Fysiologie van de slaap

Sleep can be classified in two fundamental different types of sleep: slow wave and REM sleep. Slow wave sleep comprises 80% and REM sleep comprises 20% of total sleep. Slow wave sleep can be divided in deep and light slow wave sleep. Stage 1 and stage 2 belong to the light sleep and dominate in the second part of the nightly sleep, while stage 3 and stage 4 belong to deep slow wave sleep and predominantly occur in the first part of the night. Deep slow wave sleep is necessary for rest and body restoration, while light slow wave sleep seems to have a more luxury function. The function of REM sleep, a type of sleep which is associated with dreaming, is unknown, but it is often suggested that it has a cognitive function. Processing of earlier obtained information is thought to take place in REM sleep. It is remarkable that active sleep, a forerunner of REM sleep, develops at first in babies, while this type of sleep is unfolded late in evolution and occurs only in mammals.