DORSAL SPINOCEREBELLAR TRACT NEURONS IN THE CHRONIC INTACT CAT DURINGWAKEFULNESS AND SLEEP - ANALYSIS OF SPONTANEOUS SPIKE ACTIVITY

Relatively little is known about the transmission of ascending sensory information from lumbar levels across the behavioral states of sleep and wakefulness. The present study used extracellular recording method s in chronically instrumented intact behaving cats to monitor the acti vity of lumbar dorsal spinocerebellar tract (DSCT) neurons within Clar ke's column during the states of wakefulness, quiet sleep, and active sleep. Clarke's column DSCT neurons were identified using antidromic i dentification and retrograde labeling techniques. The spontaneous spik e rate and interspike interval data of DSCT neurons were quantified as a function of behavioral stale. During wakefulness and quiet sleep, t he spike rate of DSCT neurons was stable, and interspike interval hist ograms (ISIH) indicated a relatively high degree of regularity in DSCT neuronal spike train patterns. In contrast, during active sleep there was a marked reduction in the ongoing spike rate in a vast majority o f cells tested. The magnitude of change in ISIHs and interspike interv al data during active sleep depended in part on whether the reduction in cell firing was maintained or periodic throughout active sleep. Fur ther suppression of spontaneous activity also was observed during inte nse rapid-eye-movement episodes of active sleep that were associated w ith clustered pontogeniculo-occipital wave and muscular twitches and j erks. After re-awakening, spontaneous spike activity of Clarke's colum n DSCT neurons resembled that recorded during previous episodes of wak efulness. These data provide evidence that ascending proprioceptive an d exteroceptive sensory transmission through Clarke's column is dimini shed during the behavioral state of active sleep.