The effects of sleep loss on executive functioning

Most sleep loss research has concentrated on long duration, repeated measures performance of low-level, monotonous tasks, such as vigilance and reaction time, in support of the theory that sleep loss induces a decline in Non-Specific arousal while having no specific effects on functioning. Numerous studies have shown the beneficial effects of caffeine on this type of performance measure. Recent studies have been conducted on executive functioning tasks that are short, novel, and stimulating. These measures display a sensitivity to sleep loss after 36h that is not compensated by waking countermeasures such as motivation and caffeine. These findings suggest Specific effects of sleep loss, contrary to the Non-Specific theory, particularly on tasks associated with frontal lobe activation. Similarities between performance deficits following brain lesions and those observed in sleep loss subjects form the basis of a neuropsychological model of sleep function. This thesis was an endeavour to document the findings of executive functioning sensitivity following 27 and 36 hours of sleep loss, testing the effect of two common countermeasures, caffeine and a nap. It was established that the critical period of sleep loss for executive functioning performance is at 36 hours. Sleep deprivation effects for periods shorter than 36 hours can be countered by a waking countermeasure, caffeine. It was further established that a 2-hour prophylactic nap opportunity inhibited sleep deprivation effects at 36-hr performance testing for executive functions. The systematic analysis of the effects of sleep loss on language skill, a complex task which is possibly an executive functioning task associated with frontal lobe activation but largely neglected in the literature, detected an increase in variability in language skill, and a propensity towards production errors in speech, but not writing, at 36 hours without sleep. This effect was not observed at 27 hours. The findings are discussed in support of a hypothetical consolidated model of Specific and Non-Specific Effects of sleep loss.