Sleep Med Psychophysiol.  1997 Dec;4(2):147-155.

Sleep-Wake Cycles in Man

  • 1Korea University College of Medicine, Department of Psychiatry.


To assess the reliability of chronobiological models of sleep/wake regulation, it is necessary that the models predict the data which has been studied in sleep research, and they should be generalized across all ages. To date, manu adult human data on such models have accumulated, yet it is evident that a comprehensive theory of the biorhythmic aspects of sleep/wake states has not established.? Circadian rhythms such as the time going to bed, sleep onset, slow wave sleep pressure, periodicity of REM sleep, daytime performance, and early evening alertness are resumed everyday. Even in adult humans, sleep is inherently polyphasic. In both the disentrained and entrained states, naps when allowed tend to recur in a temporally lawful manner. The monophasic sleep pattern of most industrial societies therefore appears to be purely of social origin. The endogenous biorhythmic nature of circasemidian sleep tendency is supported by the ubiquity of the phenomenon across all ages. The NREM/REM sleep cycle within sleep with its inherent physiological, endocrine, and neurochemical fluctuations represents the best-documented ultradian sleep rhythms. Also, a daytime ultradian variation in sleepiness with a periodicity similar to nocturnal NREM/REM cycle(BRAC hypothesis) is suggested.? This review article provides a brief synoptic review of the evidences for circadian, circasemidian, and ultradian sleep/wak rhythms, and then the author will suggest the issues which expedite fuller modeling of sleep/wake system, to be further discussed.


Sleep/Wake cycles; Circadian; Circasemidian; Ultradian Rhythms

MeSH Terms

Circadian Rhythm
Sleep, REM
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