Two oscillatory components detected by forced splitting of the sleep-wake cycle in humans (original) (raw)

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

Abstract

The sleep-wake cycle of human subjects was artificially split into two episodes by imposing an 8-h light and 4-h dark cycle (LD 8:4) twice a day for 7 days, which was followed by a 3 day free-running session. Sleep was permitted only in the dark period. The subjects in the ordinary group were exposed to ordinary light (ca. 500 lux) in the 8-h light period, and those in the bright light group to bright (ca. 5,000 lux) and ordinary light alternatively with bright light after the 1st dark period (24:00 - 4:00 h). Split sleeps persisted in the free-running session with the major episode around the 1st dark period and the minor episode around the 2nd dark. By contrast, circadian melatonin rhythm in the free-running session significantly phase-delayed in the ordinary light group, but phase-advanced in the bright light group, keeping the melatonin rhythm un-split. The length of nocturnal melatonin secretion (NMS) was significantly shortened in the bright light group. Interestingly, the fal...

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