Visual cortical units associated with phasic activity in REM sleep and wakefulness

Abstract

Single unit activity was studied in the cat visual cortex in natural transitions of sleep and wakefulness with special reference to phasic activity in desynchronized sleep and wakefulness. Among half the samples which held certain relations to ponto-geniculo-occipital (PGO) waves in sleep, a small portion of units (5%, 7 of 140 units) had a time-locked phase relationship to PGO waves in sleep. They started rapid firing immediately after the onset of PGO waves and the facilitation lasted for 100–250 msec. Most units in the non-striate cortex had positive relationships to PGO waves, while in the striate cortex the majority showed no correlation with PGO waves. In wakefulness, a small number of units (7%, 4 of 56 units) showed a definite relationship to PGO-like waves in the background EEG, whereas a majority (86%) had no correlation with PGO-like waves. One unit ceased to fire and 3 others accelerated in discharge immediately after the onset of PGO-like waves. Mechanisms underlying these two phasic events at different vigilance levels and their possible biological significance are discussed.