The impact of sleep vs. sleep deprivation on emotional memories

Abstract

Sleep plays a pivotal role in the off-line processing of emotional memory. However, large remains unknown for sleep’s immediate vs. long-term influences on emotional memories and their affective tones. Here, we employed behavioral and electrophysiological measures to investigate the short- and long-term impacts of sleep vs. sleep deprivation on emotional memory. Fifty-nine participants incidentally learnt 60 negative and 60 neutral pictures in the evening and were randomly assigned to either sleep or sleep deprivation conditions. We measured memory recognition and subjective affective ratings in 12- and 60-hour post-encoding tests. We additionally recorded EEGs during the 60-hour delayed test. We found that, in the12-hour post-encoding test, compared to sleep deprivation, sleep equally preserved both negative and neutral memory, as well as their affective tones. In 60-hour post-encoding test, negative and neutral memories declined significantly in the sleep group, which are accompanied by attenuated emotional ratings to negative memories. In contrast, only neutral memories declined significantly in Sleep Deprivation group. Furthermore, in the 60-hour post-encoding EEG tests, two groups showed spatial-temporally distinguishable eventrelated brain potentials (ERPs): while both groups showed the old/new frontal negativity (300-500 ms, FN400) that may indicate familiarity, sleep-deprived participants additionally showed an oldnew parietal, Late Positive Component effect (600-1000 ms, LPC) that may indicate recollection. Multivariate whole brain ERPs decoding analyses further suggested that sleep prioritized neural representation of valence over memory processing; while they were less distinguishable in sleep deprivation group. These data suggested that sleep’s impact on emotional memory and affective responses are time-dependent: sleep preserved memories and affective tones in the short term, while ameliorating affective tones in the long term. In terms of brain responses, univariate ERP results suggest that sleep and sleep deprivation participants engaged different neurocognitive processes in recognition of remote, emotional memories. Moreover, multivariate ERP decoding results suggest that sleep and sleep deprivation had different impact on processing of emotional information and memory.