Dynamic Relation of Sleep Spindles and K-Complexes to Spontaneous Phasic Arousal in Sleeping Human Subjects

Abstract

K-complexes unaccompanied by sleep spindles (K₀-complexes) and isolated sleep spindles during stage 2, non-rapid eye movement (NREM) sleep were examined before and after transient activation phase (AP) and also pseudo-AP during human sleep to determine the relationship of K₀-complexes and sleep spindles to APs. Sixteen sleep records obtained from 16 young adult males were scanned for isolated APs during stage 2 NREM sleep. One hundred APs and 62 pseudo-APs were identified and analyzed. The number of sleep spindles decreased and reached its minimum at the onset of APs, when an increase was observed in the number of K₀-complexes. APs occurred when a decrease in sleep spindles was coupled with an increased incidence of K₀-complexes, thus forming an antagonistic relation. A similar antagonism was observed between sleep spindles and slow waves. A working hypothesis was formulated to interpret a triad of sleep events: sleep spindles, K₀-complexes, and slow wave sleep. Three kinds of sleep-REM, spindles-dominant, and slow-wave-dominant-are suggested as more useful classifications than the Rechtschaffen and Kales categories.