Last-order interneurones controlling activity of elbow extensor motoneurones during forelimb fictive locomotion in the cat

Abstract

Last-order interneurones, which were identified by antidromic invasion from the elbow extensor motor nuclei (triceps brachii), were examined for rhythmic activity during fictive locomotion. Last-order neurones with activity modulated were divided into 3 groups: one exhibited flexor-like activity, another extensor-like, and the third activity which had properties of both. Flexor-like neurones, presumably inhibitory, were located in the rostral segments (C 6–C 7), whereas extensor-like ones, presumably excitatory, were located in the caudal (C 7-T 1). Neurones of the third group were found in the most caudal segments (C 8-T 1). The results seem to suggest the existence of functional localization in the stepping generator.