부산대학교 도서관

Human behavioral and physiological processes are under the dual control of circadian rhythmicity and sleep‐wake homeostasis. In mammalian species, the underlying mechanism for the generation of most circadian rhythms is located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Sleep‐wake homeostasis is an hourglass‐like mechanism relating sleep propensity and intensity to the duration of prior wakefulness. Studies under “constant routine conditions” have facilitated the detection of circadian and sleep regulation and have delineated the temporal variations over the 24‐hr day of subjective alertness (or its antonym, subjective sleepiness), cognitive performance (i.e. objective alertness), and mood, as well as endocrine, metabolic, and cardiovascular function. Subjective and objective alertness vary in parallel, with detectable decreases starting around the usual bedtime until a minimum is reached in the early morning hours, and then increase during the daytime hours. Decreased sleep quality and sleep loss due to voluntary behavioral alterations or to pathological conditions are associated with disturbances of a variety of neurobehavioral, physiological parameters, as well as of subjective alertness, mood, and cognitive performance. Aging is commonly associated with pronounced alterations of both the homeostatic process and the circadian pacemaker. Strategies to improve sleep quality may have beneficial effects on mental and physical well‐being.