Neurocognitive Consequences of Sleep Deprivation

Jeffrey S. Durmer, MD, PhD; David F. Dinges, PhD

Disclosures

Semin Neurol. 2005;25(1):117-129. 

In This Article

Sleep Deprivation and Sleep-Wake Regulation

An understanding of the effects of sleep deprivation on human neurobehavioral functions has improved as the neural systems controlling circadian and sleep homeostatic mechanisms have been identified.[23,30,31,32] Although much is known about the neurobiology of hypothalamic mechanisms involving sleep-wake regulation, much less is known about how these systems interact and alter waking neurocognitive functions. It is clear that both wakefulness and sleep are modulated by an endogenous biological clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus. The impact of the biological clock goes beyond compelling the body to fall asleep and to wake up again. The biological clock also modulates waking behavior, as reflected in sleepiness and cognitive performance, generating circadian rhythmicity in almost all neurobehavioral variables investigated.[33,34] Theoretical conceptualizations of the daily temporal modulation of sleep and wakefulness (and to a lesser extent the modulation of waking cognitive functions) have been instantiated in the two-process mathematical model of sleep regulation[35,36] and many mathematical variants of this model.[37] The two-process model of sleep regulation has been applied to describe the temporal profiles of sleep and wakefulness.[33,34] The model consists of a sleep homeostatic process (process S) and a circadian process (process C), which interact to determine the timing of sleep onset and offset, as well as the stability of waking neurocognitive functions.[33,34,38] The homeostatic process represents the drive for sleep that increases during wakefulness and decreases during sleep. When this drive increases above a certain threshold, sleep is triggered; when it decreases below another threshold, wakefulness is invoked. The circadian process represents daily oscillatory modulation of these threshold levels. The circadian drive for wakefulness may be experienced as the spontaneously enhanced alertness in the early evening even after a sleepless night. On the other hand, deprivation of sleep can elevate homeostatic pressure to the point that waking neurocognitive functions will be degraded even at the time of peak circadian drive for wakefulness.[39]

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