ventomedial cord ( F i g . 28) r e s u l t e d i n animals which recovered locomotor c a p a b i l i t y r a t h e r q u i c k l y . Descending pathways which t r a v e l i n the l e s i o n e d area i n c l u d e the p e r i a q u a d u c t a l g r e y - s p i n a l , pontine r e t i c u l o s p i n a l , p o r t i o n s of the v e s t i b u l o s p i n a l , and p a r t of the r a p h e - s p i n a l ( F i g . 34). T h i s l e s i o n l e a v e s i n t a c t the f u n i c u l i 76 which were l e s i o n e d by the ventromedial l e s i o n and destroyed the m a t e r i a l l e f t i n t a c t by the ventromedial l e s i o n . The p e r i a q u a d u c t a l g r e y - s p i n a l and pontine r e t i c u l o s p i n a l pathways l e f t i n t a c t i n t h i s l e s i o n do not appear to be necessary f o r the p r o d u c t i o n of locomotion. However, maintenance of p a r t s of the v e s t i b u l o s p i n a l and the raphe p a l 1 i d u s / o b s c u r u s / r e t i c u l o s p i n a l pathways c a r r i e d i n the ventromedial cord appears t o allow r e t u r n of f u n c t i o n f o l l o w i n g l e s i o n of the r e s t of the c o r d . L e s i o n i n g of the s p i n a l cord l e a v i n g both v e n t r o l a t e r a l quadrants i n t a c t a l s o produced animals capable of normal locomotion. Therefore, i t appears that maintenance of the v e n t r a l i n t e r m e d i a t e cord a l l o w s the standing and the i n i t i a t i o n of locomotion i n the goose. Descending pathways c a r r i e d i n t h i s area i n c l u d e the i p s i l a t e r a l p r o j e c t i o n from the medial r e t i c u l a r f ormation Nucleus r e t i c u l a r i s g i g a n t o c e l 1 u l a r i s , the pathway from the nucleus raphe pal 1idus/obscurus, and the v e s t i b u l o s p i n a l p r o j e c t i o n s ( F i g . 34). Removal of a l l descending p r o j e c t i o n s except those t r a v e l l i n g i n one v e n t r a l quadrant ( F i g . 32) a l s o allowed b i l a t e r a l locomotion, although the q u a l i t y of movement was somewhat reduced owing t o an apparent p a r e s i s and lack of s t r e n g t h i n these p r e p a r a t i o n s . The hindlimb i p s i l a t e r a l t o the spared white matter produced stronger s t e p p i n g than i n the c o n t r a l a t e r a l hindlimb. These animals were capable of b i l a t e r a l s t a n d i n g and stepping ( F i g . 33) but locomotion d i d not r e t u r n to normal a b i l i t y . The rec o v e r y p e r i o d was a l s o c o n s i d e r a b l y longer (35 days) f o r these geese than f o r the animals wherein a l a r g e r area of v e n t r a l cord remained i n t a c t . 77 The r e s u l t s o-f s e l e c t i v e l e s i o n s t o the s p i n a l cord demonstrate that the v e n t r a l s p i n a l cord i s e s s e n t i a l f o r the i n i t i a t i o n , modulation and c o n t i n u i t y of a c t i v a t i o n of locomotion. F u r t h e r , u n i l a t e r a l s p a r i n g of a s i n g l e v e n t r a l quadrant p r o v i d e s s u f f i c i e n t descending i n f o r m a t i o n t o promote r e l a t i v e l y normal locomotor p a t t e r n s . L o c a l i z a t i o n of s p e c i f i c pathways u t i l i z i n g t h i s method has demonstrated t h a t s e v e r a l known descending pathways may be i n v o l v e d . The v e s t i b u l o s p i n a l pathway has p r e v i o u s l y been i m p l i c a t e d i n c o n t r o l of extensor elements of the step c y c l e (Orlovsky, 1972a). However, Yu and E i d e l b e r g (1981) have shown t h a t b i l a t e r a l l e s i o n of the v e s t i b u l a r n u c l e i i n the cat d i d not a b o l i s h r e t u r n of locomotor f u n c t i o n . T h i s r e s t i t u t i o n of f u n c t i o n remained s t a b l e i n the c a t s even when a d o r s a l cord l e s i o n was performed, thus e l i m i n a t i n g the p o s s i b i l i t y t h a t compensation was o c c u r r i n g v i a the mammalian c o r t i c o s p i n a l and/or r u b r o s p i n a l descending pathways (Yu and E i d e l b e r g , 1981). Due to the p h y l o g e n e t i c d i f f e r e n c e s between mammals and avian s p e c i e s , i t i s d i f f i c u l t t o separate the r o l e played by the v e s t i b u l a r pathways i n the goose from that of other pathways present i n the v e n t r a l c o r d . L e s i o n i n g of the d o r s a l s p i n a l cord and v e s t i b u l a r n u c l e i would be necessary to determine the importance of the v e s t i b u l o s p i n a l pathway f o r the i n i t i a t i o n of locomotion. The r a p h e - s p i n a l pathway, the major component of which i n the v e n t r a l cord a r i s e s from the caudal p o r t i o n s of the raphe p a l l i d u s and obscurus n u c l e i , has not yet been i m p l i c a t e d i n any locomotor pathways but i s thought t o p l a y a major r o l e i n the i n n e r v a t i o n of p r e g a n g l i o n i c sympathetic components of the avian nervous system 78 (Cabot et a l . , 1982). The i p s i l a t e r a l r e t i c u l o s p i n a l pathways which t r a v e l i n the v e n t r a l -funiculus i n c l u d e the pontine r e t i c u l o s p i n a l pathway o r i g i n a t i n g -from the nucleus r e t i c u l a r i s p o n t i s c a u d a l i s , pars g i g a n t o c e l l u l a r i s and nucleus r e t i c u l a r i s p o n t i s o r a l i s , as well as a p r o j e c t i o n o r i g i n a t i n g from the medial medullary r e t i c u l a r nucleus r e t i c u l a r i s g i g a n t o c e l 1 u l a r i s ( F i g . 3 4 ) . Complete b i l a t e r a l l e s i o n of the pontine r e t i c u l o s p i n a l pathway produced no observable change i n locomotion. T h e r e f o r e i t i s u n l i k e l y t h at t h i s pathway p l a y s a predominant r o l e i n the i n i t i a t i o n of avian walking. B i l a t e r a l p a r t i a l l e s i o n s i n the medial medullary r e t i c u l a r nucleus r e t i c u l o s p i n a l pathway a l s o produced l i t t l e o b s e r v able d i f f e r e n c e . However, u n i l a t e r a l l e s i o n of both pathways appeared t o i n c r e a s e the length of the r e c o v e r y p e r i o d and decrease the q u a l i t y of locomotion. One might hypothesize that the medullary r e t i c u l o s p i n a l pathway o r i g i n a t i n g from N. r e t i c u l a r i s g i g a n t o c e l l u l a r i s t r a v e l l i n g as a d i f f u s e p r o j e c t i o n i n the v e n t r a l s p i n a l cord p l a y s an important r o l e i n the v o l i t i o n a l c o n t r o l of locomotion. L e s i o n i n g of the s p i n a l cord and v e s t i b u l a r n u c l e i i n t e r r u p t i n g the flow of i n f o r m a t i o n i n the ventromedial cord and d o r s a l cord would help t o e s t a b l i s h the v e r a c i t y of t h i s l a t t e r h y p o t h e s i s . The r e s u l t s of t h i s study support those found i n monkey ( E i d e l b e r g et a l . , 1981a), cat (Steeves and Jordan, 1980) ( E i d e l b e r g et a l . , 1981c) and s t i n g r a y (Williams et a l . , 1984) namely, t h a t r e s t i t u t u t i o n of f u n c t i o n occurs f o l l o w i n g s p i n a l cord l e s i o n s i n both acute and c h r o n i c animals i f a s i n g l e v e n t r a l quadrant of s p i n a l cord remains i n t a c t . Although the 79 stepping/swimming seen i n these animals i n i t i a l l y appears u n i l a t e r a l l y , a f t e r a p e r i o d of ti m e * the s t e p p i n g becomes b i l a t e r a l . I t i s p o s t u l a t e d t h a t the descending pathway<s) c o n t r o l l i n g locomotion e i t h e r i n n e r v a t e s the locomotor generators b i l a t e r a l l y at the a p p r o p r i a t e l e v e l or that i t i n n e r v a t e s u n i l a t e r a l l y and the neuronal c i r c u i t s of the p a t t e r n g e n e r a t o r s p r o v i d e the necessary c o n t r a l a t e r a l i n t e r c o n n e c t i o n s . The r e s u l t s support the hy p o t h e s i s t h a t the medullary r e t i c u l o s p i n a l pathway p l a y s an important r o l e i n the i n i t i a t i o n of locomotion and does not negate the h y p o t h e s i s that the v e s t i b u l o s p i n a l t r a c t p l a y s some a d j u n c t i v e r o l e (Yu and E i d e l b e r g , 1981) i n the s u p r a s p i n a l c o n t r o l of locomotion. 80 Diagrammatic r e p r e s e n t a t i o n o-f attempted low t h o r a c i c s p i n a l cord l e s i o n s used to d e l i n e a t e descending s p i n a l cord pathways r e s p o n s i b l e f o r the s u p r a s p i n a l c o n t r o l of locomotion i n the hindlimb. Lined areas i n d i c a t e l e s i o n e xtent. A= Sham Operate, B= Complete T r a n s e c t i o n , C= Hemisection, D= Dorsal Cord T r a n s e c t i o n , E= U n i l a t e r a l V e n t r a l Quadrant L e s i o n , F= B i l a t e r a l L a t e r a l Margins Lesion, G= B i l a t e r a l V e n t r o l a t e r a l L e s i o n , H= Ventromedial Lesi o n , 1= Ventromedial I n t a c t , J= B i l a t e r a l V e n t r o l a t e r a l I n t a c t , K= V e n t r a l Quadrant I n t a c t . 81 82 P o s t o p e r a t i v e electromyographic r e c o r d s from l e f t and r i g h t hindlirnb ITC and FCL muscles during t r e a d m i l l locomotion i n a sham operated goose during t r e a d m i l l walking. ITC i s a f l e x o r a c t i v e during the swing phase. FCL i s an extensor a c t i v e during the stance phase of walking. The r e c o r d s show a l t e r n a t i n g a c t i v i t y of homologous hindlirnb muscles during walking ( b e l t speed= 0.3m/sec). A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 83 RIGHT I LEFT 1.0 sec. 84 FIGURE 14 Diagrammatic r e p r e s e n t a t i o n o-f a c r o s s s e c t i o n through the low t h o r a c i c s p i n a l cord o-f a Sham Operated goose showing the absence of any l e s i o n i s shown i n A. B i s a photograph of i n t a c t s p i n a l cord from the Sham Operated goose. 0 85 86 EIG.URE. 15 Diagrammatic r e p r e s e n t a t i o n o-f a c r o s s s e c t i o n through the l e s i o n s i t e i n a goose f o l l o w i n g a complete t r a n s e c t i o n . The diagram i s a composite compiled from s e r i a l s e c t i o n s through the l e s i o n s i t e . The l i n e d area i n d i c a t e s the completeness of the attempted l e s i o n . 88 EIBURE, 16 Electromyographic r e c o r d s -from l e f t and r i g h t hindlirnb ITC and FCL muscles during " s p i n a l " s tepping i n a completely t r a n s e c t e d animal. Records from the l e f t l e g show a l t e r n a t i n g a c t i v i t y of f l e x o r (ITC) and extensor (FCL) muscles. Simultaneous a c t i v a t i o n of f l e x o r b u r s t s between l e f t and r i g h t ITC muscles demonstrate the "pushing o f f " or "hopping" nature of the " s p i n a l " locomotor behaviour. A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 89 RIGHT LEFT 1.0 sec. 90 FIGURE 17 Diagrammatic r e p r e s e n t a t i o n o-f a c r o s s s e c t i o n through the low t h o r a c i c s p i n a l cord of a Hemisected b i r d . The diagram i s a composite made from s e r i a l s e c t i o n s through the l e s i o n s i t e . The l i n e d area shows the l e s i o n extent, with s p a r i n g of a p o r t i o n of the d o r s a l columns and d o r s a l horn gray matter. 91 92 P o s t o p e r a t i v e electromyographic r e c o r d s of the goose hindlimb f l e x o r (ITC) and extensor (FCL) muscles duri n g t r e a d m i l l walking ( b e l t speed= 0.4 m/sec) f o l l o w i n g a c h r o n i c s p i n a l cord hemisection. A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC^ i l i o t i b i a l i s c r a n i a l i s . 93 1.0 sec. 94 FIGURE 19 Diagrammatic r e p r e s e n t a t i o n o-f a c r o s s s e c t i o n through the low t h o r a c i c s p i n a l cord f o l l o w i n g a Dorsal Cord T r a n s e c t i o n (A). The diagram i s a composite made from s e r i a l s e c t i o n s through the l e s i o n s i t e . The l i n e d area shows the l e s i o n extent, with s p a r i n g of the cord v e n t r a l t o the c e n t r a l c a n a l . B i s a photograph of one s e c t i o n through the l e s i o n s i t e . 95 A B 96 P o s t o p e r a t i v e electromyographic (EliG) r e c o r d s of the goose hindlimb f l e x o r (ITC) and extensor (FCL) muscles during t r e a d m i l l walking ( b e l t speed= 0.3 m/sec) f o l l o w i n g a c h r o n i c Dorsal Cord T r a n s e c t i o n . The EMG r e c o r d s show normal a l t e r n a t i n g a c t i v i t y of a n t a g o n i s t i c muscles of each limb and a l t e r n a t i o n of c o n t r a l a t e r a l homologous muscles. A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 97 1.0 sec. 98 ) FIGURE 21 P o s t o p e r a t i v e electomyographic r e c o r d s of the goose hindlimb f l e x o r (ITC) and extensor (FCL) muscles during t r e a d m i l l walking f o l l o w i n g a c h r o n i c U n i l a t e r a l V e n t r a l Quadrant L e s i o n . ITC a l t e r n a t e s out of phase with i t s i p s i l a t e r a l a n t a g o n i s t (FCL) and c o n t r a l a t e r a l homolog (ITC). A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 99 100 E l i U B i 22 A Diagrammatic r e p r e s e n t a t i o n o-f a c r o s s s e c t i o n through the low t h o r a c i c s p i n a l cord f o l l o w i n g a U n i l a t e r a l V e n t r a l Quadrant l e s i o n . The diagram i s a composite made from s e r i a l s e c t i o n s though the l e s i o n s i t e . Lined areas i n d i c a t e the l e s i o n extent. The s e c t i o n of s p i n a l cord i n the diagram i s s l i g h t l y r o s t r a l t o the l e s i o n e d area. B i s a photograph of one t r a n s v e r s e s e c t i o n through the l e s i o n s i t e . 101 102 FIGURE 23 Cross s e c t i o n through the low t h o r a c i c s p i n a l cord o-f a goose •following a B i l a t e r a l L a t e r a l Margins L e s i o n <B> . The diagram (A) i s a composite made from s e r i a l s e c t i o n s through the l e s i o n s i t e -Lined areas demonstrate the l e s i o n extent, with s p a r i n g of the m a j o r i t y of medial s p i n a l cord. 103 104 EIGLJRE 24 P o s t o p e r t i v e electromyographic r e c o r d s o-f the f l e x o r (ITC) and extensor <FCL) muscles during t r e a d m i l l walking t h i r t y days a f t e r a B i l a t e r a l L a t e r a l Margins L e s i o n . A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 105 1-0 sec. 106 FIGURE 25 Diagrammatic r e p r e s e n t a t i o n of a c r o s s s e c t i o n through the low t h o r a c i c s p i n a l cord f o l l o w i n g a B i l a t e r a l V e n t r o l a t e r a l Lesion.' The diagram i s a composite made from s e r i a l c r o s s s e c t i o n s through the l e s i o n s i t e . The l i n e d area shows the l e s i o n extent. 107 108 E i i U B i 26 Diagram showing the l e s i o n extent a f t e r a Ventromedial L e s i o n . The diagram i s a composite drawn from s e r i a l s e c t i o n s through the l e s i o n s i t e (A). The l i n e d area d e l i m i t s the l e s i o n extent, with p a r t i a l l e s i o n i n g of the d o r s a l columns and complete l e s i o n i n g of the ventromedial cord. The photograph (B) shows a p a r t i a l d e l i n e a t i o n of the l e s i o n extent through one t r a n s v e r s e s e c t i o n . 109 B 110 FIGURE 27 P o s t o p e r a t i v e electromyographic r e c o r d s o-f b i l a t e r a l hindlirnb f l e x o r (ITC) and extensor (FCL) muscles during t r e a d m i l l walking f o l l o w i n g a c h r o n i c Ventromedial L e s i o n . A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . I l l ITC 1.0 sec. 112 Diagrams showing the l e s i o n extent r e s u l t i n g from Ventromedial I n t a c t l e s i o n s i n the low t h o r a c i c s p i n a l cord. The diagrams are composites drawn from s e r i a l c r o s s s e c t i o n s i n A and s e r i a l l o n g i t u d i n a l s e c t i o n s i n B. The l i n e d areas i n d i c a t e l e s i o n extent. The s p i n a l cord o u t l i n e u t i l i z e d i n F i g u r e A i s s l i g h t l y r o s t r a l t o the l e s i o n , while t h a t of F i g u r e B i s cord m a r g i n a l l y caudal to the l e s i o n s i t e . The photograph (C) shows a p o r t i o n of the l e s i o n produced i n A. 114 FIGURE 29 P o s t o p e r a t i v e electromyographic r e c o r d s of f l e x o r (ITC) and extensor (FCL) muscle a c t i v i t y during t r e a d m i l l walking f o l l o w i n g the c h r o n i c Ventromedial I n t a c t s p i n a l cord l e s i o n . The EMG r e c o r d s i n d i c a t e normal hindlirnb walking by both l e g s . A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 1.0 sec. 116 EIGyR.! 30 Diagrammatic r e p r e s e n t a t i o n of c r o s s s e c t i o n s through the low t h o r a c i c s p i n a l cord f o l l o w i n g the B i l a t e r a l V e n t r o l a t e r a l I n t a c t l e s i o n . The l e s i o n e x t e n t s i n both A and B were determined by examination of e i t h e r s e r i a l c r o s s (A) or s e r i a l l o n g i t u d i n a l (B) s e c t i o n s through the l e s i o n s i t e s . Lined areas i n d i c a t e the extent of l e s i o n e d s p i n a l cord. F i g u r e C i s a photograph of a l o n g i t u d i n a l s e c t i o n through the l e s i o n . Note the completeness of the d o r s o v e n t r a l l e s i o n i n t h i s medial cord s e c t i o n . A b b r e v i a t i o n s : cc= c e n t r a l c a n a l , D= d o r s a l , V= v e n t r a l . 117 118 FIGURE 31 Electromyographic r e c o r d s of the goose hindlimb f l e x o r (ITC) and extensor (FCL) muscles during t r e a d m i l l walking. The locomotion EMG r e s u l t s demonstrate the normal a l t e r n a t i n g a c t i v i t y of a n t a g o n i s t i c hindlimb and c o n t r a l a t e r a l homologous muscles f o l l o w i n g a B i l a t e r a l V e n t r o l a t e r a l I n t a c t l e s i o n . A b b r e v i a t i o n s : FCL= f l e x o r c r u r i s l a t e r a l i s , ITC= i l i o t i b i a l i s c r a n i a l i s . 119 RIGHT LEFT 1.0 sec. 120 FIGURE 32 Composite c r o s s s e c t i o n a l diagram of the low t h o r a c i c s p i n a l cord of a goose f o l l o w i n g a V e n t r a l Quadrant I n t a c t l e s i o n . The l e s i o n extent, which i s marked by the l i n e d area, demonstrates t h a t only p o r t i o n s of the v e n t r a l quadrant remained i n t a c t . 121 122 EliURE 33 P o s t o p e r a t i v e electromyographic r e c o r d s o-f -flexor (ITC) and extensor (FCL) muscles of the hindlirnb d u r i n g supported t r e a d m i l l walking. The EliG r e c o r d s show a l t e r n a t i n g a c t i v i t y of the a n t a g o n i s t i c muscles (ITC/FCL) f o r both hindlimbs. While b r i e f p e r i o d s of a l t e r n a t i n g hindlirnb stepping were observed, no EMG data was obtained during supported t r e a d m i l l walking. 123 'IJ-II- - i - l i f^-pFf •^'Tr T T " ' ITC 1.0 sec. 124 EIBURE 34 Diagammatic r e p r e s e n t a t i o n of a c r o s s s e c t i o n through the avian b r a c h i a l s p i n a l cord showing s e v e r a l t r a j e c t o r i e s of descending b u l b o s p i n a l pathways. (Redrawn from Cabot et a l . , 1982) Area 1= hypothalamo (PVIi) - s p i n a l Area 2= per i a q u a d u c t a l gray ( i n t e r s t i t i o ) - s p i n a l Area 3= r u b r o s p i n a l (crossed p r o j e c t i o n ) Area 4= d o r s o l a t e r a l p o n t i n e - s p i n a l 4a= not known 4b= N. subcoeruleus d o r s a l i s (SCd)-spinal ( i p s i l a t e r a l ) Area 5= medial pontine (RPgc/RPO)-spinal ( i p s i l a t e r a l ) Area 6= v e s t i b u l o s p i n a l (VeD, VeLd, VeLv, Veli) Area 7= raphe (medial medullary/caudal p o n t i n e ) - s p i n a l ( r o s t r a l part) (caudal p o r t i o n of n u c l e i ) i i ) medial medullary r e t i c u l o - s p i n a l (Rgc) (i p s i 1 a t e r a l ) Area 8= d o r s a l columns n u c l e i - s p i n a l A b b r e v i a t i o n s : PVM= nucleus (n.) p e r i v e n t r i c u l a r i s magnocel1ularis, Rgc= n. r e t i c u l a r i s g i g a n t o c e l 1 u l a r i s , RPgc= n. r e t i c u l a r i s p o n t i s c a u d a l i s , pars g i g a n t o c e l 1 u l a r i s , RPQ= n. r e t i c u l a r i s p o n t i s o r a l i s , VeD= n. v e s t i b u l a r i s descendens, Vel_d= n. v e s t i b u l a r i s l a t e r a l i s , pars d o r s a l i s , VeLv= n. v e s t i b u l a r i s l a t e r a l i s , pars v e n t r a l i s , VeM= n. v e s t i b u l a r i s m e d i a l i s . 7a) N. 7b > N. 7c) i ) 125 126 QHAFTER III IfcJE PRODUCTION OF LOCOMOTION RESULTING FROM ELECTRICAL STIMULATION OF THE BRAINSTEM IN THE ACUTE DECEREBRATE BIRD 127 INTRODUCTION E l e c t r i c a l s t i m u l a t i o n of r e g i o n s i n the diencephalon (Subthalamic Locomotor Region, p e r i a q u a d u c t a l gray ( G a r c i a - R i l l et a l . , 1983a)), mesencephalon (MLR (Shik et a l . , 1966)), h i n d b r a i n (ponto-medullary locomotor s t r i p (Budakova and Shik, 1980)) and s p i n a l cord (Jacobson and Hollyday, 1982b; W i l l i a m s et a l . , 1984) produces locomotion i n a v a r i e t y of animals i n c l u d i n g s t i n g r a y , c h i c k and cat and i n many d i f f e r e n t types of p r e p a r a t i o n s such as s p i n a l i z e d , decerebrate, thalamic and mesencephalic. P h y s i o l o g i c a l and anatomical t r a c i n g s t u d i e s of s p i n a l and s u p r a s p i n a l locomotion promoting s t r u c t u r e s i n d i c a t e the p o s s i b i l i t y t h a t two or more areas may independently e f f e c t t h i s descending c o n t r o l ( G a r c i a - R i l l e t a l . , 1983b: Steeves and Jordan, 1984). However, some c o n t r o v e r s y e x i s t s as t o the r e l a t i v e importance of these areas, t h e i r s u p r a s p i n a l i n t e r c o n n e c t i o n s , and t h e i r i n t e r f a c e with descending pathways c o n t r o l l i n g locomotion. The present study was undertaken to l o c a t e and examine the r e g i o n s i n the avian brainstem which, when e l e c t r i c a l l y s t i m u l a t e d , evoke locomotion. The avian b r a i n p r o v i d e s a more simple system i n which to study evoked locomotion. U t i l i z a t i o n of t h i s model system may a l l e v i a t e some of the c o n t r o v e r s y surrounding mammalian " c o n t r o l l e d " locomotion s t u d i e s . The anatomical c l a s s i f i c a t i o n and p h y s i o l o g i c a l b ehavioural d e f i n i t i o n of locomotion-promoting s t i m u l a t i o n s i t e s i n the a v i a n b r a i n f a c i l i t a t e f u r t h e r s t u d i e s c h a r a c t e r i z i n g the neural c o n t r o l of locomotion. 128 dBIiBlALS AND METHODS Adult Canada geese, a d u l t and adolescent Pekin ducks and Pekin/Mal1ard c r o s s ducks maintained i n an outdoor e n c l o s u r e were placed i n a p r e o p e r a t i v e h o l d i n g room without -food twenty four hours p r i o r t o surgery. A l l surgery p r i o r t o halothane a n a e s t h e s i a was performed under l o c a l a n a e s t h e t i c ( X y l o c a i n e h y d r o c h l o r i d e 27.). Both wing v e i n ( b r a c h i a l or ulnar) and a r t e r y ( b r a c h i a l or ulnar) were cannulated (PE 100 and PE 90 Intramedic tubing) a f t e r r e f l e c t i o n of the o v e r l y i n g s k i n . Care was taken t o prevent damage to the u l n a r nerve which apposes the a r t e r y . The c a n n u l i were sutured t i g h t l y i n t o p o s i t i o n b e f o r e s u t u r i n g of the s k i n (000 s i l k ) . Blood p r e s s u r e was monitored from the a r t e r i a l cannula. A tracheotomy tube was implanted at the m i d - c e r v i c a l l e v e l and the i n t e r n a l c a r o t i d a r t e r i e s were surrounded with thread f o r l a t e r l i g a t i o n . Care was taken t o prevent blood and other f l u i d s from i n f i l t r a t i n g the a i r sacs l o c a t e d i n t h i s r e g i o n . A second l a r g e r tube was sutured i n t o the a n t e r i o r a i r sac t o allow f o r u n i d i r e c t i o n a l v e n t i l a t i o n (UDV) of the animal under halothane (Fluothane, Ayerst) a n a e s t h e s i a ( F i g . 3 5 ) . The u n i d i r e c t i o n a l flow (957.02/57.C02) (f low r a t e 1.5-2.4 1/min.) was e s t a b l i s h e d through the tracheotomy tube and throughout the body b e f o r e exhausting from the a n t e r i o r a i r sac. E x p e l l e d gas was c o l l e c t e d i n an Ehrlenmeyer f l a s k t o monitor any v e n t i l a t o r y d e h y d r a t i o n . The; gas was then passed through a c o l d water j a c k e t d i s t i l l a t i o n chamber and f l u s h e d i n running water. The eye n i c t a t i n g membrane r e f l e x , blood p r e s s u r e , response 129 to f o o t web pinch and independent b r e a t h i n g were a l l c r i t e r i a u t i l i z e d t o measure depth of a n a e s t h e s i a . The two methods which proved most r e l i a b l e were; D b r e a t h i n g , which stopped when the animal was deeply a n a e s t h e t i z e d and 2) f o o t web pinch, which d i d not e l i c i t a r e f l e x response when depth of a n a e s t h e s i a was s u f f i c i e n t . Blood p r e s s u r e (BP) was not r e l i a b l e as a measure of a n a e s t h e s i a , f o r a f t e r an i n i t i a l d e p r ession ( i n mammals, BP i s depressed under anaesthesia) i t r e t u r n e d to almost normal awake va l u e s . Heart r a t e was i n c r e a s e d over normal va l u e s . The n i c t a t i n g membrane response was a l s o u n r e l i a b l e with halothane, f o r i t s speed f l u c t u a t e d widely i n animals which by other c r i t e r i a were deeply a n a e s t h e t i z e d . The halothane c o n c e n t r a t i o n r e q u i r e d to maintain a n a e s t h e s i a v a r i e d c o n s i d e r a b l y between and w i t h i n animals. Induction l e v e l s were s t a n d a r d i z e d at approximately 0.5"/. with maintenance l e v e l s v a r y i n g between 0.057. and 0.17.. Once a n a e s t h e t i z e d , the animal was suspended i n a s t e r e o t a x i c apparatus (Narashige) over the t r e a d m i l l with both l e g s and wings u n r e s t r a i n e d . The e a r s were i n f i l t r a t e d with l o c a l a n a e s t h e t i c and s t e r e o t a x i c ear bars were f i x e d i n t o the a u d i t o r y c a n a l s . The beak was f i x e d t o the s t e r e o t a x i c nose p i e c e with a clamp. T h i s method produced a r e l i a b l e , r e p l i c a b l e method of i n s u r i n g the r e l a t i v e u n i f o r m i t y of head and b r a i n p o s i t i o n i n the s t e r e o t a x i c apparatus f o r each s p e c i e s . B r a i n p o s i t i o n appeared t o be r e l a t i v e l y independent of b i r d s i z e . Within a s p e c i e s , s i z e d i d not not vary s u b s t a n t i a l 1 y . A craniotomy was performed to expose the r o s t r a l t e l e n c e p h a l o n t o the r o o t of the o l f a c t o r y nerve. Enough bone was 130 removed t o r e v e a l the v e n t r o l a t e r a l aspect of the t e l e n c e p h a l o n . The bone o v e r l y i n g the caudal cerebellum almost to the l e v e l of the foramen magnum was a l s o removed. Great care was taken not to d i s t u r b the s u p e r i o r s a g i t t a l and t r a n s v e r s e s i n u s e s when one exposed the d o r s a l m i d l i n e and r o s t r a l cerebellum, r e s p e c t i v e l y , as puncture of these s i n u s e s produced severe b l e e d i n g . Care was taken a l s o i n maintenance of the dura mater, f o r f r a g i l e s u r f a c e v e s s e l s u n d e r l y i n g t h i s s t r u c t u r e were prone to b l e e d i n g . " N i p r i d e " (Sodium Ni t r o f e r r i c y a n i d e (0.144 ug/ml) i n 57. d e x t r o s e ) , a v a s o d i l a t o r , was i n f u s e d (Harvard I n f u s i o n Pump)(rate: 0.069-0.276 ml/min.) v i a venous cannula to reduce blood p r e s s u r e and minimise b l e e d i n g d u r i n g d e c e r e b r a t i o n (G. Gabbott, personal communication). The i n t e r n a l c a r o t i d s i n the neck were l i g a t e d t o reduce blood flow to the b r a i n ( J . Steeves, personal communication; Steeves and Jordan, 1980a). The dura was r e f l e c t e d from the b r a i n s u r f a c e . The s u p e r i o r s a g i t t a l s i n u s was l i g a t e d , cut, and r e f l e c t e d r o s t r o c a u d a l 1 y t o expose the e n t i r e d o r s a l and l a t e r a l s u r f a c e s of t e l e n c e p h a l o n and cerebellum. Two methods of d e c e r e b r a t i o n were attempted. I n i t i a l l y , each t e l e n c e p h a l i c lobe was l i f t e d and e x c i s e d using a s p a t u l a i n s e r t e d at the t h a i a m i c / t e l e n c e p h a l i c border. The instrument was d i r e c t e d r o s t r a l l y with a h o r i z o n t a l o r i e n t a t i o n to the a n t e r i o r cranium d o r s a l t o the o p t i c chiasm. With both lobes removed, the b l e e d i n g was c o n t r o l l e d u t i l i z i n g c o t t o n swabs, Gelfoam (absorbable g e l a t i n sponge, Upjohn) and c o t t o n b a t t i n g . The second procedure, which proved more s u c c e s s f u l , i n v o l v e d modifying the above procedure by c a u t e r i z a t i o n of the attendent t e l e n c e p h a l i c v a s c u l a t u r e before 131 e x c i s i o n of the lobes. T h i s proved t o be a r e l i a b l e method f o r preventing subequent severe blood l o s s i n the decerebrated animal. A f t e r c o n t r o l l i n g the b l e e d i n g , the animal was removed from " n i p r i d e " a l l o w i n g recovery of blood pressure t o r e l a t i v e l y normal l e v e l s . The animal was slo w l y removed from a n a e s t h e s i a but v e n t i l a t i o n was continued. In most cases, the b i r d began t o breathe independently. Subsequently, the v e n t i l a t i o n was removed a f t e r blockade of the a n t e r i o r a i r sac v e n t i l a t i o n tube. The blood pressure (BP) t y p i c a l l y remained s l i g h t l y below normal i n t a c t v a l u e s and s t r o k e volume was m a r g i n a l l y damped. There was c o n s i d e r a b l e v a r i a t i o n i n heart r a t e , BP, and s t r o k e volume depending on the p r e p a r a t i o n . Further s u r g i c a l i n t e r v e n t i o n , as i n the case of the p o s t -decerebrate t h o r a c i c cord l e s i o n , was performed by r e p l a c i n g the animal under halothane as d e s c r i b e d above. The s u r g i c a l procedure was performed i n the acute animal,using the same method as de s c r i b e d f o r the c h r o n i c animals i n Chapter I I . Fo l l o w i n g a s h o r t recovery p e r i o d , the b i r d was implanted with EliG e l e c t r o d e s i n t o muscles of the hind and f o r e l i m b using the method o u t l i n e d i n Chapter I. A movement potentiometer was attached t o each l e g to monitor l e g movement e x c u r s i o n and frequency. Leg movement potentiograms were recorded on magnetic tape and c h a r t r e c o r d e r . The s t i m u l a t i n g e l e c t r o d e (SNE 300, Kopf) was mounted i n an e l e c t r o d e c a r r i e r (Narashige HI) placed on the s t e r e o t a x i c apparatus. A ground e l e c t r o d e was c l i p p e d t o the s k i n o v e r l y i n g the craniotomy. S i n g l e square wave st i m u l u s p u l s e s (Grass S88) 132 were modulated through a constant c u r r e n t u n i t (Grass CCU 1A) to ensure uniform c u r r e n t i n t e n s i t y . Stimulus i n t e n s i t y necessary to e l i c i t locomotion and other behaviours v a r i e d from 25 microamps (uA) to 200 uA and s t i m u l u s frequency v a r i e d from 30-50 Hertz (Hz). P u l s e d u r a t i o n of 0.3 m i l l i s e c o n d s (msec) and delay of 0.01 msec remained uniform throughout a l l experiments. S t i m u l a t i o n s i t e s were i n i t i a l l y d e f i n e d by t r i a l and e r r o r i n areas which are known t o evoke locomotion i n c a t s . Subsequently, s t e r e o t a x i c c o o r d i n a t e s were e s t a b l i s h e d which allowed some measure of c e r t a i n t y i n f i n d i n g a locomotion promoting s i t e (see R e s u l t s ) . S t e r e o t a x i c zero was designated at the m i d l i n e as the most r o s t r a l c e r e b e l l a r border v i s i b l e on the d o r s a l b r a i n s u r f a c e . A behaviour was deemed "evoked" i f i t i n i t i a t e d with s t i m u l a t i o n onset and terminated when the s t i m u l a t i o n was removed. V e r i f i c a t i o n and monitoring of behaviours which were s t i m u l a t i o n evoked was e i t h e r by v i s u a l o b s e r v a t i o n , EMGs, or movement potentiometers (MPs). In some experiments, walking movements were recorded with potentiometers which gave i n f o r m a t i o n concerning limb e x c u r s i o n frequency and p a t t e r n . Walking was a l s o c h a r a c t e r i z e d u t i l i z i n g EMG e l e c t r o d e s implanted i n t o the ITC f l e x o r muscles of the hindlirnb as e s t a b l i s h e d i n Chapters I and I I . F l y i n g movements were determined by EMG r e c o r d i n g from the P e c t o r a l i s muscle of the wing and by v i s u a l o b s e r v a t i on. A s i t e which evoked locomotion was marked with an e l e c t r o l y t i c l e s i o n ( l e s i o n parameters: 1-5 m i l l i a m p s <mA) DC -d u r a t i o n 5-8 sec or 30-50 uA DC - d u r a t i o n 30-50 sec) f o r f u t u r e h i s t o l o g i c a l v e r i f i c a t i o n . 133 Each animal was s a c r i f i c e d with p e n t o b a r b i t o l ( i . v . b o l u s ) . The b r a i n was removed and preserved i n 107. f o r m a l i n PBS before washing, dehydration i n a l c o h o l s and i n f i l t r a t i o n with wax ( P a r a p l a s t or P a r a p l a s t •+•) . Thin c r o s s or s a g i t t a l s e c t i o n s (12-20 urn) were cut on a microtome (every tenth s e c t i o n i n absence of l e s i o n and s e r i a l s e c t i o n s through the l e s i o n s i t e ) . S e c t i o n s were f l o a t e d on water onto chrom alum double subbed g l a s s s l i d e s , and s t a i n e d with C r e s y l V i o l e t / E o s i n or Luxol Fast Blue S/Neutral Red b e f o r e c o v e r s l i p p i n g . H i s t o l o g i c a l v e r i f i c a t i o n of l e s i o n s i t e s was done by v i s u a l o b s e r v a t i o n i n the s t a i n e d s e c t i o n s using a s t e r e o d i s s e c t i n g microscope. Anatomical d e f i n i t i o n of the s i t e s evoking locomotion u t i l i z e d the avian s t e r e o t a x i c a t l a s e s of Zweers (1971) and Karten and Hodos (1967). 134 RESULTS T r a n s e c t i o n Level. The l e v e l of d e c e r e b r a t i o n f o r each animal i s demonstrated i n F i g . 36 ( n = l l ) . E x c i s i o n of t e l e n c e p h a l i c s t r u c t u r e s r o s t r a l t o the l i n e shown i n F i g . 36, Level 1, named the decerebrate p r e p a r a t i o n (Wetzel and S t u a r t , 1976), maintained the i n t e g r i t y of the o p t i c chiasm and the thalamus, although a c e r t a i n amount of damage to these u n d e r l y i n g s t r u c t u r e s probably r e s u l t e d from the s u r g i c a l procedure. C h a r a c t e r i s t i c s of these p r e p a r a t i o n s f o l l o w i n g a n a e s t h e t i c removal, but p r i o r t o e l e c t r o d e i m p l a n t a t i o n and e l e c t r i c a l s t i m u l a t i o n , i n c l u d e d an e l e v a t e d heart r a t e , decreased s y s t o l i c / d i a s t o l i c amplitude and s l i g h t l y decreased blood pressure. Reflex withdrawal t o f o o t web pinch was e l i c i t e d but no stepping movements co u l d be produced from t a c t i l e s t i m u l a t i o n of the f o o t dorsum by the o p e r a t i n g t r e a d m i l l b e l t . With the exception of Expt. 11, a high decerebrate p r e p a r a t i o n (with probable r e t e n t i o n of t e l e n c e p h a l i c s t r u c t u r e s r o s t r a l t o Level 1 ( F i g . 36)), no p r e s t i m u l a t i o n locomotor a c t i v i t y was evident i n these animals. Spontaneous p r e s t i m u l a t i o n locomotor a c t i v i t y was recorded f o r the wings and l e g s i n Expt.11 as shown i n F i g . 37. F l y i n g was represented by simultaneous P e c t o r a l i s muscle induced d e p r e s s i o n of the wings (EMGs). The absence of l e g movements was recorded by movement potentiometers (MPs). Animals with the t r a n s e c t i o n shown i n Fig.36, Level 2, (n=2), 135 named the "thalamic" p r e p a r a t i o n demonstrated s h o r t bouts o-f spontaneous s t e p p i n g and wing -flapping a c t i v i t y . A l t e r n a t i n g s t e p p i n g c o u l d be evoked by l i g h t t a c t i l e s t i m u l a t i o n of the f o o t dorsum or a n t e r i o r l e g and by s t i m u l a t i o n from the moving t r e a d m i l l b e l t . T r e a d m i l l evoked walking tended t o f o l l o w the v e l o c i t y of the b e l t . Wing f l a p p i n g ( f l y i n g ) u s u a l l y accompanied the walking. Locomotor movements of both f o r e - and hindlimb could a l s o be e l i c i t e d by p e r i - a n a l s t i m u l a t i o n . A t h i r d l e v e l of t r a n s e c t i o n (n=l) shown i n F i g . 36, Level 3, the "mesencephalic" p r e p a r a t i o n , i n which both thalamus and hypothalamus were e x c i s e d , d i s p l a y e d no spontaneous p o s t - o p e r a t i v e movements and resembled the decerebrate p r e p a r a t i o n i n response to f o o t web pinch and t a c t i l e s t i m u l a t i o n . Sti_mul_ati_gn Si_tes I n t r o d u c t i o n of the s t i m u l a t i n g e l e c t r o d e i n t o the b r a i n t i s s u e normally d i d not produce any v i s i b l e e f f e c t s . In s e v e r a l cases, however, t r a n s l a t i o n of the e l e c t r o d e t o the most v e n t r a l aspect of the brainstem produced a s h o r t d u r a t i o n movement which appeared to be more akin to d i s c o m f o r t than t o any locomotor p a t t e r n . T h i s phenomenon disappeared w i t h i n a few seconds even when the e l e c t r o d e was l e f t i n p o s i t i o n . E l e c t r i c a l s t i m u l a t i o n at a v a r i e t y of s i t e s produced s e v e r a l d i f f e r e n t b e h a v i o r a l responses. Table 3 l i s t s the r e s u l t s from eleven d i f f e r e n t experiments u t i l i z i n g Canada geese (Branta 136 E§Qi*densis) , Pekin Ducks (Anas Elatyrhynchos) , and Peki n/Mal 1 a r d -c r o s s Ducks (Anas P.Iatyrhynchgs) . Animals i n Experiments 3 and 7 (Table 3) were "thalamic" p r e p a r a t i o n s . The animal i n Experiment 8 was a "mesencephalic" p r e p a r a t i o n . The remaining experiments demonstrate the "decerebrate" p r e p a r a t i o n shown i n F i g 36, Level 1. Brainstem s t i m u l a t i o n of areas medial t o or i n the Nucleus et t r a c t u s descendens n e r v i t r i g e m i n i (TTD)(Expts. l b , 2a, 3b, 3c, 6b, 12b, 13a, and 13b) ( F i g s . 38,39) produced walking and f l y i n g movements at low (30-100uA/50Hz) s t i m u l u s i n t e n s i t i e s . S t i m u l a t i o n of caudal brainstem s t r u c t u r e s i n or around TTD, with the e x c e p t i o n of Expt. 13a, demonstrate both f l y i n g and walking or f l y i n g and running movements. However, s t i m u l a t i o n o c c a s i o n a l l y r e s u l t e d i n f l y i n g movements alone (Expt 13a, Table 3). At higher s t i m u l u s i n t e n s i t i e s , t h i s f l y i n g was accompanied by a g i t a t e d f o o t movements which d i d not resemble walking. Foot movement was of higher i n t e n s i t y i n the hindlirnb c o n t a l a t e r a l t o the s t i m u l a t i o n s i t e . S t i m u l a t i o n at the more r o s t r a l extent of TTD shows both walking alone and f l y i n g alone behaviours. S t i m u l a t i o n of the goose i n Expt. 2a (Table 1) e l i c i t e d f l y i n g behaviour with some i n i t i a l running. T h i s behaviour resembled the c r o s s o v e r p o i n t between running and t a k e o f f during normal locomotion i n f l y i n g b i r d s . In one duck (Table 3, Expt. 12b), s t i m u l a t i o n of TTD e l i c i t e d walking only. S t i m u l a t i o n - i n d u c e d walking i s demonstrated i n F i g . 40 with EMG and movement potentiometer r e c o r d s from both l e g s . The r e c o r d s show a l t e r n a t i n g s t e p p i n g movements c h a r a c t e r i z e d by i n c r e a s e d EMG a c t i v i t y i n ITC b i l a t e r a l l y and potentiometer r e c o r d i n g s of r o s t r o c a u d a l e x c u r s i o n s of both l e g s . 137 P i n i o n i n g of the wings during s t i m u l a t i o n - i n d u c e d walking and f l y i n g i n Expt. lb demonstrated the a b i l i t y of the animal t o continue i t s s t e p p i n g movements i n the absence of f o r e l i m b locomotion. Holding the l e g s d u r i n g bimodal locomotion d i d not appear t o i n h i b i t wing f l a p p i n g when s t i m u l a t i o n occurred i n the r e g i o n of TTD. E l e c t r i c a l s t i m u l a t i o n of the t r i g e m i n a l nerve p r i n c i p l e sensory nucleus at a more r o s t r a l pontine l e v e l (Expt. l a . Fig.41) a l s o evoked both f l y i n g / r u n n i n g and f l y i n g motions at a more a n t e r i o r s i t e . It must be noted that the area encompassing the l e s i o n s i t e and TTD i n s e v e r a l experiments <Expts.3b,3c,13a) was i n c l o s e p r o x i m i t y to the s u b s t a n t i a g e l a t i n o s a Rolandi t r i g e m i n i (BG). Owing to p o s s i b l e s t i m u l u s c u r r e n t spread through the t i s s u e , t h i s area cannot be excluded from p u t a t i v e locomotion producing s i t e s . A second major area which produced locomotion i n the s t i m u l a t e d experimental animals was the Nucleus c e n t r a l i s medulla oblongata, pars d o r s a l i s (Cnd) and pars v e n t r a l i s (Cnv). T h i s s i t e , i l l u s t r a t e d i n s e v e r a l experiments (Expts. 2c, 3c, 4, 10a, 11a, 13b) ( F i g . 42), produced walking and f l y i n g s e p a r a t e l y (Expt.2c), f l y i n g / r u n n i n g together (Expt.3c), f l y i n g / w a l k i n g together (Expt.1 la,13b,) (Figs.43,44), walking only (Expt.lOa) and f l y i n g / l e g f l e x i o n (Expt.4). H i s t o l o g i c a l examination of the l e s i o n s i t e s i n these t r i a l s shows the m a j o r i t y of d o r s a l s t i m u l a t i o n s i t e s i n c l o s e p r o x i m i t y t o the major s t i m u l a t i o n s i t e TTD. T h i s i s f u r t h e r d e l i n e a t e d i n the r e s u l t s recorded i n Table 3 (Expt.3c,13b). However, the s i t e 138 shown i n Expt.10a, ( F i g . 42) i s d e f i n i t e l y not w i t h i n the boundaries of TTD and l i e s more v e n t r a l l y between the d o r s a l and v e n t r a l p a r t s of the medullary c e n t r a l nucleus. I t i s p o s s i b l e t h a t the s t i m u l a t i o n s i t e shown by the l e s i o n i n F i g . 42 borders the l a t e r a l r e t i c u l a r nucleus, f o r examination of the s t e r e o t a x i c a t l a s e s of Karten and Hodos (1967) and Zweers (1971) do not c l e a r l y d i f f e r e n t i a t e between the c e n t r a l medullary and l a t e r a l r e t i c u l a r n u c l e i . The f 1 y i n g / 1 e g - f 1 e x i o n behaviour evidenced i n Expt. 4 r e f l e c t s the presence of a c h r o n i c low t h o r a c i c s p i n a l cord l e s i o n produced i n the b i r d p r i o r t o t h i s acute brainstem s t i m u l a t i o n study. The animal, d u r i n g the experimental p e r i o d , d i s p l a y e d only rudimentary hindlirnb locomotor c a p a b i l i t y p r i o r t o d e c e r e b r a t i o n and was not able to support i t s e l f d uring overground locomotion. The wings of the animal were u n a f f e c t e d by the t h o r a c i c l e s i o n . A s t i m u l a t i o n s i t e ( F i g . 45) i n the l a t e r a l r e t i c u l a r nucleus (RL) (Expts. 2b,6a,10a) evoked f l y i n g and running movements at low s t i m u l u s i n t e n s i t y t h r e s h o l d s . S t i m u l a t i o n at two caudal areas (Expts.2b,6a) produced f l y i n g combined with running movements and at a t h i r d s i t e produced walking only (Expt.10a) i n the duck. Stimulus spread from the l e s i o n s i t e i n RL to the more medial N. c e n t r a l i s medulla oblongata, pars v e n t r a l i s (Cnv) was a p o s s i b i l i t y . S t r u c t u r e s which were c l o s e t o the s t i m u l a t i o n s i t e and t h e r e f o r e cannot be discounted as being p o s s i b l e areas which e l i c i t locomotion i n c l u d e the v e n t r a l (VSCT) and d o r s a l (DSCT) s p i n o c e r e b e l l a r t r a c t s (Expt.6a> and Cnd/Cnv (Expt.10a). While VSCT and DSCT are not r e p e a t e d l y represented, s t i m u l a t i o n of the area surrounding Cnd/Cnv has a l r e a d y been shown t o produce 139 locomotion. S t i m u l a t i o n of the midbrain s t r u c t u r e s near the l a t e r a l and medial s p i r i f o r m n u c l e i and Ansa l e n t i c u l a r i s (Table 1, Expt.12c,12d, Fig.46) produced walking at low and f l y i n g at higher s t i m u l u s i n t e n s i t i e s . S t i m u l a t i o n of the c o n t r a l a t e r a l s i d e (same co o r d i n a t e s ) with no h i s t o l o g i c a l v e r i f i c a t i o n r e p l i c a t e d t h i s r e s u l t . Other areas c l o s e to the s t i m u l a t i o n s i t e i n c l u d e the N. hypothalamicus p o s t e r i o r , pars l a t e r a l i s and the l a t e r a l g e n i c u l a t e nucleus. E l e c t r i c a l s t i m u l a t i o n of an area encompassed by the medial lemniscus, Cnv, and c l o s e to N. raphe (Expt.8, Fig.47) i n the medulla produced walking i n the absence of any f l y i n g movements. An i n c r e a s e i n c u r r e n t s t i m u l u s i n t e n s i t y produced i n c r e a s e d f o r c e of s t e p p i n g but no frequency change. Increase i n t r e a d m i l l v e l o c i t y produced i n c r e a s e s i n f o o t f a l l frequency. EMG and MP data (Fig.48) show rhythmic a l t e r n a t i n g s t e p p i n g movements i n both h i n d l i mbs. S t i m u l a t i o n Parameters Changing s t i m u l a t i o n parameters during evoked locomotion were examined i n Expt.12. In c r e a s i n g t r e a d m i l l b e l t v e l o c i t y , (Fig.49) h o l d i n g e l e c t r i c a l s t i m u l u l a t i o n parameters constant, r e s u l t e d i n an i n c r e a s e i n s t e p p i n g frequency without an i n c r e a s e i n e x c u r s i o n l e n g t h . I n c r e a s i n g s t i m u l a t i o n frequency d i d not produce a s i g n i f i g a n t change to stepping behaviour when the b e l t was held at 140 constant speed. An i n c r e a s e i n s t i m u l a t i o n s t r e n g t h produced i n c r e a s e s i n the frequency of st e p p i n g ( F i g . 50). An i n c r e a s e i n cu r r e n t i n t e n s i t y was a l s o observed t o produce an i n c r e a s e i n the f o r c e of st e p p i n g . Acyt§ Spinal. Cord L e s i o n s Attempts t o determine the l o c a t i o n of s p i n a l cord pathways c a r r y i n g descending i n f o r m a t i o n during acute experiments was i n pa r t r e f l e c t e d by the r e s u l t s from Expts. 6 and 12. In Expt. 6, a p r e l e s i o n e d c h r o n i c animal (dorsal columns l e s i o n extent F i g . 51) was decerebrated before s t i m u l a t i o n . The hindlimb locomotor c a p a b i l i t y of t h i s animal was s e v e r e l y r e s t r i c t e d . S t i m u l a t i o n of the b i r d e l i c i t e d normal wing f l a p p i n g ( f l y i n g ) movements and some degree of hindlimb f l e x i o n . These o b s e r v a t i o n s r e f l e c t e d the p r e -decerebrate locomotor c a p a c i t y of the animal. In Expt. 12, f o l l o w i n g establishment of a s t i m u l u s s i t e i nducing a locomotor behaviour i n a Pekin duck, an acute low t h o r a c i c Dorsal Cord T r a n s e c t i o n was performed ( l e s i o n extent F i g . 52). Acute p o s t -t r a n s e c t i o n s t i m u l a t i o n at the same st i m u l u s s i t e r e s u l t e d i n normal a l t e r n a t i n g t r e a d m i l l s t e p p i n g i n i t i a l l y at higher s t i m u l a t i o n i n t e n s i t y and s h o r t l y t h e r e a f t e r walking at lower t h r e s h o l d (Table 1, Expt. 12b). T h i s behaviour i s documented u t i l i z i n g EMG and MP r e c o r d s shown i n F i g . 53. 141 DISCUSSION E l e c t r i c a l s t i m u l a t i o n of r e g i o n s i n the diencephalon, midbrain, h i n d b r a i n , and high c e r v i c a l s p i n a l cord has been shown t o produce " c o n t r o l l e d " locomotion i n a v a r i e t y of s p e c i e s (Kashin et a l . , 1974; Shik et a l . , 1966,; Jacobson and Hollyday, 1982: W i l l i a m s et a l . , 1984; E i d e l b e r g et a l . , 1981; M c C l e l l a n , 1984). S t i m u l a t i o n i n the area of the subthalamic nucleus <STN) (the Subthalamic Locomotor Region (SLR)) produces locomotion i n the l i g h t l y a n a e s t h e t i z e d c a t (Wal1er,1940) and the "thalamic" cat (Orlovsky, 1969). S t i m u l a t i o n of the p o s t e r i o r s u b s t a n t i a n i g r a e l i c i t s l e s s normal walking i n the p r e c o l 1 i c u l a r postmammi11ary cat ( G a r c i a - R i l l , 1983). S t i m u l a t i o n of two n u c l e i i n the mesencephalon, the pedunculopontine nucleus (PF'N) and cuneiform nucleus (CFN), e l i c i t s locomotion i n the p r e c o l 1 i c u l a r ~ postmammi11ary cat (Shik, S e v e r i n , and Orlovsky, 1967). These two d i s t i n c t n u c l e i are thought to be the anatomical c o r r e l a t e s of the p r e v i o u s l y p h y s i o l o g i c a l l y d e f i n e d Mesencephalic Locomotor Region (MLR) ( G a r c i a - R i l l , 1983). E l e c t r i c a l s t i m u l a t i o n of the pontobulbar locomotor s t r i p (PLS) evokes locomotion i n the p r e c o l 1 i c u l a r postmami11ary cat (Mori et a l . , 1977; Budakova and Shik, 1980) and high c e r v i c a l cord s t i m u l a t i o n w i l l evoke b i l a t e r a l locomotion i n lower v e r t e b r a t e s (Jacobson and Hollyday, 1982b; W i l l i a m s et a l . , 1984). The r e s u l t s of t h i s study i n d i c a t e t h a t c o r r e l a t e s of s e v e r a l of these s u p r a s p i n a l s t r u c t u r e s a l s o e x i s t i n avians. 142 IC§lQI§ecti on Level_ The l e v e l of t r a n s e c t i o n a f f e c t s the p r e s t i m u l a t i o n locomotor c a p a b i l i t i e s of the experimental b i r d s . T r a n s e c t i o n at the l e v e l shown i n F i g . 36, Level 1, l e a v i n g p o r t i o n s of the thalamus and hypothalamus i n t a c t , produces an animal devoid of any spontaneous a c t i v i t y . A comparison of the exact l e v e l of t r a n s e c t i o n between mammals and a v i a n s i s d i f f i c u l t t o d i s c e r n due to the absence of the mammalian corpo r a quadrigemina and mammillary bodies i n b i r d s . However, the anatomical c o r r e l a t e s between these animals i n d i c a t e that t h i s l e v e l of d e c e r e b r a t i o n i n b i r d s i s comparable t o the cat thalamic p r e p a r a t i o n of Orlovsky and Shik (1976). Hinsey et a l . (1930) repo r t e d t h a t c a t s can walk almost normally f o l l o w i n g t h i s t r a n s e c t i o n i f the caudal subthalamus i s l e f t i n t a c t . Owing to an evident p a u c i t y of anatomical i n f o r m a t i o n , t h i s r e s e a r c h e r cannot ensure the i n t e g r i t y of the subthalamus i n the p r e p a r a t i o n s i n t h i s study. However, Brauth et a l . (1978) r e p o r t that a p o s s i b l e homolog to the mammalian subthalamic nucleus may be the avian Ansa 1 e n t i c u l a r i s , pars a n t e r i o r . T h i s s t r u c t u r e was a n a t o m i c a l l y preserved i n t r a n s e c t i o n s of t h i s study, although t h e r e e x i s t s the p o s s i b i l i t y t h a t i t may have s u f f e r e d damage by the s u r g i c a l procedure. T h i s may account f o r the absence of p r e s t i m u l a t i o n locomotion i n the m a j o r i t y of experiments and would make these t r a n s e c t i o n s comparable to the thalamic p r e p a r a t i o n of Orlovsky and Shik (1976). Support f o r t h i s l a t t e r h y p o t h e s i s was s u b s t a n t i a t e d i n Expt. 11, where more r o s t r a l t r a n s e c t i o n of the v e n t r a l b r a i n y i e l d e d spontaneous locomotion. Fur t h e r s t u d i e s are 143 r e q u i r e d t o de-fine t h i s problem. T r a n s e c t i o n producing a "thalamic" ( F i g . 36, Level 2) p r e p a r a t i o n allowed spontaneous locomotion t o occur. Anatomical c o r r e l a t i o n between c a t and avian s p e c i e s i n d i c a t e s t h a t t h i s spontaneously locomoting p r e p a r a t i o n i s comparable t o the precol1icular-premami11ary t r a n s e c t i o n d e s c r i b e d by G r i l l n e r and Shik (1973). The "mesencephalic" p r e p a r a t i o n ( F i g . 36, Level 3) d i s p l a y e d no a c t i v i t y f o l l o w i n g the s u r g i c a l procedure. T h i s t r a n s e c t i o n i s s i m i l a r t o the mesencephalic p r e p a r a t i o n ( p r e c o l 1 i c u l a r — postmami11ary t r a n s e c t i o n ) of Orlovsky and Shik (1976) and G r i l l n e r and Shik (1973) i n which acute experimental c a t s d i s p l a y e d no spontaneous movements excep t i n g when the mesencephalic locomotor r e g i o n was e l e c t r i c a l l y s t i m u l a t e d . P r e s e n t l y , t h e r e i s no s u b s t a n t i v e body of r e s e a r c h t o e x p l a i n how v a r y i n g t r a n s e c t i o n l e v e l s e f f e c t locomotion. P o s s i b l e c o n n e c t i o n s between more r o s t r a l areas which are known t o e f f e c t locomotion such as the entopeduncular nucleus of the basal g a n g l i a and more caudal locomotor r e g i o n s s t r u c t u r e s are c u r r e n t l y being i d e n t i f i e d (Garcia-Ri11 et a l . 1983; Steeves and Jordan, 1984). The p h y s i o l o g i c a l importance and s i g n i f i c a n c e of these c o n n e c t i o n s on changes i n spontaneous locomotor a b i l i t y due t o t r a n s e c t i o n l e v e l has not yet been determined. §timulati_gn Si_tes The r e s u l t s i n d i c a t e that a s t i m u l u s s i t e i n the r e g i o n of the l a t e r a l / m e d i a l s p i r i f o r m nucleus and the l a t e r a l p a r t of the 144 p o s t e r i o r hypothalamic nucleus produces locomotion i n avians. Reiner et a l . (1982) and Brauth et a l . (1978) have demonstrated a heavy p r o j e c t i o n -from the l a t e r a l s p i r i f o r m nucleus (SpL) to the tectum ( l a y e r s 11-13). These t e c t a l l a y e r s , which do not appear t o descend d i r e c t l y t o the s p i n a l cord (Cabot et a l . ( 1 9 8 2 ) , p r o v i d e a major crossed descending input to the h i n d b r a i n r e t i c u l a r •formation which g i v e s r i s e t o the r e t i c u l o s p i n a l pathways thought t o e f f e c t the i n i t i a t i o n and c o n t r o l of locomotion (Reiner et a l . , 1982). Fu r t h e r , SpL r e c e i v e s a s i g n i f i c a n t input both from the N. ansa l e t i c u l a r i s , pars a n t e r i o r (ALa), which i s suggested to be the avian e q u i v a l e n t of the mammalian subthalamic nucleus and the p a l e o s t r i a t u m primitivum, the avian e q u i v a l e n t of the mammalian basal g a n g l i a (Reiner et a l . , 1982). The subthalamic nucleus and hypothalamic n u c l e i ( p o s t e r i o r and l a t e r a l ) have p r e v i o u l y been i m p l i c a t e d as a locomotor r e g i o n (subthalamic locomotior r e g i o n (SLR)) i n s t i m u l a t e d c a t s (Orlovsky and Shik, 1976, Steeves and Jordan, 1984). The mammalian basal g a n g l i a have long been b e l i e v e d to have importance to the i n i t i a t i o n and c o n t r o l of locomotion i n humans and cat ( G a r c i a - R i l l et a l . , 1983a; Neafsey et a l . , 1978). B i l a t e r a l l e s i o n s of SpL do not, however, produce d e f i c i t s i n locomotor behaviours (Bugbee, 1979). T h i s i n d i c a t e s t h a t , l i k e the r e g i o n of the SLR and MLR i n c a t s (Mori et a l . 1977; G a r c i a - R i l l et a l . , 1983b), SpL may e f f e c t locomotion but i s not e s s e n t i a l to i t s p r o d u c t i o n . The r e s u l t s from s t i m u l a t i n g i n the area of the N. et T r a c t u s descendens n e r v i t r i g e m i n i (TTD) and the p r i n c i p l e sensory nucleus of nerve V (PrV) showed t h a t s t i m u l a t i o n i n d e c e r e b r a t e s e l i c i t e d 145 behaviours approaching normal locomotion i n i n t a c t animals. Shik and Yagodnitsyn (1977) were the f i r s t to demonstrate that e l e c t r i c a l s t i m u l a t i o n of the pontobulbar "locomotor s t r i p " (PLS), an area emanating from the MLR. and t r a v e l l i n g i n the d o r s o l a t e r a l medullary r e t i c u l a r formation, evoked walking i n the c a t . G a r c i a -R i l l et al.(1983a) d e s c r i b e the PLS as being e q u i v a l e n t t o Probst's t r a c t , a pathway which i s i n t i m a t e l y a s s o c i a t e d with the t r i g e m i n o s p i n a l system. The f i n d i n g s i n cat concur with those i n the present study t h a t s t i m u l a t i o n of t h i s area produces locomotion. The a s s o c i a t i o n of s t i m u l u s s i t e s i n i t i a t i n g hindlimb and f o r e l i m b locomotion c o r r e l a t e s well with a long r o s t r o c a u d a l s t r i p which t r a v e l s i n the avian d o r s o l a t e r a l h i n d b r a i n r e t i c u l a r formation and which c o u l d be the e q u i v a l e n t of the cat PLS. However, the a s s o c i a t i o n of P r o b s t ' s t r a c t , which i s not a n a t o m i c a l l y d e f i n e d f o r avians, with the system e l i c i t i n g locomotion i n mammals appears anomalous. Truex and Carpenter (1969) d e s c r i b e P r o b s t ' s t r a c t as a r i s i n g from c e l l s of the noradrenergic nucleus Locus Coeruleus. Steeves et a l . (1980) depleted both n o r a d r e n a l i n e and 5-hydroxytryptamine i n the cat without f i n d i n g e f f e c t on MLR s t i m u l a t i o n - i n d u c e d locomotion. One can i n f e r t h a t e i t h e r the a n a t o m i c a l l y p o o r l y d e f i n e d P r o b s t ' s t r a c t i s not r e s p o n s i b l e f o r s t i m u l a t i o n evoked locomotion or the c e l l s of the Locus Coeruleus do not g i v e r i s e t o t h i s descending bundle. However, evidence from d e p l e t i o n s t u d i e s i s seldom c o n c l u s i v e (Steeves, personal communication). Since MLR i n a c t i v a t i o n has l i t t l e e f f e c t on PLS s t i m u l a t i o n induced locomotion (Shefchyk et a l . , 1984), locomotion induced by s t i m u l a t i o n of the t r i g e m i n a l system i s probably not mediated by 146 the MLR r e g i o n and produces i t s e f f e c t s v i a an a l t e r n a t e r o u t e . As the t r i g e m i n o s p i n a l system has not been shown to e x i s t below a high c e r v i c a l l e v e l i n humans (Carpenter, 1978) and pigeon (Cabot et a l . , 1982), i t i s u n l i k e l y t h e r e f o r e t h a t t h i s system c o n t r o l s hindlirnb locomotion d i r e c t l y v i a descending t r i g e m i n o s p i n a l pathways. The c o n n e c t i o n s through which t h i s area e x e r t s i t s i n f l u e n c e are s t i l l unknown. E l e c t r i c a l s t i m u l a t i o n of s i t e s i n the m e d i o l a t e r a l pons and medulla produced locomotion i n the decerebrate goose and duck. In some cases, i t was p o s s i b l e that the s t i m u l a t i o n i n c l u d e d areas of the t r i g e m i n a l system a l r e a d y d i s c u s s e d , although s t i m u l u s spread at the c u r r e n t l e v e l s used i s probably i n s u f f i c i e n t t o cause s t i m u l a t i o n of t h i s s i t e (Bagshaw and Evans, 1976). Als o , the l o c a t i o n of s e v e r a l locomotion evoking s t i m u l a t i o n s i t e s which were more ventromedial, p r e c l u d e s the p o s s i b i l i t y t h a t they were i n the t r i g e m i n a l area. S t i m u l a t i o n near the c e n t r a l nucleus of the medulla, pars d o r s a l i s and v e n t r a l i s (Cnd,Cnv) evoked locomotion i n the decerebrate b i r d . T h i s area i s continuous with the r e t i c u l a r formation of the more r o s t r a l medulla and caudal pons but i s c y t o a r c h i t e c t o n i c a l 1 y d i s t i n c t from these s t r u c t u r e s (Cabot e t a l . , 1982). S t i m u l a t i o n i n the area of the l a t e r a l r e t i c u l a r nucleus at more r o s t r a l l e v e l s a l s o l e d to locomotor a c t i v i t y . These r e s u l t s i n d i c a t e t h a t the above r e t i c u l a r formation s t r u c t u r e s may be e q u i v a l e n t to those found i n the c a t , where s t i m u l a t i o n of the r e t i c u l a r formation g i g a n t o c e l 1 u l a r and magnocel1ular n u c l e i (Steeves and Jordan, 1984; Budakova and Shik, 1980) produces locomotion. 147 S t i m u l a t i o n Parameters The r e s u l t s of changing s t i m u l a t i o n parameters c o r r e l a t e s well with those found i n mammals. Increases i n t r e a d m i l l b e l t v e l o c i t y with the maintenance of s t i m u l a t i o n s t r e n g t h produces i n c r e a s e s i n s t e p p i n g frequency without changes i n e x c u r s i o n length ( F i g . 49). T h i s c o r r o b o r a t e s r e s u l t s found i n cat (Orlovsky and Shik, 1976), where i n c r e a s i n g the v e l o c i t y of the t r e a d m i l l b e l t r e s u l t e d i n a temporal s h o r t e n i n g of the step c y c l e i n MLR s t i m u l a t e d animals. Modulation of the s t i m u l a t i o n s t r e n g t h produced changes i n the s t r e n g t h and frequency of stepping i n both extensor and f l e x o r muscles ( F i g . 50). As i n c a t s (Orlovsky and Shik, 1976), i n c r e a s i n g s t i m u l a t i o n s t r e n g t h produced i n c r e a s e d f o r c e of stepping and a s l i g h t i n c r e a s e i n step frequency. Orlovsky and Shik (1976) conclude t h a t , at l e a s t i n the case of MLR s t i m u l a t i o n , the s t i m u l a t i o n s t r e n g t h determines the s t r e n g t h of s t e p p i n g and the frequency changes r e s u l t i n d i r e c t l y from t h i s i n c r e a s e i n muscle a c t i v i t y . T h i s h y p o t h e s i s has not, to my knowledge, been t e s t e d i n decerebrate p a r a l y s e d animals where a f f e r e n t sensory input ( " f i c t i v e " p r e p a r a t i o n ) , which might modulate t h i s r e s u l t , has been e l i m i n a t e d . These r e s u l t s a l s o correspond to those found i n f i s h , where i n c r e a s i n g s t i m u l a t i o n i n the midbrain tegementum r e s u l t e d i n i n c r e a s i n g locomotor behaviours which resembled swimming (Kashin, Feldman, and Orlovsky, 1974). Changing the frequency of s t i m u l a t i o n , h o l d i n g other parameters constant, does not appear to s i g n i f i c a n t l y e f f e c t the speed or s t r e n g t h of s t e p p i n g . / 148 Acute Sfj^nal. Cord L e s i o n s L e s i o n s of the s p i n a l cord i n acute decerebrate brainstem s t i m u l a t e d b i r d s demonstrate t h a t the d o r s a l h a l f of the cord i s not necessary to the p r o d u c t i o n of locomotion. T h i s i s i n agreement with p r e v i o u s f i n d i n g s of other experimenters i n a v a r i e t y of c h r o n i c and acute experimental animals (Steeves and Jordan, 1980; E i d e l b e r g et a l . , 1981; W i l l i a m s et a l . , 1984) i n t h a t s u f f i c i e n t pathways subserving locomotion are present i n the v e n t r a l hemicord t o allow locomotion to occur. It appears from the r e s u l t s i n both c h r o n i c and acute animals that the r e t i c u l o s p i n a l pathways may p l a y an important r o l e i n the i n i t i a t i o n and c o n t r o l of locomotion i n a v i a n s . However, i n order to more p r e c i s e l y determine the importance and l o c a t i o n of t h i s and other p o s s i b l y important i n f o r m a t i o n c a r r y i n g pathways, i t w i l l be necessary t o i n c o r p o r a t e i n t o the acute s t i m u l a t i o n experiments a more complete study i n v o l v i n g acute l e s i o n s of both t h o r a c i c and c e r v i c a l s p i n a l c o r d . C o n clusion It i s apparent from s t i m u l a t i o n s t u d i e s i n the goose and duck that a strong p a r a l l e l e x i s t s between s t i m u l a t i o n induced locomotor behaviours i n the avian and mammalian systems. In order to f u r t h e r compare these systems, i t w i l l be necessary to a n a t o m i c a l l y as well as p h y s i o l o g i c a l l y d e f i n e the l o c a t i o n s of 149 s i t e s evoking locomotor behaviours. F u r t h e r , i t w i l l be necessary t o determine a n a t o m i c a l l y both the o r i g i n o-f the pathway (s) descending to the s p i n a l cord which subserve locomotor behaviours and the connection between these pathway(s) and more r o s t r a l s t r u c t u r e s which could i n i t i a t e these behaviours. 150 TABLE I I I EXPT.# STIMULATION SITE BEHAVIOUR STIMULATION THRESHOLD la) Nucleus (N.) s e n s o r i u s p r i n c i p a l i s n e r v i t r i g e m i n i ( A n t e r i o r (A) 2, L a t e r a l (L) 3)(K&H, Al.OO) -wing -flapping, running -wing f l a p p i n g alone 50uA/ 50Hz b) Between d o r s a l motor nuc. of vagus ( s o l i t a r y t r a c t ) and descending t r i g e m i n a l nucleus and roo t (P7,L1) <K&H, P3.75) (Zweers, P3.48) -walking and f l a p p i n g 50-100 -when wings he l d , uA/50Hz continued stepping Ha) Area of N. et t r a c t u s descendens t r i g e m i n i (A1,L4)(K&H, PI.25) (Zweers, P2.32) - f l y i n g with some i n i t i a l running 75uA/ 50Hz b) N. r e t i c u l a r i s l a t e r a l i s (P5,L2) (K&H, P3.25) (Zweers, P3.48) -running and f l y i n g 25uA/ 50Hz c) N. c e n t r a l i s medulla oblongata, pars d o r s a l i s (P7,L1)(K&H, P4.0) (Zweers, P4.35) -walking becomes f l y i n g 50-100 as s t i m u l a t i o n uA/50H: i n t e n s i t y i n c r e a s e s 3a) N. vagi d o r s o l a t e r a l i s of Zweers, N. n e r v i g l o s s o -d o r s a l i s n e r v i vagi (K?<H, PI.75) (Zweers, P2.32) -swallowing response 50uA/ 50Hz b) area between N. s o l i t a r i u s , s u b s t a n t i a g e l a t i n o s a Rolandi ( t r i g e m i n i ) and N. et t r a c t u s descendens ne r v i t r i g e m i n i (P6,L1.5) (K&H, P3.50) (Zweers, P3.48) -walking and f l y i n g 40uA/ 50Hz c) area of N. c e n t r a l i s medulla -walking and f l y i n g oblongata, pars d o r s a l i s and medial to s u b s t a n t i a g e l a t i n o s a Rolandi t r i g e m i n i i n area of N. et t r a c t u s descendens n e r v i 30uA/ 50Hz 151 t r i g e m i n i (P8.0,LI.5)(K&H, (Zweers, P5.22) 4) N. c e n t r a l i s medulla oblongata, pars d o r s a l i s (P7,L2) (K2<H, P3.75) (Zweers, P3.77) (Goose Chronic Expt. 39) 6a) l a t e r a l r e t i c u l a r -formation (may a l s o be v e n t r a l or d o r s a l s p i n o c e r e b e l l a r tracts)(P7,L2.0)(K&H, P3.50) (Zweers, P4.06) b) N. et t r a c t u s descendens n e r v i t r i g e m i n i (P7,L1.5) <K8<H, P3.50)(Zweers, P4.06) 7) no l e s i o n s (Duck) 8) medial 1emniscus,central nucleus medulla oblongata pars v e n t r a l i s , or raphe nucleus.(K&H, P2.5) (Zweers, P2.61)(Duck) 10a) N. c e n t r a l i s medulla oblongata, pars v e n t r a l i s (dorsal i s border) and l a t e r a l r e t i c u l a r nucleus (P7,L2)(K&H, P3.75) (Zweers, P3.48) (Duck) 11a) N. c e n t r a l i s medulla oblongata, pars v e n t r a l i s (P3.5 K&H) b) (P2,L2) no h i s t o l o g i c a l ver i f" i cat i on . 0) -wing -flapping, s l i g h t 75uA/ f l e x i o n of r i g h t l e g 50Hz during f l y i n g , v o c a l -i z a t i o n , decreased blood pressure and b r a d y c a r d i a -wing f l a p p i n g & 50uA/ running 50Hz - f l y i n g and running 50uA/ 50Hz -spontaneous response t o t r e a d m i l l , wing f l a p p i n g and walking. Reflex withdrawal to f o o t web pinch and f l y i n g and running response t o p e r i - a n a l s t i m u l a t i o n . -walking only, 75-150 i n c r e a s i n g s t i m u l u s uA/50Hz i n t e n s i t y causes i n c r e a s e s i n f o r c e of st e p p i n g but no i n c r e a s e i n frequenc, changes i n step p i n g frequency accompany t r e a d m i l l v e l o c i t y changes -walking only 75uA/ 50Hz -walking and f l y i n g 75uA/ 50Hz -walking and f l y i n g 75uA/ 50Hz 152 12a) area of l a t e r a l r e t i c u l a r nucleus, s p i n a l lemniscus, and medial 1emniscus.(P4,L2) <K?<H, P3.00) (Zweers, 3. 1?) (Duck) -swal1owi ng 75uA/ 50Hz b)-between N. r e t i c u l a r i s p a r v o c e l 1 u l a r i s and N. et T r a c t u s descendens n e r v i t r i g e m i n i of K&H. - L a t e r a l t o N. subcoeruleus and medial t o N. r a d i c u s descendens n e r v i t r i g e m i n i of Zweers (PI,LI) (KS<H, P0.25-AP0.00) (Zweers, P0.29) - b i l a t e r a l walking 100-125 f o l l o w i n g s p i n a l cord uA/50Hz d o r s a l columns l e s i o n went t o walking only no wing 75uA/ movement 50Hz c) -area of l a t e r a l and medial -s p i r i f o r m nucleus and ansa l e n t i c u l a r i s of K&H. -N. hypothalamicus p o s t e r i o r , pars l a t e r a l i s or N. g e n i c u l a t u s l a t e r a l i s of Zweers. (A3,LI) (KS<H, A5.00)(Zweers, A6.3B) (Right side) •walking at low s t i m u l u s 75uA/ s t r e n g t h and f l y i n g 50Hz at higher s t i m u l u s i n t e n s i t y . d) ( A 3 , L I ) ( L e f t s i d e ) no l e s i o n -walking and f l y i n g 75uA/ 50Hz 13a) s u b s t a n t i a g e l a t i n o s a Rolandi t r i g e m i n i and N. et T r a c t u s descendens t r i g e m i n i (P6,L2) (K8/.H, P3.75) (Zweers, 4.06) (Le f t side)(Duck) b) N. c e n t r a l i s medulla oblongata, pars d o r s a l i s and Plexus of Horsley; a l s o c l o s e t o N. et ra d i x descendens n e r v i t r i g e m i n i (P6,L1)(K&H, P3.75) (Zweers, P4.06)(Right side) - f l y i n g o n l y with l e g s 60uA/ tucked under body. An 50Hz i n c r e a s e i n s t i m u l u s i n t e n s i t y i n c r e a s e s f o r c e of f l a p p i n g . A g i t a t e d f o o t movements during f l y i n g show higher i n t e n s i t y i n r i g h t l e g than i n l e f t - f l y i n g and walking 100uA/ 50Hz 153 Abbrevi a t i o n s : (P. . . ,L. . . ) = S t e r e o t a x i c c o o r d i n a t e s of l e s i o n s i t e u sing r o s t r a l c e r e b e l l a r border as a n t e r o p o s t e r i o r (AP) s t e r e o t a x i c zero. (K&H,.«..)= E q u i v a l e n t t o s t e r e o t a x i c a t l a s l e v e l of Karten and Hodos (1967) (Zweers,..)= E q u i v a l e n t t o s t e r e o t a x i c a t l a s l e v e l of Zweers (1971) uA= microamperes Hz= Hertz ( c y c l e s per second) 154 Experimental apparatus u t i l i s e d during acute avian brainstem s t i m u l a t i o n experiments. See t e x t f o r f u r t h e r i n f o r m a t i o n . A b b r e v i a t i o n s : b.p.= blood pressure, ccu= constant c u r r e n t u n i t (Brass), E.M.6.= electromyographic e l e c t r o d e s . 155 Brain Stimulation Experimental Apparatus 156 FIGURE 36 P a r a s a g g i t a l s e c t i o n ( l a t e r a l 0.5) of the b r a i n of the Canada goose (Branta canadensis) showing the l e v e l s of t r a n s e c t i o n produced by the d e c e r e b r a t i o n procedure. Level 1- decerebrate p r e p a r a t i o n , Level 2= "thalamic" p r e p a r a t i o n , Level 3= "mesencephalic" p r e p a r a t i o n ( a d d i t i o n a l i n f o r m a t i o n i s s u p p l i e d i n the t e x t ) . A l s o shown are the p o s i t i o n s of some a n a t o m i c a l l y i d e n t i f i a b l e s t r u c t u r e s i n the avian b r a i n . Lined areas i n d i c a t e s t r u c t u r e s l a t e r a l to plane of s e c t i o n . A b b r e v i a t i o n s : B0= o l f a c t o r y bulb, Ca= a n t e r i o r commissure, Cb= cerebellum, C0= o p t i c chiasm, GCt= s u b s t a n t i a g r i s e a c e n t r a l i s , Hb= habenular nucleus, 10= i n f e r i o r o l i v a r y nucleus, nIV= nucleus of t r o c h l e a r nerve, nIX= nucleus of glossopharyngeal nerve, nX= nucleus of vagus nerve, NIII= occulomotor nerve r o o t , 0v= ovoid nucleus, RPgc= nucleus r e t i c u l a r i s p o n t i s caudal i s , pars g i g a n t o c e l 1 u l a r i s , Ru= red nucleus, SpL= l a t e r a l s p i r i f o r m nucleus, TU= t u b e r a l nucleus, V= v e n t r i c l e , Veli= medial v e s t i b u l a r nucleus (nomenclature c i t e d from Karten and Hodos, 1967) o o 158 FIGURE 37 Electromyographic r e c o r d s o-f p r e s t i m u l a t i o n spontaneous locomotion with the wings (Pect) i n the acute decerebrate b i r d . No hindlimb a c t i v i t y was apparent from the potentiometer r e c o r d s . A b b r e v i a t i o n s : L= l e f t , R= r i g h t , Hind.= hindlimb, Pect.= P e c t o r a l i s Q 159 J| A /J R. PECT. L PECT. R. HIND. I Flexion 6 — L. HIND. 1.0 sec. 160 EIGURE 38 Diagrammatic r e p r e s e n t a t i o n (A) of a t r a n s v e r s e s e c t i o n through the r o s t r a l medulla i n d i c a t i n g the s i t e of e l e c t r i c a l s t i m u l a t i o n ( l e s i o n s i t e ) which evoked walking and f l y i n g movements i n the acute decerebrate avian of E>:pt. 6b. B i s a photograph of a s e c t i o n through the l e s i o n s i t e . The area of s t i m u l a t i o n l i e s s l i g h t l y medial to SG and i s encompassed by TTD. The s e c t i o n l e v e l i s comparable to that of s t e r e o t a x i c c o o r d i n a t e P o s t e r i o r (P) 3.5 of Karten and Hodos (1967). A b b r e v i a t i o n s : Cb= cerebellum, cc= c e n t r a l c a n a l , FLM= medial l o n g i t u d i n a l f a s c i c u l u s , IM= nucleus (n.) intermedins, 10= i n f e r i o r o l i v a r y nucleus, n.X= nucleus of vagus nerve, n.XII= n. hypoglossal nerve, NX= vagus nerve, NX11 == hypoglossal nerve, SG= s u b s t a n t i a g e l a t i n o s a Rolandi ( t r i g e m i n i ) . ( M a g n i f i c a t i o n : 17.5x) 161 162 FIGURE 39 Diagrammatic r e p r e s e n t a t i o n (A) o-f a t r a n s v e r s e s e c t i o n through the r o s t r a l medulla/caudal pons showing the s i t e of e l e c t r i c a l s t i m u l a t i o n which evoked f l y i n g and running movements i n the acute decerebrate avian of Expt. 2a. The area of s t i m u l a t i o n i s contained w i t h i n TTD. F i g . B shows a photograph of a s e c t i o n through the l e s i o n s i t e . S e c t i o n l e v e l i s comparable t o the s e c t i o n l e v e l PI.25 of Karten and Hodos (1967). A b b r e v i a t i o n s : FLM= medial l o n g i t u d i n a l f a s c i c u l u s , MC= nucleus (n.) magnocel l u l a r i s, nIX= n. of glossopharyngeal nerve, Nv"III = v e s t i b u l o c o c h l e a r nerve, R= raphe nucleus, TTD= descending t r a c t and nucleus of the t r i g e m i n a l nerve, VeD= n. v e s t i b u l a r i s descendens. ( M a g n i f i c a t i o n : 9x). 164 FIBURE 40 St i m u l a t i o n - i n d u c e d walking i n the acute decerebrate duck. Electromyographic r e c o r d s demonstrate a l t e r n a t i n g a c t i v i t y of the f l e x o r muscles (ITC) of the hindlimb d u r i n g t r e a d m i l l walking. Potentiometer r e c o r d s show a l t e r n a t i n g f l e x i o n and extension e x c u r s i o n s of both l e g s . The walking movements r e s u l t e d from s t i m u l a t i o n i n the re g i o n of TTD (Expt. 12b). A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , Hind.= hindlimb. 165 L. ITC adi*-* ii R. ITC R. HIND. 1 Flexion L. HIND. 1.0 sec. 166 FIGURE 41 Diagrammatic r e p r e s e n t a t i o n (A) of- a t r a n s v e r s e s e c t i o n through the mid-pontine r e g i o n (A1.0 of Karten and Hodos (1967)) showing the s i t e ( l e s i o n ) which evoked f l y i n g and running movements when st i m u l a t e d ( E x p t . l a ) . B i s a photograph of a s e c t i o n through the l e s i o n s i t e . The l e s i o n i n d i c a t e s the s t i m u l a t i o n l o c a t i o n to be i n or near PrV. A b b r e v i a t i o n s : FLM= medial l o n g i t u d i n a l f a s c i c u l u s , PrV= p r i n c i p l e sensory nucleus of the t r i g e m i n a l nerve, R= raphe nucleus. ( M a g n i f i c a t i o n : 9x) B 168 EIGLJR! 42 Transverse s e c t i o n (B) and diagrammatic r e p r e s e n t a t i o n (A) through the r o s t r a l medulla d i s p l a y i n g the s t i m u l a t i o n s i t e ( l e s i o n ) which evoked locomotion i n the acute decerebrate duck (Expt.10a). The s t i m u l a t i o n s i t e l i e s w i t h i n the boundaries of Cnv. The s e c t i o n l e v e l i s comparable to P3.25 of Karten and Hodos (1967). A b b r e v i a t i o n s : Cnd= c e n t r a l nucleus of medulla oblongata, pars d o r s a l i s , Cnv= c e n t r a l nucleus of medulla oblongata, pars v e n t r a l i s , FLM= medial l o n g i t u d i n a l f a s c i c u l u s , nX= d o r s a l motor nucleus of vagus nerve, 01= i n f e r i o r o l i v a r y nucleus, R= raphe nucleus. ( M a g n i f i c a t i o n : 17.5x) 169 170 FIGURE 43 Simultaneous hindlimb and wing movements evoked by s t i m u l a t i o n i n the area of Cnv/Cnd are demonstrated by potentiometer ( l e f t and r i g h t hindlimbs) and electromyographic r e c o r d s ( l e f t p e c t ) ( E x p t . 1 l a ) . Although o n l y a s i n g l e pect was implanted with e l e c t r o d e s f o r the EMG r e c o r d s , rhythmic concurrent f l a p p i n g movements occurred b i l a t e r a l l y . A b b r e v i a t i o n s : Hind.= hindlimb, Pect.= P e c t o r a l i s 171 L. PECT. L. HIND. Flexion R. HIND. 172 FIGURE 44 Electromyographic and potentiometer r e c o r d s o-f walking i n the e l e c t r i c a l l y s t i m u l a t e d a v i a n . The EMG r e c o r d of hindlirnb s t e p p i n g c o r r o b o r a t e s the potentiometer r e c o r d s showing a l t e r n a t i n g a c t i v i t y of hindlirnb f l e x o r (ITC) muscles during stimulation-evoked t r e a d m i l l walking. The s t i m u l a t i o n s i t e was w i t h i n Cnd (see F i g . 43, Expt. 11a). A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , Hind.= hindlirnb. 174 FIGURE 45 Diagrammatic r e p r e s e n t a t i o n (A) of a t r a n s v e r s e s e c t i o n through the medulla o u t l i n i n g the s t i m u l a t i o n s i t e ( l e s i o n ) which evoked f l y i n g and t r e a d m i l l running at low c u r r e n t s t i m u l u s i n t e n s i t y (25uA) . The photograph i n B shows the a c t u a l l e s i o n . The s t i m u l u s area i s bounded by RL and Cnv. The s e c t i o n l e v e l i s comparable t o P3.75 of Karten and Hodos (1967). A b b r e v i a t i o n s : Cb= cerebellum, Cnd= c e n t r a l nucleus of medulla oblongata, pars d o r s a l i s , Cnv= c e n t r a l nucleus of medulla oblongata, pars v e n t r a l i s , Fl_li= medial l o n g i t u d i n a l f a s c i c u l u s , I l i - i n t e r m e d i a t e nucleus, nX= d o r s a l motor nucleus of vagus nerve, 01= i n f e r i o r o l i v a r y nucleus, RL= l a t e r a l r e t i c u l a r nucleus, SG= s u b s t a n t i a g e l a t i n o s a Rolandi ( t r i g e m i n i ) . ( M a g n i f i c a t i o n : 17.5x). 176 FIGURE 46 Transverse s e c t i o n through the r o s t r a l mesencephalon d i s p l a y i n g the s t i m u l a t i o n s i t e ( l e s i o n ) which produced walking and wing •flapping movements i n an acute decerebrate duck (Expt. 12c, d) . The area o-f s t i m u l a t i o n i s centered near AL and SpL. S e c t i o n l e v e l i s comparable t o A4.75 of Karten and Hodos (1967). A b b r e v i a t i o n s : AL= ansa l e n t i c u l a r i s , CF= campi F o r e l i , Dli= o c c i p i t o m e s e n c e p h a l i c t r a c t , PT= p r e t e c t a l nucleus, QF= q u i n t o f r o n t a l t r a c t , SCE= e x t e r n a l c e l l u l a r stratum, SGF= stratum griseum e t fibrosum s u p e r f i c i a l e , SpL= l a t e r a l s p i r i f o r m nucleus, SpM= medial s p i r i f o r m nucleus, VIII= v e n t r i c l e III ( M a g n i f i c a t i o n : 13x) 178 FIGURE 47 Diagrammatic r e p r e s e n t a t i o n (A) and photograph (B) o-f a t r a n s v e r s e s e c t i o n through the medulla ( e q u i v a l e n t t o Karten and Hodos F:'3.5) showing the s t i m u l a t i o n s i t e ( l e s i o n ) which produced t r e a d m i l l walking during e l e c t r i c a l s t i m u l a t i o n (Expt.8). The s t i m u l a t i o n s i t e l i e s medial t o the i n f e r i o r o l i v a r y nucleus i n Cnv. A b b r e v i a t i o n s : Cb= cerebellum, cc= c e n t r a l c a n a l , Cnv= c e n t r a l nucleus of the medulla oblongata, pars v e n t r a l i s , FLIi= medial l o n g i t u d i n a l f a s c i c u l u s , Ifi= i n t e r m e d i a t e nucleus, nX = d o r s a l motor nucleus of vagus nerve, nXII= nucleus of hypoglossal nerve, NX= vagus nerve, 01= i n f e r i o r o l i v a r y nucleus. (Magn i f i c at i on: 13x ) . 180 FIGURE 48 Electromyographic (ITC) and potentiometer (HIND.) r e c o r d s showing hindlimb a c t i v i t y during e l e c t r i c a l l y evoked walking i n the decerebrate avian (Expt.8). A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , HIND.= hindlimb. 181 L. ITC R. HIND. I Flexion V W W W \ L- HIND. 1.0 sec. 182 EIBURE 49 Potentiometer r e c o r d s showing the e f f e c t of i n c r e a s i n g t r e a d m i l l b e l t v e l o c i t y during evoked locomotion. The l i n e s below the potentiometer r e c o r d s f o r the l e f t hindlirnb mark maximal r o s t r a l e x c u r s i o n of the limb and demonstrate t h a t i n c r e a s e d frequency of stepping occurs with r e l a t i v e i n c r e a s e s i n t r e a d m i l l v e l o c i t y . A b b r e v i a t i o n : HIND.= hindlirnb 183 lexion 5.5 5.0 4.5 L. HIND. 5.5 5.0 R. HIND. 4.5 1.0 sec 184 FIGURE 50 Electromyographic and potentiometer r e c o r d s showing the e-ffects o-f i n c r e a s i n g s t i m u l a t i o n c u r r e n t i n t e n s i t y during evoked locomotion. EMG r e c o r d s -from le-ft and r i g h t f l e x o r (ITC) muscles show i n c r e a s e d frequency of a c t i v i t y i n response to augmented c u r r e n t s t r e n g t h . Potentiometer r e c o r d s demonstrate an i n c r e a s e i n the frequency of stepping with i n c r e a s e d s t i m u l u s i n t e n s i t y . The t r e a d m i l l b e l t v e l o c i t y and s t i m u l a t i o n frequency were he l d constant. A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , HIND.= hindlimb, uA= microamperes 185 niw^v^*^^'' >«4> • H»* 100 uA L ITC • ^ W * ^ ^ ^ ^ 125 JJA 100 JJA | | r ^ ^ 4 H f ^ M ^ 4 ' 125 MA R ' I T C 100 JJA 1 0 C MA L H I N D 125 JJA Flexion 1 100 uA . O C A R. HIND. 125 JJA U) sec. 186 FIGURE 51 Diagrammatic r e p r e s e n t a t i o n (A) o-f a c r o s s s e c t i o n through the low t h o r a c i c s p i n a l cord f o l l o w i n g a c h r o n i c Dorsal Cord T r a n s e c t i o n (Expt.6). A p o r t i o n of the t o t a l l e s i o n i s shown i n B. The diagram i s a composite from s e r i a l s e c t i o n s through the l e s i o n s i t e . The l i n e d area demonstrates complete l e s i o n extent. 187 B 188 FIGURE 52 Transverse s e c t i o n (B) through the low t h o r a c i c s p i n a l cord •following an acute s p i n a l cord t r a n s e c t i o n (Expt. 12) . H i s t o l o g i c a l v e r i f i c a t i o n of the l e s i o n extent ( l i n e d area) was made using a composite of s e r i a l c r o s s s e c t i o n s (a sample c r o s s s e c t i o n i s shown i n B) through the l e s i o n s i t e . 190 FIGURE. 53 Electromyographic <EMG) and potentiometer r e c o r d s -from hindlimb muscles (ITC) and l e g s f o l l o w i n g an acute low t h o r a c i c s p i n a l cord Dorsal Cord T r a n s e c t i o n i n a decerebrate brainstem s t i m u l a t e d animal (Expt.12). EMG r e c o r d s show a l t e r n a t i n g a c t i v i t y i n homologous hindlimb f l e x o r s (ITC), with more c l e a r l y d e f i n e d rhythmic f l e x i o n i n the r i g h t ITC than the l e f t ITC. Potentiometer r e c o r d s d i s p l a y the r o s t r o c a u d a l e x c u r s i o n s of both hindlimbs. They i n d i c a t e t h a t stepping of the r i g h t l e g i s rhythmic, with d e f i n i t i v e e x c u r s i o n s , while that of the l e f t hindlimb i s l e s s pronounced. The s t i m u l u s on/off arrows i n d i c a t e s t i m u l u s onset and t e r m i n a t i o n . Walking commenced with onset and ceased at s t i m u l u s t e r m i n a t i o n . A b b r e v i a t i o n s : ITC= i l i o t i b i a l i s c r a n i a l i s , HIND.= hindlimb. 191 L. ITC R. ITC • L. HIND. I-Flexion R. HIND. | 1.0 sec. I Stimulus on Stimulus off 192 CONCLUSIONS The f i n d i n g s of t h i s study e s t a b l i s h p a r a l l e l s between avian and mammalian descending systems c o n t r o l l i n g locomotion. These i n c l u d e : the locomotor program f o r ste p p i n g ( i e . s p i n a l stepping) i s i n t r i n s i c t o the s p i n a l cord i n both b i r d s and mammals ex c l u d i n g primates; at l e a s t one i n t a c t s p i n a l cord v e n t r a l quadrant i s necessary f o r the pr o d u c t i o n of v o l u n t a r y locomotion i n both b i r d and mammal; e l e c t r i c a l s t i m u l a t i o n of areas i n the brainstem can evoke locomotion i n acute decerebrate p r e p a r a t i o n s of both groups; and the e l e c t r i c a l l y s t i m u l a t e d locomotion evoking s i t e s i n the brainstem have anatomical c o r r e l a t i o n between b i r d s and mammals. "Spinal s t e p p i n g " occurred f o l l o w i n g s p i n a l cord t r a n s e c t i o n at the low t h o r a c i c l e v e l i n b i r d s . Whether " s p i n a l f l y i n g " can a l s o be produced remains t o be determined. However, c e r v i c a l cord t r a n s e c t i o n r o s t r a l t o the c e r v i c a l enlargement i n c h r o n i c animals may show the e x i s t e n c e of an i n t r i n s i c s p i n a l cord locomotor f l i g h t generator. The d i f f e r e n t types of locomotion i n b i r d s may allow experimenters t o d e f i n e the neuronal c i r c u i t s and i n t e r c o n n e c t i o n s of the two p o s s i b l y d i f f e r e n t c e n t r a l p a t t e r n generators. The r e t i c u l o s p i n a l pathways are i m p l i c a t e d i n the s u p r a s p i n a l descending c o n t r o l of locomotion i n both b i r d s and mammals. However, the r e s u l t s of t h i s study cannot d i f f e r e n t i a t e the r o l e i n locomotion of the r e t i c u l o s p i n a l pathway from t h a t of the 193 v e s t i b u l o s p i n a l pathway which t r a v e l s i n the same s p i n a l cord area. B i l a t e r a l l e s i o n i n g o-f the v e s t i b u l a r n u c l e i , combined with s e l e c t i v e s p i n a l cord l e s i o n s i n c h r o n i c animals would determine the requirement of t h i s pathway -for the p r o d u c t i o n of v o l u n t a r y hindlimb locomotion. As the r e s u l t s of c h r o n i c s e l e c t i v e l e s i o n i n g expereriments i n t h i s study apply o n l y t o hindlimb locomotion, i t w i l l be i n t e r e s t i n g t o use the same technique to examine descending pathways c o n t r o l l i n g f o r e l i m b locomotion. Jacobson and Hollyday (1982b) have p o s t u l a t e d the e x i s t e n c e of two separate pathways i n the c e r v i c a l s p i n a l cord c o n t r o l l i n g locomotion i n the c h i c k . These may a l s o be examined using s e l e c t i v e l e s i o n s t u d i e s t o determine t h e i r n e c e s s i t y i n locomotor behaviours. The o r i g i n of the pathway(s) r e s p o n s i b l e f o r descending c o n t r o l can be c l a r i f i e d by neuroanatomical t r a c i n g s t u d i e s u sing r e t r o g r a d e horse r a d i s h peroxidase (HRP) and/or True Blue (TB) techniques combined with s e l e c t i v e s p i n a l cord l e s i o n s . R e s u l t s from the acute brainstem s t i m u l a t i o n experiments have produced p a r a l l e l s between the avian and mammalian systems. Three areas known to evoke locomotion i n the c a t appear from t h i s study to have c o r r e l a t e s i n b i r d s . However, more a n a l y s i s must be done t o examine the interdependency of these areas, t h e i r i n t e r c o n n e c t i o n s , and the n e c e s s i t y of these areas t o locomotion b e f o r e a complete comparison can be made. Experiments u t i l i z i n g s e l e c t i v e b i l a t e r a l l e s i o n s of locomotion evoking s t r u c t u r e s w i l l determine the interdependence of these s t u c t u r e s . Anatomical t r a c i n g s t u d i e s using HRP or TB can be used i n combination with e l e c t r i c a l s t i m u l a t i o n t o d e l i m i t the i n t e r c o n n e c t i o n s of these s t r u c t u r e s . The dependence of locomotion on these s u p r a s p i n a l 194 s t r u c t u r e s may be determined by both s e l e c t i v e b i l a t e r a l l e s i o n s and by a b l a t i n g these s t r u c t u r e s by changing the t r a n s e c t i o n l e v e l i n acute decerebrate p r e p a r a t i o n s . The b i r d has been r e l a t i v e l y unexplored n e u r o p h y s i o l o g i c a l l y with regard t o i t s locomotor mechanisms yet i t s a t t r i b u t e s p r o v i d e an e x c e l l e n t s u b s t r a t e f o r locomotor r e s e a r c h . The r e s u l t s of t h i s study are the groundwork f o r f u t u r e , p o t e n t i a l l y f r u i t f u l , s t u d i e s i n t o a vian locomotion. 195 REFERENCES A-felt Z. 1974. F u n c t i o n a l s i g n i f i c a n c e o-f v e n t r a l descending t r a c t s of the s p i n a l cord o-f the c a t . Acta N e u r o b i o l . Exper. 34:393-407. Bagshaw E.V. and M.H. Evans. 1976. Measurement of c u r r e n t spread -from m i c r o e l e c t r o d e s when s t i m u l a t i n g w i t h i n the nervous system. Exp. B r a i n Res. 25:391-400. Basmajian J.V. 1962. Muscles a l i v e : t h e i r f u n c t i o n s r e v e a l e d by electromyography. W i l l i a m s and W i l k i n s Co.,, Ba l t i m o r e . Brauth S.E., J.L. Ferguson, C.L. K i t t . 1978. P r o s e n c e p h a l i c pathways r e l a t e d t o the p a l e o s t r i a t u m of the pigeon. (Qolumba l i v i a . B r a i n Research 147:205-221. Brown-Sequard C.E. 1870. Course of l e c t u r e s on the p h y s i o l o g y and pathology of the nervous system. I I I . on hemiparaplegia. Lancet 1:1-4 Bugbee N. 1979. The e f f e c t of b i l a t e r a l l e s i o n s i n the nucleus s p i r i f o r m i s l a t e r a l i s on v i s u a l l y guided behaviour i n the pigeon. Ph.D. t h e s i s . U n i v e r s i t y of Maryland, C o l l e g e park, Maryland. i_n Reiner A., N.C. Brecha, and H.J. Karten. 1982. Basal g a n g l i a pathways t o the tectum: the a f f e r e n t and e f f e r e n t c onnections of the l a t e r a l s p i r i f o r m nucleus of pigeon. J . Comp. Neurol. 208:16-36 Budakova N.N. and M.L. Shik. 1980. Walking does not r e q u i r e c o n t i n u i t y of the medullary "locomotor s t r i p " . B i a l l . Eksp. B i o l . Med. 89:3-6. B u t l e r P.J., N.J. West, and D.R. Jones. 1977. R e s p i r a t o r y and c a r d i o v a s c u l a r responses of the pigeon t o s u s t a i n e d l e v e l f l i g h t i n a wind t u n n e l . J . Exp. B i o l . 71:7-26 Cabot, J.B., A. Reiner, and N.Bogan. 1982. Avian b u l b o s p i n a l pathways: anterograde and r e t r o g r a d e s t u d i e s of c e l l s of o r i g i n , f u n i c u l a r t r a j e c t o r i e s , and laminar t e r m i n a t i o n s . Prog. Br. Res. 57:79-108. Carpenter M.B. 1978 Core Text of Neuroanatomy. W i l l i a m and W i l k i n s , Baltimore, pp. 249-254. Cohen A.H. and P. Wallen. 1980. The neuronal c o r r e l a t e of locomotion i n f i s h . Exper. B r a i n Res. 41:11-18 C r a c r a f t J . 1971. The f u n c t i o n a l morphology of the hindlimb of the domestic pigeon, Qgl_umba l i y i a . B u l l . Am. Mus. Nat. H i s t . 44:171-268. 196 Denny-Brown D. 1966 The C e r e b r a l C o n t r o l o-f Movement. T h o m a l : S p r i n g f i e l d . E i d e l b e r g E., Woolf, C.J. K r e i n i c k , and F. Davis. 1976. Role of the d o r s a l f u n i c u l i i n movement c o n t r o l . B r a i n Res. 114:427-438. E i d e l b e r g E. , J.G. Walden, and L.H. Nguyen. 1981a Locomotor Contr i n Macaque Monkeys. B r a i n 1045 647-663. E i d e l b e r g , E. 1981b Consequences of s p i n a l cord l e s i o n s upon motor f u n c t i o n , with s p e c i a l r e f e r e n c e t o locomotor a c t i v i t y . Prog, i n N e u r o b i o l . V o l . 17:185-202. E i d e l b e r g E., J.L. Story, J.G. Walden, and B.L. Meyer. 1981c. Anatomical c o r r e l a t e s of r e t u r n of locomotor f u n c t i o n a f t e r p a r t i a l s p i n a l cord l e s i o n s i n c a t s . Exp. B r a i n Res. 42:81-88. Fedde M.R. 1978. Drugs used f o r avian a n a e s t h e s i a : a review. P o u l t r y Science 57:1376-1399 F e r r a r o A. and S.E. B a r r e r a . 1934. E f f e c t s of experimental l e s i o n s of the p o s t e r i o r columns i n Macacus rhesus monkeys. B r a i n 62:307-332 F i s h e r H.I. 1946. Adaptations and comparative anatomy of the locomotor apparatus of new world v u l t u r e s . Am. M i d i . Nat. 35:545-727. F i s h e r H.I. and D.C. Goodman. 1955. The myology of the whooping crane, Grus americana. 111. B i o l . Monogr. 24:1-127 Freusberg A. 1874 Ref1exbewegungen beim Hund. Pfugers. Arch, ges. P h y s i o l . 9; 358-391. (from Wetzel M.C. and D.G. S t u a r t . 1976. Ensemble c h a r a c t e r i s t i c s of c a t locomotion and i t s neural c o n t r o l . Prog.Neurobiol. 7:1-98.) Freusberg A. and F r . G o l t z . 1874a Ueber gefasserwesternde nerven. P f l u g e r s . Arch. ges. P h y s i o l . 9; 174-197 (from Wetzel M.C. and D.G. S t u a r t . 1976. Ensemble c h a r a c t e r i s t i c s of cat locomotion and i t s neural c o n t r o l . Prog. N e u r o b i o l . 7:1-98. Freusberg A. and F r . G o l t z . 1874b Ueber den e i n f l u s s des nervensystems auf dei vorgange wahrend der schwangershaft ude des gebarackts. P f l u g e r s . Arch. ges. P h y s i o l . 9; 552-565.(from Wetzel M.C. and D.G. S t u a r t . 1976. Ensemble c h a r a c t e r i s t i c s a cat locomotion and i t s neural c o n t r o l . Prog. N e u r o b i o l . 7:1-98. ) F u j i o k a T. 1959. On the o r i g i n s and i n s e r t i o n s of the muscles of the t h o r a c i c limb i n the fo w l . Jap. J . Vet. S c i . 24:183-199 ( i n Japanese): from Vanden Berge J.C. 1979. Myology. InNomina anatomica avium. E d i t e d by J . J . Baumel. Academic Press, London. 197 Gadow H. and E. Selenka. 1891. V o g e l : I . Anatomischer T h e i l . In "Bronn's Klassen und Drdnungen des T h i e r — R e i c h s " , Bd 6(4), C.F. Winter, ( L e i p z i g ) . G a r c i a - R i l l E., R.D. Skinner, M.B. Jackson, and M.M. Smith. 1983a. Connections of the mesencephalic locomotor r e g i o n (MLR) I. s u b s t a n t i a n i g r a a f f e r e n t s . Br. Res. B u l l . , V o l . 10:57-62. G a r c i a - R i l l E., R.D. Skinner, S.A. Gilmore, and R. Owings. 1983b. Connections of the mesencephalic locomotor r e g i o n (MLR) I I . a f f e r e n t s and e f f e r e n t s . Br. Res. B u l l . , V o l . 10:63-71. G a r c i a - R i l l E. 1983c. Connections of the mesencephalic locomotor r e g i o n (MLR) I I I . i n t r a c e l l u l a r r e c o r d i n g s . Br. Res. B u l l . , V o l . 10:73-81. G a r c i a - R i l l E., R.D. Skinner, and J.A. F i t z g e r a l d . 1983d. A c t i v i t y i n the mesencephalic locomotor r e g i o n during locomotion. E x p t l . Neural. 82:609-622. Gillman S. and D. Denny-Brown. 1966. D i s o r d e r s of movement and behaviour f o l l o w i n g d o r s a l column l e s i o n s . B r a i n 89:397-418 George J.C. and A.J. Berger. 1966. Avian myology. Academic Press, New York. Graham-Brown T. 1911. The i n t r i n s i c f a c t o r s i n the act of p r o g r e s s i o n i n the mammal. Royal S o c i e t y of London, Proceedings, B, V o l . 84:308-319. Graham-Brown T. 1914. On the nature of the fundamental a c t i v i t y of the nervous c e n t r e s ; together with an a n a l y s i s of the c o n d i t i o n i n g of rhythmic a c t i v i t y i n p r o g r e s s i o n , and a theory of the e v o l u t i o n of f u n c t i o n i n the nervous system. J . P h y s i o l . 48:1-46 Gray J . and H.M. Lissman. 1946. F u r t h e r o b s e r v a t i o n s on the e f f e c t of d e a f f e r e n t a t i o n on the l a b o r a t o r y a c t i v i t y of amphibian limbs. J . E x p t l . B i o l . 23:121-132 G r i l l n e r S. and S. Lund. 1968. The o r i g i n of a descending pathway with monosynaptic a c t i o n on f l e x o r motoneurons. Acta p h y s i o l . scand. 87:274-284 G r i l l n e r S. 1974. On the g e n e r a t i o n of locomotion i n the s p i n a l d o g f i s h . E x p t l . Br. Res. 20:159-170 G r i l l n e r S. and M.L. Shik. 1973. On the descending c o n t r o l of the lumbosacral s p i n a l cord from the "Mesencephalic Locomotor Region". Acta p h y s i o l . scand. 87:320-333 G r i l l n e r S. 1975. Locomotion i n v e r t e b r a t e s : c e n t r a l mechanisms and r e f l e x i n t e r a c t i o n . P h y s i o l o g i c a l Reviews 198 55:249-304 G r i l l n e r S. and P. Zangger. 1975. On the c e n t r a l generation o-f locomotion i n the low s p i n a l c a t . E x p t l . Br. Res. 20:241-261 G r i l l n e r S. and P. Wallen. 1977. Is t h e r e a p e r i p h e r a l c o n t r o l of the c e n t r a l p a t t e r n generators f o r swimming i n d o g f i s h . Br. Res. 127:291-295. G r i l l n e r S.. A. M c C l e l l a n , and K. S i g v a r d t . 1982. Mechanosensitive neurons i n the s p i n a l cord of the Lamprey. Br. Res. 235:169-173. H a e r t i g E.W. and J.H. liasserman. 1940. Hypothalamic l e s i o n s and pneumonia i n c a t s . With notes on behaviour changes. J . Neurophysiol. 3:293-299. Hinsey J.C., S.W. Ranson, and R.F. McNattin. 1930. The r o l e of the hypothalamus and mesencephalon i n locomotion. Arch. Neurol. P s y c h i a t . 23;1-43 (from Wetzel M.C. and D.G. S t u a r t . 1976. Ensemble c h a r a c t e r i s t i c s of cat locomotion and i t neural c o n t r o l . Prog. N e u r o b i o l . 7:1-98.) Howell A.B. 1938. Muscles of the avian hip and t h i g h . Auk 55:71-81. Hudson G.E. 1937. S t u d i e s on the muscles of the p e l v i c appendage i n b i r d s . Am. M i d i . Nat. 18:1-108. Ingram., W.R. and S.W. Ranson. 1932. E f f e c t s of l e s i o n s i n the red n u c l e i i n c a t s . Arch. Neural. P s y c h i a t . 28:482-513. Jacobson R.D., and M. Hollyday. 1982a. A b e h a v i o r a l and electromyographic study of walking i n the c h i c k . J . Neurophysiol. 48:238-256. Jacobson R.D., and M. Hollyday. 1982b E l e c t r i c a l l y evoked walking and f i c t i v e locomotion i n the c h i c k J . Neurophysiol. 48:257-270. Karten H.J. and W. Hodos. 1967. A s t e r e o t a x i c a t l a s of the b r a i n of the pigeon (Columba 1 i y i a ) . John Hopkins Press. B a l t i m o r e . 193 pages. Kashin S.M., A.G. Feldman, G.N. Orlovsky. 1974. Locomotion of f i s h evoked by e l e c t r i c a l s t i m u l a t i o n of the b r a i n . B r a i n Res. 82." 41-?. Kaupp B.F. 1918. The anatomy of the domestic fowl. W.B. Saunders Co., P h i l a d e l p h i a and London. K i t t C.A. and S.E. Brauth. 1981. P r o j e c t i o n s of the p a l e o s t r i a t u m upon the midbrain tegmentum i n the pigeon. Neuroscience 6, No.8:1551-1556. 199 Kuypers, H.J.G.M. 1964 The descending pathways t o the s p i n a l cord, t h e i r anatomy and f u n c t i o n . In Progress i n B r a i n Research, O r g a n i z a t i o n of the S p i n a l Cord, V o l . I I , J.C. E c c l e s and J.P. Schade (eds.). E l s e v i e r Biomedical Press, Amsterdam, pp. 178-200. Kuypers, H.J.G.M. 1982 A new look at the o r g a n i z a t i o n of the motor system. In Progress i n B r a i n Research, Anatomy of Descending Pathways t o the S p i n a l Cord, Kuypers, H.J.G.M. and Marti n , G.F. (eds.). E l s e v i e r Biomedical Press, Amsterdam, pp 381-403. Kuypers H.J.G.M. and A.M. Huisman. 1982. The new anatomy of the descending b r a i n pathways, i n B r a i n Stem C o n t r o l of S p i n a l Mechanisms. B. Sjo l u n d and A. Bj o r k l u n d (eds.). E l s e v i e r Biomedical Press, pp. 29-54. Lassek A.M. and P.A. Anderson. 1961. Motor f u n c t i o n a f t e r spaced c o n t r a l a t e r a l hemisections i n the s p i n a l c o r d . Neurology 11:362-365 Laughton N.B. 1924. S t u d i e s on the nervous r e g u l a t i o n of pr o g r e s s i o n i n mammals. Am. J . P h y s i o l . 70:358-384. Lawrence D.G. and H.G.J.M. Kuypers. 1968a. The f u n c t i o n a l o r g a n i z a t i o n of the motor cortex i n monkey I. The e f f e c t s of b i l a t e r a l pyramidal l e s i o n s . B r a i n 91:1-14. Lawrence D.G. and H.G.J.M. Kuypers. 1968b. The f u n c t i o n a l o r g a n i z a t i o n of the motor cortex i n monkey I I . The e f f e c t s of l e s i o n s of the descending brainstem pathways. B r a i n 91:15-36. Marsden CD., P. A. Merton, and H.B. Morton. 1981. Maximal tw i t c h e s from s t i m u l a t i o n of the motor cortex i n man. J . Physiol.(Lond.) 312:5P. Marshall C D . 1895. On the changes i n movement and s e n s a t i o n produced by h e i s e c t i o n of the s p i n a l cord i n the c a t . Proc. R. Soc. 57:475-476. M c C l e l l a n A.D. 1984 Descending c o n t r o l and sensory g a t i n g of ' f i c t i v e * swimming and t u r n i n g responses e l i c i t e d i n an i n v i t r o p r e p a r a t i o n of the lamprey b r a i n s t e m / s p i n a l cord. B r a i n Research 302:151-162. Mori S., M.L. Shik, and A.S. Yagodnitsyn. 1977. Role of pontine tegmentum f o r locomotor c o n t r o l i n mesencephalic c a t . J . Neurophysiol. 40:284-295. Mori S., H. Nishimura, C Kurakami, T. Yamamura, and M. Aoki. 1978. C o n t r o l l e d locomotion i n the mesencephalic c a t : d i s t r i b u t i o n of f a c i l i t a t o r y and i n h i b i t o r y r e g i o n s w i t h i n pontine tegmentum. J . Neur o p h y s i o l . 41:1580-1591 200 Neafsey E.J., C D . H u l l , and N.A. Buchwald. 1978. P r e p a r a t i o n f o r movement i n the cat I I I . Unit a c t i v i t y i n the basal g a n g l i a . E l e c t r o e n c e p h . C l i n . N e u r o p hysiol. 44:706-713 N i c k e l R., A. Schummer, and E. S e i f e r l e . 1977. Anatomy of the domestic b i r d s , ( t r a n s l a t i o n by W.G. S i l l e r and P.A.L. Wight). V e r l a g Paul Parey, B e r l i n and Hamburg. Orlovsky G.N. 1969 Spontaneous and induced locomotion i n the thalamic c a t . B i o p h y s i c s 14:1154-1162 ( E n g l i s h t r a n s l a t i o n of B i o f i z i c a 14:1095-1102.) 1970a. Connexions of the r e t i c u l o - s p i n a l neurones with the "locomotor s e c t i o n s " of the b r a i n stem. B i o f i z i k a 15, No.1:171-177. 1970b. Work of the r e t i c u l o - s p i n a l neurones during locomotion. B i o f i z i k a 15, No. 4:728-737. 1972a. The e f f e c t of d i f f e r e n t descending systems on f l e x o r and extensor a c t i v i t y during locomotion. Br. Res. 40:359-371. 1972b. A c t i v i t y of v e s t i b u l o s p i n a l neurons during locomotion. B r a i n Res. 46:85-98. 1972c. A c t i v i t y of r u b r o s p i n a l neurons during locomotion. B r a i n Res. 46:99-112. Orlovsky G.N. and l i . L . Shik. 1976. C o n t r o l of locomotion: a n e u r o p h y s i o l o g i c a l a n a l y s i s of the c a t locomotor system. In I n t e r n a t i o n a l Review of Physiology, Neurophysiology I I , V o l . 10, P o r t e r , E. (ed.), U n i v e r s i t y Park Press, B a l t i m o r e . pp. 281-317. P h i l l i p p s o n l i . 1905 L'anatomie et l a c e n t r a l i z a t i o n dans l e system nerveux des animaux. Trav. Lab. P h y s i o l . Inst. Solvay, B r u x e l l e s 7:1-208. Reiner A., N.C. Brecha, H.J. Karten. 1982. Basal g a n g l i a pathways t o the tectum: the a f f e r e n t and e f f e r e n t connections of the l a t e r a l s p i r i f o r m nucleus of pigeon. J . Comp. Neurol. 208:16-36. Reiner A. and H.J. Karten. 1982. Laminar d i s t r i b u t i o n of the c e l l s of o r i g i n of the descending t e c t o f u g a l pathways i n the pigeon (Columba l.ivia) . J . Comp. Neurol. 204:165-187. Romer A.S. 1927. The development of the t h i g h musculature of the c h i c k . J . l i o r p h o l . P h y s i o l . 43:347-385. Schwartzman R.J., E. E i d e l b e r g , G.li. Alexander, and J . Yu. 1983. Regional metabolic changes i n the s p i n a l cord r e l a t e d t o s p i n a l shock and l a t e r hyperref1 e x i a i n monkeys. Annals of Neurology 14, No.1:33-37. 201 Shefchyk, S.J., R.M. J e l l , and L.M. Jordan. 1984. R e v e r s i b l e c o o l i n g of the brainstem r e v e a l s areas r e q u i r e d f o r mesencephalic locomotor r e g i o n evoked t r e a d m i l l locomotion. Exp. Br. Res. ( i n p r e s s ) . S h e r r i n g t o n L.S. 1910. F l e x i o n - R e f l e x of the limb c r o s s e d e x t e n s i o n r e f l e x , and r e f l e x s t e p p i n g and s t a n d i n g . J . P h y s i o l . 40;28-121. Shik l i . L . , F.V. S e v e r i n , and G.N. Orlovsky. 1966. C o n t r o l of walking and running by means of e l e c t r i c a l s t i m u l a t i o n of the midbrain. B i o f i z i c a 11:756-765. Shik M.L., G.N. Orlovsky, and F.V. S e v e r i n . 1968 Locomotion of the mesencephalic cat e l i c i t e d by s t i m u l a t i o n of the Pyramids. B i o p h y s i c s 13:143-152. Shik M.L. and G.N. Orlovsky. 1976. Neurophysiology of locomotor automatism. P h y s i o l o g i c a l Reviews, V o l . 56, No.3:465-501 Shik M.L. and A.S. Yagodnitsyn. 1977. The pontobulbar "locomotor s t r i p " . Neurophysiology 9:95-97. Sh u f e l d t R.W. 1890. The myology of the raven (Cgryus cgrgx si,nuatus) . Maxmillan, London. S i r o t a M.6. and M.L. Shik. 1973. The c a t locomotion e l i c i t e d through the e l e c t r o d e implanted i n the midbrain. Sechenov. P h y s i o l . J . USSR 59:1314-1321 ( i n Russian) ( c . f . Shik M.L. and G.N. Orlovsky. 1976. Neurophysiology of locomotor automatism. P h y s i o l o g i c a l Reviews, V o l . 5, No. 3:465-501). Steeves J.D. and L.M. Jordan. 1980a. L o c a l i z a t i o n of a descending pathway i n the s p i n a l cord which i s necessary f o r c o n t r o l l e d t r e a d m i l l locomotion. N e u r o s c i . L e t t . 20:283-288. Steeves J.D., B.J. Schmidt, B.J. Skovgaard, and L.M. Jordan. 1980b. E f f e c t of n o r a d r e n a l i n e and 5-Hydroxytryptamine d e p l e t i o n on locomotion i n the c a t . Br. Res.185:349-362. Steeves J.D. and L.M. Jordan. 1984. A u t o r a d i o g r a p h i c demonstration of the p r o j e c t i o n s from the Mesencephalic Locomotor Region. Br. Res. 307:263-276. S t e l z n e r D.J., W.B. E i c h l e r , and E.D. Weber. 1975. E f f e c t s of s p i n a l t r a n s e c t i o n i n neonatal and weanling r a t s : s u r v i v a l of f u n c t i o n . Exp. Neurol. 46:156-177. S u l l i v a n G.E. 1962. Anatomy and embryology of the wing musculature of the domestic fowl (Gal^lus). A u s t r a l . J . Zool . 10:458-518. Tarchanoff J . 1895. Movement f o r c e s des canards d e c a p i t e s . 202 Compt. Rend. Soc. B i o l . 47:454. Ten Cate J . 1960. Locomotor movements i n the s p i n a l pigeon. J . E x p t l . B i o l . 37:609-613. 1962. Innervation o-f locomotor movements by the lumbosacral cord i n b i r d s and mammals. J . E x p t l . B i o l . 39:239-1965. Automatic a c t i v i t y o-f the locomotor c e n t r e s of the lumbar cord i n l i z a r d s . J . E x p t l . B i o l . 43:181-184. Truex R.C. and M.B. Carpenter. 1969. Human Anatomy. W i l k i n s and W i l k i n s , B a l t i m o r e Vanden Berge J.C. 1975. Aves myology. In"Sisson and Grossman's" The anatomy of the domestic animals, V o l . 2, E d i t e d by R. Getty. 5th e d i t i o n , Saunders, Phi 1 i d e l phi a, pp.175-219. 1979. l i y o l o g i a . In Nomina anatomica avium. E d i t e d by J . J . Baumel. Academic Press, London, pp.175-219. Waller W.H. 1940. P r o g r e s s i o n movement e l i c i t e d by subthalamic s t i m u l a t i o n . J . Neurophysiol. 3:300-307. Weinstein G.N., C. Anderson, and J.D. Steeves. 1984. F u n c t i o n a l c h a r a c t e r i z a t i o n of limb muscles i n v o l v e d i n locomotion i n the Canada goose, Branta canadensis. Can. J . Zool. 62:1596-1604 Weiss N. 1879. Untersuchungen uber d i e 1eitungsbahen im ruckenmarke des hindes. Sher. Konig. Akad. Wiss. Wien 80:34-56 i n E i d e l b e r g E. 1981. Consequences of s p i n a l cord l e s i o n s upon motor f u n c t i o n , with s p e c i a l r e f e r e n c e t o locomotor a c t i v i t y . Prog. N e u r o b i o l . 17:185-202. Wetzel M.C. and D.G. S t u a r t . 1976. Ensemble c h a r a c t e r i s t i c s of cat locomotion and i t s neural c o n t r o l . Progress i n Neurobiology 7:1-98. Wilcox H.H. 1952. The p e l v i c musculature of the loon, Gayi^a immer. Am. M i d i . Nat. 48:513-573. W i l l i a m s B.J., C.A. L i v i n g s t o n , and R.B. Leonard. 1984. S p i n a l cord pathways i n v o l v e d i n i n i t i a t i o n of swimming i n the s t i n g r a y , D a s y a t i s sabina: S p i n a l cord s t i m u l a t i o n and l e s i o n s . J . N europhysiol. 51, No. 3:578-591. Yu J . and E. E i d e l b e r g . 1981 E f f e c t s of v e s t i b u l o s p i n a l neurons upon locomotor f u n c t i o n i n c a t s . Br. Res. 220:179-183. Zweers G.A. 1971. A s t e r e o t a x i c a t l a s of the brainstem of the M a l l a r d (Anas e l a t y r h y n c h g s L-.) • Van Gorcum and Co., N.V. Assen. The Netherlands, pp. 1-148. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0096213/manifest

Comment

Related Items