Investigating the Functional Role of Sleep in Waking Cognitive and Emotion Processing

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Sleep is a complex behaviour consisting of two distinct states observed in the EEG (i.e., electrical recordings of brain wave activity). Non-REM sleep is characterized by slow brain oscillations and signature waveforms called spindles and K-complexes. REM sleep is paradoxical in that it looks much like waking EEG, yet is difficult to awaken the sleeper. Past research from the Sleep Research Laboratory at Brock has investigated how sleep and sleep disruption affect cognition, memory, and emotion processing. We have shown that disruptions to sleep lead to emotion dysregulation including heightened neural processing of negative picture scenes and threatening facial expressions, yet blunted responses to sad expressions as seen in event-related potential brain recordings. Our long-term goal is to understand the functional role of sleep in waking cognitive and emotion processing. Continuing from our published studies on total sleep deprivation and short-term sleep restriction, we will now investigate the more precise roles of REM and non-REM sleep mechanisms in waking emotion perception. Accurate and rapid detection of emotion in others, and emotionally-relevant stimuli in our environment, is important for decision making, social interactions, and even self-preservation. We have recently developed a new battery of emotion perception tasks. For example, one task measures a threshold of detection in identifying emotion in faces that dynamically change expression from neutral. Another task requires participants to judge the predominate emotional expression in a crowd of faces. These tasks have been designed to have greater real-world applicability than past studies that have used mainly static picture stimuli presented in isolation. We will first investigate how natural variation in sleep in a student population affects emotion processing (sleep durations vary considerably in this age group). We will also carry out a chronic sleep restriction study where we will curtail sleep to five hours per night over a week. The sleep period will either be early or late to disrupt non-REM versus REM selectively. Last, we will manipulate sleep through separate REM sleep deprivation and deep sleep enhancement protocols. In this series of studies, we will record sleep and waking EEG from 64-channels to investigate the temporal and spatial patterns of sleep EEG and its role in waking emotion perception, with the aim to understand the respective roles of non-REM and REM sleep. As well, we will follow up on our recent work investigating the moderating role of sex and hormones (cortisol, testosterone, estradiol, progesterone) and heart rate variability as markers of resiliency/vulnerability to sleep disruption. As many Canadians do not get the sleep they need, this research may help people to optimize performance (work, scholastic, sport) through sleep, and may also inform intervention strategies in individuals with sleep, emotion, or behavioural disorders.