Neurobehavioural and physiological consequences of sleep deprivation in humans

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The functions of sleep remain largely a mystery. One way to investigate the functions of sleep is by examining the effects of varying amounts of sleep on specific brain processes. My lab has focused on the role of sleep in cognitive processing and emotion regulation. A large body of research has shown that sleep loss impairs alertness, attention, memory, and mood, but the neural basis of these impairments remains poorly understood. While subjective mood complaints have long been known to be a consequence of poor sleep, researchers have only recently begun to investigate the role of sleep in emotion regulation, including how the brain processes emotional information in pictures and facial expressions, and how sleep loss contributes to aggressive behaviour. Our recent work showed that one night of sleep deprivation (about 33 hours awake) led to behavioural and neural reactivity for threat-related Angry and Fearful facial expressions, yet a blunted response to Sad facial expressions. This differential processing for emotional expressions informs us about the nature of cognitive processes that are affected by sleep loss, and has significant implications for many sleep deprived groups. We were also the first to report that one night of sleep loss was associated with a substantial decrease in testosterone levels in men and an associated reduction in aggressive behaviour on a laboratory task. The research proposed in the next grant period will expand on these novel findings in a number of ways, as well as pursue new approaches to studying the role of sleep in emotion regulation. First, we will study a less extreme level of sleep disruption by examining sleep that is restricted to 3, 4, or 5 hours per night, over one or more nights; this is a level of sleep loss that is commonly experienced and leads to cumulative deficits in alertness and attention. We will further investigate the role of sleep in processing emotional information by examining brain responses to faces, pictures, and audio and video clips that vary in emotional valance (from neutral to positive and negative). In addition, we will again investigate the role of sleep and hormones in aggressive behaviour, by studying both men and women (while controlling for hormone use and phases of the menstrual cycle) using two different validated tasks of aggression. We will further explore the nature of the sleep-related change in emotion processing and aggressive behaviour by measuring resting heart rate because it is considered a marker of individuals’ ability to respond to affective information. Lastly, since REM sleep (the sleep stage commonly associated with dreaming) has been proposed to play a functional role in emotion regulation, we will examine the effects of selective REM sleep deprivation on emotion processing and memory. Specifically, we will explore whether REM sleep plays a role in both consolidation of emotional material as well as an adaptive function to lessen the “sting” of emotional stimuli. Examining physiological activity that is associated with altered perception and behaviour as a result of sleep loss will help us to understand how and why sleep loss impacts waking function. These studies will advance our knowledge of the basic functional role of sleep in waking cognitive function and emotion regulation. The outcomes of this research will have implications for understanding human behaviour in many sleep deprived groups, especially for those with a sleep disruption and affective component at play, such as children and adolescents, and forensic and psychiatric populations.