Cognitive abilities such as vigilance, attention, memory, and executive functioning can be degraded significantly following extended periods of wakefulness. Although much evidence suggests that sleep-loss induced deficits in alertness and vigilance can be reversed or mitigated by stimulants such as caffeine, it is not clear how these compounds may affect other higher level cognitive processes such as emotional perception and judgment. Following 47 h of sleep deprivation, the study examined the effect of three stimulant medications (modafinil 400 mg, dextroamphetamine 20 mg, caffeine 600 mg) or placebo on the ability of 54 healthy participants to discriminate and label simple emotional expressions versus complex affect blends (created by morphing photographs of two different affective facial expressions). For simple affective faces, neither sleep loss nor stimulant medications made any difference on the accuracy of judgments. In contrast, for complex emotion blends, all three stimulant medications significantly improved the ability to discriminate subtle aspects of emotion correctly relative to placebo, but did not differ from one another. These findings suggest that all three stimulant medications are effective at restoring some aspects of subtle affective perception.

Sleep loss temporarily impairs vigilance and sustained attention. Because these cognitive abilities are believed to be mediated predominantly by the right cerebral hemisphere, this article hypothesized that continuous sleep deprivation results in a greater frequency of inattention errors within the left versus right visual fields. Twenty-one participants were assessed several times each day during a 40-h period of sustained wakefulness and following a night of recovery sleep. At each assessment, participants engaged in a continuous serial addition task while simultaneously monitoring a 150 degrees visual field for brief intermittent flashes of light. Overall, omission errors were most common in the leftmost peripheral field for all sessions, and did not show any evidence of a shift in laterality as a function of sleep deprivation. Relative to rested baseline and postrecovery conditions, sleep deprivation resulted in a global increase in omission errors across all visual locations and a general decline in serial addition performance. These findings argue against the hypothesis that sleep deprivation produces lateralized deficits in attention and suggest instead that deficits in visual attention produced by sleep deprivation are global and bilateral in nature.

Sleep deprivation impairs a variety of cognitive abilities including vigilance, attention, and executive function. Although sleep loss has been shown to impair tasks requiring visual attention and spatial perception, it is not clear whether these deficits are exclusively a function of reduced attention and vigilance or if there are also alterations in visuospatial perception. Visuospatial perception and sustained vigilance performance were therefore examined in 54 healthy volunteers at rested baseline and again after one night of sleep deprivation using the Judgment of Line Orientation Test and a computerized test of psychomotor vigilance. Whereas psychomotor vigilance declined significantly from baseline to sleep-deprived testing, scores on the Judgment of Line Orientation did not change significantly. Results suggest that documented performance deficits associated with sleep loss are unlikely to be the result of dysfunction within systems of the brain responsible for simple visuospatial perception and processing of line angles.