RELATION OF DISCHARGE FREQUENCY TO CONDUCTION VELOCITY IN PYRAMIDAL TRACT NEURONS

Abstract

Pyramidal tract neurons in the precentral gyrus of the monkey were identified by their antidromic responses to electrical stimulation of the medullary pyramid. Units with short antidromic response latencies (< 1 msec.) tended to be phasically active during contralateral arm movement and to be relatively inactive in the absence of movement. Units with longer antidromic response latencies (> 1 msec.) tended to have tonic, regular discharge in the absence of movement and showed both upward and downward shifts in discharge frequency with movement. Increase in over-all amount of discharge with movement was greatest for the shortest latency units and least for the longest latency units. With sleep, the clear differences between discharge patterns of long and short latency units disappeared, both types of neurons discharging in sporadic bursts.