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


This study examined several aspects of the neural control of locomotion in birds. Initially, it was necessary to define an index of normal locomotor functions. This was accomplished for both flying and walking using electromyographic analysis of forelimb and hindlimb musculature to determine which muscles best define the flight and walking patterns respectively. Secondly, in chronic surviving birds, a series of subtotal spinal lesioning experiments were performed to determine which descending pathways were responsible for the initiation of hindlimb locomotion. Thirdly, results were recorded from brainstem electrical stimulation studies designed to determine the location of locomotor areas in the avian brainstem which effected the initiation and descending control of locomotion in these animals. Results indicated the iliotibialis cranialis (ITC) and flexor cruris lateralis (FCL) muscles best define the swing and stance phases of hindlimb locomotion, respectively. Muscles which best defined the elevator and depressor phases of flying were deltoideus major (DM) and pectoralis (Pect), respectively. Results of the low thoracic selective lesioning experiments support the hypothesis that the medullary reticulospinal pathway is necessary to the initiation and control of volitional hindlimb locomotion. Further, descending input to spinal cord pattern generators via the vestibulospinal pathways may play some adjunctive role or be necessary for the descending control of locomotion. Electrical stimulation of the brainstem in acute decerebrate birds elicited locomotor behaviours in both hindlimbs and forelimbs. Four areas, including; an area near the lateral /medial spiriform nucleus; nucleus et tractus descendens trigemini; and central nucleus of the medulla, pars ventralis and dorsalis; and the lateral reticular nucleus produced varying locomotor behaviours when stimulated. Acute dorsal cord transection did not affect the electrically stimulated behaviour, indicating that descending pathways from supraspinal centres which travel in the dorsal cord do not affect the descending control of locomotion. A strong parallel exists between the results of this study in two avian species and those found in the mammalian literature.

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