Rhythmic slow waves of lateral geniculate nucleus in the cat: relation to vigilance.

Rhythmic slow waves (RSWs) of 3.2-4.5 (mean 3.8) Hz occurred in the lateral geniculate nucleus of the cats; most frequently during slow wave sleep, less frequently during paradoxical sleep and drowsiness, and only occasionally during quiet wakefulness. It was not observed during attentive wakefulness. The amplitude of RSWs was 0.1 mV or less and could be differentiated easily from PGO waves and sleep spindles. Hippocampal theta waves, when they appeared together, did not show a consistent phase relationship with the RSWs. Similar bursts of waves showing a good synchronization with the geniculate RSWs were also recorded from the visual cortex. This suggests the presence of a pace maker which is active in a state-dependent manner and may synchronously modulate the activity of different sites in the visual system.