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Event-related brain potentials recorded during performance of a perceptual-motor task Jutai, Jeffrey William 1983

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EVENT-RELATED BRAIN POTENTIALS RECORDED DURING PERFORMANCE OF A PERCEPTUAL-MOTOR TASK by JEFFREY WILLIAM JUTAI B . S c , The U n i v e r s i t y o f T o r o n t o , 1 9 7 8 M.A., The U n i v e r s i t y o f B r i t i s h Columbia, 1 9 8 0 A THESIS SUBMITTED^IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (Department o f P s y c h o l o g y ) We a c c e p t t h i s t h e s i s as conforming to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA November 1 9 8 3 (c) J e f f r e y W i l l i a m J u t a i , 1 9 8 3 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 s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for s c h o l a r l y purposes may be granted by the head of my, department or by his or her representatives. I t i s understood that copying or pu b l i c a t i o n 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 Psychology The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date Dec. 5, 1983 - i i -S u p e r v i s o r : Dr. Robert D. Hare ABSTRACT T h i s t h e s i s examined the e v e n t - r e l a t e d b r a i n p o t e n t i a l s r e c o r d e d w h i l e s u b j e c t s p e r f o r m a c o n t i n u o u s involvement p e r c e p t u a l - m o t o r t a s k . I t was found t h a t p o t e n t i a l s a s s o c i a t e d w i t h p s y c h o l o g i c a l p r o c e s s e s o f a n t i c i p a t i o n and s e l e c t i v e a t t e n t i o n c o u l d be r e l i a b l y measured. A p o s t - s t i m u l u s n e g a t i v e s h i f t o b s e rved i n response t o a t t e n d e d s t i m u l i was found to be composed o f two types o f e l e c t r o c o r t i c a l a c t i v i t y . The f i r s t and e a r l i e s t to appear was s e n s i t i v e to the d i f f e r e n c e between channels ( i . e . e a r s ) c a r r y i n g r e l e v a n t and i r r e l e v a n t a u d i t o r y i n f o r m a t i o n . The second was s e n s i t i v e to the d i r e c t i o n i n which s u b j e c t s o r i e n t e d t h e i r a t t e n t i o n d u r i n g the t a s k . Between 200 msec and 300 msec a f t e r s t i m u l u s o n s e t , these two a c t i v i t i e s or p r o c e s s e s i n t e r a c t e d such t h a t the e l e c t r o c o r t i c a l e f f e c t o f s e l e c t i v e a t t e n t i o n became l a r g e s t i n the c e r e b r a l hemisphere c o n t r a l a t e r a l to the d i r e c t i o n o f o r i e n t a t i o n . P r e d i c t e d r e l a t i o n s h i p s between b r a i n p o t e n t i a l s and t a s k performance on a t r i a l - t o - t r i a l b a s i s were not found. The r e s u l t s are d i s c u s s e d i n terms o f the c u r r e n t u n d e r s t a n d i n g o f the e l e c t r o p h y s i o l o g y o f human a t t e n t i o n . - I l l -TABLE OF CONTENTS Abstact 1 1 . L i s t of Tables v i . L i s t of Figures V i i . . Acknowledgements x i . I. I n t r o d u c t i o n 1. I I . Experiment 1: Q u a l i t a t i v e d e s c r i p t i o n of ERPs 9. A. Method 9. 1. Subjects 9. 2. Apparatus 10. 3. Procedure 15. 4. Data q u a n t i f i c a t i o n and a n a l y s i s 16. B. Results 18. 1. Eve n t - r e l a t e d p o t e n t i a l s 18. 2. P h y s i o l o g i c a l a r t i f a c t r e j e c t i o n 26. 3. Eve n t - r e l a t e d EMG 28. 4. I n t e r s u b j e c t v a r i a b i l i t y i n ERPs 34. 5. Behavioural data 37. C. D i s c u s s i o n v 37. 1. A n t i c i p a t o r y ERPs 37. 2. ERPs and s e l e c t i v e a t t e n t i o n 40. - i v -3. ERPs and focused a t t e n t i o n 41. 4. I m p l i c a t i o n s f or f u r t h e r study 41. I I I . Experiment 2: Examination of v i s u a l ERP a c t i v i t y 44. A. Method 44. 1. Subjects 44. 2. Apparatus 45. 3. Procedure 45. 4. Data q u a n t i f i c a t i o n and a n a l y s i s 45. B. Results 46. C. D i s c u s s i o n 49. IV. Experiment 3: Q u a n t i t a t i v e a n a l y s i s of ERPs 51. A. Method 55. 1. Subjects 55. 2. Apparatus 55. 3. Procedure. 55. 4. Data q u a n t i f i c a t i o n and a n a l y s i s 56. B. Results 57. 1. Video game performance 58. 2. ERPs as s o c i t e d w i t h racquet h i t s t i m u l i on re l e v a n t channel 60. 3. ERPs associated w i t h racquet h i t s t i m u l i on i r r e l e v a n t channel 69. 4. ERPs associated w i t h w a l l bounce s t i m u l i .. 76. 5. R e j e c t i o n of p h y s i o l o g i c a l a r t i f a c t 88. - v -C. D i s c u s s i o n 89. V. B r i e f summary of main f i n d i n g s 4. References 6. - VI -LIST OF TABLES Table 1. Mean amplitude and latency of ERP components assoc-i a t e d with 1000 Hz 'racquet h i t ' tone on rel e v a n t ( l i v e audio) channel for groups N and R 65 Table 2. Between-subject Pearson c o r r e l a t i o n s between prestimulus ERP component amplitudes and between pre- and poststimulus amplitudes 68 Table 3. Mean latency of ERP components associated with 'racquet h i t ' tone on rel e v a n t channel, recorded over l e f t (C^) and r i g h t (C^) hemisphere scalp l o c a t i o n s (averaged across groups and t r i a l s ) ^ Table 4. Mean amplitude and latency of ERP components assoc-i a t e d w i t h 1000 Hz 'racquet h i t 1 tone on i r r e l e v a n t (pre-recorded audio) channel f o r Groups N and R .... 74 Table 5. Mean late n c y of ERP components associated with "racquet h i t ' tone on i r r e l e v a n t channel f o r Groups N and R, and for recording s i t e s and 75 Table 6. Mean amplitude and latency of ERP components assoc-i a t e d with 500 Hz 'wall bounce' tone on rel e v a n t ( l i v e audio) and i r r e l e v a n t (pre-recorded audio) channels f o r Groups N and R 81 Table 7. Mean N l , P2 and N2 amplitudes to 500 Hz 'wall bounce tone i n r e l e v a n t (R) and i r r e l e v a n t ( I ) channels .... 8-2 - VL1 " LIST OF FIGURES Figure 1. General layout of the video game task 11 Figure 2. Group averaged prestimulus ERPs associated with 1000 Hz 'racquet h i t ' tone on re l e v a n t channel for t r i a l s 1-10 19 Figure 3. Group averaged poststimulus ERPs associated w i t h 1000 Hz 'racquet h i t ' tone on re l e v a n t channel f o r t r i a l s 1-10 20 Figure 4. Group averaged ERPs to 1000 Hz 'racquet h i t ' tone on i r r e l e v a n t channel f o r t r i a l s 1-10 22 Figure 5. Group averaged ERPs to 500 Hz 'wall bounce' tone on re l e v a n t ( l i v e audio) and i r r e l e v a n t (pre-recorded audio) channels f o r scalp s i t e . C ^ 24 Figure 6. Group averaged ERPs to 500 Hz 'wall bounce' tone on r e l e v a n t and i r r e l e v a n t channels for scalp s i t e Figure 7. Group averaged ERPs recorded during c o n t r o l c o n d i t i o n 27 Figure 8. Group averaged EOG associated with 1000 Hz tone on re l e v a n t channel f o r t r i a l s 1-10 29 Figure 9. Group averaged EOG associated with 1000 Hz tone on i r r e l e v a n t channel f o r t r i a l s 1-10 30 - V l l l -Figure 10. Group. •_. averaged EOG associated with 500 Hz tone on rel e v a n t channel f or t r i a l s 1-10 31 Figure 11. Group averaged EOG associated with 500 Hz tone on i r r e l e v a n t channel f o r t r i a l s 1-10 32 Figure 12. Group averaged EOG recorded during c o n t r o l c o n d i t i o n 33 Figure 13. Group averaged EMG associated with 1000 Hz tone on re l e v a n t channel f o r t r i a l s 1-10 35 Figure 14. E l e c t r o p h y s i o l o g i c a l waveforms f o r Subject 7 during t r i a l 1 36 Figure 15. Group averaged game performance across t r i a l s 1-10 38 Figure 16. Group averaged ERPs associated w i t h racquet h i t for t r i a l 1 47 Figure 17. Group averaged ERPs to w a l l bounce f o r t r i a l 1 ... 48 Figure 18. ERP waveforms f o r Subject 2 on t r i a l 1 50 Figure 19. Mean performance scores (number of misses) f o r subjects i n normal (N) and reversed (R) o r i e n t -a t i o n groups while p l a y i n g video games 59 Figure 20. Averaged prestimulus ERPs associated w i t h 1000 Hz 'racquet h i t ' tone on re l e v a n t ( l i v e audio) channel f o r Groups N and R on t r i a l 1 61 - IX -Figure 21. Averaged poststimulus ERPs associated with 'racquet h i t ' tone on relevant channel f o r Groups N and R on t r i a l 1 62. Figure 22. Averaged prestimulus ERPs associated with 1000 Hz tone on relevant channel f o r Subjects N3 and R6 on t r i a l 1 63. Figure 23. Averaged poststimulus ERPs associated w i t h 1000 Hz tone on re l e v a n t channel f o r Subjects N3 and R6 on t r i a l 1 64. Figure 24. Mean API, AP2 and P2 amplitudes to 1000 Hz 'racquet h i t ' tone as a f u n c t i o n of Groups (N and R) and recording s i t e (C^ and C^) 67. Figure 25. Averaged ERPs associated with 1000 Hz 'racquet h i t ' tone on i r r e l e v a n t (pre-recorded audio) channel for Groups N and R on t r i a l 1 71. Figure 26. Averaged ERPs associated w i t h 1000 Hz tone on i r r e l e v a n t channel f o r Subjects N3 and R6 on t r i a l 1 72. Figure 27. Averaged ERPs as s o c i a t e d w i t h 500 Hz 'wall bounce' tone on r e l e v a n t ( l i v e audio) channels for Groups N and R on t r i a l 1 77. Figure 28. Averaged EOG waveforms associated with 500 Hz tone on r e l e v a n t and i r r e l e v a n t channels for Groups N and R on t r i a l 1 78. - x -F i g u r e 29. Averaged ERPs a s s o c i a t e d w i t h 500 Hz tone on r e l e v a n t and i r r e l e v a n t channels f o r S u b j e c t s N3 and R6 on t r i a l 1 ;• 79. F i g u r e 30. Averaged EOG waveforms a s s o c i a t e d w i t h 500 Hz tone on r e l e v a n t and i r r e l e v a n t channels f o r S u b j e c t s N3 and R6 on t r i a l 1 80. F i g u r e 31. Mean Nl and N2 amplitudes t o 500 Hz ' w a l l bounce 1 tone f o r r e c o r d i n g s i t e s C^ and C^ 84. F i g u r e 32. Mean PI and N2 amplitudes to 500 Hz ' w a l l bounce' tone i n r e l e v a n t and i r r e l e v a n t a u d i t o r y c h annels f o r r e c o r d i n g s i t e s C„ and C. 85. 3 4 F i g u r e 33. Mean N2 amplitude to 500 Hz ' w a l l bounce' tone as a f u n c t i o n o f Group (N and R), Hemisphere (C^ and C^) and Channel ( r e l e v a n t and i r r e l e v a n t ) 87. - x i -ACKNOWLEDGEMENTS I would l i k e to thank my t h e s i s committee members, Dr. A.R. Hakstian, Dr. W. Iacono and Dr. A. Treisman f o r t h e i r guidance and ass i s t a n c e i n r a t h e r t r y i n g circumstances. I am g r a t e f u l f o r the help of John Lind i n the pre p a r a t i o n of computer programs, of Ad e l l e Forth who a s s i s t e d i n the s e l e c t i o n and t e s t i n g of su b j e c t s , and of Dr. J.F. Connolly who commented on an e a r l i e r v e r s i o n of t h i s t h e s i s . To my su p e r v i s o r , Dr. Robert D. Hare, I owe the i n s p i r a t i o n f o r t h i s research. I cannot thank him enough f o r the personal warmth and generosity which has c h a r a c t e r i z e d our c o l l a b o r a t i o n on t h i s and on other p r o j e c t s over the past few years. - 1 -I. I n t r o d u c t i o n T h i s t h e s i s p r o v i d e s a q u a l i t a t i v e and q u a n t i t a t i v e d e s c r i p t i o n of the e l e c t r o c o r t i c a l phenomena a s s o c i a t e d w i t h performance of a p e r c e p t u a l -motor t a s k . The t a s k d i f f e r s from most o t h e r s which have been used to study these phenomena i n t h a t i t c o n t i n u o u s l y engages the i n t e r e s t of the s u b j e c t and p r o v i d e s him w i t h a r e a l i s t i c i n f o r m a t i o n l o a d . ( S a b a t , 1978). The e l e c t r o c o r t i c a l events r e c o r d e d i n t h i s r e s e a r c h are known as e v e n t -r e l a t e d p o t e n t i a l s (ERPs) and are c l o s e l y a s s o c i a t e d w i t h p s y c h o l o g i c a l p r o c e s s e s of a n t i c i p a t i o n and s e l e c t i v e a t t e n t i o n . The aims o f t h i s p r o j e c t were t w o f o l d . The f i r s t was to demonstrate t h a t ERPs c o u l d be r e l i a b l y r e c o r d e d i n a perceptual-motor' t a s k , and t h a t these ERPs compare f a v o u r a b l y w i t h those which have been observed i n the more a u s t e r e p a r a -digms of p r e v i o u s i n v e s t i g a t i o n s of a n t i c i p a t i o n and a t t e n t i o n . The second was to suggest a f u n c t i o n a l i n t e r d e p e n d e n c e between a n t i c i p a t o r y and a t t e n t i o n a l e l e c t r o c o r t i c a l systems. T r a d i t i o n a l l y i n ERP s t u d i e s , the b a s i c d i s t i n c t i o n between a n t i c i p a t i o n and s e l e c t i v e a t t e n t i o n i s t h a t between e l e t r o c o r t i c a l a c t i v i t y measured p r i o r to and consequent to a g i v e n event. Slow n e g a t i v e s h i f t s i n the ERP are u s u a l l y c o n s i d e r e d " a n t i c i p a t o r y " i f they are a s s o c i a t e d w i t h p r e p a r a t o r y p r o c e s s e s . These p r o c e s s e s may be s t i m u l u s - o r i e n t e d and p r e p a r a t o r y to i n f o r m a t i o n p r o c e s s -i n g , o r e l s e r e s p o n s e - o r i e n t e d and p r e p a r a t o r y to e f f e c t i v e motor r e s p o n d i n g ( R o c k s t r o h , E l b e r t , Birbaumer and L u t z e n b e r g e r , 1982). P o s t s t i m u l u s n e g a t i v e e l e t r o c o r t i c a l a c t i v i t y , f i r s t o b s e rved i n the ERP waveform -at around 100 msec, has been r e l a t e d to s e l e c t i v e a t t e n t i o n . The word " s e l e c t i v e " i s meant to imply t h a t s t i m u l i d e s i g n a t e d as b e i n g r e l e v a n t - 2 -are p r o c e s s e d more e f f e c t i v e l y than i r r e l e v a n t s t i m u l i , and i n the ERP one observes g r e a t e r n e g a t i v i t y i n response t o a t t e n d e d , r e l e v a n t s t i m u l i ( H i l l y a r d , 1982). More s p e c i f i c i n f o r m a t i o n about e l e c t r o c o r t i c a l n e g a t i v i t i e s w i l l be p r o v i d e d i n the f o l l o w i n g i n t r o d u c t i o n to ERP t e r m i n o l o g y . ERPs can be r e c o r d e d from many l o c a t i o n s on the s c a l p s u r f a c e . They are u s u a l l y q u a n t i f i e d by t a k i n g the averaged response t o many i d e n t i c a l s t i m u l i and then measuring the d i f f e r e n c e i n amplitude ( i n m i c r o v o l t s ) between each p o s t - s t i m u l u s peak or t r o u g h and the average l e v e l o f p r e s t i m u l u s a c t i v i t y . T h i s b a s e l i n e - t o - p e a k method i s p r e f e r r e d over t r o u g h - t o - p e a k or p e a k - t o - t r o u g h t e c h n i q u e s which measure amplitude d i f f e r e n c e s between a d j a c e n t ERP components. The main rea s o n f o r the p r e f e r e n c e i s the s u b s t a n t i a l body o f e v i d e n c e showing the independence of s u c c e s s i v e components i n terms o f s e n s i t i v i t y to e x p e r i m e n t a l m a n i p u l a t i o n and g e n e r a t o r source (Desmedt and Debecker, 1979; K n i g h t , H i l l y a r d , Woods and N e v i l l e , 1980; T u e t i n g and S u t t o n , 1973; W i l k i n s o n , M o r l o c k and W i l l i a m s , 1966). ERPs a r e c l a s s i f i e d a c c o r d i n g t o whether they are s t r i c t l y evoked by the p h y s i c a l p r o p e r t i e s o f s t i m u l i ( r e f e r r e d t o as "exogenous" ERPs), e m i t t e d i n c o n j u n c t i o n w i t h some i n t e r n a l c o g n i t i v e p r o c e s s ( r e f e r r e d t o as ' e n d o g e n o u s " E R P s ) , - 3 -or c o n s t i t u t e a compromise between these two s i t u a t i o n s ( H i l l y a r d and P i c t o n , 1979). An abrupt a c o u s t i c stimulus w i l l evoke an ERP over the c e n t r a l s c a l p region w i t h a negative peak at about 100 msec poststimulus. This peak, c a l l e d Nl or , , i s an example of a compromise or "mesogenous" ERP component. _ I t s amplitude i s not only r e l a t e d to stimulus p r o p e r t i e s such as p i t c h or i n t e n s i t y ( P i c t o n , H i l l y a r d , Krausz and Galambos, 1974), but also to the amount of a t t e n t i o n paid to the stimulus or to a l l events i n the channel (e.g., the ear) c a r r y i n g the stimulus ( H i l l y a r d and P i c t o n , 1979; Hink, H i l l y a r d and Benson, 1978; Parasuraman, 1978; Schwent and H i l l y a r d , 1975). S e l e c t i v e a t t e n t i o n experiments i n which the subject i s required to attend to s t i m u l i i n one channel, say the r i g h t ear, and to ignore s t i m u l i i n the other ear u s u a l l y show a l a r g e r Nl response to information i n the attended channel. This e f f e c t i s more pronounced under c o n d i t i o n s of high information load, and has been shown to be independent of n o n s p e c i f i c f a c t o r s such as f l u c t u a t i o n s i n general arousal ( H i l l y a r d and P i c t o n , 1979). I t was o r i g i n a l l y proposed that Nl was an e l e c t r o c o r t i c a l index of Broadbent 1s (1970) "stimulus s e t " , that i s , channel s e l e c t i o n based upon a n a l y s i s of simple stimulus a t t r i b u t e s ( H i l l y a r d and P i c t o n , 1979). More recent research suggests that the e f f e c t of s e l e c t i v e a t t e n t i o n on Nl i s not simply an increase i n the amplitude of the exogenous component, but r a t h e r a modulation of the e n t i r e ERP by the superimposition on i t of an endogenous slow negative s h i f t (Hansen and H i l l y a r d , 1980; O k i t a , 1981, Parasuraman, 1980; see NSatanen, 1982, for a thorough review). This work questions the i n t e r p r e t a t i o n of Nl - 4 -as r e f l e c t i n g some simple e a r l y f i l t e r or gating mechanism i n s e l e c t -i v e a t t e n t i o n . A n e a r o a n a t o m i c a l d i s s o c i a t i o n between Nl and endogenous n e g a t i v i t y was r e p o r t e d by K n i g h t , H i l l y a r d , Woods and N e v i l l e (1981) who showed t h a t l e s i o n s o f f r o n t a l c o r t e x a t t e n u a t e d the a t t e n t i o n - r e l a t e d n e g a t i v e s h i f t w i t h o u t a l t e r i n g Nl a m p l i t u d e . Two o t h e r important endogenous ERPs are the contringrentt n e g a t i v e v a r i a t i o n (CNV) and the r e a d i n e s s p o t e n t i a l (RP). Both are n e g a t i v e p o t e n t i a l s which are e m i t t e d i n a n t i c i p a t i o n o f a s e n s o r y and/or motor ev e n t . The CNV, sometimes c a l l e d the expectancy wave (E wave), i s a l a r g e slow p o t e n t i a l change o c c u r r i n g i n the i n t e r v a l between a warning s t i m u l u s and an i m p e r a t i v e s t i m u l u s to which a response i s r e q u i r e d ( W a l t e r , Cooper, A l d r i d g e , McCallum and W i n t e r , 1964), a l t h o u g h the s t r i c t p a i r i n g o f s t i m u l i i s not always n e c e s s a r y f o r i t s p r o d u c t i o n (McCallum, 1980). The RP, or B e r e i t s c h a f t s p o t e n t i a l (BP), i s a s m a l l e r p o t e n t i a l which b u i l d s j u s t p r i o r t o the i n i t i a t i o n o f v o l u n t a r y limb movement (Deecke and Kornhuber, 1977). The CNV i s u s u a l l y l a r g e r over f r o n t a l than over c e n t r a l s c a l p r e g i o n s and i s b i l a t e r a l l y s y m m e t r i c a l , w h i l e the RP i s more prominent c e n t r a l l y and i s a s y m m e t r i c a l l y d i s t r i b u t e d , b e i n g l a r g e r over the hemisphere c o n t r a -l a t e r a l to the r e s p o n d i n g limb (Becker, Iwase, Jurgens and Kornhuber, 1976; Deecke, Becker, G r o z i n g e r , S c h e i d and Kornhuber, 1973; G e r b r a n d t , 1978; H i l l y a r d , 1973; Hink, K o h l e r , Deecke and Kornhuber, 1982). CNV amplitude i s enhanced by a c t i v e a t t e n t i o n to s t i m u l i - 5 -( P i c t o n , H i l l y a r d , Galambos and S c h i f f , 1971) and reduced by d i s t r a c t i o n d u r i n g the i n t e r v a l between warning and i m p e r a t i v e s t i m u l i ( H i l l y a r d , 1973; Tecce and H a m i l t o n , 1973). L a r g e r a m p l i t u d e s and slower r a t e s o f h a b i t u a t i o n are a s s o c i a t e d w i t h good performance and h i g h e r l e v e l s o f t a s k m o t i v a t i o n (McCallum, 1976; W a l t e r , 1965; W a l t e r et a l . , 1964). / RP amplitude i s g e n e r a l l y h i g h e r p r i o r to slow movements than to r a p i d movements (Becker et a l . , 1976), and i n c r e a s e s w i t h muscular e f f o r t ( B r u n i a and V i n g e r h o e t s , 1981). There seems to be a g e n e r a l agreement t h a t at l e a s t one component of the RP r e f l e c t s the s u b j e c t ' s i n t e n t i o n to a c t (Hink et a l . , 1982; Deecke, 1978; L i b e t , Wright and G l e a s o n , 1982), w h i l e another i s s e n s i t i v e to the demands made on the s u b j e c t ' s a t t e n t i o n (Deecke and Kornhumber, 1977; Grunewald-Z u b e r b i e r , Grunewald, Runge, Netz and Homberg, 1981). T r a d i t i o n a l d i s t i n c t i o n s between the CNV and the RP have been b l u r r e d somewhat i n r e c e n t y e a r s by r e s e a r c h which has i s o l a t e d CNV compon-ents d e s c r i b e d as " e a r l y " o r ' l a t e " , depending on when they r e a c h peak amplitude ( G a i l l a r d and NHHtMnen, 1976; Tecce, 1971). The e a r l y CNV seems to be e s p e c i a l l y s e n s i t i v e to a r o u s a l and a t t e n t i o n , w h i l e the l a t e CNV i s g e n e r a l l y i n d i s t i n g u i s h a b l e from the RP ( G a i l l a r d , 1980; Rohrbaugh, Syndulko and L x n d s l e y , 1976). The RP too has been found - 6 -to have a b i l a t e r a l C N V - like component as w e l l as a l a t e r a l i z e d n e g a t i v e s h i f t more c l o s e l y r e l a t e d to response i n i t i a t i o n (Grunewald-Z u b e r b i e r et a l . , 1981; Kutas and Donchin, 1977). T h i s s u p p o r t s the n o t i o n t h a t the CNV and the RP are both members o f the same f a m i l y o f endogenous n e g a t i v e waves (Kutas and Donchin, 1977), and t h a t they l i k e l y o v e r l a p i n t a s k s i t u a t i o n s i n v o l v i n g s h o r t i n t e r - s t i m u l u s i n t e r n a l s (Rohrbaugh e t a l . , 1976). In t h i s t h e s i s the f a m i l y of p r e s t i m u l u s n e g a t i v e s h i f t s w i l l be r e f e r r e d t o by the g e n e r a l l a b e l , a n t i c i p a t o r y p o t e n t i a l s ( A P s ) . In most e l e c t o r c o r t i c a l i n v e s t i g a t i o n s of s e l e c t i v e a t t e n t i o n the amplitude of the p o s t s t i u m l u s Nl component has been the dependent measure. A l t h o u g h i t was suggested some time ago t h a t APs and the N l might be " s i g n s of the same f u n c t i o n a l system, one r e p r e s e n t i n g a more t o n i c , the o t h e r a more p h a s i c a c t i v i t y " ( j M r v i l e h t o and F r u h s t o r f e r , 1970, p 315), v e r y l i t t l e i s known about the r e l a t i o n s h i p of APs to s e l e c t i v e i n f o r m a t i o n p r o c e s s i n g (Hansen and H i l l y a r d , 1980; H i l l y a r d and P i c t o n , 1979). In r e c o g n i t i o n o f the f a c t t h a t s e l e c t i v e a t t e n t i o n need not be u n i q u e l y indexed by any s i n g l e p h y s i o l o g i c a l v a r i a b l e ( H i l l y a r d , 1973), t h e r e i s a need to study b o t h p r e s t i m u l u s and post s t i m u l u s ERPs i n a g i v e n e x p e r i m e n t a l c o n t e x t . The problem i s n i c e l y i l l u s t r a t e d by r e f e r e n c e to an example of r e s e a r c h i n which the d u a l - v a r i a b l e approach might have been h e l p f u l . - 7 -J u t a i and Hare (1983) s t u d i e d ERPs and s e l e c t i v e a t t e n t i o n i n groups of p s y c h o p a t h i c and non p s y c h o p a t h i c p r i s o n inmates. B i n a u r a l r e p e t i t i v e tone p i p s were p r e s e n t e d through s t e r e o headphones w h i l e s u b j e c t s p l a y e d d ' i f f e r e n t ' types o f v i d e o s k i l l games. The tones were i r r e l e v a n t to v i d e o events and s u b j e c t s were i n s t r u c t e d to i g n o r e them. F o r nonpsychopaths, i t was found t h a t improvement i n game per-formance a c r o s s t r i a l s was accompanied by s m a l l e r N l responses to the i r r e l e v a n t t o n e s . The p s y c h o p a t h i c group showed Nl responses s m a l l e r than those o f the o t h e r group throughout the game t r i a l s and y e t they were unable to s u s t a i n the l e v e l s o f performance a c h i e v e d by non-psychopaths. The i n t r i n s i c a l l y i n t e r e s t i n g n a t u r e o f the v i d e o game t a s k ( r e p o r t e d by a l l s u b j e c t s ) h e l p e d e l i m i n a t e the p o s s i b i l i t y t h a t group d i f f e r e n c e s i n m o t i v a t i o n c o n t r i b u t e d to the f i n d i n g s . The r e s u l t s were i n t e r p r e t e d as p r o v i d i n g support f o r the h y p o t h e s i s t h a t psychopaths e f f e c t i v e l y i g n o r e s t i m u l i which are not of immediate i n t e r e s t to them. S i n c e ERPs were not r e c o r d e d to s t i m u l i c o i n c i d e n t w i t h v i d e o e v e n t s , i t c o u l d not be determined whether p s y c h o p a t h i c s u b j e c t s were a l s o l e s s e f f i c i e n t than nonpsychopaths at d i s t r i b u t i n g a t t e n t i o n a l r e s o u r c e s among these e v e n t s . For example, had APs been r e c o r d e d they might have shown t h a t psychopaths had g r e a t e r d i f f i c u l t y a n t i c i p a t i n g important, v i d e o e v e n t s , which may or may not have been r e l a t e d to t h e i r a b i l i t y to a t t e n d s e l e c t i v e l y . The r e s e a r c h d e s c r i b e d i n t h i s t h e s i s a l s o used a v i d e o game as the b a s i c e x p e r i m e n t a l t a s k because i t r e q u i r e s o f the s u b j e c t t h a t - 8 -he both a n t i c i p a t e and s e l e c t i v e l y a t t e n d to s t i m u l i . Furthermore i t a v o i d s the a r t i f i c i a l n a t u r e of the t y p i c a l CNV paradigm i n which " s m a l l i s l a n d s o f S1-S2 ( i . e . , warning s t i m u l u s - i m p e r a t i v e s t i m u l u s ) a c t i v i t y are s e p a r a t e d by p e r i o d s of i n a c t i v i t y d u r i n g which the s u b j e c t ' s p s y c h o l o g i c a l and b e h a v i o u r a l s t a t e i s r e l a t i v e l y p o o r l y c o n t r o l l e d " (McCallum, 1976, p. 4 6 ) , by making c o n t i n u o u s demands on a t t e n t i o n . A l s o , s i n c e the t a s k i s i n t r i n s i c a l l y m o t i v a t i n g and r e l a t i v e l y simple to l e a r n to p l a y , i t s h o u l d be p o s s i b l e to use i t to study ERPs i n a wide range o f s u b j e c t s . I n v e s t i g a t o r s have o f t e n commented on the f a i l u r e o f c o n v e n t i o n a l s t i m u l i l i k e tones and l i g h t f l a s h e s to engage the i n t e r e s t o f s u b j e c t s such as c h i l d r e n and c l i n i c a l p a t i e n t s - s u b j e c t s whose a t t e n t i o n a l a b i l i t i e s or d i s a b i l i t i e s might be o f c r i t i c a l importance to these i n v e s -t i g a t o r s ( T e c c e , 1971). The use o f u n i n t e r e s t i n g s t i m u l i can i n f l a t e e s t i m a t e s o f d i s t r a c t i b i l i t y i n these s u b j e c t s and might a c t u a l l y i n c r e a s e the l i k e l i h o o d o f p h y s i o l o g i c a l a r t i f a c t s r e s u l t i n g from random eye movements (T e c c e , 1971). L i k e the experiment by J u t a i and Hare (1983) s u b j e c t s i n the p r e s e n t s t u d i e s were r e q u i r e d to p l a y v i d e o games w h i l e l i s t e n i n g to tone p i p s through s t e r e o headphones. Only the tone p i p s i n one e a r were c o i n c i d e n t w i t h s a l i e n t events shown on the v i d e o s c r e e n . L i k e theuexperiment by- J u t ai.-and_, Hare (1983) s u b j e c t s ! i n the .present s t u d i e s were r e q u i r e d I t o . p l a y v i d e o games w h i l e l i s t e n i n g to tone p i p s through s t e r e o headphones. Only the tone p i p s i n one^ea-r, however, were i r r e l e v a n t to the t a s k . Those i n the o t h e r ear were c o i n c i d e n t w i t h s a l i e n t events shown on the v i d e o s c r e e n . The s t i m u l i i n both e a r s were p h y s i c a l l y i d e n t i c a l . P r e s t i m u l u s and p o s t s t i m u l u s ERPs a s s o c i a t e d w i t h tones i n both - 9 -e a r s were measured. Two experiments e s t a b l i s h e d t h a t genuine AP and Nl phenomena are r e l i a b l y r e c o r d e d i n t h i s type of e x p e r i m e n t a l s i t u a t i o n . A t h i r d experiment e x p l o r e d r e l a t i o n s h i p s among the v a r i o u s types of ERPs and f u r t h e r d i s s o c i a t e d ERP e f f e c t s from those a t t r i b u t a b l e to eye movement or muscular a r t i f a c t . Two major hypotheses were t e s t e d i n t h i s experiment. The f i r s t was t h a t e l e c t r o c o r t i c a l s i g n s of a n t i c i p a t o r y r e a d i n e s s and s e l e c t i v e a t t e n t i o n are i n t e r r e l a t e d by v i r t u e o f t h e i r b e i n g dependent to some e x t e n t on the d i r e c t i o n i n which a s u b j e c t o r i e n t s h i s a t t e n t i o n d u r i n g task performance. The second was t h a t the a m p l i t u d e s of these ERPs are p o s i t i v e l y c o r r e l a t e d i w i t h task performance. I I . Experiment 1: Q u a l i t a t i v e d e s c r i p t i o n o f ERPs T h i s p r e l i m i n a r y study was d e s i g n e d to examine the n a t u r e o f the v a r i o u s ERPs which c o u l d be r e c o r d e d i n a paradigm such as t h a t d e s c r i b e d above. I t was important to a s c e r t a i n whether e x t r a - c e r e b r a l p h y s i o l o g i c a l a r t i f a c t s , such as eye movements, might obscure the i n t e r p r e t a t i o n o f observed ERP phenomena. Method S u b j e c t s E l e v e n r i g h t - h a n d e d males between the ages o f 18 and 29 (mean = 21.45, SD = 2.81) s e r v e d as p a i d v o l u n t e e r s . A l l s u b j e c t s were i n good g e n e r a l h e a l t h at the time o f study, and had normal - 10 -v i s i o n and h e a r i n g . These s u b j e c t s r e p r e s e n t e d a wide range o f p r e v i o u s e x p e r i e n c e w i t h v i d e o games although none had p l a y e d the p a r t i c u l a r game used i n t h i s study. None had p r i o r e x p e r i e n c e as a s u b j e c t i n an ERP experiment. S u b j e c t s were informed o f the g e n e r a l n a t u r e o f the sudy, but s p e c i f i c hypotheses were not d i s c u s s e d u n t i l a f t e r the e x p e r i m e n t a l s e s s i o n . T e c h n i c a l and p r o c e d u r a l m o d i f i c a t i o n s r e s u l t e d i n f i v e s u b j e c t s out o f the o r i g i n a l e l e v e n e x p e r i e n c i n g the procedure as i t i s o u t l i n e d below. The d a t a d e s c r i b e d below, t h e r e f o r e , p e r t a i n to these f i v e s u b j e c t s . Only r i g h t - h a n d e d s u b j e c t s were s t u d i e d s i n c e r e s u l t s o b t a i n e d w i t h l e f t - h a n d e r s tend to be h i g h l y v a r i a b l e when measures of p r e s t i m u l u s , a n t i c i p a t o r y ERP a c t i v i t y are used (Kutas and Donchin, 1977). Apparatus The e x p e r i m e n t a l t a s k was a v i d e o squash game generated by a Ridgewood Gamatic 7600 v i d e o game system, and was p r e s e n t e d on an 18cm X 23cm b l a c k and white t e l e v i s i o n s c r e e n . F i g u r e 1 d e p i c t s the g e n e r a l e x p e r i m e n t a l l a y o u t . Three o f the f o u r b o u n d a r i e s of a r e g u l a r squash c o u r t were d i s p l a y e d as white l i n e s a g a i n s t a b l a c k background on the T.V. s c r e e n . L i n e s r e p r e s e n t i n g the two s i d e w a l l s ran a l o n g the top and bottom of the s c r e e n . The back ( o r s e r v i c e ) w a l l extended a l o n g the f a r l e f t s i d e o f the s c r e e n . The view thus p r e s e n t e d to the s u b j e c t was o f a squash c o u r t as seen from above. The s u b j e c t ' s squash r a c q u e t appeared as a s m a l l white bar which c o u l d be moved a l o n g an i n v i s i b l e v e r t i c a l a x i s l o c a t e d about T.V. Screen w i th Game Disp lay F i g u r e 1. G e n e r a l l a y o u t o f t h e v i d e o g a m e t a s k ( s e e t e x t f o r d e t a i l s ) - 12 -one - q u a r t e r o f the way a c r o s s the s c r e e n from the r i g h t . The ra c q u e t c o n t r o l mechanism was housed i n a s m a l l , l i g h t w e i g h t p l a s t i c box h e l d i n the l e f t hand. C o n t r o l was e f f e c t e d by d i a l i n g , a knob on the box w i t h the f i n g e r s and thumb o f the r i g h t hand; v e r y l i t t l e e f f o r t was r e q u i r e d t o execute these movements. The squash b a l l (a s m a l l white dot) was se r v e d a u t o m a t i c a l l y , always from the s e r v i c e w a l l , and would rebound upon c o n t a c t w i t h the ra c q u e t o r any o f the t h r e e c o u r t w a l l s . The s u b j e c t ' s task was t o keep the b a l l i n p l a y w i t h i n the c o u r t f o r as l o n g as p o s s i b l e d u r i n g each game t r i a l . A 'miss' o c c u r r e d when the b a l l escaped c o n t a c t w i t h the r a c q u e t and passed i n t o the a r e a on the f a r r i g h t o f the s c r e e n , at which time another b a l l was s e r v e d . The number of misses was d i s p l a y e d as a r u n n i n g t o t a l at the upper l e f t c o r n e r o f the s c r e e n . The s u b j e c t wore a p a i r o f AKG 140 s t e r e o headphones. In one ear he he a r d the l i v e a u d i o p o r t i o n o f the game he was a c t u a l l y p l a y i n g . T h i s c o n s i s t e d of 500 Hz, 1000 Hz and 2000 Hz tones which c o i n c i d e d e x a c t l y w i t h w a l l bounces, r a c q u e t h i t s and m i s s e s , r e s p e c t i v e l y . In the o t h e r ear the s u b j e c t h e a r d the same s t i m u l i c a r r i e d on the p r e - r e c o r d e d audio p o r t i o n o f a game which had been p l a y e d by an a s s o c i a t e o f the e x p e r i m e n t e r . Thus, one earphone p r e s e n t e d a u d i t o r y i n f o r m a t i o n r e l e v a n t to e x p e r i m e n t a l t a s k performance - 13 -w h i l e the o t h e r c a r r i e d i n f o r m a t i o n which was p o t e n t i a l l y d i s t r a c t i n g s i n c e i t was r a r e l y (and then, o n l y by chance) a s s o c i a t e d w i t h a c t i v i t y on the T.V. s c r e e n . The assignment of r e l e v a n t or i r r e l e v a n t a u d i t o r y i n f o r m a t i o n to the l e f t o r r i g h t ear was c o u n t e r b a l a n c e d a c r o s s s u b j e c t s . Only the 500 Hz and 1000 Hz tones were used as t r i g g e r s i n subsequent ERP a n a l y s e s . These were 40 msec i n d u r a t i o n w t i h 10 msec r i s e and f a l l times i n c l u d e d . The i n t e n s i t y o f the tones was 70 dB SPL d e l i v e r e d a g a i n s t a c o n t i n u o u s background o f 50 dB white n o i s e . The average i n t e r - t o n e i n t e r v a l per ear chan n e l was 1.5 s e c . The 2000 Hz 'miss' tone was omitted from d a t a a n a l y s i s f o r two r e a s o n s . F i r s t , i t was not synchronous w i t h the p r e c i s e p o i n t i n time at which the b a l l passed by the r a c q u e t ; i t a c t u a l l y f o l l o w e d the event by about 1 s e c . Second, on a v e r -age i t o c c u r r e d too i n f r e q u e n t l y w i t h i n a game t r i a l to p e r m i t an adequate a r t i f a c t - f r e e sample s i z e f o r ERP a v e r a g i n g . A Beckman Type R 711 p o l y g r a p h was used to r e c o r d EEG, eye movement (EOG) and muscular a c t i v i t y (EMG). Monopolar EEG r e c o r d i n g s were o b t a i n e d from Beckman EE& e l e c t r o d e s p l a c e d over and s i t e s , r e f e r e n c e d t o l i n k e d e a r l o b e s . C„ and C, r e f e r to l e f t hemisphere and r i g h t hemisphere r e c o r d i n g s i t e s , r e s p e c t i v e l y . Each l i e s 20% o f the d i s t a n c e from the c e n t e r ( o r " v e r t e x " ) o f an - 14 -imaginary l i n e e x t e n d i n g from e a r to ear at r i g h t a n g l es to a l i n e e x t e n d i n g from n a s i o n to i n i o n . These p o s i t i o n s o v e r l i e l e f t and r i g h t p o r t i o n s of the R o l a n d i c f i s s u r e . C e n t r a l s i t e s were used s i n c e the slow n e g a t i v e p o t e n t i a l s which a n t i c i p a t e limb movement are r e c o r d e d m a x i m a l l y over these areas ( e . g . , Deecke arid Kornhuber 1977), e s p e c i a l l y when the s u b j e c t knows i n advance the n a t u r e o f the r e q u i r e d movement ( L o v e l e s s , 1979). The l i n k e d - e a r s r e f e r e n c e i s p r e f e r r e d among i n v e s t i g a t o r s of slow p o t e n t i a l s (Donchin, Gallaway, Cooper, Desmedt, G o f f , H i l l y a r d and S u t t o n , 1977), p r i m a r i l y because o f i t s r e l a t i v e e l e c t r i c a l i n d i f f e r e n c e (Vaughan, Co s t a and R i t t e r , 1968), and because i t seems to e l i m i n a t e the a r t i f a c t u a l c o n t r i b u t i o n to s c a l p r e c o r d i n g s o f h o r i z o n t a l eye movements ( G e r b r a n d t , 1978). In o r d e r to m o n i t o r gross eye movement an EOG r e c o r d i n g was made w i t h Beckman m i n i a t u r e e l e c t r o d e s p l a c e d above and on the o u t e r canthus o f the r i g h t eye. Both EEG and EOG s i g n a l s were fed i n t o Type 9806A A.C. coupers w i t h bandpass set at 0.16 Hz to 30 Hz (3 dB r o l l o f f ) . G i v e n the i n t e r s t i m u l u s i n t e r v a l used i n t h i s study, the low fequencey c u t o f f (time c o n s t a n t = 1 sec.) would ensure minimal d i s t o r t i o n o f the slow ERPs (Cooper, 1976; Donchin, 1973; G e r b r a n d t , 1978). EMG a c t i v i t y was r e c o r d e d w i t h m i n i a t u r e e l e c t r o d e s p l a c e d midway between the w r i s t and the elbow of the r i g h t arm, over the f l e x o r and e x t e n s o r m u s c l e s . T h i s p l a c e -ment was found to be the one most s e n s i t i v e t o c o n t r o l - k n o b r o t a t i o n -'15 -i n b oth d i r e c t i o n s . A Type 9852 c o u p l e r w i t h bandpass s e t at 0.80 to 30Hz was used to produce an i n t e g r a t e d EMG s i g n a l . A l l e l e c t r o d e s i t e s were p r e p a r e d by r u b b i n g w i t h Redux p a s t e , and impedances were kept under 5 Kilohms. The EEG, EOG, EMG and s i g n a l marker data were r e c o r d e d and s t o r e d on magnetic tape. P rocedure The experiment was conducted i n a sound-proofed and e l e c t r i c a l l y s h i e l d e d chamber. The s u b j e c t was se a t e d c o m f o r t a b l y a t an e y e - l e v e l d i s t a n c e o f 136 cm from the c e n t e r o f the T.V. s c r e e n . At t h i s d i s t a n c e the maximum v e r t i c a l and h o r i z o n t a l eye movements r e q u i r e d t o pe r f o r m the ta s k were 8° and 10° r e s p e c t i v e l y . The s u b j e c t was g i v e n a b r i e f o v e r v i e w o f the experiment and a d e s c r i p t i o n o f the n a t u r e and f u n c t i o n o f the e l e c t r o d e s . E l e c t r o d e s were then a t t a c h e d and the s u b j e c t completed s e v e r a l s h o r t c consent forms and a handedness q u e s t i o n a i r r e . Maximum v e r t i c a l and h o r i z o n t a l eye movements were c a l i b r a t e d on the p o l y g r a p h , and a check was made on the s e n s i t i v i t y o f the EMG r e c o r d i n g t o c o n t r o l -knob r o t a t i o n s . Task i n s t r u c t i o n s were then g i v e n . The s u b j e c t was t o l d d t h a t t h e r e xTOuld be a s e r i e s o f s h o r t game t r i a l s , each l a s t i n g s e v e r a l m i nutes, and t h a t he sh o u l d c o n c e n t r a t e on - 16' -m i n i m i z i n g the s c o r e on the T.V. s c r e e n ( i . e . , the number o f m i s s e s ) by k e e p i n g the b a l l i n p l a y i n the squash c o u r t . M a n i p u l a t i o n o f the c o n t r o l knob was c a r e f u l l y demonstrated and the s u b j e c t i n s t r u c t e d t o r e s t r i c t v o l u n t a r y muscular a c t i v i t y to the e x e c u t i o n . o f t h i s r e s p o n s e . The s u b j e c t was informed t h a t tone p i p s would be p r e s e n t e d through the headphones throughout each t r i a l , and was t o l d t h a t no b e h a v i o u r a l response was r e q u i r e d to these tones and t h a t a t t e n t i o n s h o u l d be f o c u s s e d on the T.V. s c r e e n . No i n f o r m a t i o n was p r o v i d e d about r e l a t i o n s h i p s between tone p i p s and v i d e o e v e n t s . The s u b j e c t then p l a y e d a s e t o f t e n 4-minute game t r i a l s w i t h a 30-sec pause between t r i a l s . The games were folowed by a 4-min p e r i o d i n which the s u b j e c t l i s t e n e d w i t h eyes c l o s e d to a b i n a u r a l p r e s e n t a t i o n o f p r e - r e c o r d e d game a c t i v i t y , and was r e q u i r e d t o keep a mental count o f the number o f o c c u r r e n c e s o f the 2000 Hz tone. A f t e r w a r d , the t o t a l count was r e p o r t e d to the ep x e r i m e n t e r . T h i s c o n t r o l c o n d i t i o n was used to examine ERPs to the 500 Hz and 1000 Hz tones i n a s i n g l e c h a n n e l , focused, a t t e n t i o n s i t u a t i o n . The e n t i r e s e s s i o n l a s t e d about 90 minutes. - 17 -" Data q u a n t i f i c a t i o n and a n a l y s i s The e l e c t r o p h y s i o l o g i c a l s i g n a l s were a n a l y z e d o f f l i n e by a microcomputer. The sampling epoch extended from 500 msec p r e -s t i m u l u s to 1000 msec f o l l o w i n g s t i m u l u s o n s e t . The computer sampled at a r a t e o f 200/sec, r e t a i n i n g 500 msec's worth o f d a t a u n t i l t r i g g e r onset at which time every second d a t a p o i n t i n the p r e s t i m u l u s p o r t i o n o f the epoch was d i s c a r d e d . T h i s r e s u l t e d i n e f f e c t i v e p r e - and p o s t s t i m u l u s d i g i t i z a t i o n r a t e s o f 100/sec and 200/sec, r e s p e c t i v e l y . T h i s procedure was used because o f d a t a s t o r a g e l i m i t a t i o n s on magnetic f l o p p y d i s k s . A l t h o u g h a 100 Hz sampling r a t e i s adequate f o r the measurement of slow p o t e n t i a l s , r e s o l u t i o n s o f l a t e n c y components i n the p r e -s t i m u l u s p e r i o d cannot be expected to be q u i t e as good as t h a t f o r p o s t s t i m u l u s components. The computer was programmed to r e j e c t t r i a l s on which EOG and EMG amplitudes exceeded i n d i v i d u a l l y d etermined c r i t e r i o n r a n g e s , i n a p e r i o d e x t e n d i n g from 500 msec b e f o r e to 500 msec a f t e r t r i g g e r o n s e t . F o r the EMG, t h i s p r o c e d u r e was d e s i g n e d to d i s c a r d o n l y those t r i a l s i n which v e r y l a r g e a mplitude transients o c c u r r e d . These are a r t i f a c t s u s u a l l y a s s o c i a t e d w i t h gross body movements. The EOG and EMG were averaged and p l o t t e d over the same epoch as the EEG. The s u c c e s s of a r t i f a c t r e j e c t i o n p r o c e d u r e s was v e r i f i e d by v i s u a l i n s p e c t i o n o f the averaged EOG and EMG t r a c i n g s . - 18 -Averaged ERPs were computed f o r the f i r s t 25 epochs f r e e of a r t i f a c t i n each o f the 10 game t r i a l s , and were t r i g g e r e d on tone o n s e t . Four passes of the d a t a on each t r i a l were r e q u i r e d , one f o r each c o m b i n a t i o n o f tone f r e q u e n c y (500 Hz, 1000 Hz) and ear cha n n e l ( l i v e a u d i o , p r e - r e c o r d e d a u d i o ) . In each pass the computer a u t o m a t i c a l l y r e j e c t e d t r i a l s i n which another tone event, i n c l u d i n g the designated.: t r i g g e r , o c c u r r e d i n the same 1000 msec p e r i o d used f o r r e j e c t i o n o f p h y s i o l o g i c a l a r t i f a c t . Thus each average was f r e e o f E0G-, EMG--and non-trigger- and d o u b l e - t r i g g e r EEG a r t i f a c t f o r a 500 msec p e r i o d b e f o r e and a f t e r t r i g g e r o n s e t . R e s u l t s E v e n t - r e l a t e d p o t e n t i a l s F i g u r e 2 shows the group averaged p r e s t i m u l u s ERPs a s s o c i a t e d w i t h 1000 Hz tone ( r a c q u e t h i t ) o f the s u b j e c t ' s game so u n d t r a c k . R e l a t i v e to p o s t s t i m u l u s a c t i v i t y (see F i g u r e 3 ) , these ERPs d i s p l a y c o n s i d e r -a b l e e l e c t r o c o r t i c a l n e g a t i v i t y . A n e g a t i v e component r i s e s s t e e p l y over both C3 and C4 from about -450 msec to about -350 msec. The peak l a t e n c y o f t h i s ' e a r l y component-' seems to v a r y from t r i a l to t r i a l . Beyond t h i s p o i n t i n time, d r a m a t i c d i f f e r e n c e s emerge between C3 and C4 waveforms. N e g a t i v i t y at C3 e i t h e r c o n t i n u e s to msec msec F i g . 2. Group a v e r a g e d p r e s t i m u l u s ERPs a s s o c i a t e d w i t h 1000 Hz t o n e on r e l e v a n t c h a n n e l , f o r t r i a l s 1-10. F i g . 3. Group a v e r a g e d p o s t s t i m u l u s ERPs a s s o c i a t e d w i t h 1000 Hz t o n e on r e l e v a n t c h a n n e l , f o r t r i a l s 1-10. - 21 -b u i l d or e l s e l e v e l s o f f about 100 msec b e f o r e s t i m u l u s o n s e t , w h i l e at C4 n e g a t i v i t y i s waning. The amplitude o f the e a r l y component d e p i c t e d i n F i g u r e 2 ranges from 3y^ V to 7^V. The d i f f e r e n c e between C3 and C4 ERPs at s t i m u l u s onset v a r i e s from 2.5^1 to 6^V. F i g u r e 3 p r e s e n t s the p o s t s t i m u l u s p o r t i o n s of the waveforms shown i n F i g u r e 2 (note the change i n time s c a l e ) . C3 and C4 t r a c i n g s are a l i g n e d such t h a t the amplitudes o f the s m a l l p o s i t i v e d e f l e c t i o n a p p e a r i n g between 50 msec and 100 mesec p o s t s t i m u l u s a r e e q u i v a l e n t . T h i s emphasizes d i f f e r e n c e s between C3 and C4 i n the s i z e and l a t e n c y o f the Nl component. The g e n e r a l e f f e c t s o f the l a r g e r p r e s t i m u l u s n e g a t i v i t y on p o s t s t i m u l u s components r e c o r d e d at G3 r e l a t i v e to C4 are a r e t a r d a t i o n of component peak l a t e n c i e s by about 15 msec, an a t t e n u a t i o n of Nl amplitude and g r e a t e r p o s i t -i b i t y i n p o r t i o n s o f the waveform e x t e n d i n g beyond 200 msec from s t i m u l u s o n s e t . F o r both C3 and C4 t h e r e are n o t i c e a b l e f l u c t u a t i o n s i n N l l a t e n c y a c r o s s t r i a l s . Group averaged ERPs r e c o r d e d i n response to the 1000 Hz tones on the p r e - r e c o r d e d soundtrack are shown i n F i g u r e 4. There was no a p p r e c i a b l e n e g a t i v e b u i l d u p : i n the p r e s t i m u l u s p e r i o d , hence o n l y poststimulus-. waveforms a r e d e p i c t e d . An N l component i s prominent i n each t r i a l , and C3 appears to e x h i b i t s l i g h t l y more n e g a t i v i t y 50 100 150 200 250 300 50 100 150 200 250 300 msec msec F i g . 4. Group a v e r a g e d ERPs t o 1000 Hz tone on i r r e l e v a n t c h a n n e l , f o r t r i a l s 1-10. - 123 •-than C4 i n e a r l y and l a t e r p o r t ions of the waveforms. A comparison of Figures 3 and 4 h i g h l i g h t s the d i s t o r t i o n s of the ERP when i t has been preceded by a prestimulus negative s h i f t . These include a t t e n u a t i o n of Nl amplitude and enlargement of the N1-P2 peak-to-peak d i f f e r e n c e , where P2 i n the p o s i t i v e d e f l e c t i o n o c c u r r i n g immediately a f t e r N l . These f i n d i n g s however should not be understood to imply that prestimulus n e g a t i v i t y s t r i c t l y determines the form of the poststimulus ERP. R e c a l l that Nl i s often r e f e r r e d to as a "mesogenous" component,,sensitive to both p h y s i c a l and p s y c h o l o g i c a l manipulation. I t i s conceivable that Nl could be d i r e c t l y a f f e c t e d by the same p s y c h o l o g i c a l process which gives r i s e to the prestimulus s h i f t . Of course such an e f f e c t i s not e a s i l y d i s t i n g u i s h a b l e from d i s t o r t i o n produced by the temporal overlap of pre- and poststimulus a c t i v i t y . None-t h e l e s s , d i r e c t manipulation of N l , independent of mediation by prestimulus n e g a t i v i t y , has been demonstrated i n the past (see meview by Na^tanen, 1982) and was v i s i b l e i n the a n a l y s i s of ERPs to 'wall bounce' tones. Figures 5 and 6 present ERPs associated with 500 Hz 'wall bounce' tones recorded at C3 and C4, r e s p e c t i v e l y . There was no appreciable n e g a t i v i t y i n the prestimulus wave-forms. In most t r i a l s and across both recording s i t e s there i s a s i z e a b l e d i f f e r e n c e i n Nl amplitude between responses to s t i m u l i i n the rel e v a n t 50 100 150 200 250 ms ec 300 50 100 150 200 msec 250 300 F i g . 5. Group a v e r a g e d ERPs t o 500 Hz ton e on r e l e v a n t (GAME) and i r r e l e v a n t (TAPE) c h a n n e l s , f o r s i t e C3. msec msec F i g . 6. Group a v e r a g e d ERPs t o 500 Hz tone on r e l e v a n t (GAME) and i r r e l e v a n t (TAPE) c h a n n e l s , f o r s i t e Ck. - 26 -and i r r e l e v a n t audio c h a n n e l s . Moreover, ERPs to r e l e v a n t tones demonstrate g r e a t e r n e g a t i v i t y throughout most o f the waveform on each t r a i l . There seems to be c o n s i d e r a b l e t r i a l - t o - t r i a l v a r -i a b i l i t y i n the d i f f e r e n c e i n o v e r a l l ERP n e g a t i v i t y between c h a n n e l s . ERPs r e c o r d e d d u r i n g the s i n g l e s e n s o r y channel c o n t r o l c o n d i t i o n are d i s p l a y e d i n F i g u r e 7. N l amplitude seems to be l a r g e r at C4 than a t C3, and P2 appears l a r g e r i n response to 500 Hz tones than to 1000 Hz t o n e s . In t h i s f o c u s e d a t t e n t i o n c o n d i t i o n the Nl component was g e n e r a l l y l a r g e r than i t was w h i l e s u b j e c t s p l a y e d the v i d e o game. There i s l i t t l e e v i d e n c e of the l a t e n e g a t i v i t y which dominates many of the ERP t r a c i n g s o f F i g u r e s 5 and 6. P h y s i o l o g i c a l a r t i f a c t r e j e c t i o n On the average, 1 out o f e v e r y 4 sampled epochs was d i s c a r d e d because of eye movement a r t i f a c t . A l t h o u g h i t may be h i g h by the s t a n d a r d s o f some o t h e r ERP s t u d i e s , t h i s r e j e c t i o n r a t i o i s not u n a c c e p t a b l e g i v e n the c o m p l e x i t y of the e x p e r i m e n t a l t a s k used. The p e r c e n t a g e s of t r i a l s r e j e c t e d (out of the t o t a l r e q u i r e d f o r 25 c l e a n averages) f o r averaged ERPs a s s o c i a t e d w i t h 1000 Hz ' h i t ' and 500 Hz ' w a l l bounce' i n f i r s t the r e l e v a n t , Fig . 7. Group averaged ERPs recorded during control cond i t i on . - 2 8 -then the i r r e l e v a n t channels were 21.53, 25.37, 27.16 and 24.59. The s u c c e s s o f the EOG r e j e c t i o n s t r a t e g y i s v e r i f i e d by i n s p e c t i o n o f F i g u r e s 8-12. F i g u r e 8 p r e s e n t s averaged EOG waveforms which were c o n c u r r e n t w i t h the ERPs to ' h i t ' tones i n the r e l e v a n t c h a n n e l . A r a c q u e t h i t was i n v a r i a b l y a s s o c i a t e d with l e f t - t o - r i g h t eye movement immediately b e f o r e the h i t , f o l l o w e d by a r i g h t - t o - l e f t d e f l e c t i o n as the b a l l rebounded from the r a c q u e t . For the purpose o f a r t i f a c t r e j e c t i o n i t was n e c e s s a r y t o keep the sampling epoch f r e e o f movements which d i d not conform to t h i s i n v a r i a n t p a t t e r n . These i n c l u d e d b l i n k s and u n u s u a l l y l a r g e o r sudden eye r o t a t i o n s . EOG a r t i f a c t c o n t r o l was a c h i e v e d i n the r e m a i n i n g e x p e r i m e n t a l and c o n t r o l c o n d i t i o n epochs as shown i n F i g u r e s 9-12. The number o f EMG a r t i f a c t s was n e g l i g i b l e , a v e r a g i n g o n l y a few p e r c e n t f o r any s i n g l e ERP epoch. A p p a r e n t l y s u b j e c t s had l i t t l e d i f f i c u l t y r e s t r i c t i n g limb a c t i v i t y to o n l y those f i n g e r movements r e q u i r e d f o r c o n t r o l - k n o b m a n i p u l a t i o n . E v e n t - r e l a t e d EMG Group averaged EMG waveforms a s s o c i a t e d w i t h the 1000 Hz tone ERPs i n the r e l e v a n t channel are d i s p l a y e d i n F i g u r e 13 - 29 -msec F i g . 8. Group averaged EOG associated with 1000 Hz tone on relevant channel, for t r i a l s 1-10-(0=stimulus onset) 2 msec msec F i g . 9. Group a v e r a g e d EOG a s s o c i a t e d w i t h 1000 Hz tone on i r r e l e v a n t c h a n n e l , f o r t r i a l s 1-.10. msec msec Fig.1 0 . Group a v e r a g e d EOG a s s o c i a t e d w i t h 500 Hz t o n e on r e l e v a n t c h a n n e l , f o r t r i a l s 1-10. 1 F i g . 11. G r o u p . a v e r a g e d EOG a s s o c i a t e d w i t h 500 Hz t o n e on i r r e l e v a n t c h a n n e l , f o r t r i a l s 1-10. - 33 -12. Group averaged EOG recorded during control cond i t ion . - 34 -(note the d i f f e r e n c e i n p r e - and p o s t s t i m u l u s time s c a l e s ) . P r e s t i m u l u s a c t i v i t y folows a r a m p - l i k e c o u r s e , p e a k i n g between 50 msec and 200 msec b e f o r e tone o n s e t . T h i s suggests t h a t , i n g e n e r a l , the i n i t i a t i o n and c o m p l e t i o n : of p r e p a r a t o r y musc-u l a r a c t i v i t y was c o n f i n e d to t h i s p e r i o d . Thus, on the average, s u b j e c t s had p r o p e r l y p o s i t i o n e d the r a c q u e t so as to i n t e r c e p t the b a l l at l e a s t 50 msec p r i o r to the tone. F o l l o w i n g the s t i m -u l u s the waveform r e t u r n s to b a s e l i n e w i t h i n 200 msec. A comparison o f F i g u r e s 2 and 13 r e v e a l s an o v e r a l l s i m i l a r i t y between the EMG and the ERP r e c o r d e d at C3, i . e . over the hemisphere c o n t r a l a t -e r a l to f i n g e r movement. Note t h a t d u r i n g the p r e s t i m u l u s p e r i o d n e g a t i v i t y r e c o r d e d a t C4 was d e c r e a s i n g at a time when EMG was p e a k i n g . In g e n e r a l , the ERP a c i t i v i t y peaked e a r l i e r than the EMG. Furthermore, t h e r e appeared to be no b u r s t of EMG a c t i v i t y c o n c u r r e n t w i t h the peak of the ' e a r l y component' observed i n the ERP. I n t e r s u b j e c t v a r i a b i l i t y i n ERPs In o r d e r t h a t the r e a d e r might a s s e s s the adequacy o f the e l e c t r o p h y s i o l o g i c a l R e c o r d i n g techniques,.-used i n . t h i s study, a sampling o f a s i n g l e s u b j e c t ' s waveforms r e c o r d e d d u r i n g T r i a l 1 i s p r o v i d e d i n F i g u r e 14. I t s h o u l d be apparent from the f i g u r e F i g . 13. Group averaged EMG associated with 1000 Hz tone on relevant channel, for t r i a l s 1-10. (0=stimulus onset) • • • I I I I I I I 50 100 150 200 250 300 50 100 150 200 250 300 msec msec F i g . 14. E l e c t r o p h y s i o l o g i c a l waveforms f o r S u b j e c t 7, d u r i n g t r i a l 1: A, p r e s t i m u l u s ERP t o 1000 Hz tone on r e l e v a n t c h a n n e l ; B, p r e s t i m u l u s EMG to 1000 Hz tone on r e l e v a n t c h a n n e l ; C, ERP t o 1000 Hz tone on i r r e l e v a n t c h a n n e l ; D, p o s t i m u l u s ERP t o 1000 Hz tone on r e l e v a n t c h a n n e l ; E, ERP t o 500 Hz tone on r e l e v a n t ( G A M E ) and i r r e l e v a n t ( T A P E ) c h a n n e l s , f o r s i t e C3; F, ERP t o 500 Hz tone on r e l e v a n t ( G A M E ) and i r r e l e v a n t ( T A P E ) c h a n n e l s , f o r s i t e Ck. - 37 -that the e s s e n t i a l features of the ERPs described f o r group data are r e a d i l y observable i n the data of Subject 7. Behavioural data Performance data were not of prime importance to t h i s prelimimary i n v e s t i g a t i o n . Nonetheless, Figure 15 present the group mean trend i n game scores across t r i a l s . There was a gradual improvement i n performance ( i . e . , d e c l i n e i n number of misses) throughout the f i r s t h a l f of the t r i a l s e t . Scores peaked between t r i a l s 4 and 6 and then began to-fluctuate. I n t e r s u b j e c t v a r i a b i l i t y was qu i t e l a r g e . D i s c u s s i o n The r e s u l t s of t h i s experiment suggest that a v a r i e t y of i n t e r e s t i n g ERPs can be r e l i a b l y recorded i n t h i s paradigm. The most important of these are ERPs which might r e f l e c t s e l e c t i v e a t t e n t i o n and psychomotor p r e p a r a t i o n / a n t i c i p a t i o n . A n t i c i p a t o r y ERPs The prestimulus n e g a t i v i t y observed i n the ERPs to 1000 Hz ' h i t ' tones i n the relevant auditory channel has features i n common with the CNV and RP phenomena described i n the l i t e r a t u r e . L i k e the 'Type A' or 'early' CNV, t h i s waveform i s c h a r a c t e r i z e d by a r e l a t i v e l y large and sudden i n i t i a l negative s h i f t (Deecke and - 38 -F i g . 15. Group averaged game performance across t r i a l s 1-10. - 39 -Korhuber, 1 9 7 7 ; . G a i l l a r d and tfaHthnen, 1976; Tecce, 1971). L i k e the r e a d i n e s s p o t e n t i a l , the l a t e r p o r t i o n o f t h i s ERP i s a s y m m e t r i c a l l y d i s t r i b u t e d , b e i n g a few m i c r o v o l t s l a r g e r i n r e c o r d i n g s made over the hemisphere c o n t r a l a t e r a l to the r e s p o n d i n hand (Becker e t a l . , 1976; Deecke et al., 1973; G a i l l a r d , 1980; Hink et a l . , 1982; Kutas and Donchin, 1977). T h i s study d i f f e r e d from most RP s t u d i e s , however, i n t h a t feedback d i d not immediately f o l l o w upon e x e c u t i o n o f the r e q u i r e d motor r e s p o n s e . On the average t h e r e was at l e a s t 50 msec between t e r m i n a t i o n of the p r e p a r a t o r y motor response and onset o f the feedback or ' h i t ' s t i m u l u s . T h i s means t h a t one c o u l d w e l l expect some a n t i c i p a t o r y n e g a t i v i t y not a s s o c i a t e d w i t h motor r e a d i n e s s to have c a r r i e d on beyond the peak of motor preparedness to s t i m u l u s o n s e t . I t has been shown, f o r example, t h a t s u s t a i n e d p r e s t i m -u l u s n e g a t i v i t y can o c c u r w h i l e a s u b j e c t w a i t s f o r feedback, even though the feedback does not r e q u i r e a response (Weinberg, 1973). In f a c t the s t r u c t u r e o f the e n t i r e n e g a t i v e waveform observed i n t h i s study i s remarkably s i m i l a r t o t h a t o f the " g o a l - d i r e c t e d movement p o t e n t i a l " (GDMP) d e s c r i b e d by Grunewald-Zu^erbier. et a l (1981). These a u t h o r s examined the ERPs which accompany s k i l l e d slow p o s i t i o n i n g movements. S u b j e c t s were r e q u i r e d to i n i t i a t e p a r t i c u l a r p o s i t i o n i n g movements and t e r m i n a t e them when a t a r g e t p o s i t i o n was reached. They r e p o r t e d t h a t a slow n e g a t i v e shift---(-BP-)- p recedes EMG onset o f the p o s i t i o n i n g movement. I t - 40 -b e g i n s s y m m e t r i c a l l y rover both hemispheres but, p r i o r t o EMG on s e t , i t becomes s i g n i f i c a n t l y more n e g a t i v e at the r e c o r d i n g s i t e c o n t r a l a t e r a l to the moving hand. T h i s pre-EMG n e g a t i v i t y c o n t i n u e d to i n c r e a s e , p a s t EMG on s e t , u n t i l the t a r g e t p o s i t i o n was a t t a i n e d . Grunewald-Zuberbier et a l . (1981) suggested t h a t the GDMP r e p r e s e n t e d more than j u s t motor a c t i v i t y ) t h a t i t was s e n s i t i v e to the a t t e n t i o n a l demands o f the t a s k . The ERP i n t h i s study might s i m i l a r l y be composed o f an e a r l y , B P - l i k e wave which a n t i c i p a t e s a motor response and a l a t e , GDMP which a n t i c i p a t e s the r a c q u e t h i t . I s h a l l h e n c e f o r t h r e f e r t o these two a n t i c i p a t o r y components as API and AP2, r e s p e c t i v e l y . ERPs and s e l e c t i v e a t t e n t i o n D e s p i t e the f a c t t h a t s u b j e c t s were not g i v e n s p e c i f i c i n f o r m a t i o n about the nat u r e o f the a u d i t o r y s t i m u l i , and were not r e q u i r e d to o v e r t l y respond to s t i m u l i i n e i t h e r e a r c h a n n e l , a drama t i c d i f f e r e n c e appeared between ERPs t o r e l e v a n t and i r r e l e v a n t t o n e s . R e l a t i v e t o ERPs to 500Hz 'wall bounce' tones i n the i r r e l e v a n t c h a n n e l , r e l e v a n t 'bounce' ERPs seemed to be c h a r a c t e r i z e d by a ' p r o c e s s i n g n e g a t i v i t y ' , the m o d u l a t i o n o f the exogenous ERP by an endogenous slow n e g a t i v e wave (Hansen and H i l l y a r d , 1980; O k i t a , 1981; Parasuraman, 1980). T h i s suggests t h a t a u d i t o r y i n f o r m a t i o n which i s c o i n c i d e n t w i t h a t t e n d e d v i s u a l events - 41 -a u t o m a t i c a l l y r e c e i v e s more a t t e n t i o n than i n f o r m a t i o n which i s n o t . ERPs and focused' a t t e n t i o n A comparison of ERPs to ' w a l l bounce' tones w i t h ERPs to tones i n the focused^ a t t e n t i o n (count tones) c o n d i t i o n f u r t h e r s p e c i f i e s the type o f a t t e n t i o n a s s o c i a t e d w i t h p r o c e s s i n g n e g a t i v i t y . N e i t h e r ERPs to p a s s i v e l y - a t t e n d e d , i r r e l e v a n t 'bounce' tones nor ERPs to a c t i v e l y - a t t e n d e d tones d u r i n g focused'j , s i n g l e -c h a n n e l a t t e n t i o n e v i d e n c e d the degree o f n e g a t i v e s h i f t observed i n ERPs to r e l e v a n t 'bounce' t o n e s . In f a c t , d u r i n g f o c u s e d " a t t e n t i o n p r o c e s s i n g n e g a t i v i t y was almost e n t i r e l y a bsent. T h i s suggests t h a t p r o c e s s i n g n e g a t i v i t y i s i n d e e d p e c u l i a r to the s e l e c t i v e a s p e c t of m u l t i - c h a n n e l s e n s o r y i n f o r m a t i o n p r o c e s s i n g and not s i m p l y due to g r e a t e r e x p e n d i t u r e o f a t t e n t i v e e f f o r t . I m p l i c a t i o n s f o r f u r t h e r sutdy The r e s u l t s c l e a r l y suggest t h a t ERP measures o f a n t i c i a p t i o n and s e l e c t i v e a t t e n t i o n can be o b t a i n e d from a c o n t i n u o u s i n v o l v e m e n t , p e r c e p t u a l - m o t o r t a s k . N e g a t i v e s h i f t s i n the p r e -s t i m u l u s ERP appear tb r e p r e s e n t a n t i c i p a t i o n o f , or p r e p a r a t i o n - 42 -f o r , a r a c q u e t h i t . P o s t s t i m u l u s ' p r o c e s s i n g n e g a t i v i t y ' seems to c h a r a c t e r i z e the ERP to s t i m u l i which are the o b j e c t s o f s e l e c t i v e a t t e n t i o n , such as ' w a l l bounce' tones i n the r e l e v a n t a u d i t o r y c h a n n e l . D e s p i t e the c o m p l e x i t y o f the ta s k as compared to more t r a d i t i o n a l l a b o r a t o r y paradigms, ERP r e c o r d i n g s were not b a d l y d i s r u p t e d by the more common sources o f EOG a r t i f a c t such as b l i n k s and random eye movements. T h i s s u p p o r t s Tecce's (1971) n o t i o n t h a t the use o f i n t e r e s t i n g , i n t r i n s i c a l l y m o t i v a t i n g s t i m u l i can reduce d i s t r a c t i b i l i t y i n s u b j e c t s and de c r e a s e the l i k e l i h o o d o f EOG a r t i f a c t . However, t h e r e may s t i l l be o t h e r s o u r c e s o f d i f f i c u l t y i n the i n t e r p r e t a t i o n o f the ERP waveforms. Alt h o u g h i t i s e x t r e m e l y u n l i k e l y t h a t eye movement p o t e n t i a l s c o n t r i b u t e d a r t i f a c t u a l l y to the asymmety i n ERPs observed i n a n t i c i p a t i o n of a r a c q u e t h i t , the maintenance o f a r i g h t w a r d o r i e n t a t i o n o f v i s u a l a t t e n t i o n might have produced t h i s e f f e c t . Asymmetry might a l s o have been enhanced by an e f f e c t o f s o m a t o s e n s o r y r e a f f e r e n c e on r e c o r d i n g s made at C3, the r e c o r d i n g s i t e c o n t r a l a t -e r a l to the r e s p o n d i n g hand. T h i s would have had i t s g r e a t e s t impact on the AP2:,, Nl and P2 components. A f i n a l p o i n t o f c o n c e r n i s t h a t the ERP e f f e c t s a t t r i b u t e d t o s e l e c t i v e a t t e n t i o n might have i n s t e a d been the r e s u l t o f b i s e n s o r y ( a u d i t o r y p l u s v i s u a l ) s t i m u l a t i o n . A p r e d o m i n a n t l y n e g a t i v e - g o i n g ERP a s s o c i a t e d perhaps - 43 -w i t h the v i s u a l event o f a w a l l bounce might have been superimposed upon the a u d i t o r y ERP to the simultaneous 500 Hz tone. I s s u e s i n v o l v i n g the d i r e c t i o n o f o r i e n t a t i o n and somatosensory r e a f f e r e n c e are d i s c u s s e d i n some d e t a i l i n S e c t i o n IV. Experiment 2 examines the p o s s i b i l i t y o f b i s e n s o r y s t i m u l a t i o n . - 44 -I I I . Experiment 2: E x a m i n a t i o n of v i s u a l ERP a c t i v i t y A n d r e a s s i and Greco (1975) demonstrated t h a t b i s e n s o r y ( a u d i t o r y and v i s u a l ) s t i m u l a t i o n produced l a r g e r amplitude ERPs than d i d u n i s e n s o r y s t i m u l a t i o n i n e i t h e r m o d a l i t y , and produced f a s t e r r e a c t i o n times to s t i m u l i . T h i s seemed to support the i d e a t h a t i n f o r m a t i o n p r o c e s s i n g can be f a c i l i t a t e d by s e n s o r y i n t e r a c t i o n o c c u r r i n g i n the c e n t r a l nervous system. The second experiment was d e s i g n e d t o a s c e r t a i n whether t h e r e were ERPs produced i n response to the s a l i e n t events i n the v i s u a l d i s p l a y - ERPs which c o u l d p o s s i b l y combine w i t h ERP.S to co i n c i d e n t a u d i t o r y t o n e s . Method. S u b j e c t s The s u b j e c t s were f i v e r i g h t - h a n d e d males between the ages o f 18 and 31 (mean = 23.0, SD = 5.15). They were v o l u n t e e r s , and were p a i d $5.00 each f o r t h e i r p a r t i c i p a t i o n . A l l were i n good g e n e r a l h e a l t h and had normal v i s i o n and h e a r i n g . The p r e v i o u s e x p e r i e n c e o f these s u b j e c t s w i t h v i d e o games and ERP experiments was s i m i l a r t o t h a t o f the s u b j e c t s i n the f i r s t e xperiment. - 45 -Apparatus The n a t u r e o f the e x p e r i m e n t a l t a s k and the p h y s i o l o g i c a l r e c o r d i n apparatus were as d e s c r i b e d i n Experiment 1 w i t h two e x c e p t i o n s . In o r d e r to reduce the magnitude o f gross eye movements a s s o c i a t e d w i t h the t a s k a s m a l l e r T.V. s c r e e n was used. The new v i d e o d i s p l measured 8 cm X 10 cm. Maximum v e r t i c a l and h o r i z o n t a l eye movements were 3° and 4° r e s p e c t i v e l y , at a v i e w i n g d i s t a n c e o f 152 cm. A l s o , a l t h o u g h the s u b j e c t wore a p a i r o f headphones d u r i n g the s e s s i o n no a u d i t o r y s t i m u l i were p r e s e n t e d . The head-phones s e r v e d o n l y to permit communication w i t h the s u b j e c t once the e x p e r i m e n t e r l e f t the chamber. Procedure The p r o c e d u r e was as o u t l i n e d i n Experiment 1 w i t h the e x c e p t i o n t h a t no i n s t r u c t i o n s were g i v e n to the s u b j e c t about a u d i t o r y s t i m u l i . A 'count t o n e s ' f o l l o w - u p task was not i n c l u d e d . Data q u a n t i f i c a t i o n and a n a l y s i s The computer was t r i g g e r e d by the 500 Hz and 1000 Hz tones which were c o i n c i d e n t w i t h w a l l bounces and r a c q u e t h i t s , r e s p e c t i v e l y . - 46 -Only two passes o f the d a t a were r e q u i r e d s i n c e t h e r e was o n l y one s i g n a l marker channel i n v o l v e d ( l i v e a u d i o ) . In a l l o t h e r r e s p e c t e s the dat a a n a l y s i s was as d e s c r i b e d i n Experiment 1. R e s u l t s The group averaged ERPs a s s o c i a t e d w i t h r a c q u e t h i t s On the v i d e o d i s p l a y d u r i n g the f i r s t game t r i a l are p r e s e n t e d i n F i g u r e 16. The p r e s t i m u l u s waveforms are e a s i l y r e c o g n i z a b l e by t h e i r s i m i l a r i t y t o those o b t a i n e d i n Experiment 1 ( F i g u r e 2 ) . P o s t s t i m u l u s waveforms, however, showed l i t t l e t r a c e o f the exogenous N—^j- component observed i n the a u d i t o r y ERP to r a c q u e t h i t tones (see F i g u r e 3 ) . F i g u r e 17 shows the group averaged ERPs a s s o c i a t e d w i t h w a l l bounces on the T.V. s c r e e n d u r i n g the same t r i a l . There i s no e v i d e n c e o f v i s u a l ERP components c o i n c i d e n t w i t h those d e s c r i b e d e a r l i e r i n a u d i t o r y ERP t r a c i n g s ( F i g u r e s 5 and 6 ) . Nor i s t h e r e e v i d e n c e o f any s u s t a i n e d p o s t s t i m u l u s n e g a t i v e t r e n d i n these waveforms. The waveforms d e p i c t e d i n F i g u r e s 16 and 17 are e n t i r e l y r e p r e s e n t a t i v e msec F i g u r e 1 6 . G r o u p a v e r a g e d E R P s a s s o c i a t e d w i t h r a c q u e t h i t f o r t r i a l 1 - 48 -5 u V + -100 -20 100 200 300 msec F i g u r e 1 7 . G r o u p a v e r a g e d E R P s t o w a l l b o u n c e f o r t r i a l 1 - 49 -o f those observed i n t r i a l s 2-10. S i n g l e s u b j e c t d a t a f o r t r i a l 1 i s shown i n F i g u r e 18. D i s c u s s i o n I t seems t h a t b i s e n s o r y s t i m u l a t i o n cannot account f o r the d i f f e r e n c e i n waveforms between ERPs to r e l e v a n t and i r r e l e v a n t 500 Hz tones i n Experiment 1. Racquet h i t and w a l l bounce o c c u r r e n c e s on the T.V. s c r e e n do no appear to be d i s c r e t e and i n t e n s e enough to generate v i s u a l ERPs. Furthermore, s u s t a i n e d n e g a t i v i t y a s s o c i a t e d w i t h p r e p a r a t i o n f o r a r a c q u e t h i t , on a v e r a does not appear i n the ERP which f o l l o w s a w a l l bounce event f o r at l e a s t 500 msec. T h i s suggests t h a t the i n c r e a s e d n e g a t i v i t y o f ERPs to r e l e v a n t 500 Hz tones i n the f i r s t experiment r e p r e s e n t s s e l e c t i v e a t t e n t i v e p r o c e s s i n g o f these p a r t i c u l a r a u d i t o r y events and not a n t i c i p a t i o n o f a subsequent r a c q u e t h i t . The f o l l o w i n g experiment attempted a q u a n t i t a t i v e a n a l y s i s o f ERPs o b t a i n e d i n t h i s type o f p e r c e p t u a l - m o t o r t a s k . - 50 --loo -to too zoo 300 msec u r e 1 8 . E R P w a v e f o r m s f o r S u b j e c t 2 o n t r i a l 1 - 51 -IV. Experiment 3: Q u a n t i t a t i v e a n a l y s i s o f ERPs In a d d i t i o n to the q u a n t i t a t i v e a n a l y s i s o f the ERP waveforms observed i n a r e p l i c a t i o n of Experiment 1, t h i s experiment examined the e f f e c t o f d i r e c t i o n o f gaze on ERP asymmetry. A l t h o u g h i t has be e s t a b l i s h e d t h a t downward eye movements can produce a l a r g e n e g a t i v e s h i f t i n the CNV ( S t r a u m a n i s , Shagass and Overton, 1969; H i l l y a r d and Galambos, 1970), i t i s e x t r e m e l y u n l i k e l y t h a t eye movement p o t e n t i a l s were r e s p o n s i b l e f o r the asymmetry i n p r e s t i m u l u s ERPs observed i n the f i r s t two e x p e r i m e n t s . F i r s t , v e r t i c a l eye movements c o u l d not have produced an ERP asymmetry (Anderson, 1977). Second, h o r i z o n t a l eye movements do not c o n t r i b u t e a r t i f a c t u a l l y to ERP r e c o r d i n g s when the l i n k e d - e a r l o b e s r e f e r e n c e i s used ( G e r b r a n d t , 1978). While p o t e n t i a l s p r e p a r a t o r y t o eye movements may appear over the c o r t e x , they are q u i t e s p e c i f i c to p r e f r o n t a l r e g i o n s and do not s y s t e m a t i c a l l y i n f l u e n c e c e n t r a l or o c c i p i t a l r e c o r d i n g s (Rosen, Robinson and L o i s e l l e , 1978). However, t h i s e v i d e n c e i s not m a r s h a l l e d i n o r d e r to deny an important r e l a t i o n s h i p between o r i e n t a t i o n and ERPs, i n which eye movements might p l a y an i n t e g r a l r o l e ( G r a t t o n , C o l e s and Donchin, 1983; L o v e l e s s , 1979). Good performance on the v i d e o games would have r e q u i r e d a n t i c i p a t i o n o f a r a c q u e t h i t . I t i s r e a s o n a b l e to - 52 -expect t h a t s u b j e c t s would have d i r e c t e d a l a r g e p r o p o r t i o n o f t h e i r a t t e n t i o n a l r e s o u r c e s t o the r i g h t s i d e o f the v i d e o s c r e e n , where the r a c q u e t was l o c a t e d , i n a n t i c i p a t i o n o f a h i t . While eye p o s i t i o n can be important i n the c o n t r o l o f a t t e n t i o n ( R e i s b e r g , S c h e i b e r and Potemken, 1981), r e s e a r c h a l s o shows t h a t o r i e n t a t i o n o f a t t e n t i o n can o c c u r i n d e p e n d e n t l y o f the l i n e o f s i g h t (Posner, N i s s e n and Ogden, 1978). I t has been f o r c e f u l l y argued th a t a t t e n t i o n can s e l e c t i v e l y a c t i v a t e one hemisphere ( K i n s b o u r n e , 1975), and Posner et a l . (1978) f u r t h e r s p e c i f y t h a t when an a t t e n t i o n a l s e t i s m a i n t a i n e d at a g i v e n s p a t i a l l o c a t i o n , i t "... i s mediated by a s h i f t o f a t t e n t i o n to a p o s i t i o n i n the b r a i n t h a t would be c o n t a c t e d by the e x t e r n a l e v e n t " (p. 143). In support o f t h i s i d e a , Roland ( c i t e d i n NHHtanen, 1982) used r e g i o n a l c e r e b r a l b l o o d flow (rCBF) measurement t e c h n i q u e s to show t h a t when a t t e n t i o n i s foc u s e d on some p a r t o f the s k i n on one s i d e o f the body, t h e r e i s p r e p a r a t o r y a c t i v a t i o n o f r e l e v a n t s o m a t o - t o p i c a l c o r t e x i n the c o n t r a -l a t e r a l hemisphere. T h i s might suggest t h a t when s u b j e c t s i n the p r e s e n t study m a i n t a i n an a t t e n t i o n a l s e t on the r i g h t s i d e o f the v i d e o s c r e e n , the l e f t hemisphere i s s e l e c t i v e l y a c t i v a t e d , i r r e s p e c t i v e o f eye movements. The r e s u l t would be l a r g e r ERPs at C3. D o u b t l e s s some p a r t o f the p r e s t i m u l u s ERP asymmetry observed e a r l i e r i s a s s o c i a t e d w i t h c o n t r a l a t e r a l ( i . e . , r i g h t hand) motor p r e p a r a t i o n . N o n e t h e l e s s , by the r e a s o n i n g developed thus f a r , one s h o u l d expect the asymmetry to weaken or perhaps even r e v e r s e when - 53 -s u b j e c t s are r e q u i r e d t o o r i e n t a t t e n t i o n more to the l e f t s i d e o f the s c r e e n . In o r d e r to t e s t t h i s h y p o t h e s i s , two groups of s u b j e c t s were t e s t e d . One group (Group N) p l a y e d the v i d e o games i n the u s u a l way. F o r the second group (Group R), the flow o f a c t i o n on the s c r e e n was r e v e r s e d , i . e . , the r a c q u e t appeared on the l e f t s i d e and b a l l s were s e r v e d from the r i g h t . I t was e x p e c t e d t h a t s u b j e c t s i n Group N would o r i e n t a t t e n t i o n p r i m a r i l y t o the r i g h t s i d e o f the T.V. s c r e e n , where r a c q u e t h i t s o c c u r r e d . A n t i c i p a t i o n o f a r a c q u e t h i t i s accompanied by a p r e s t i m -u l u s n e g a t i v e s h i f t i n the ERP ( i . e . an AP). APs s h o u l d be l a r g e r over C3 ( l e f t hemisphere) than over C4 ( r i g h t hemisphere) f o r Group N i f indeed p r e p a r a t o r y c o r t i c a l a c t i v a t i o n i s g r e a t e r i n the hemisphere c o n t r a l a t e r a l to the d i r e c t i o n o f o r i e n t a t i o n . S u b j e c t s i n Group R sh o u l d o r i e n t more to the l e f t s i d e o f the s c r e e n , i n which case APs s h o u l d be l a r g e r over C4 than over C3. A l t h o u g h API and AP2 might r e a s o n a b l y be e x p e c t e d to be s e n s i t i v e to motor p r e p a r a t i o n and feedback a n t i c i p a t i o n , r e s p e c t i v e l y , response and feedback v a r i a b l e s were not m a n i p u l a t e d i n t h i s experiment. I t i s d i f f i c u l t t h e r e f o r e to p r e d i c t the c o r r e l a t i o n between these two p r e s t i m u l u s components. The p r e p a r a t o r y a c t i v a t i o n or p r i m i n g of the c o n t r a l a t e r a l hemisphere ind u c e d by o r i e n t a t i o n might have i m p l i c a t i o n s f o r s t i m u l i o t h e r - 54 -than those d i r e c t l y a s s o c i a t e d w i t h the a n t i c i p a t e d r a c q u e t h i t , such as ' w a l l bounce' tones, a l t h o u g h a p r i o r i these are not c l e a r . D i r e c t i o n a l o r i e n t a t i o n might prime the c o n t r a l a t e r a l hemisphere to g i v e l a r g e r ERPs i n response to a l l o t h e r s t i m u l i i n the t a s k environment, e q u a l l y to both r e l e v a n t and i r r e l e v a n t ' w a l l bounce' tones f o r example. On the o t h e r hand, such p r i m i n g might a c t s e l e c t i v e l y t o enhance a t t e n t i o n p a i d to r e l e v a n t s t i m u l i o n l y . I f t h i s were t r u e one would expect an ERP e f f e c t o f s e l e c t i v e a t t e n t i o n ( i . e . , l a r g e r p o s t s t i m u l u s ERP response to r e l e v a n t bounce t o n e s ) to be g r e a t e r f o r the primed hemisphere ( i . e . , the hemisphere w i t h the l a r g e r AP). Note t h a t p r e s t i m u l u s APs and a n t i c i p a t i o n are d i s c u s s e d i n c o n n e c t i o n w i t h one type of e v e n t , a r a c q u e t h i t , w h i l e p o s t s t i m u l u s p r o c e s s i n g n e g a t i v i t y (measured at P i , N l , P2 and N2 l a t e n c i e s ) and s e l e c t i v e a t t e n t i o n are a s s o c i a t e d w i t h e n t i r e l y d i f f e r e n t e v e n t s , namely w a l l bounces. I f r e l e v a n t ' w a l l bounce' tones were a l s o r e l i a b l y preceded by A P - l i k e n e g a t i v e s h i f t s , i t would be i n c o r r e c t to assume t h a t a p o s t s t i m u l u s n e g a t i v e s h i f t r e f l e c t e d o n l y s e l e c t i v e , " p r o c e s s i n g n e g a t i v i t y " and not some n o n s p e c i f i c , a n t i c i p a t o r y p r o c e s s . I n s t e a d , i t i s suggested here t h a t one type of event ( r a c q u e t h i t s ) might p o s s i b l y be used to prime a hemisphere to respond s e l e c t i v e l y t o d i f f e r e n t events ( w a l l bounce tones) which are not a n t i c i p a t e d . - 55 -Method S u b j e c t s S i x t e e n r i g h t - h a n d e d males between the ages of 18 and 36 (mean = 21.3, SD = 4.91) v o l u n t e e r e d to s e r v e as s u b j e c t s . Each was p a i d $5.00 f o r h i s p a r t i c i p a t i o n i n the s t u d y . A l l s u b j e c t s had normal h e a r i n g and normal or c o r r e c t e d - t o - n o r m a l v i s i o n , and were i n good g e n e r a l h e a l t h . The s u b j e c t s r e p r e s e n t e d a wide range of p r e v i o u s e x p e r i e n c e w i t h v i d e o games. None had p r i o r ' e x p e r i e n c e as a s u b j e c t i n an ERP experiment. Apparatus The n a t u r e of the e x p e r i m e n t a l t a s k and the p h y s i o l o g i c a l r e c o r d i n g apparatus were as r e p o r t e d i n Experiment 1 w i t h two e x c e p t i o n s . The T.V. s c r e e n set-up d e s c r i b e d i n Experiment 2 was used, and, the l e f t - r i g h t f l o w of v i d e o game a c t i v i t y was r e v e r s e d f o r h a l f o f the s u b j e c t s by i n v e r t i n g the T.V. s c r e e n . Procedure The same pro c e d u r e o u t l i n e d i n Experiment 1 was f o l l o w e d e x c e p t i n g t h a t s u b j e c t s were randomly a s s i g n e d to normal (Group N) and r e v e r s e d (Group R) o r i e n t a t i o n groups. A l s o , s u b j e c t s were i n s t r u c t e d to i g n o r e the changing s c o r e which appeared on the T.V. - 56 -s c r e e n and to c o n c e n t r a t e i n s t e a d on k e e p i n g the b a l l i n p l a y f o r as l o n g a p e r i o d as p o s s i b l e . T h i s change i n i n s t r u c t i o n was n e c e s s a r y s i n c e f o r Group R the s c o r e appeared i n v e r t e d on the T.V. s c r e e n and might not t h e r e f o r e have been as e f f e c t i v e a cue f o r Group R as f o r Group N. Scores c o u l d not be h i d d e n from s u b j e c t s s i n c e i t was n e c e s s a r y f o r the exp e r i m e n t e r t o mon i t o r and to r e c o r d t h i s i n f o r m a t i o n . Furthermore, s u b j e c t s were s p e c i f i c a l l y i n s t r u c t e d as to the n a t u r e o f tone s t i m u l i p r e s e n t e d to each e a r . Data q u a n t i f i c a t i o n and a n a l y s i s Computer ay.e.na.ginjg and a r t i f a c t r e j e c t i o n p r o c e d u r e s were those used i n Experiment 1. ERP components were s c o r e d i n fhe f o l l o w i n g manner. Four components were s c o r e d f o r ERPs a s s o c i a t e d w i t h 1000 Hz ' h i t ' tones i n the r e l e v a n t ( l i v e a udio) c h a n n e l . API was taken to be the amplitude o f the most n e g a t i v e p o i n t o c c u r r i n g between -400 msec and -300 msec r e l a t i v e t o the amplitude at t = -500 msec. AP2 was the amplitude of the most n e g a t i v e p o i n t o c c u r r i n g between -150 msec and -50 msec, r e l a t i v e t o the amplitude of the most p o s i t i v e p o i n t i n the p e r i o d immdeiately b e f o r e t = -150 mesec but a f t e r t = -300 msec. Nl was s c o r e d as the amplitude o f the most n e g a t i v e p o i n t i n the p e r i o d e x t e n d i n g from 70 msec to 1-50 msec p o s t s t i m u l u s , r e l a t i v e to the p o i n t o f maximum - 57 -p o s i t i v i t y immediately p r i o r to i t . P2 amplitude was taken to be the d i f f e r e n c e i n amplitude between Nl and the p o i n t o f maximum p o s t i v i t y i n the p e r i o d e x t e n d i n g from 200 msec to 300 msec p o s t s t i m u l u s . T h i s measure o f P2 has been found not to s p u r i o u s l y i n f l a t e an i n v e r s e c o r r e l a t i o n between AP and P2 magnitudes and agrees w e l l w i t h P 2 - t o - b a s e l i n e type measures (Ruchkin and S u t t o n 1979) J API-, AP2-, Nl-and P2-type measure were a l s o taken from the averaged EOG and EMG waveforms. Four components x^ere s c o r e d f o r ERPs a s s o c i a t e d w i t h 500 Hz 'wa l l bounce' tones i n the r e l e v a n t channel and 500 Hz 'w a l l bounce' and 1000 Hz ' h i t ' tones i n the i r r e l e v a n t c h a n n e l . A l l a m p l i t u d e s were s c o r e d r e l a t i v e to the mean amplitude of the EEG 100 msec p r i o r t o tone o n s e t . PI was the p o i n t o f maximum p o s i t i v i t y i n the p e r i o d e x t e n d i n g from 50 msec to 100 msec p o s t s t i m u l u s . N l was the p o i n t o f g r e a t e s t n e g a t i v i t y subsequent to PI. P2 was the l a r g e t p o s i t i v e p o i n t a f t e r N l , and N2 was the p o i n t o f o f maximum n e g a t i v i t y f o l l o w i n g P2 up to 300 msec a f t e r tone onset, The peak l a t e n c i e s f o r a l l components were a l s o s c o r e d . In o r d e r to p r o t e c t a g a i n s t type 1 e r r o r w i t h so many v a r i a b l e s b e i n g a n a l y z e d , m u l t i v a r i a t e a n a l y s i s o f v a r i a n c e (MANOVA) were used on the d a t a . - 58 -Repeated measures MANOVAs were performed w i t h a BMD programme (Dixon, 1981). The s t e p w i s e m u l t i v a r i a t e procedure d e s c r i b e d by H a r r i s (1975, pp. 118-120) was f o l l o w e d ; u n i v a r i a t e t e s t s o f s i g n i f i c a n c e were c o n s i d e r e d o n l y i n the c o n t e x t o f a s t a t i s t i c a l l y s i g n i f i c a n t m u l t i v a r i a t e e f f e c t f o r a l l dependent measures. A B o n f e r r o n i adjustment was.made to the.\.re j e c t i o n . r e g i o n a s s o c i a t e d w i t h each of these tests i- ' such t h a t the r-egeetion p r o b a b i l i t y was s e t at .05/p, where p e q u a l s the number of dependent v a r i a b l e s . Performance was a s s e s s e d by means o f r e p e a t e d measures a n a l y s i s of v a r i a n c e o f the number of misses per t r i a l u s i n g a BMD ANOVA program (Di x o n , 1981). Data o b t a i n e d from the p o s t - e x p e r i m e n t a l 'count t o n e s ' c o n d i t i o n are not r e l e v a n t to the major h y p o t h e s e s t e s t e d and were t h e r e f o r e e x c l u d e d from a n a l y s i s . R e s u l t s V ideo game performance The performance o f Groups N and R i s shown i n F i g u r e 19. There was a g e n e r a l improvement i n s c o r e s a c r o s s t r i a l s (F(9,126) = 15.59, p<.0001), w i t h s i g n i f i c a n t l i n e a r ( F ( l , 1 4 ) = 83.43, p .0001), q u a d r a t i c ( F ( l , 1 4 ) = 20.63, p<.0005) and c u b i c ( F ( l , 1 4 ) = 5.88, p<T.03) components of t r e n d . Post hoc t e s t s u s i n g the Tukey method ( K i r k , 1968, pp. 88-90) r e v e a l e d t h a t performance on t r i a l 1 was s i g n i f i c a n t l y p o o r e r than each of t r i a l s 3 through 10, t r i a l 2 was -I 1 1 I 1 1 1 1 1 1 1 2 3 4 5 6 7 8 9 10 T R I A L g u r e 1 9 . M e a n p e r f o r m a n c e s c o r e s ( n u m b e r o f m i s s e s ) f o r s u b j e c t s i n n o r m a l (IN) a n d r e v e r s e d ( R ) o r i e n t a t i o n g r o u p s w h i l e p l a y i n g v i d e o g a m e s - 60 -po o r e r than each o f t r i a l s 4 through 10, t r i a l 3 po o r e r than t r i a l s 9 and 10, and t r i a l 4 po o r e r than t r i a l 10 (q(10,135) = 4.47, p<C.05). There was an o v e r a l l d i f f e r e n c e between groups ( F ( l , 1 4 ) = 6.25, p^.03), but no s i g n i f i c a n t Group X T r i a l i n t e r a c t i o n . Mean s c o r e s f o r Groups N and R were 26.13 and 3 9 . 4 6 ^ r e s p e c t i v e l y . ERPs a s s o c i a t e d w i t h r a c q u e t h i t s t i m u l i on r e l e v a n t channel Examples o f averaged ERPs a s s o c i a t e d w i t h the 1000 Hz 'racquet h i t ' tone on the r e l e v a n t ( l i v e a udio) channel f o r Groups N and R are p r e s e n t e d i n F i g u r e 20 ( p r e s t i m u l u s ERP) and F i g u r e 21 ( p o s t s t i m u l u s ERP). S i m i l a r r e p r e s e n t a t i o n s o f s i n g l e s u b j e c t waveforms are shown i n F i g u r e s 22 and 23. The f o u r dependent v a r i a b l e s s u b j e c t e d to a n a l y s i s o f v a r i a n c e were API, AP2, N l and P2. Mean amplitude and l a t e n c y o f these components f o r Groups N and R as a f u n c t i o n o f r e c o r d i n g s i d e are p r e s e n t e d i n T a b l e 1. The o n l y s i g n i f i c a n t e f f e c t to emege from an a n a l y s i s o f component amplitudes was a Group X Hemisphere i n t e r a c t i o n ( F ( 4 , l l ) = 4.51, p/.025). U n i v a t i r a t e t e s t s were s i g n i f i c a n t f o r P2 ( F ( l , 1 4 ) = 12.06,p<T.005) but not f o r API ( F ( l , 1 4 ) = 3.98, pC07) and AP2 ( F ( l , 1 4 ) = 3.65, pC08. Though not s t a t i s t i c a l l y s i g n i f i c a n t Group N Group R Figure 20. Averaged prestimulus ERPs associated with 1000 Hz 'racquet hit' tone on relevant (live audio) channel for Groups N and R on t r i a l 1 Group N Group R 100 200 300 100 200 300 msec msec Figure 21. Averaged poststimulus ERPs associated with 'racquet h i t ' tone on relevant channel for Groups N and R on t r i a l 1 Subject N3 Subject R6 I I I I * I • I I I -500 -400 -300 -200 -100 -500 -400 -300 -200 -100 Figure 22. Averaged prestimulus ERPs associated with 1000 Hz t o n e on relevant channel for Subjects N3 and R6 on t r i a l 1 Subject N3 Subject R6 100 200 300 100 200 300 Figure 23. Averaged poststimulus ERPs associated with 1000 Hz tone on relevant channel for Subjects N3 and R6 on t r i a l 1 - 65 -T a b l e 1 Mean a m p l i t u d e and l a t e n c y o f ERP components a s s o c i a t e d w i t h 1000 Hz ' r a c q u e t h i t ' t o n e on r e l e v a n t ( l i v e a u d i o ) c h a n n e l f o r Groups N and R ( s t a n d a r d e r r o r i n p a r e n t h e s e s ) Group N Group R Component S i t e Amp. L a t . Amp. L a t API C3 -3 .065 -348 -4 .183 -344 (0 .252) (6) (0 .298) (6) C4 -2 .360 -355 -5 .001 -351 (0 .246) (6) (0 .410) (6) AP2 C3 -3 . 717 -100 -3 .819 -115 (0 .163) (7) (0 .209) (7) C4 -3 .656 -109 -4 .350 -122 (0 .167) (6) (0 .274) (7) N l C3 -1 . 442 121 -1 .132 116 (0 .185) (2) (0 .123) (2) C4 -1 .585 111 -1 .377 108 (0 .171) (2) (0 .1.46 ) (2) P2 C3 10 .340 262 10 .180 277 (0 .407) (4) (0 .320) (5) C4 10 .000 247 12 .280 268 (0 .434) (4) (0 .354) (5) - 66 -the API and AP2 r e s u l t s were n o n e t h e l e s s i n the p r e d i c t e d d i r e c t i o n and were c e r t a i n l y s t r o n g enough to warant f u r t h e r e x a m i n a t i o n . For each component Group N showed g r e a t e r l e f t - o v e r - r i g h t hemisphere asymmetry w h i l e Group R showed the r e v e r s e ( F i g u r e 24). D i f f e r e n c e s between means were probed f u r t h e r u s i n g t e s t s o f simple main e f f e c t s ( K i r k , 1968, pp 179-182) s i n c e these are r o u t i n e l y computed by the BMD P4V program. API amplitude r e c o r d e d at G4 was l a r g e r f o r Group R than f o r Group N ( F ( l , 1 4 ) = 6.65, p < 0 3 ) . R i g h t v s . l e f t hemisphere d i f f e r e n c e s i n AP2 and P2 amplitude were s t a t i s t i c a l l y s i n g i f i c a n t f o r Group R o n l y ( F ( l , 1 4 ) = 5.86, p<.03; F ( l , 1 4 ) = 17.83), p^.001). There were no s i g n i f i c a n t main e f f e c t s or i n t e r a c t i o n s i n v o l v i n g the T r i a l s f a c t o r . The API and AP2 r e s u l t s support the h y p o t h e s i s t h a t the hemisphere c o n t r a l a t e r a l to the presumed d i r e c t i o n o f o r i e n t a t i o n ( i . e . , r i g h t w a r d f o r Group N, l e f t w a r d f o r Group R) shows g r e a t e r p r e p a r a t o r y e l e c t r o c o r t i c a l a c t i v a t i o n or p r i m i n g . Pearson c o r r e l a t i o n s between p r e s t i m u l u s ERP component a m p l i t u d e s , and between p r e - and p o s t s t i m u l u s a m p l i t u d e s , are shown i n T a b l e 2. API and AP2 had a moderate p o s i t i v e c o r r e l a t i o n . S i m i l a r l y , moderate p o s i t i v e c o r r e l a t i o n s were found between each of these components and p o s t s t i m u l u s P2 a m p l i t u d e . C o r r e l a t i o n s w i t h Nl were n e g l i g i b l e . An a n a l y s i s o f EOG a c t i v i t y c o i n c i d e n t w i t h the ERP components produced a main e f f e c t o f Group ( F ( 4 , l l ) = 6.44, p<.007). Figure 2 4 . M e a n A P 1 , A P 2 a n d P 2 a m p l i t u d e s t o 1 0 0 0 H z ' r a c q u e t h i t ' t o n e s a s a f u n c t i o n o f G r o u p ( N a n d R ) a n d r e c o r d i n g s i t e ( C 3 a n d C 4 ) - 68 -T a b l e 2 P e a r s o n c o r r e l a t i o n s b e t w e e n p r e s t i m u l u s ERP component a m p l i t u d e s , and b e t w e e n p r e - and p o s t s t i m u l u s a m p l i t u d e s S i t e V a r i a b l e s C3 C4 A P I , AP2 0.50* 0.51* A P I , N l -0.26 -0.19 A P I , P2 0.43 0.50* AP2, N l 0.06 0.03 AP2, P2 0.34 0.47 *p<.05 - 69 -The mean EOG amplitudes f o r Group R (mean API = 4.41, SD = 0.30; mean AP2 = 3.54, SD = 0.20) were l a r g e r than those f o r Group N (mean API = 2.60, SD = 0.31; mean AP2 = 2.53, SD = 0.17; however, these d i f f e r e n c e s were not s t a t i s t i c a l l y s i g n i f i c a n t ; No s i g n i f i c a n t r e s u l t s emerged from a n a l y s e s o f EMG waveforms. There was a s i g n i f i c a n t main e f f e c t o f Hemisphere f o r ERP l a t e n c y d a t a (6,9) = 27.07, p<.0001). U n i v a r i a t e t e s t s were s i g n i f i c a n t f o r AP2 ( F ( l , 1 4 ) = 12.36, p<.004), Nl ( F ( l , 1 4 ) = 117.91, p<;.0001) and P2 ( F ( l , 1 4 ) = 26.36, p<.0002). Mean l a t e n c i e s are p r e s e n t e d i n T a b l e 3. A l l ERP components peaked e a r l i e r i n the r i hemisphere than i n the l e f t . ERPs a s s o c i a t e d w i t h r a c q u e t h i t s t i m u l i on i r r e l e v a n t channel Examples o f averaged ERPs a s s o c i a t e d w i t h the 1000 Hz 'racquet h i t tone on the i r r e l e v a n t ( p r e - r e c o r d e d audio) channel f o r Groups N and R are shown i n F i g u r e 25. S i n g l e s u b j e c t ERPs are r e p r e s e n t e d i n F i g u r e 26. A n a l y s i s o f v a r i a n c e was performed on the f o u r p o s t s t i m u l u s components P i , N l , P2 and N2. Mean amplitude and l a t e n c y o f - 70 -T a b l e 3 Mean l a t e n c y o f ERP c o m p o n e n t s a s s o c i a t e d w i t h ' r a c q u e t h i t ' t o n e on r e l e v a n t c h a n n e l , r e c o r d e d o v e r l e f t (C^) and r i g h t (C^) h e m i s p h e r e s c a l p l o c a t i o n s ( a v e r a g e d a c r o s s g r o u p s and t r i a l s ) ( s t a n d a r d e r r o r i n p a r e n t h e s e s ) S i t e Component C3 C4 API -346 -353 (4) (5) AP2 -107 -115 (5) (5) N l 118 109 (1) (1) P2 270 258 (3) (4) - 71 -+ -100 -20 100 200 300 msec 2-5 uV F i g u r e 2 5 . A v e r a g e d E R P s a s s o c i a t e d w i t h 1 0 0 0 H z ' r a c q u e t h i t ' t o n e o n i r r e l e v a n t ( p r e r e c o r d e d a u d i o ) c h a n n e l f o r G r o u p s N a n d R o n t r i a l 1 - 72 --100 -20 100 200 300 msec 5uV -100 -20 100 200 300 msec Figure 26. Averaged ERPs associated with 1000 irrelevant channel for Subjects N3 t r i a l 1 Hz tone on and R6 on - 73 -these components for groups N and R as a f u n c t i o n of recording s i t e are displayed i n Table 4. There was a s t a t i s t i c a l l y s i g n i f i c a n t e f f e c t of Hemisphere on ERP amplitudes ( F ( 4 , l l ) = 6.21, p^.008). U n i v a r i a t e - t e s t s showed that r i g h t hemisphere amplitudes were l a r g e r than l e f t hemisphere amplitudes for P2 ( F ( l , 1 4 ) = 25.56, p^.0002), and to a l e s s e r extent f o r PI (F ( l , 1 4 ) = 3.29, p>.05). Mean C4 amplitudes f o r PI and P2 were 0.82^ (SD = 0.16) and 0.92y/ (SD = 0.21). Mean C3 amplitudes were 0.65^ (SD = 0.15) and 0.47^ (SD =.0.17), r e s p e c t i v e l y . The hemispheres d i d not d i f f e r i n Nl or N2 amplitude. There were no main e f f e c t s or i n t e r a c t i o n s i n v o l v i n g Group or T r i a l f a c t o r s . ERP l a t e n c i e s were shorter f o r Group R than for Group N ( F ( 4 , l l ) = 6.54, p£006). This was e s p e c i a l l y true f o r Nl (F ( l , 1 4 ) = 13.59, p<;.003), P2 ( F ( l , 1 4 ) 18.30, p<.0008) and N2 (F ( l , 1 4 ) = 10.67, p^.006). Means are presented i n Table 5. This f i n d i n g suggests that Group R required l e s s time than Group N to decide on the i r r e l e v a n c e of these tones. Latencies were shorter f o r the r i g h t hemisphere than the l e f t ( F ( l , 1 4 ) = 24.55), p^.0001). This was the case f o r a l l components; PI ( F ( l , 1 4 ) = 42.65, p^.0001), Nl (F ( l , 1 4 ) = 49.56, p<.0001), P 2 ( F ( l , 1 4 ) = 63.03), p<.0001) and N2 ( F ( l , 1 4 ) = 27.67, p<1.0001) (see Table 5). There were no s i g n i f i c a n t e f f e c t s i n v o l v i n g the T r i a l s f a c t o r . - 74 -T a b l e 4 Mean a m p l i t u d e and l a t e n c y o f ERP components a s s o c i a t e d w i t h 1000 Hz ' r a c q u e t h i t ' t o n e on i r r e l e v a n t ( p r e r e c o r d e d a u d i o ) c h a n n e l f o r Groups N and R (standard error i n parentheses) Group N Group R Component S i t e Amp. L a t . Amp. L a t PI C3 0 . 776 81 0 .529 79 (0 .213) (2) (0 .201) (2) C4 0 .905 74 0 . 739 71 (0 .223) (2) (0 .231) (2) N l C3 -2 . 503 137 -2 . 051 127 (0 .224) (2) (0 .249 ) (2) C4 -2 . 326 127 -2 .226 115 (0 .239) (2) (0 .276) (2) P2 C3 0 .650 204 0 .284 178 (0 .271) (3) (0 . 255 ) (3) C4 1 .099 191 0 . 740 166 (0 .276) (3) (0 .317) (3) N2 C3 -1 .532 259 - 2 .142 233 (0 .288) (4) (0 .265) (4) C4 -1 .309 246 - 2 .293 224 (0 .276) (4) (0 .332) (5) - 75 -T a b l e 5 Mean l a t e n c y o f ERP c o m p o n e n t s a s s o c i a t e d w i t h ' r a c q u e t h i t ' t o n e on i r r e l e v a n t c h a n n e l f o r G r o u p s N and R, and f o r r e c o r d i n g s i t e s C_ and C ( s t a n d a r d e r r o r i n p a r e n t h e s e s ) Component Group N Group R C3 C4 P I 78 75 80 73 (1) (2) (1) (1) N l 132 121 132 121 (1) (2) (2) (2) P2 198 172 191 179 (2) (2) (2) (2) ' N2 253 229 246 235 (3) (3) (3) (3) - 76 -ERPs a s s o c i a t e d w i t h w a l l bounce s t i m u l i Sample ERP waveforms a s s o c i a t e d w i t h the 500 Hz 'wal l bounce'' tones i n the r e l e v a n t and i r r e l e v a n t audio channels f o r Groups N and R are shown i n F i g u r e 27. EOG t r a c i n g s are d i s p l a y e d i n F i g u r e 28. S i n g l e s u b j e c t r e p r e s e n t a t i o n s o f the waveforms o f F i g u r e s 26 and 27 are p r e s e n t e d i n F i g u r e s 29 and 30, r e s p e c t i v e l y . The f o u r p o s t s t i m u l u s ERP components PI, N l , P2 and N2 were a n a l y z e d as a f u n c t i o n of Channel ( r e l e v a n t v s . i r r e l e v a n t ) , Group, Hemisphere and T r i a l . Mean amplitudes and l a t e n c i e s of these components are c o n t a i n e d i n T a b l e 6. The Channel ( o r s e l e c t i v e a t t e n t i o n ) e f f e c t was s i g n i f i c a n t ( F ( 4 , l l ) = 9.60, p<.002). Amplitudes were l a r g e r to s t i m u l i i n the r e l e v a n t than i n the i r r e l e v a n t channel f o r N l ( F ( l , 1 4 ) = 10.75), p<.006) and N2 ( F ( l , 1 4 ) = 37.35, pCOOOl), but s m a l l e r f o r P2 ( F ( l , 1 4 ) = 29.11, pCOOOl) (see T a b l e 7 ) . S i n c e a l l measures were r e l a t i v e to a p r e s t i m u l u s b a s e l i n e , these r e s u l t s a t t e s t to the n e g a t i v e s h i f t i n the p o s t s t i m u l u s waveform o f ERPs to the r e l e v a n t tones. There was a s i g n i f i c a n t Group X Hemisphere - 77 -Group N 2-5 uV • i » -100 - 2 0 1 0 0 2 0 0 msec 3 0 0 Group R 2-5 uV •100 - 2 0 1 0 0 2 0 0 msec 3 0 0 F i g u r e 27. A v e r a g e d E R P s a s s o c i a t e d w i t h 500 Hz ' w a l l b o u n c e ' t o n e o n r e l e v a n t ( l i v e a u d i o ) a n d i r r e l e v a n t ( p r e -r e c o r d e d a u d i o ) c h a n n e l s f o r G r o u p s N a n d R o n t r i a l 1 - 78 F i g u r e 2 8 . A v e r a g e d E O G w a v e f o r m s a s s o c i a t e d w i t h 5 0 0 H z t o n e o n r e l e v a n t a n d i r r e l e v a n t c h a n n e l s f o r G r o u p s N a n d R o n t r i a l 1 - 79 -r • - — — 1 1 • — - 1 0 0 - 2 0 100 2 0 0 3 0 0 msec u r e 2 9 . A v e r a g e d E R P s a s s o c i a t e d w i t h 5 0 0 H z t o n e o n r e l e v a n t a n d i r r e l e v a n t c h a n n e l s f o r S u b j e c t s N 3 a n d R 6 o n t r i a l 1 - 8 0 -Subject N3 Subject R6 -100 -20 100 200 300 msec F i g u r e 3 0 . A v e r a g e d E O G w a v e f o r m s a s s o c i a t e d w i t h 5 0 0 Hz t o n e o n r e l e v a n t a n d i r r e l e v a n t c h a n n e l s f o r S u b j e c t s I\I3 a n d R 6 o n t r i a l 1 T a b l e 6 Mean a m p l i t u d e and l a t e n c y o f ERP components a s s o c i a t e d w i t h 500 Hz ' w a l l bounce' t o n e on r e l e v a n t ( l i v e a u d i o ) and i r r e l e v a n t ( p r e - r e c o r d e d a u d i o ) c h a n n e l s f o r Groups N and R ( s t a n d a r d e r r o r i n p a r e n t h e s e s ) Group N Group R C3 C4 C3 C4 C h a n n e l R e l e v a n t Component Amp. L a t . Amp. L a t . Amp. L a t . Amp. L a t . PI 0.453 83 0.413 78 0.539 86 0.096 79 (0.174) (2) (0.197) (2) (0.186) (2) (0.249) (2) Nl -3.489 147 -3.481 135 -2.771 137 -3.256 126 (0.222) (2) (0.242) (2) (0.238) (3) (0.264) (3) P2 -0.646 209 -0.382 197 -0.917 181 -1.308 171 (0.222) (2) (0.278) (3) (0.299) (3) (0.319) (3) N2 -4.039 288 -3.513 272 -3.884 260 -5.110 249 (0.236) (2) (0.265) (4) (0.319) (4) (0.357) (4) PI 0.425 87 0.659 77 0. 743 80 1.026 74 (0.206) (2) (0.196) (2) (0.194) (2) (0.215) (2) Nl -2.573 142 -2.355 129 -1.679 124 -1.784 117 (0.194) (2) (0.213) (2) (0.251) (3) (0.317) (3) P2 0.623 203 0.915 189 0. 763 178 0.940 168 (0.267) (3) (0.270) (3) (0.279) (4) (0.331) (4) N2 -2.385 275 -2.156 • 260 -2.490 258 -2.472 245 (0.271) (4) (0.255) (4) (0.264) (5) (0.307) (5) - 82 -T a b l e 7 Mean N l , P2 and N2 a m p l i t u d e s t o 500 Hz ' w a l l b o u n c e ' t o n e i n r e l e v a n t (R) and i r r e l e v a n t ( I ) c h a n n e l s ( s t a n d a r d e r r o r i n p a r e n t h e s e s ) C h a n n e l Component R _I P I 0. 375 0. 713 (0. 1 0 2 ) ( 0 . 1 0 2 ) N l - 3.249 - 2.098 (0. 1 2 2 ) ( 0 . 1 2 5 ) P2 - 0 . 8 1 3 - 0.810 ( 0 . 1 4 2 ) ( 0 . 1 4 3 ) N2 - 4.136 - 2.3 76 (0. 1 5 2 ) ( 0 . 1 3 7 ) - 83 -i n t e r a c t i o n ( F ( 4 , l l ) = 8.38, p^.003). U n i v a r i a t e t e s t s v e r i f i e d an i n t e r a c t i o n f o r N2 ( F ( l , 1 4 ) = 27.75, p.<0001)and to some e x t e n t f o r Nl ( F ( l , 1 4 ) , = 4.57, p>.05), which are d e p i c t e d i n F i g u r e 31. T e s t s of simple main e f f e c t s on Nl amplitudes showed t h a t r i g h t hemisphere responses were l a r g e r than l e f t f o r Group R ( F ( l , 1 4 ) = 4.77, pC05. N2 amplitudes were l a r g e r over the l e f t than the r i g h t hemisphere f o r Group N ( F ( l , 1 4 ) = 8.21, p < 0 1 3 ) , but l a r g e r over the r i g h t than the l e f t f o r Group R ( F ( l , 1 4 ) = 21.02, p^.0005). These r e s u l t s complement those p r e s e n t e d i n F i g u r e 24 and suggest a g e n e r a l tendency f o r ERP amplitudes to be l a r g e r i n the hemishpere c o n t r a l t e r a l to the presumed d i r e c t i o n o f o r i e n t a t i o n . A Channel X Hemisphere i n t e r a c t i o n was n e a r l y s i g n i f i c a n t ( F ( 4 , l l ) = 3.15, p^.06). A u n i v a r i a t e t e s t was s i g n i f i c a n t f o r PI ( F ( l , 1 4 ) = 13.44, p<^.003) and was n e a r l y so f o r N2 ( F ( l , 1 4 ) = 5.62, p<^.04). The e f f e c t s are portrayed i n F i g u r e 32, T e s t s o f simple main e f f e c t s on PI amplitudes r e v e a l e d t h a t r i g h t hemishpere amplitudes were s m a l l e r than l e f t to tones i n the r e l e v a n t channel ( F ( l , 1 4 ) = 5.30, P<.04), but were l a r g e r to tones i n the i r r e l e v a n t channel ( F ( l , 1 4 ) = 5.08, p<.05). In a d d i t i o n , channel s e p a r a t i o n was g r e a t e s t i n t h e l i r i g h t hemisphere ( F ( l , 1 4 ) = 5.39, p<].04). Responses to r e l e v a n t tones produced l a r g e r N2 amplitudes than those to i r r e l e v a n t tones i n both the l e f t ( F ( l , 1 4 ) = 26.47, p<.0001) and the r i g h t hemispheres F i g u r e 3 1 . M e a n N1 a n d N 2 a m p l i t u d e s t o 5 0 0 H z ' w a l l b o u n c e ' t o n e s f o r r e c o r d i n g s i t e s C 3 a n d C 4 f o r G r o u p s N a n d R F i g u r e 3 2 . M e a n P 1 a n d N 2 a m p l i t u d e s t o 5 0 0 H z ' w a l l b o u n c e ' t o n e s i n r e l e v a n t ( R ) a n d i r r e l e v a n t ( I ) a u d i t o r y c h a n n e l s f o r r e c o r d i n g s i t e s C 3 a n d C 4 - 86 -( F ( l , 1 4 ) = 40.62, p^.0001). Asymmetry i n N2 amplitude i n f a v o u r of the r i g h t hemisphere was s i g n i f i c a n t o n l y f o r responses to r e l e v a n t tones ( F ( l , 1 4 ) = 4.19, p < « 0 6 ) . A t r i p l e i n t e r a c t i o n of Group X Hemisphere X Channel ( F ( 4 , l l ) = 3.41, p<C.05) proved to be s i g n i f i c a n t by u n i v a r i a t e t e s t f o r N2 o n l y ( F ( l , 1 4 ) = 14.87, p<.002). F i g u r e 33 shows t h a t a s e l e c t i v e a t t e n t i o n e f f e c t ( i . e . , r esponses to r e l e v a n t s t i m u l i were g r e a t e r than those to i r r e l e v a n t s t i m u l i ) was o b t a i n e d w i t h i n each hemishpere f o r each group, but i t d i d v a r y i n s i z e . The e f f e c t appeared to be s t r o n g e s t f o r the hemisphere c o n t r a l a t e r a l to the presumed d i r e c t i o n of o r i e n t a t i o n of each group. Tukey t e s t s were s i g n i f i c a n t f o r the channel comparison i n the r i g h t hemisphere f o r Group R (q(8,49) = 4.484, p^.05). Responses to i r r e l e v a n t tones were o n l y s l i g h t l y l a r g e r i n the l e f t than i n the r i g h t hemisphere f o r both groups. Responses to r e l e v a n t tones were n o t i c e a b l y l a r g e r i n the hemisphere c o n t r a -l a t e r a l to the presumed d i r e c t i o n o f o r i e n t a t i o n of each group. N2 a mplitudes were comparable f o r the two groups i n the l e f t hemisphere but tended to be l a r g e r i n the r i g h t f o r Group R, e s p e c i a l l y f o r responses to r e l e v a n t t o n e s . T h i s N2 f i n d i n g suggests t h a t above and beyond a g e n e r a l e f f e c t o f c o n t r a l a t e r a l dominance, d i r e c t i o n Figure 3 3 . M e a n N 2 a m p l i t u d e t o 5 0 0 H z ' w a l l b o u n c e ' t o n e s a s a f u n c t i o n o f G r o u p ( N a n d R ) , H e m i s p h e r e ( C 3 a n d C 4 ) a n d C h a n n e l ( R = r e l e v a n t , I = i r r e l e v a n t ) - 88 -of o r i e n t a t i o n appears to a f f e c t h e m i p h e r i c asymmetry i n the p o s t s t i m u l u s ERP s e l e c t i v e a t t e n t i o n e f f e c t . The T r i a l s f a c t o r produced no s i g n i f i c a n t main e f f e c t s or i n t e r a t i o n s . ERP l a t e n c i e s were s h o r t e r f o r Group R than f o r Group N ( F ( 4 , l l ) = 5.78, p C . O l ) , e s p e c i a l l y f o r Nl ( ( F ( l , 1 4 ) = 8.88, p C 0 1 ) , P 2 ( F ( l , 1 4 ) 24.22, p<.0002) and to a l e s s e r degree f o r N2 ( F ( l , 1 4 ) = 8.12, pC. 02). F o r a l l components, l a t e n c i e s were e a r l i e r i n the r i g h t than i n the l e f t hemishpere ( F ( 4 , l l ) = 77.53, p C O O O l ) ; P l ' ( F ( l , 1 4 ) = 73.57 p C O O O l ) , Nl ( F ( l , 1 4 ) = 156.13, p C O O O l , P2 ( F ( l , 1 4 ) = 80.15, p C O O O l ) and N2 ( F ( l , 1 4 ) = 78.82), p C O O O l ) . There were no s i g n i f i c a n t e f f e c t s i n v o l v i n g T r i a l s , nor were t h e r e any s i g n i f i c a n t i n t e r a c t i o n s between the o t h e r f a c t o r s . I t would appear then t h a t d i r e c t i o n of o r i e n t a t i o n , hemisphere o f r e c o r d i n g and s e l e c t i v e a t t e n t i o n have a d d i t i v e e f f e c t s on response l a t e n c y . R e j e c t i o n o f p h y s i o l o g i c a l a r t i f a c t . On the average about 22% of t r i a l s were d i s c a r d e d because of eye movement a r t i f a c t . T h i s f i g u r e d i d not s i g n i f i c a n t l y v a r y a c r o s s e x p e r i m e n t a l c o n d i t i o n s , and i t i s comparable to those p e r c e n t a g e s r e p o r t e d i n Experiment 1. As was t r u e f o r the f i r s t experiment, EMG a r t i f a c t s were n e g l i g i b l e , a v e r a g i n g o n l y about 3% a c r o s s - 89 -e x p e r i m e n t a l c o n d i t i o n s . D i s c u s s i o n The group d i f f e r e n c e s i n p a t t e r n of AP asymmetry cannot be e a s i l y e x p l a i n e d by f a c t o r s o t h e r than the o r i e n t a t i o n of a t t e n t i o n . The groups d i d not d i f f e r i n amplitude of EMG a c i t i v i t y r e c o r d e d both b e f o r e and a f t e r a r a c q u e t h i t . T h i s argues a g a i n s t e f f e c t s o f g e n e r a l t e n s i o n , somatic a n x i e t y or muscular e f f o r t . I t i s t r u e t h a t somatosensory ERPs may be generated by the response to a s t i m u l u s i n a t a s k such as t h i s ( L o v e l e s s , 1979). These ERPs c o u l d c o n c e i v a b l y a f f e c t e l e c t r o c o r t i c a l a c t i v i t y measured at AP2, N l and even P2 l a t e n c i e s (Hink et a l . , 1982; P a p a k o s t o p o u l o s , 1978). The l a c k of s i g n i f i c a n t d i f f e r e n c e s i n EMG p a t t e r n s between groups, however, makes i t most u n l i k e l y t h a t d i f f e r e n t i a l r e a f f e r e n t a c t i v i t y i n f l u e n c e d the f i n d i n g s (see P a p a k o s t o p o u l o s , 1978). Furthermore, r e a f f e r e n c e wouldrnot e x p l a i n the .opposite asymmetries shown .by" the two groups g i v e n t h a t both used the same hand to respond. .. -5 , ' - 90 -The m a n i p u l a t i o n of o r i e n t a t i o n was p a r t i a l l y v e r i f i e d by the d i r e c t i o n o f the averaged EOG a s s o c i a t e d w i t h a r a c q u e t h i t , which was r i g h t w a r d f o r Group N and l e f t w a r d f o r Group R. A n a l y s i s o f EOG showed t h a t Group R tended to produce l a r g e r amplitude eye movements. However, e v i d e n c e p r o v i d e d by o t h e r r e s e a r c h e r s a g a i n s t an e f f e c t o f eye movements on c e n t r a l l y - r e c o r d e d ERP asymmetry was c i t e d at the b e g i n n i n g of t h i s s e c t i o n . ERP a mplitudes are known to be s e n s i t i v e t o f l u c t u a t i o n s i n n o n s p e c i f i c a r o u s a l ( K h a c h a t u r i a n and Gluck, 1969; NHytHnen, 1982), but t h i s too i s an u n l i k e l y e x p l a n a t i o n of group d i f f e r e n c e s i n AP asymmetry. In t h i s experiment ERPs a s s o c i a t e d w i t h f o u r d i f f e r e n t s t i m u l i were measured c o n c u r r e n t l y . The responses o f Group R were by no means c o n s i s t e n t l y l a r g e r ( o r s m a l l e r ) than those of Group N (see T a b l e s 1, 4 and 6; McCallum, 1976). The performance r e s u l t s suggest t h a t Group R found the t a s k to be more d i f f i c u l t than Group N. A l t h o u g h an attempt was made p r i o r : : t o e x p e r i m e n t a t i o n to equate the two groups on l e v e l o f p r e v i o u s e x p e r i e n c e w i t h v i d e o games, o n l y one s u b j e c t i n each group a c t u a l l y - 91 -c l a i m e d never to have p l a y e d t h i s type o f game b e f o r e . Thus s u b j e c t s i n Group R might have e x p e r i e n c e d g r e a t e r d i f f i c u l t y w i t h the unusual s c r e e e n o r i e n t a t i o n p r e s e n t e d to them. The i n v e r t e d s c o r e might have c o n t r i b u t e d to t h i s d i f f i c u l t y . None-t h e l e s s , i t i s u n l i k e l y t h a t t a s k d i f f i c u l t y produced o p p o s i t e AP asymmetries i n Groups N and R. V a r i a t i o n w i t h i n each group i n performance a c r o s s t r i a l s was at l e a s t as g r e a t as t h a t between groups and y e t r e s p e c t i v e p a t t e r n s o f asymmetry f o r the groups were i n v a r i a n t a c r o s s t r i a l s . The most s a t i s f a c t o r y e x p l a n a t i o n seems to be t h a t a n t i c i p a t o r y e l e t r o c o r t i c a l n e g a t i v i t y i s l a r g e r i n the hemisphere c o n t r a l a t e r a l to the d i r e c t i o n o f o r i e n t a t i o n . These p h y s i o l o g i c a l f i n d i n g s support the i d e a t h a t r e a d i n e s s i s indeed s e n s i t i v e to a t t e n d e d l o c a t i o n (Posner, Davidson and Snyder, 1980). E x p l a n a t i o n s of group d i f f e r e n c e s i n the ' s i z e of AP asymmetry might c o n c e i v a b l y i n v o l v e f a c t o r s o t h e r than o r i e n t a t i o n . G r e a t e r mental e f f o r t , as might be r e q u i r e d to p e r f o r m a t a s k o f g r e a t e r d i f f i c u l t y , has been shown to i n c r e a s e the amplitude of AP-type components w i t h o u t , however, i n f l u e n c i n g t h e i r l a t e r a l i z a t i o n - 92 -(Grunewald-Zuberbier et a l . , 1981; McCarthy and Donchin, 1978). The EOG r e s u l t s c o u l d r e f l e c t the g r e a t e r e x p e n d i t u r e of mental e f f o r t by Group R. I t i s a l s o p o s s i b l e t h a t i n d i v i d u a l d i f f e r e n c e s i n degree o f asymmety might be i n v o l v e d d e s p i t e e f f o r t s to randomly a l l o c a t e s u b j e c t s to the two groups. In Experiment 3 s u b j e c t s i n both Garoups N and R were r i g h t - h a n d e d and performed the t a s k u s i n g the p r e f e r r e d hand. E f f e c t s of handedness and o f r e s p o n d i n g hand were not i n v e s t i g a t e d . N e v e r t h e l e s s , based on p r e v i o u s r e s e a r c h , i t i s p o s s i b l e to s p e c u l a t e on the p o s s i b l e importance o f these two f a c t o r s to the p r e s e n t f i n d i n g s . In a d e t a i l e d r e p o r t , Kutas and Donchin (1977) examined the r e a d i n e s s p o t e n t i a l (RP) i n groups o f r i g h t - and l e f t - h a n d e d s u b j e c t s . In g e n e r a l they found l e s s v a r i a b i l i t y i n the waveforms of r i g h t - h a n d e d s u b j e c t s . Asymmetry i n the RP f a v o u r e d the hemisphere c o n t r a l a t e r a l to the r e s p o n d i n g hand f o r r i g h t hand responses by both groups of s u b j e c t s . F o r l e f t hand responses c o n t r a l a t e r a l dominance was p r e s e n t ( a l t h o u g h reduced) i n r i g h t - h a n d e d s u b j e c t s . L e f t - h a n d e r s however, showed b i l a t e r a l l y symmetric waveforms when u s i n g the p r e f e r r e d hand. To the e x t e n t - 93 -to which the RP s t u d i e d by Kutas and Donchin (1977) i s s i m i l a r t o the APs d e s c r i b e d i n the p r e s e n t s t u d i e s (and the s i m i l a r i t y i s p r o b a b l y g r e a t f o r A P I ) , one c o u l d expect the AP r e s u l t s o f Experiment 3 to r e p l i c a t e when r i g h t - h a n d e d s u b j e c t s use the l e f t hand. R e s u l t s f o r l e f t - h a n d e r s are o b v i o u s l y l e s s p r e d i c t a b l e p o s s i b l y due to g r e a t e r h e t e r o g e n e i t y i n i n t e r - h e m i s p h e r i c r e l a t i o n s i n t h i s p o p u l a t i o n (Kutas and Donchin, 1977). Themoderate c o r r e l a t i o n between API and AP2 amplitudes suggests t h a t these two components r e f l e c t a common p r o c e s s of psychomotor p r e p a r a t i o n but at the same time do not p r o v i d e c o m p l e t e l y redundant i n f o r m a t i o n about t h i s p r o c e s s ( J ^ r v i l e h t o and F r u h s t o r f e r , 1970). U n f o r t u n a t e l y Experiment 3 was unable to f u n c t i o n a l l y s e p a r a t e these two components. As w i t h p r e v i o u s r e s e a r c h ( e . g . , Smith, 1976) th e r e was a tendency f o r l a r g e r APs to be a s s o c i a t e d w i t h g r e a t e r p o s i t i v i t y i n the p o s t s t i m u l u s p o r t i o n o f the ERP. The asymmetry i n P2 amplitude which developed a f t e r a r a c q u e t h i t c o u l d i n d i c a t e t h a t P2 l a r g e l y r e p r e s e n t e d a phenomenon l i k e CNV r e s o l u t i o n , i n which the r e t u r n to b a s e l i n e o f a n t i c i p a t o r y n e g a t i v i t y depends upon the e x t e n t to which the i m p e r a t i v e s t i m u l u s or manual response completes the p r o c e s s i n g o f t a s k r e l e v a n t i n f o r m a t i o n , - 94 -or o t h e r w i s e " r e s o l v e s " the s i t u a t i o n (Weinberg, 1973; W i l k i n s o n , 1976). A l t e r n a t i v e l y i t c o u l d be argued t h a t the P2 i s much more of an independent event (Donald and G o f f , 1973; R u c k i n and S u t t o n , 1979), s e n s i t i v e to d e t e c t i o n o f t a r g e t s t i m u l i T h i s means d e s c r i b i n g P2 as a P'^ QQ' " l i k e component, and s u g g e s t i n g t h a t t a r g e t d e t e c t i o n has a g r e a t e r impact on the hemisphere c o n t r a l a t e r a l to the d i r e c t i o n o f o r i e n t a t i o n . T h i s l a t t e r i n t e r p r e t a t i o n r e c e i v e s added support from the f a c t t h a t Nl a m p l i t u d e , from which P2 measures were taken, was u n r e l a t e d to the l e v e l o f a n t i c i p a t o r y n e g a t i v i t y immediately p r e c e d i n g the s t i m u l u s ( i . e . , AP2). In any event, moderate p o s i t i v e c o r r e l a t i o n s between components and f u n c t i o n a l d i s s o c i a t i o n o f components are not n e c e s s a r i l y m u t u a l l y e x c l u s i v e phenomena ( T u e t i n g and S u t t o n ^ 1973). A comparison of the p o s t s t i m u l u s ERP a s s o c i a t e d w i t h a r e l e v a n t 1000 Hz tone and the ERP to an i r r e l e v a n t 1000 Hz tone p o i n t s out d i f f e r e n c e s between ERPs preceded and not preceded by a n t i c i p a t o r y n e g a t i v i t y which appear to be h i g h l y r e p r o d u c i b l e . The d i s t i n g u i s h i n g f e a t u r e s o f the former are a p o s i t i v e s h i f t i n a l l components which appear a f t e r about 50 msec, s h o r t e r Nl l a t e n c y , and s m a l l e r N l a m p l i t u d e (Smith, 1976). A g a i n , hoi-jever, i t must be noted t h a t - 95 -a n t i c i p a t o r y n e g a t i v i t y i t s e l f need not have c o m p l e t e l y determined the p o s t s t i m u l u s waveform of the ERP to a r e l e v a n t 1000 Hz tone (see Experiment 1: R e s u l t s ) . The P^QTJ " l i k e form o f the P2 component i n ERPs to r a c q u e t h i t tones i n the r e l e v a n t channel does not appear to be s p e c i f i c to the p h y s i c a l q u a l i t i e s of a 1 0 0 0 Hz tone. ERPs to 1000 Hz tones i n the i r r e l e v a n t channel showed no l a r g e p o s t - N l p o s i t i v e d e f l e c t i o n s . In f a c t these ERPs were v e r y s i m i l a r to those r e c o r d e d i n response to 500 Hz tones i n the same c h a n n e l , even though the 1000 Hz tones o c c u r r e d l e s s f r e q u e n t l y . Thus n e i t h e r r e l a t i v e r a r i t y o f o c c u r r e n c e nor p h y s i c a l s i m i l a r i t y to t a r g e t events ( r e l e v a n t 1000 Hz tones) - two s i t u a t i o n s o f t e n a s s o i c a t e d x^ith the p r o d u c t i o n o f P'JQQ responses ( P r i t c h a r d , 1980) - was s u f f i c i e n t to induce l a t e p o s i t i v i t y i n the ERPs to i r r e l e v a n t 1000 Hz tones. I t i s l i k e l y t h a t the t a s k used i n t h i s experiment, when c o u p l e d w i t h the p r e s e n t a t i o n of d i s t r a c t i n g t o n e s , was d i f f i c u l t enough to r e q u i r e s e l e c t i v e a t t e n t i o n to r e l e v a n t s t i m u l i . Under such c i r c u m -s t a n c e s l a t e p o s i t i v i t y i s o n l y o c c a s i o n a l l y p r e s e n t i n ERPs to d e v i a n t s t i m u l i i n an unattended c h a n n e l ( e . g . H i l l y a r d , Hink Schwent and P i c t o n , 1 9 7 3 ) . - 96 -The most c o m p e l l i n g e v i d e n c e o f s e l e c t i v e a t t e n t i o n i n ' t h i s experiment r e s u l t e d from comparisons between ERPs to 500 Hz tones p r e s e n t e d i n r e l e v a n t and i r r e l e v a n t ear c h a n n e l s . The former were c h a r a c t e r i z e d by a n e g a t i v e s h i f t t h a t i s not e x p l a i n e d by a d i f f e r e n c e between the tones i n p h y s i c a l q u a l i t y ( t h e y were i d e n t i c a l i n the two c h a n n e l s ) or by eye movement a r t i f a c t . R e c a l l a l s o the f i r s t two experiments which showed t h a t b i s e n s o r y s t i m u l a t i o n , and the a n t i c i p a t i o n of r a c q u e t h i t s and r e l e v a n t tones d i d not c o n t r i b u t e to t h i s e f f e c t (see a l s o F i g u r e 27 on the l a t t e r p o i n t ) . The s h i f t l i k e l y r e p r e s e n t s the " p r o c e s s i n g n e g a t i v i t y " a s s o c i a t e d w i t h the i d e n t i f i c a t i o n of t a r g e t f e a t u r e s (NHHtHnen, 1982). I t does not seem to be a s i g n t h a t the r e l e v a n t tones r e c e i v e f u r t h e r p r o c e s s i n g because i t emerged i n t h i s experiment, as i n o t h e r s (e . g . Schwerit, H i l l y a r d and Galambos, 1976), even though t h e r e was no r e q u i rement f o r tone, d i s c r i m i n a t i o n . I t i s not c l e a r from t h i s study though whether the ERP d i f f e r e n c e s were mediated more by s p a t i a l l o c a t i o n ( r i g h t o r l e f t e a r ) o r by temporal c o r r e l a t i o n w i t h v i s u a l e v e n t s , s i n c e these f a c t o r s were confounded. S e l e c t i v e a t t e n t i o n does appear to have been an a utomatic p r o c e s s ^ at l e a s t i n the sense t h a t i t was i n v o l u n t a r y (Kahneman and Treisman, 1983). S u b j e c t s d i d not seem cap a b l e of i g n o r i n g tones p r e s e n t e d on the r e l e v a n t c h a n n e l even when i t might have worked to t h e i r advantage - 97 -to i g n o r e tones a l t o g e t h e r and c o n c e n t r a t e on the v i d e o s c r e e n , e s p e c i a l l y s i n c e no tone d i s c r i m i n a t i o n was n e c e s s a r y . I n s t e a d they made s p a t i a l l o c a t i o n a t a r g e t f e a t u r e and s e l e c t e d as o b j e c t s of a t t e n t i o n any a u d i t o r y event i n a p a r t i c u l a r l o c a t i o n ( e a r ) which was c o i n c i d e n t w i t h a s a l i e n t v i s u a l e vent. The e a r l i e s t ERP components to show a s e l e c t i v e a t t e n t i o n e f f e c t was P i , at about 80 msec, and t h i s o c c u r r e d o n l y i n the r i g h t hemisphere. Amplitudes were s m a l l e r i n response t o r e l e v a n t ' w a l l bounce' tones than to i r r e l e v a n t t o n e s . T h i s a t t e n u a t i o n o f the amplitude o f a p o s i t i v e peak i n the ERP i s c o n s i s t e n t w i t h a " p r o c e s s i n g n e g a t i v i t y " i n t e r p r e t a t i o n o f the s e l e c t i v e a t t e n t i o n e f f e c t . That i s , an endogenous slow n e g a t i v e s h i f t d e v elops i n the ERP to s e l e c t e d i n f o r m a t i o n . T h i s s h i f t d i s p l a c e s the e n t i r e p o s t s t i m u l u s waveform i n a n e g a t i v e d i r e c t i o n , enhancing the am p l i t u d e o f n e g a t i v e components w h i l e a t t e n u a t i n g those o f p o s i t i v e components l i k e P i . S e l e c t i v e p r o c e s s i n g may have begun e a r l i e r than 80 msec s i n c e P i was si m p l y the f i r s t component measured. In f a c t some a t t e n t i o n - r e l a t e d a u d i t o r y ERP e f f e c t s have been observed as e a r l y as 15 msec p o s t s t i m u l u s , a l t h o u g h these d i d not appear to be l a t e r a l i z e d (McCallum, C u r r y , Cooper, - 98 -Pocock and P a p a k o s t o p o u l o s , 1983). Asymmetries i n v i s u a l ERPs have been r e p o r t e d , but these emerge much l a t e r i n the p r o c e s s i n g sequence, a f t e r about 200 msec (Kostandov, 1980), and a f t e r the b i l a t e r a l appearance o f a s l e c t i o n e f f e c t i n c e n t r a l c o r t i c a l areas ( H a r t e r , Aine and Schroeder, 1982). The f i n d i n g i s c o n s i s t e n t w i t h the n o t i o n o f r i g h t hemisphere s p e c i a l i z a t i o n f o r s t i m u l u s l o c a l i z a t i o n and a n a l y s i s o f s p a t i a l i n f o r m a t i o n (Heilman and Van Den A b e l l , 1980; K o l b and Whishaw, 1980, pp. 246-247, 266). From about 120 msec to about 200 msec, a f t e r s t i m u l u s p r e s e n t a t i o n the s e l e c t i v e a t t e n t i o n e f f e c t was s y m m e t r i c a l l y d i s t r i b u t e d over the hemispheres, as shown by the Nl and P2 amplitude r e s u l t s . T h a t . i s , Nl amplitude was l a r g e r and P2 amplitude s m a l l e r i n response to r e l e v a n t ' w a l l bounce' tones than to i r r e l e v a n t t o n e s , r e g a r d l e s s o f hemisphere. At about 120 msec another, a p p a r e n t l y independent, p r o c e s s r e p r e s e n t i n g the e f f e c t o f d i r e c t i o n o f o r i e n t a t i o n (the Group v a r i a b l e ) on h e m i s p h e r i c asymmetry a l s o began to d e v e l o p and to c o n t i n u e on i n p a r a l l e l w i t h the s e l e c t i v e a t t e n t i o n p r o c e s s . T h i s was hsown by the s t a t i s t i c a l independence of the Nl s e l e c t i o n e f f e c t from the Group X Hemisphere i n t e r a c t i o n . Somewhere between 200 msec and 300 msec p o s t s t i m u l u s the two p r o c e s s e s i n t e r a c t e d as r e v e a l e d by the dependence of the s i z e o f the N2 - 99 -s e l e c t i v e a t t e n t i o n e f f e c t on p a r t i c u l a r combinations of hemisphere and d i r e c t i o n o f o r i e n t a t i o n . At t h i s time i n the i n f o r m a t i o n p r o c e s s i n g sequence s e l e c t i o n was maximal i n the hemisphere c o n t r a l a t e r a l to the d i r e c t i o n o f o r i e n t a t i o n . These f i n d i n g s p r o v i d e s t r o n g support f o r a d u a l component model of the endogenous n e g a t i v e s h i f t ( O k i t a , 1981). One component r e f l e c t s e l e c t r o c o r t i c a l a c t i v i t y a s s o c i a t e d w i t h s e l e c t i v e i n f o r m a t i o n p r o c e s s i n g and, i n Experiment 3, was f i r s t o bserved i n the ERP at about 80 msec p o s t s t i m u l u s . The second component i n v o l v e s a c t i v i t y a s s o i c a t e d w i t h o r i e n t a t i o n to the source of r e l e v a n t i n f o r m a t i o n , and i t was measurable l a t e r i n the ERP at around 120 msec p o s t s t i m u l u s . T h i s experiment demonstrated t h a t the e f f e c t of h a v i n g s u b j e c t s o r i e n t i n one d i r e c t i o n or the o t h e r i s to prime the hemisphere c o n t r a l a t e r a l to t h a t d i r e c t i o n . When s u b j e c t s expected important events l i k e r a c q u e t h i t s to take p l a c e on e i t h e r the l e f t or the r i g h t s i d e of t h e i r v i s u a l f i e l d , a n t i c i p a t o r y n e g a t i v e s h i f t s i n e l e c t r o c o r t i c a l a c t i v i t y p r i o r to these events were l a r g e r i n the c o n t r a l a t e r a l hemisphere. U n f o r t u n a t e l y t h e r e was no b e h a v i o u r a l e v i d e n c e a t t e s t i n g to the b e n e f i t s of t h i s p r i m i n g . There was - 100 -however, e l e c t r o c o r t i c a l e v i d e n c e of the success o f p r i m i n g i n the a n a l y s i s o f ERPs o t h e r than the a n t i c i p a t o r y p o t e n t i a l s . S e l e c t i v e a t t e n t i o n e f f e c t s observed i n l a t e r components o f ERPs to w a l l bounce s t i m u l i were g r e a t e s t i n the primed hemisphere. Thus the e l e c t r o c o r t i c a l system, l i k e the b e h a v i o u r a l , i s i n t e r n a l l y c o n s i s t e n t i n s u g g e s t i n g t h a t p r i m i n g enhances the a b i l i t y t o a t t e n d s e l e c t i v e l y . These r e s u l t s p r o v i d e a h i t h e r t o m i s s i n g l i n k between the endogenous e l e c t r o c o r t i c a l n e g a t i v i t i e s (Hansen and H i l l y a r d , 1980; H i l l y a r d and P i c t o n , 1979). Two f i n a l p o i n t s d e serve mention. F i r s t , v i r t u a l l y a l l ERP component l a t e n c i e s measured i n t h i s experiment were s h o r t e r i n the r i g h t hemisphere than i n the l e f t , f o r both groups o f s u b j e c t s . T h i s might i n d i c a t e t h a t i n g e n e r a l ERPs are o r g a n i z e d e a r l i e r i n the r i g h t hemisphere (Kostandov, 1980), and i t would be c o n s i s t e n t w i t h b e h a v i o u r a l e v i d e n c e t h a t t h i s hemisphere i s an e a r l y i n f o r m a t i o n p r o c e s s o r ( S e r g e n t , 1982). The second p o i n t concerns the f a i l u r e to observe s i g n i f i c a n t changes a c r o s s t r i a l s i n ERPs d e s p i t e s i g n i f i c a n t changes i n performance. In many s t u d i e s o f r e a c t i o n time and the CNV, r e a c t i o n time reaches - 101 -an o p t i m a l l e v e l a f t e r a few t r i a l s and remains f a i r l y c o n s t a n t at t h a t l e v e l ( e . g . , McCallum, 1978). T h i s seemed t o be the p a t t e r n of the performance measure i n t h i s experiment. The CNV however, o f t e n shows a steady d e c l i n e ( H i l l y a r d , 1973; McCallum, 1978; Weinberg, C u r r y and P e t e r s , 1978). The d e c l i n e has been a t t r i b u t e d to o v e r l e a r n i n g as the s u b j e c t ' s performance ceases to be f o c a l ( " s c o p e u t i c mode") and i n s t e a d becomes automatic ( " c a t e g o r i c mode") (Cooper, McCallum and Pa p a k o s t o p o u l o s , 1979). For some t i n e now McCallum (1976; 1978) has been a r g u i n g t h a t the t y p i c a l CNV paradigm does not s u f f i c i e n t l y m o t i v a t e a s u b j e c t to m a i n t a i n involvement i n the t a s k , and t h a t the steady d e c l i n e i n CNV amplitude c o u l d be a r r e s t e d i f the e x p e r i m e n t a l t a s k kept performance from becoming a u t o m a t i c . The v i d e o game used i n the p r e s e n t experiment was chosen because i t demanded c o n t i n u o u s involvement on the s u b j e c t ' s p a r t and t h i s might e x p l a i n why the amplitude o f the CNV-like a n t i c i p a t o r y p o t e n t i a l s (APs) f a i l e d to d e c l i n e or o t h e r w i s e change s i g n i f i c a n t l y w i t h time on t a s k . With r e s p e c t to s e l e c t i v e a t t e n t i o n e f f e c t s , the no n s p y c h o p a t h i c s u b j e c t s i n the J u t a i and Hare (1983) study g r a d u a l l y a p p r e c i a t e d t h a t a l l a u d i t o r y s t i m u l i were i r r e l e v a n t and c o n s e q u e n t l y devoted l e s s a t t e n t i o n to them, p r o d u c i n g a ste a d y drop i n ERP am p l i t u d e . - 102 -Psychopaths made t h i s assessment almost immediately and e f f e c t i v e l y i g n o r e d tones throughout game t r i a l s . In the p r e s e n t study, the need to a t t e n d s e l e c t i v e l y would have remained c o m p a r a t i v e l y c o n s t a n t a c r o s s t r i a l s s i n c e some but not a l l tones were r e l e v a n t , t h e r e b y p r e v e n t i n g a d e c r e a s e i n s i z e o f ERP s e l e c t i o n e f f e c t s . C o r r e l a t i o n s between b e h a v i o u r and ERP components may w e l l have emerged had more f i n e g r a i n e d performance measures been employed, but i t i s not at a l l c l e a r what form these measures s h o u l d t a k e . P o s t s t i m u l u s components l i k e N l are v e r y d i f f i c u l t t o c o r r e l a t e w i t h r e a c t i o n time to i n d i v i d u a l s t i m u l u s p r e s e n t a t i o n s because of the need f o r a v e r a g i n g . Although t h i s i s l e s s o f a problem f o r a n t i c i p a t o r y p o t e n t i a l s because of t h e i r much l a r g e r s i z e and l o n g e r d u r a t i o n , r e l i a b l e r e l a t i o n s h i p s w i t h performance are e l u s i v e (Rebert and Tecce, 1973). I n t e r p r e t a t i o n o f c o r r e l a t i o n s i s not made e a s i e r by the f a c t t h a t r e a c t i o n time i t s e l f i s m u l t i p l y determined by motor and p e r c e p t u a l f a c t o r s which l i m i t s i t use as an index of any one p a r t i c u l a r p s y c h o l o g i c a l p r o c e s s ( H i l l y a r d , 1973). E f f o r t , i n d e p e n d e n t l y of performance, seems to be the p r i m a r y determ-i n a n t o f AP amplitude (Deecke, 1978), but e f f i c i e n c y o f e f f o r t e x p e n d i t u r e c o u l d be expected to p r e d i c t performance ( P i c t o n , - 103 -Campbell, B a r i d e a u - B r a u n and P r o u l x , 1978). However, at p r e s e n t t h e r e i s a l a c k o f s u i t a b l e t e c h i n i q u e s f o r the measurement of p s y c h o p h y s i o l o g i c a l e f f i c i e n c y . - 104 -V. B r i e f summary o f main f i n d i n g s T h i s t h e s i s demonstrated t h a t e v e n t - r e l a t e d p o t e n t i a l s (ERPs) a s s o c i a t e d w i t h p s y c h o l o g i c a l p r o c e s s e s o f a n t i c i p a t i o n and s e l e c t i v e a t t e n t i o n can be r e l i a b l y r e c o r d e d when s u b j e c t s p e r f o r m a c o n t i n u o u s involvement p e r c e p t u a l - m o t o r t a s k . A n t i c i p a t o r y p o t e n t i a l s (APs) c o n s i s t e d o f slow n e g a t i v e s h i f t s i n the EEG which o c c u r r e d d u r i n g the 500-msec p e r i o d p r i o r t o a r a c q u e t h i t i n the v i d e o game t a s k . These APs l i k e l y r e p r e s e n t e d both the psycho-motor p r e p a r a t i o n f o r a r a c q u e t h i t and the a n t i c i p a t i o n o f the feedback s t i m u l u s (1000 Hz tone) which s i g n a l l e d a s u c c e s s f u h i t . APs were found to have g r e a t e r amplitude over the hemisphere c o n t r a l a t e r a l to the p r i m a r y d i r e c t i o n o f the s u b j e c t ' s o r i e n t a t i o n That i s , APs were l a r g e r over the l e f t hemisphere f o r s u b j e c t s i n Group N, and l a r g e r over the r i g h t f o r s u b j e c t s i n Group R. S e l e c t i v e a t t e n t i o n was measured by the d i f f e r e n c e i n p o s t s t i m u l u s ERP n e g a t i v i t y between w a l l bounce tone p r e s e n t e d i n r e l e v a n t and i r r e l e v a n t a u d i t o r y c h a n n e l s . Between 120 msec and 200 msec a f t e r s t i m u l u s p r e s e n t a t i o n , ERP n e g a t i v i t y was g r e a t e r i n response to r e l e v a n t s t i m u l i . At around 200 msec p o s t s t i m u l u s i t was shown - 105 -t h a t t h i s s e l e c t i v e a t t e n t i o n e f f e c t was g r e a t e r i n the hemisphere c o n t r a l a t e r a l to the d i r e c t i o n o f the s u b j e c t ' s o r i e n t a t i o n . T h i s r e s u l t suggested t h a t o r i e n t a t i o n may have primed the c o n t r a l a t e r a l hemisphere as e v i d e n c e d by the AP asymmetries, and t h a t the e f f e c t of t h i s p r i m i n g might be to enhance c e r t a i n a s p e c t s of s e l e c t i v e a t t e n t i o n which are measured i n the ERP at around 200 msec a f t e r s t i m u l u s o n s e t . - 106 -R e f e r e n c e s Anderson, S.W. L a n g q u a g e - r e l a t e d asymmetries o f eye-movement and evoked p o t e n t i a l s . I n - S.Harnad e t a l . (eds . ) , L a t e r a l i z a t i o n  i n the nervous system. New York: Academic P r e s s , 1977. A n d r e a s s i , J . L . and Greco, J.R. E f f e c t s of b i s e n s o r y s t i m u l a t i o n on r e a c t i o n time and the evoked c o r t i c a l p o t e n t i a l . P h y s i o l o g i c a l  P s y c h o l o g y , 1975, 3. 189-194. Becker, W. , Iwase, K. , J l l r g e n s , R. and Kornhuber, H.H. B e r e i t s c h a f t s -p o t e n t i a l p r e c e d i n g v o l u n t a r y slow and r a p i d hand movements. In: W.C. McCallum and J.R. Knott ( e d s . ) , The r e s p o n s i v e b r a i n . B r i s t o l : John Wright and Sons, 1976. Broadbent, D.E. S t i m u l u s s e t and response s e t : Two k i n d s o f s e l e c t i v e a t t e n t i o n . I n : D.I. M o s t o f s k y ( e d . ) , A t t e n t i o n : Contemporary  t h e o r y and a n a l y s i s . New York: A p p l e t o n , Century, C r o f t s , 1970. B r u n i a , C.H.M. and V i n g e r h o e t s , A.J.J.M. O p p o s i t e hemisphere d i f f e r e n c e s i n movement r e l a t e d p o t e n t i a l s p r e c e d i n g f o o t and f i n g e r f l e x i o n s . B i o l o g i c a l P s y c h o l o g y , 1981, 1_3, 261-269. Cooper, R. Methodology of slow p o t e n t i a l changes. I n : W.C. McCallum and J.R. K n o t t ( e d s . ) , The r e s p o n s i v e b r a i n . B r i s t o l : John Wright and Sons, 1976. Cooper, R., McCallum, W.C. and P a p a k o s t o p o u l o s , D. A bimodal slow p o t e n t i a l t h e o r y of c e r e b r a l p r o c e s s i n g . In: J.E. Desmedt ( e d . ) , C o g n i t i v e components i n c e r e b r a l e v e n t - r e l a t e d p o t e n t i a l s and  s e l e c t i v e a t t e n t i o n . P r o g r e s s i n c l i n i c a l n e u r o p h y s i o l o g y (Vo1. 6.) B a s e l : Karger7 1979. ' Deecke, L. D i s s o c i a t i o n s between performance (time o f movement o n s e t ) and slow p o t e n t i a l s ( B e r e i t s c h a f t s p o t e n t i a l and CNV") . I n : W.A. Cobb and H. Van D u i j n ( e d s . ) , Contemporary c l i n i c a l  n e u r o p h y s i o l o g y . E l e c t r o e n c e p h a l o g r a p h y and C l i n i c a l N e u r o p h y s i o l o g y (Supplement No. 34), 1978. : ~ Deecke;-!:,. and Kornhuber, H.H. C e r e b r a l p o t e n t i a l s and the i n i t i a t i o n o f v o l u n t a r y movement. In: J . E . Desmedt ( e d . ) , A t t e n t i o n ,  v o l u n t a r y c o n t r a c t i o n and event r e l a t e d c e r e b r a l p o t e n t i a l s .  P r o g r e s s i n c l i n i c a l n e u r o p h y s i o l o g y ( V o l . 1 . ) . B a s e l : K a r g e r , 1977. Deecke, L., Becker, W., G r o z i n g e r , B., S c h e i d , P. and Kornhuber, H. Human b r a i n p o t e n t i a l s p r e c e d i n g v o l u n t a r y limb movements. In: W.C. McCallum and J.R. K n o t t ( e d s . ) , E v e n t - r e l a t e d slow p o t e n t i a l s  o f the b r a i n : • T h e i r r e l a t i o n s to b e h a v i o u r . E l e c t r o e n c e p h a l o g r a p h y and C l i n i c a l N e u r o p h y s i o l o g y ( S u p p l e m e n t N o . 3 3 ) , 1 9 7 3 . - 107 -Desmedt, J.E. and Debecker, J . Wave form and n e u r a l mechanism o f the d e c i s i o n P 350 e l i c i t e d w i t h o u t p r e s t i m u l u s CNV o r r e a d i n e s s p o t e n t i a l i n random sequences of n e a r - t h r e s h o l d a u d i t o r y c l i c k s and f i n g e r s t i m u l i . E l e c t r o e n c e p h a l o g r a p h y and C l i n i c a l Neuro-p h y s i o l o g y , 1979, 47, 648-670. Dixon, W.J. ( e d . ) , B i o m e d i c a l computer programs: P - s e r i e s . B e r k e l e y : U n i v e r s i t y of C a l i f o r n i a P r e s s , 1981. Donald, M.W. and G o f f , W.R. C o n t i g e n t n e g a t i v e v a r i a t i o n and s e n s o r y evoked r e s p o n s e s : T h e i r i n t e r a c t i o n and r e l a t i o n s h i p to a u d i t o r y d i s c r i m i n a t i o n . In: W.C. McCallum and J.R. K n o t t ( e d s , ) , Event -r e l a t e d slow p o t e n t i a l s of the b r a i n : T h e i r r e l a t i o n s to b e h a v i o u r .  E l e c t r o e n c e p h a l o g r a p h y arid C l i n i c a l N e u r o p h y s i o l o g y (Supplement No. 3 3 ) , 1973. ~~ : Donchin, E. M e t h o d o l o g i c a l i s s u e s i n CNV r e s e a r c h : A reivew. I n : W.C. McCallum and J.R. K n o t t ( e d s . ) , E v e n t - r e l a t e d slow p o t e n t i a l s o f the b r a i n : T h e i r r e l a t i o n s to b e h a v i o u r . E l e c t r o e n c e p h a l o g r a p h y and C l i n i c a l N e u r o p h y s i o l o g y (Supplemtn Nol 3 3 ) , 1973. Donchin, E., Callaway, E., Cooper, R., Desmedt, J.E., G o f f , W.R., H i l l y a r d , S.A. and S u t t o n , S. P u b l i c a t i o n c r i t e r i a f o r s t u d i e s of evoked p o t e n t i a l s (EP) i n man: Report o f a committee. In J.E. Desmedt ( e d . ) , A t t e n t i o r i , v o l u n t a r y c o n t r a c t ion and event-r e l a t e d c e r e b r a l p o t e r i t i a l s . P r o g r e s s i r i C l i n i c a l N e u r o p h y s i o l o g y ( V o l . 1 ) . B a s e l : K a r g e r , 1977. " G a i l l a r d , A.W.K. C o r t i c a l c o r r e l a t e s o f motor p r e p a r a t i o n . I n : R.S. N i c k e r s o n ( e d . ) , A t t e n t i o n and performance. V I I I . H i l l s d a l e , N.J.: Lawrence Erlbaum A s s o c i a t e s , 1980. G a i l l a r d , A.W. and NHStMnen, R. M o l a l i t y e f f e c t s on the c o n t i n g e n t n e g a t i v e v a r i a t i o n i n a simple r e a c t i o n - t i m e t a s k . I n : W.C. McCallum and J.R. Knott ( e d s . ) , The r e s p o n s i v e b r a i n . B r i s t o l : John Wright and Sons, 1976. G e r b r a n d t , L. M e t h o d o l o g i c a l c r i t e r i a f o r the v a l i d a t i o n o f movement r e l a t e d p o t e n t i a l s . I n : D.A. Otto ( e d . ) , M u l t i d i s c i p l i r i a r y  p e r s e p c t i v e s i n e v e n t - r e l a t e d b r a i n p o t e n t i a l r e s e a r c h (EPA 600/9 -77-043). Washington, D.C.: U.S. Government P r i n t i n g O f f i c e , 1978. G r a t t o n , G'.-, C o l e s , M.G.H. and Donchin, E. A new method f o r o f f - l i n e removal o f o c u l a r a r t i f a c t . E l e c t r o e n c e p h a l o g r a p h y arid C l i n i c a l  N e u r o p h y s i o l o g y , 1983, 55, 468-484. - 108 -Grunewald-Zuberbier, E., Grunewald, G. , Runge, H., Netz, J . and HHmberg, V. C e r e b r a l p o t e n t i a l s d u r i n g s k i l l e d slow p o s i t i o n i n g movements. B i o l o g i c a l P s y c h o l o g y , 1981, 13, 71-87. Hansen, J.C. and H i l l y a r d , S.A. Endogenous b r a i n p o t e n t i a l s a s s o c i a t e d w i t h s e l e c t i v e a u d i t o r y a t t e n t i o n . E l e c t r o e n c e p h a l o g -raphy and C l i n i c a l N e u r o p h y s i o l o g y , 1980, '49, 277-290. H a r r i s , R.J. A primer Of m u l t i v a r i a t e s t a t i s t i c s . New York: Academic P r e s s , 1975. H a r t e r , M.R., A i n e , C. and Schroeder, C. Hem i s p h e r i c d i f f e r e n c e s i n the n e u r a l p r o c e s s i n g o f s t i m u l u s l o c a t i o n and type: E f f e c t s o f s e l e c t i v e a t t e n t i o n on v i s u a l evoked p o t e n t i a l s . N e u r o p s y c h o l o g i a , 1982, 20, 421-438. Heilman, K.M. and Van Den A b e l l , R. R i g h t hemisphere dominance f o r a t t e n t i o n : The mechanism u n d e r l y i n g h e m i s p h e r i c asymmetries o f i n a t t e n t i o n ( n e g l e c t ) . Neurology, 1980, 3_0, 327-330. H i l l y a r d , S.A. S e l e c t i v e a t t e n t i o n i n man. I n : R, Galambos and S.A. H i l l y a r d ( e d s . ) , E l e c t r o p h y s i o l b g y Of c o g n i t i v e p r o c e s s i n g  N e u r o s c i e n c e s Research Program B u l l e t i n , 1982,'20, 167-171. H i l l y a r d , S.A. The CNV and human b e h a v i o r : A review. In E.C. McCallum and J.R. Kn o t t ( e d s . ) , E v e n t - r e l a t e d slow p o t e n t i a l s o f the b r a i n : T h e i r r e l a t i o n s to b e h a v i o u r . E l e c t r o e n c e p h a l o g r a p h y  and C l i r Y J C a l N e u r o p h y s i o l o g y (Supplement No. 33), 1973. . H i l l y a r d , S.A. and Galambos, R. Eye movement a r t i f a c t i n the CNV. E l e c t r o e n c e p h a l o g r a p h y arid C l i n i c a l N e u r o p h y s i o l o g y , 1970, 2j3, 173-182. H i l l y a r d , S.A. and P i c t o n , T.W. E v e n t - r e l a t e d b r a i n p o t e n t i a l s and s e l e c t i v e i n f o r m a t i o n p r o c e s s i n g i n man. In: JLEL Desmedt ( e d . ) , C o g n i t i v e components i n c e r e b r a l e v e n t - r e l a t e d  p o t e n t i a l s arid s e l e c t i v e a t t e n t i o n . P r o g r e s s i n c l i n i c a l n e u r o p h y s i o l o g y ( V o l . 6 ) . B a s e l : K a r g e r , 1979. H i l l y a r d , S.A., Hink, R.F., Schwent, V.L. and P i c t o n , T.W. E l e c t r i c a l s i g n s o f s e l e c t i v e a t t e n t i o n i n the human b r a i n . S c i e r i c e , 1973, 182, 177-180. Hink, R.F., H i l l y a r d , S.A. and Benson, P.J. E v e n t - r e l a t e d b r a i n p o t e n t i a l s and s e l e c t i v e a t t e n t i o n t o a c o u r s t i c and p h o n e t i c cues. B i o l o g i c a l p s y c h o l o g y , 1978, 6, 1-16. - 109 -Hink, R. F., .Kohler, H., Deecke, L. and Kornhumber, H.H. R i s k - t a k i n g and the human b e r e i t s c h a f t s p o t e n t i a l . E l e c t r o - encephalography and C l i n i c a l Neurophysiology, 1982, 53, 361-373. j H r v i l e h t o , R. and F r u h s t o r f e r , H. D i f f e r e d t i a t i o n between slow c o r t i c a l p o t e n t i a l s associated with motor and mental acts i n man. Experimental B r a i n Research, 1970, 11, 309-317. J u t a i , J.W. and Hare, R.D. Psychopathy and s e l e c t i v e a t t e n t i o n during performance of a complex perceptual-motor task. Psychophysiology, 1983, 20, 146-151. Kahneman, D. and Treisman, A. Changing views of a t t e n t i o n and au t o m a t i c a l l y . In: R. Parasuraman, R. Davies and J . Beatty (eds.), V a r i e t i e s of a t t e n t i o n . New York: Academic Press, i n press. Khachaturian, Z.S. and Gluck, H. The e f f e c t s of arousal on the amplitude of evoked p o t e n t i a l s . B r a i n Research, 1969, 14, 589-606. Kinsbourne, M. The mechanism of hemispheric c o n t r o l of the . l a t e r a l gradient of a t t e n t i o n . In: P.M.A. Rabbit and S. Dornic (eds.), A t t e n t i o n and performance. V. London: Academic Press, 1975. K i r k , R.E. Experimental design: Procedures f o r the behavioural  s c i e n c e s ! B e l m o n t , C a l i f . : B r o o k s / C o l e , 1 9 6 8 . Knight, R.T., H i l l y a r d , S.A., Woods, D.L. and N e v i l l e , H.J. The e f f e c t s of f r o n t a l cortex l e s i o n s on event ^ r e l a t e d p o t e n t i a l s during auditory s e l e c t i v e a t t e n t i o n . Electroencephalography  and C l i n i c a l Neurophysiology, 1981, 5_2, 571-582. Knight, R.T., H i l l y a r d , S.A., Woods, D.L. and N e v i l l e , H.J. The e f f e c t s of f r o n t a l and t e m p o r a l - p a r i e t a l l e s i o n s on the auditory evoked p o t e n t i a l i n man. Electroencephalography  and C l i n i c a l Neurophysiology, 1980, '50, 112-124. Kolb, B. and Whishaw, 1.0. Fundamentals of human neurophysiology. San F r a n c i s c o : Freeman, 1980. - 110 -Kostandov, E.A..Asymmetry of v i s u a l p e r c e p t i o n and i n t e r h e m i s p h e r i c i n t e r a c t i o n . N e u r o s c i e n c e and B e h a v i o u r a l P h y s i o l o g y , 1980, 10, 36-47. ~ " " " — Kutas, M. and Donchin, E. The e f f e c t o f handedness of r e s p o n d i n g hand, and of response f o r c e on the c o n t r a l a t e r a l dominance of the r e a d i n e s s p o t e n t i a l . I n : J.E. Desmedt ( e d . ) , A t t e n t i o n ,  v o l u n t a r y c o n t r a c t i o n and e v e n t - r e l a t e d c e r e b r a l p o t e n t i a l s .  P r o g r e s s i n c l i n i c a l n e r u o p h y s i o l o g y ( V o l . 1 ) . B a s e l : K a r g e r , 1977. L i b e t , B., W r i g h t , E.W. and G l e a s o n , C.A. R e a d i n e s s - p o t e n t i a l s p r e c e d i n g u n r e s t r i c t e d 'spontaneous' v s . p r e p l a n n e d v o l u n t a r y a c t s . E l e c t r o e n c e p h a l o g r a p h y and C l i n i c a l N e u r o p h y s i o l o g y , 1982, 54, 322-335. L o v e l e s s , N.E. E v e n t - r e l a t e d slow p o t e n t i a l s o f the b r a i n as e x p r e s s i o n s o f o r i e n t i n g f u n c t i o n . I n : H.D. Kimmel, E.H. Van 01st and J . F . Orlebeke ( e d s . ) , The o r i e n t i n g r e f l e x i n humans. H i l l s d a l e , N.J.: Erlbaum, 1979. McCallum, W.C. B r a i n slow p o t e n t i a l changes e l i c i t e d by m i s s i n g s t i m u l i and by e x t e r n a l l y paced v o l u n t a r y r e s p o n s e s . B i o l o g i c a l  P s y c h o l o g y . 1980, 1_1, 7-19. McCallum, W.C. Some anomalies found i n r e l a t i o n s h i p s between event-r e l a t e d p o t e n t i a l s and performance. In: W.A. Cobb and H. Van D u i j n ( e d s . ) , Contemporary c l i n i c a l n e u r o p h y s i o l o g y . E l e c t r o - encephalography and C l i n i c a l N e u r o p h y s i o l o g y (Supplement No. 34), 1978. McCallum, W.C. B r a i n slow p o t e n t i a l changes and motor response i n a v i g i l a n c e s i t u a t i o n . In W.C. McCallum and J.R. K n o t t ( e d s . ) , The r e s p o n s i v e b r a i n . B r i s t o l : John Wright and Sons, 1976. McCallum, W.C, C u r r y , S.H., Cooper, R. , Pocock, P.V. and Papakostopoulos D. B r a i n e v e n t - r e l a t e d p o t e n t i a l s as i n d i c a t o r s o f e a r l y s e l e c t i v e p r o c e s s e s i n a u d i t o r y t a r g e t l o c a l i z a t i o n . P s y c h o p h y s i o l O g y , 1983, 20, 1-17. McCarthy, G. and Donchin, E. B r a i n p o t e n t i a l s a s s o c i a t e d w i t h s t r u c t u r a l and f u n c t i o n a l v i s u a l matching. 'Neuropsychologia, 1978, ' 16, , 571-585. - I l l -Ncia'tHnen, R. P r o c e s s i n g n e g a t i v i t y : an e v o k e d - p o t e n t i a l r e f l e c t i o n o f s e l e c t i v e a t t e n t i o n . P s y c h o l o g i c a l B u l l e t i n ^ 1982, 92, 605-640. O k i t a , T. Slow n e g a t i v e s h i f t s o f the human e v e n t - r e l a t e d p o t e n t i a l a s s o c i a t e d w i t h s e l e c t i v e i n f o r m a t i o n p r o c e s s i n g . B i o l o g i c a l P s y c h o l o g y , 1981, _12, 63-75. P a p a k o s t o p o u l o s , D. E l e c t r i c a l a c t i v i t y o f the b r a i n a s s o c i a t e d w i t h s k i l l e d performance. I n : D.A. Otto ( e d . ) , M u l t i d i s c i p l i n a r y p e r s e p c t i v e s i n e v e n t - r e l a t e d b r a i n p o t e n t i a l r e s e a r c h (EPA 600/9,-,7"7-,043). Washington, D.C.: U.S. Government P r i n t i n g O f f i c e , 1978. Parasuraman, R. E f f e c t s o f i n f o r m a t i o n p r o c e s s i n g demands on slow n e g a t i v e s h i f t l a t e n c i e s and N100 amplitude i n s e l e c t i v e and d i v i d e d a t t e n t i o n . B i o l o g i c a l • P s y c h o l o g y , 1980, 11, 217-233. Parasuraman, R. A u d i t o r y evoked p o t e n t i a l s and d i v i d e d a t t e n t i o n . P s y c h o p h y s i o l o g y , 1978, 1_5, 460-465 P i c t o n , T.W., Campbell, K.B., Bar i b e a u - B r a u n , J . and P r o u l x , G.B. The n e u r o p h y s i o l o g y o f human a t t e n t i o n : A - t u t o r i a l r e view. I n : J Requin ( e d . ) , A t t e n t i o n and performance. V I I H i l l s d a l e , N.J.: Erlbaum, 1978. P i c t o n , T.W., H i l l y a r d , S.A., Galambos, R. and S c h i f f , M. Human a u d i t o r y a t t e n t i o n : A c e n t r a l or p e r i p h e r a l p r o c e s s ? S c i e n c e , 1971, 173, 351-353. P i c t o n , T.W., H i l l y a r d , S.A., Kr a u s z , H.I. and Galambos, R. Human a u d i t o r y evoked p o t e n t i a l s . I: E v a l u a t i o n o f components. E l e c t r o e n c e p h a l o g r a p h y and C l i n i c a l N e u r o p h y s i o l o g y , 1974, 36.> 191-199. Posner, M.I., Davidson, B.J. and Snyder, C.R.R. A t t e n t i o n and the d e t e c t i o n o f s i g n a l s . J o u r n a l of E x p e r i m e n t a l P s y c h o l o g y : G e n e r a l . 1980, 109, 160-174. Posner, M.I., N/ssen, M.J. and Ogden, W.C. Atte n d e d and unattended p r o c e s s i n g modes: The r o l e o f se t f o r s p a t i a l l o c a t i o n . I n : H. Pick and E. Saltzman ( e d s . ) , Modes o f p e r c e i v i n g and p r o c e s s i n g i n f o r m a t i o n . New J e r s e y : Erlbaum, 197.8. -112 -P r i t c h a r d , W.S. Psychophy s i o l o g y , o f P300. P s y c h o l o g i c a l B u l l e t i n , 1981, 89, 506-540. " " R e b e r t , C.S. and Tecce, J . J . A summary of CNV and r e a c t i o n time. I n : W.C. McCallum and J.R. K n o t t ( e d s . ) , E v e n t - r e l a t e d slow p o t - e n t i a l s o f the b r a i n : T h e i r r e l a t i o h s to b e h a v i o u r . E l e c t r o e n c e - phalography and c l i n i c a l N e u r o p h y s i o l o g y (Supplement No. 33), 1973. R e i s b e r g , D., S c h e i b e r , R. and Potemken, L. Eye p o s i t i o n and the c o n t r o l o f a u d i o t r y a t t e n t i o n . J o u r n a l o f E x p e r i m e n t a l P s y c h o l o g y : Human P e r c e p t i o n and Performance, 1981, 7, 318-323. R o c k s t r o h , B. , E l b e r t , R. , Birbaumer, N. and Lu,tzenberger, W. Slow b r a i n p o t e n t i a l s and b e h a v i o u r . B a l t i m o r e : Urban and Schwarzen-b e r g , 1982. Rorhbaugh, J.W., Syndulko, K. and L i n d s l e y , D.B. B r a i n wave components of the c o n t i n g e n t n e g a t i v e v a r i a t i o n i n humans. S c i e n c e , 1976, 191, 1055-1057. Rosen, S., Robinson, J . and L o i s e l l e , D. Oculomotor components of e v e n t - r e l a t e d e l e c t r o c o r t i c a l p o t e n t i a l s i n monkeys. • In: D.A. O t t o ( e d . ) , M u l t i d i s c i p l i r i a r y p e r s p e c t i v e s i i i e v e n t - r e l a t e d b r a i n p o t e n t i a l r e s e a r c h (EPA 600/9-77-043). Washington, D.C.: U.S. Government P r i n t i n g O f f i c e , 1978. Ruchkin, D.S. and S u t t o n , S. CNV and P300 r e l a t i o n s h i p s f o r e m i t t e d and f o r evoked c e r e b r a l p o t e n t i a l s . In: J.E. Desmedt ( e d . ) , C o g n i t i v e components i n c e r e b r a l e v e n t - r e l a t e d p o t e n t i a l s and s e l e c t i v e a t t e n t i o n . P r o g r e s s ,in c l i n i c a l n e u r o p h y s i o l o g y ( V o l . 6.). B a s e l : K a r g e r , 1979. Sabat, S.R. S e l e c t i v e a t t e n t i o n , c o r t i c a l evoked r e s p o n s e s , and b r a i n f u n c t i o n i n human s u b j e c t s : A c r i t i c a l r e v i e w and t h e o r y . B i o l o g i g c a l P s y c h o l o g y . 1978, 7_, 175-201. Schwent, V.L. and H i l l y a r d , S.A. Evoked p o t e n t i a l c o r r e l a t e s o f s e l e c t i v e a t t e n t i o n with m u l t i - c h a n n e l a u d i t o r y i n p u t s . E l e c t r o e n c e p h a l o g r a p h y arid C l i n i c a l N e u r o p h y s i o l o g y , 1975, 38, 131-138. - 113 -Schwent, V.L., H i l l y a r d , S.A. and Galambos, R. S e l e c t i v e a t t e n t i o n • and the a u d i t o r y v e r t e x p o t e n t i a l : I I . E f f e c t s o f s i g n a l i n t e n s i t y and masking n o i s e . E l e c t r o e n c e p h a l o g r a p h y arid C l i n i c a l  N e u r o p h y s i o l o g y , 1 9 7 6 , 4 0 _ , 6 1 5 - 6 2 2 . Sergent, J . The c e r e b r a l b a l a n c e o f power: C o n f r o n t a t i o n or c o o p e r a t i o n ? J o u r n a l o f E x p e r i m e n t a l P s y c h o l o g y : Human  p e r c e p t i o n and Performance, 1 9 8 2 , J 3 , 2 5 3 - 2 7 2 . Smith, D.B.D. Some i n t e r r e l a t i o n s between the c o n t i n g e n t n e g a t i v e v a r i a t i o n and the evoked p o t e n t i a l . P s y c h o p h y s i o l o g y , 1 9 7 6 , 1 3 , 3 9 9 - 4 0 4 . • " Straumanis, J . J . , Shagass, C. and Overton, D.A. Problems a s s o c i a t e d w i t h a p p l i c a t i o n o f the c o n t i n g e n t n e g a t i v e v a r i a t i o n to p s y c h i a t r i c r e s e a r c h . J o u r n a l of Nervous and Mental D i s e a s e , 1 9 6 9 , 1 4 8 , 1 7 0 - 1 7 9 . Tecce, J . J . C o n t i n g e n t n e g a t i v e v a r i a t i o n and i n d i v i d u a l d i f f e r e n c e s . A r c h i v e s o f Ge n e r a l P s y c h i a t r y , 1 9 7 1 , 2 4 , 1 - 1 6 . T e c c e , J . J . and H a m i l t o n , B.T. CNV r e d u c t i o n by s u s t a i n e d c o g n i t i v e a c t i v i t y ( d i s t r a c t i o n ) . I n : W.C. McCallum and J.R, Kno t t ( e d s . ) , E v e n t - r e l a t e d slow p o t e n t i a l s o f the b r a i n : T h e i r r e l a t i o n s t o b e h a v i o u r . ' E l e c t r o e n c e p h a l o g r a p h y arid ' C l i n i c a l  N e u r o p h y s i o l o g y (Supplement No. 3 3 ) , 1 9 7 3 . T e u t i n g , P. and S u t t o n , S. The r e l a t i o n s h i p between p r e s t i m u l u s n e g a t i v e s h i f t s and p s o t s t i m u l u s components o f the averaged evoked p o t e n t i a l . I n : S. Kornblum ( e d . ) , A t t e n t i o n and  performance. IV. New York: Academic P r e s s , 1 9 7 3 . Vaughan, H.G. C o s t a , L.D. and R i t t e r , W. Topography o f the human motor p o t e n t i a l . E l e c t r o e n c e p h a l o g r a p h y arid C l i r i i c a l  N e u r o p h y s i o l o g y , 1 9 6 8 , ' 2 5 _ , 1 - 1 0 . W a l t e r , W.G. E f f e c t s on a n t e r i o r b r a i n responses o f an expec t e d a s s o c i a t i o n between s t i m u l i . J o u r n a l o f Psychosomatic Research, 1 9 6 5 , 9 , 4 5 - 4 9 . W a l t e r , W.G., Cooper, R. , A l d r i d g e , V.J.-, McCallum, W.C. and W i n t e r , A.L. C o n t i n g e n t n e g a t i v e v a r i a t i o n : An e l e c t r i c s i g n o f s e n s o r i - m o t o r a s s o c i a t i o n and expectancy i n the human b r a i n . N ature, 1 9 6 4 , 2 0 3 , 3 ' 8 0 - 3 8 4 . - 114 -Weinberg, H. The c o n t i n g e n t n e g a t i v e v a r i a t i o n : I t s r e l a t i o n to feedback and e x p e c t a n t a t t e n t i o n . In: W.C. McCallum and J.R. Knott ( e d s ) , E v e n t - r e l a t e d slow p o t e n t i a l s o f the b r a i n :  T h e i r r e l a t i o n s to b e h a v i o u r . E l e c t r o e n c e p h a l o g r a p h y and  C l i n i c a l N e u r o p h y s i o l o g y (Supplement N o . 3 3 ) , 1973. Weinberg, H., C u r r y , S.H. and P e t e r s , J . F . The i n f l u e n c e o f i n s t r u c t i o n a l s e t on e v e n t - r e l a t e d p o t e n t i a l s . I n : W.A. Cobb and H. Van D u i j n ( e d s . ) , Contemporary C l i n i c a l N e u r o p h y s i o l o g y . E l e c t r o e n c e p h a l o g r a p h y arid C l i n i c a l Neuro- p h y s i o l o g y (Supplement No. 34), 1978. W i l k i n s o n , R.T. R e l a t i o n s h i p between CNV, i t s r e s o l u t i o n and the evoked r e s p o n s e . I n : W.C. McCallum and J.R. Knott ( e d s . ) , The r e s p o n s i v e b r a i n . B r i s t o l : John Wright and Sons, 1976. W i l k i n s o n , R.T., M o r l o c k , H.C. and W i l l i a m s , H.L. Evoked c o r t i c a l r esponse d u r i n g v i g i l a n c e . PsychOriomic'Scierice, 1966, 4, 221-222. 

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