ABSTRACT
Sleep is a complex process involving recurring cycles of non-rapid-eyemovement and rapid-eye-movement (REM) sleep, each cycle lasting 90-120 min. Electroencephalographic (EEG) signals differ from those of wakefulness, particularly during non-REM sleep. The exact function of sleep is unclear, but there is no doubt that it is an essential restorative process as evidenced by experiments that have examined the physical and behavioral consequences of sleep deprivation.
