Spatiotemporal changes of slow wave activities before and after 14 Hz/12 Hz sleep spindles during stage 2 sleep.

The present study examined the spatiotemporal changes of slow wave (delta and theta bands) activities before and after 14 Hz/12 Hz sleep spindles during stage 2 sleep, using topographic mapping of electroencephalogram (EEG) power. Both types of sleep spindles appeared after slow wave activities of background EEG decreased. Moreover, the appearance of sleep spindles provided increasing EEG slow wave activities in the subsequent period. Further, the present results showed that an appearance of 14 Hz sleep spindle facilitated slow wave activities at the centro-parietal areas, while an appearance of 12 Hz sleep spindle facilitated slow wave activities at the fronto-central areas. These results suggest that sleep spindles provide cortical de-arousal, and serve to maintain sleep.