Abstract
Discharge patterns of motor coritcal neurons in cats walking steadily on a moving belt were compared with other functional characteristics of the neurons. In forelimb motor cortex rhythmic discharges occurred in cells with peripheral receptive fields in all parts of the contralateral forelimb and also in cells with no discernible receptive field. Cells discharging at similar times during the step cycle often had very different receptive fields and cells with similar receptive fields (including neighboring cells) could discharge at similar or at quite different times. In cells with a cutaneous receptive field including the forefoot the discharges during locomotion remained rhythmic (and their phasing relative to the step cycle was unchanged) when the response to mechanical stimulation in the receptive field was temporarily much reduced or abolished by local anesthesia of the skin. The proportion of neurons showing accelerated firing during different parts of the step cycle fluctuated more for antidromically identified pyramidal tract neurons (ptn) than for non-ptn and was highest during the 2nd half of stance in the contralateral forelimb and lowest during swing. When the neurons were subdivided according to the movement evoked by threshold electrical stimulation through the micro-electrode, ptn and non-ptn recorded by electrodes evoking elbow flexion showed a wide variety of discharge patterns. For ptn the discharge rate reached an average of 69 impulses/s during late stance and declined to an average of 26 impulses/s during swing.