Aspects du sommeil normal

Abstract

Three types of sleep and wakefulness are distinguishable: wakefulness, NREM (non-rapid eye movement) sleep and REM sleep. Analysis of vigilance states is based on the polysomnography, a technique derived from electroencephalography (EEG), that need to record several variables including the EEG, the electromyogram, the electro-oculogram and other autonomic variables. Most laboratories adhere to the guidelines published by Rechtschaffen and Kales (1968) to score sleep through visual analysis, however the amplitude and frequency of rhythmic EEG activity could be well-quantified using spectral analysis algorithms. The regulation of main physiological functions - ventilatory, cardio-vascular, endocrine, digestive functions and thermoregulation - differs, depending on the states of sleep and wakefulness. Improved knowledge of these interactions and thus of sleep physiology has been helpful in the development of sleep medicine. Human sleep is regulated by three different processes: the circadian process that determines sleep timing, the homeostatic one that determines its need, and the ultradian process. Basic research (especially molecular genetics) on circadian rhythms is one of the most advanced in biology. Mental activities during sleep involve hypnagogic and hypnopompic hallucinations, mental activities collected by experimental awakenings during REM sleep periods, dreams and reflexive activity during slow wave sleep closed to mental activities during wakefulness. The mechanisms of mental activity generation remain obscure, in particular, it is still unknown whether one or two generators are responsible for dream and reflexive activity generation.