The sleep-deprived human brain

Key Points Sleep deprivation triggers a set of bidirectional changes in brain activity and connectivity, depending on the specific cognitive or affective behaviours engaged. Changes in brain activity are observed when averaged across a session of task performance and during on-task performance, wherein marked brain network instability seems to be a neural hallmark of sleep deprivation. Not all changes in brain function that are associated with sleep loss are maladaptive and thus represent deficiencies, as some predict resilience in behavioural ability and are therefore compensatory. These basic scientific findings offer causal mechanistic insights into select neurological and psychiatric disorders in which abnormalities in sleep and cognition or emotion are highly comorbid, indicating that sleep intervention is an underappreciated and novel target for disease treatment and/or prevention. The robust neural and behavioural phenotypes characterized by this Review can inform debates regarding sleep recommendations for both public and professional health policies, especially in light of the escalating sleep-loss epidemic prevalent throughout industrialized nations. How does sleep deprivation affect the human brain? Walker and colleagues review neuroimaging studies on the consequences of sleep deprivation on cognition and emotion — with specific focuses on attention and working memory, positive and negative emotion, and hippocampal learning — and the mechanisms underlying these effects. How does a lack of sleep affect our brains? In contrast to the benefits of sleep, frameworks exploring the impact of sleep loss are relatively lacking. Importantly, the effects of sleep deprivation (SD) do not simply reflect the absence of sleep and the benefits attributed to it; rather, they reflect the consequences of several additional factors, including extended wakefulness. With a focus on neuroimaging studies, we review the consequences of SD on attention and working memory, positive and negative emotion, and hippocampal learning. We explore how this evidence informs our mechanistic understanding of the known changes in cognition and emotion associated with SD, and the insights it provides regarding clinical conditions associated with sleep disruption.