Slow-wave Sleep

Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage 3 and 4 of non-rapid eye movement sleep, according to the Rechtschaffen & Kales (R & K) standard of 1968. As of 2008, the American Academy of Sleep Medicine (AASM) has discontinued the use of stage 4, such that the previous stages 3 and 4 now are combined as stage 3. An epoch (30 seconds of sleep) which consists of 20% or more slow wave (delta) sleep, now is considered to be stage 3.

Slow-wave sleep is considered important to consolidate new memories.

Sleep deprivation studies with humans suggest that the primary function of slow-wave sleep may be to allow the brain to recover from its daily activities. As it turns out, glucose metabolism in the brain increases as a result of tasks that demand mental activity. Other functions slow-wave sleep can effect includes the secretion of growth hormone. It is always greatest during this stage. It is also thought to be responsible for a decrease in sympathetic and increase in parasympathetic neural activity.