Sleep and Emotion Processing in Individuals with Insomnia Symptoms and Good Sleepers
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Despite complaints of deficits in waking socioemotional functioning by individuals with insomnia, only a few studies have investigated waking emotion processing performance in this group. Additionally, the role of sleep in socioemotional processing has not been investigated using quantitative measures of sleep. The thesis investigated sleep and behavioural processing of emotionally expressive faces in individuals with insomnia symptoms (n=14) compared to healthy, good sleepers (n=15). The primary aim was to investigate the degree to which sleep predicted emotion processing. Participants completed two nights of at-home polysomnography-recorded sleep, and sleep diaries, which was followed by an afternoon of in-lab performance testing on tasks measuring processing of emotional facial expressions with an emotional Stroop task and a face categorization and intensity rating task. The insomnia group reported less total sleep time on their diary but no other differences in subjective or objective sleep were observed. No behavioural differences in emotion processing were observed overall. Post-hoc analysis of the individuals with insomnia symptoms that had a poor night of sleep on the night prior to performance assessment (n=8) revealed that a poor night of sleep in insomnia was associated with reduced time in Stage 2, REM and NREM sleep, and, there was trending support for elevated Sigma and Beta activity throughout the night as well as performance deficits for identifying emotional face expressions. For individuals with insomnia symptoms, greater levels of Beta EEG activity throughout sleep was associated with greater intensity ratings of happy, fearful, and sad faces. In conclusion, the thesis identified that the hyperarousal phenomenon in insomnia was related to altered waking salience assessments and gives promise for a new stream of research that investigates the relationship between hyperarousal in sleep and waking emotion functioning in insomnia.