Neurons of upper cervical segments responding to stimulation of the bulbar locomotor strip

Abstract

Synaptic responses of single neurons of upper cervical segments to stimulation of the bulbar "locomotor strip" were recorded extracellularly in mesencephalic cats. The stimulating current being about 30 muA, these responses usually had 2-7 ms latencies and appeared in neurons located at a depth of 2-4 mm from the dorsal surface (Rexed's laminae V-VIII). These neurons cannot be excited antidromically either from lumbar or lower cervical segments. However antidromic responses, could be evoked by stimuli applied 3-5 mm caudally of the recording electrode. It is assumed that neurons in C2, C3 excited from the "locomotor strip" are elements of the cell column which is responsible for the polysynaptic propagation of activity to the spinal generators of stepping.