TEMPORAL PATTERNS OF DISCHARGE OF PYRAMIDAL TRACT NEURONS DURING SLEEP AND WAKING IN THE MONKEY

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Abstract
Pyramidal tract (PT) neurons in the precentral gyrus of the intact, unanesthetized monkey were identified by antidromic responses to stimulation of the medullary pyramid and their activity was recorded during waking in the absence of movement (W), sleep with EEG slow waves (S), and sleep with low voltage fast EEG activity (S-LVF). During W, PT neurons show regular discharge with an absence of high frequency bursts and periods of silence. During S, bursts and periods of silence appear, and over-all amount of activity falls. During S-LVF, both bursts and intervening periods of silence increase in length, and over-all amount of discharge increases. Total amount of activity during W and S-LVF is approximately the same. It is suggested that the occurrence of high frequency bursts during S and S-LVF may result from a reduction in the effectiveness of some frequency-limiting mechanism which acts to stabilize discharge during W. The decrease in over-all amount of activity with S indicates that S is associated with a reduction in excitatory drive. When movement occurs during W, over-all amount of activity is greater than at any other time, but high frequency bursts do not occur. Thus, the pattern of discharge during S-LVF is entirely different from that during waking, either with or without movement.