The vicissitudes of affective valence across the night: A high-density electroencephalographic study.

Abstract

Despite the popular belief in the mood-regulatory function of dreaming, the picture of the overnight changes in affective valence is far from complete. Previous studies largely focused on negative emotions and clinical populations and missed out on some rapid-eye-movement (REM) sleep periods because either of low REM-mentation retrieval rates or other methodological limitations. This study, therefore, made use of the high-density electroencephalogram and progressive-awakening protocol to maximize dream retrieval and to chart the vicissitudes of both positive and negative affect across all sleep cycles of the night for ordinary people. Twenty young adult subjects slept at the laboratory for electroencephalographic and REM-mentation recordings. Mentation reports were obtained from 96.4% of REM awakenings. Most dreams were characterized by mixed feelings or were positively toned. Positive emotions were stronger than negative emotions across all waking and REM stages. The intensities of both positive and negative emotions reached the peaks in the third and sixth REM episodes, hit the bottom of the overnight trajectory in the fifth REM episode, and as compared with the presleep ratings significantly dropped after sleep. These findings do not support the mood-regulation theory that positive emotions progressively increase across successive REM dreams in lieu of negative emotions. They instead suggest that affect valence, whether it is positive or negative, mounts to the climax in the third REM episode and/or the latter REM episode, depending on the length of sleep and the qualities of presleep mood. Additionally, dreaming appears to be a cathartic process through which the internal gauge for affective experiences reverts to its homeostatic constant by eliminating both the positive and negative emotions preceding sleep. (PsycINFO Database Record (c) 2016 APA, all rights reserved)