View source for Sleep deprivation

=== Cognitive ===

* '''Fundamental processes''': Speed of processing, as measured by neuropsychological tests such as the Digit Symbol Substitution Task, decreases with increasing time awake (Leproult et al., 1997). Additionally, tonic, sustained attention becomes increasingly labile during periods of sleep deprivation, leading to increased variability in reaction times, as well as a greater number of performance lapses on the Psychomotor Vigilance Test (PVT) and other tests of attention (Dinges et al., 1997). The time-on-task effect in sustained attention tasks is also more pronounced in the sleep-deprived state.  

* '''Higher cognitive functions''': The effects of sleep deprivation on tasks of higher cognitive function are less well known, and experimental results have been mixed. Numerous studies (Linde et al., 1999; Harrison and Horne, 2000) have shown that subjects are able to recruit compensatory resources and temporarily perform at a level comparable to that of rested controls when performing relatively more complex and engaging tasks. This is more apparent in convergent tasks (e.g. tasks of critical thinking and rule-based deduction), and less true of divergent ones (e.g. assimilation of changing information, updating strategies based on new information, lateral thinking, risk assessment, insight and temporal memory skills). Sleep loss also adversely affects working memory function, defined as the ability to encode, manipulate and retrieve information, in one or more sensory modalities (Chee and Choo, 2004). One unifying hypothesis arising from these results is that sleep deprivation differentially affects prefrontal-cortex-related functions while leaving executive ability associated with other brain regions relatively intact. 

* For a more complete review of the neurocognitive consequences of sleep deprivation, refer to Durmer and Dinges (2005).