[Propagation of the activity along the "stepping strip" of the spinal cord in the cat].

Three stepping points (SPs) were found in one dorsolateral funiculus of the spinal cord at the low thoracic level in mesencephalic cats. The SPs were at a distance of about 8 mm from one another, and stimulation of each SP elicited stepping of the ipsilateral hind limb. Synaptic responses of single neurons to stimulation of the caudal and rostral SPs before and after electrolytic lesion of the intermediate SP were recorded 5-17 mm caudal to the caudal SP. Neurons excited by caudal SP stimulation encountered after the lesion as often as before it, whereas stimulation of the rostral SP (4 pps) evoked responses 5 times more seldom than before lesion. Even stimulation of the rostral SP with the frequency of 40-60 pps which increased essentially a lesion firing index before coagulation, excited only a few neurons. Thus, synaptic excitation of neurons becomes significantly more difficult after damage of the stepping strip between stimulation and recording sites.