Activity of cervical neurons during forelimb fictive locomotion in decerebrate cats

Unit activities were recorded from cervical neurons during forelimb fictive locomotion. Rhythmic activities were evaluated by onset and termination. Rhythmically-active neurons were classified into 4 major groups: (1) neurons, the active periods covered the whole flexor phase; (2) f+e neurons, the active periods commenced prior to and terminated in the extensor phase; (3) e neurons, the active periods appeared within the extensor phase; (4) e+f neurons, the active periods commenced prior to and terminated in the flexor phase. In addition, a few neurons that were not classified were observed. Neuronal behaviors seemed to suggest that and e+f were grouped "flexor-like," while e and f+e were grouped as "extensor-like." "Flexor-like" neurons were likely distributed in the dorsal (lamina V-VI) and rostral (C5-C6) region, whereas "extensor-like" neurons distributed mainly in the ventral (lamina VI-VII) and caudal (C7-T1) region. Some neurons showed rhythmic activities prior to appearance of fictive locomotion (prelude rhythm). The structure of the central pattern generator was discussed.