Sleep, waking and neurobehavioural performance.

Waking neurobehavioural or cognitive functioning is largely dependent on two mechanisms both in synchrony and in opposition to each other: the sleep homeostatic and circadian systems. The influences of these systems are particularly evident during periods of sustained wakefulness or sleep deprivation. Although the effects of these two systems on neurobehavioural functioning during periods of extended wakefulness have been demonstrated experimentally, there does not exist an adequate theory to describe the underlying brain mechanisms responsible for these neurobehavioural deficits. Much research has in fact concentrated not on understanding the nature of these deficits, but rather in counteracting them, via the use of countermeasures, such as naps and wake promoting compounds.