S114 Sleep spindles and their biological significance

Abstract

Sleep spindles are periodically recurring oscillatory patterns of the non-REM sleep EEG that overlap with the 10–15 Hz (sigma) frequency band of the EEG spectral profile. Spindles are found throughout mammalian sleep, are thought to stabilize sleep and to promote memory consolidation. This overview will summarize some of the ionic, cellular and circuit bases of sleep spindle generation and spatiotemporal organization, and will then highlight a comparative analysis of sigma power dynamics in mouse and human non-REM sleep. In both species, sigma band power augments and declines over time intervals of ∼50 s, together with a varying fragility of sleep with respect to external stimuli. Over the same time intervals, electrophysiological hallmarks of memory consolidation and variations in cardiac rhythms are also coordinated. This infraslow pattern of sigma activity, likely including sleep spindles, hence hallmarks behaviorally, neuronally, and autonomically distinct non-REM sleep stages. These conform with the essential needs of sleep to be both continuous and fragile and could represent an evolutionarily conserved organizational element of mammalian non-REM sleep.