Dissociable Effects of Sleep and Memory Suppression on Emotional Memory Processing

The ability to retrieve memories of adverse events without fully reinstating their associated emotional charge is a hallmark of an adaptive memory system. This decoupling of emotional reactivity from episodic memory has been linked to two key processes: memory suppression during wakefulness and memory consolidation during sleep. Yet, the combined influences of wakeful suppression and sleep-associated memory processing on emotional affect during retrieval are unknown. We sought to address this gap in the current study. Participants learned to associate images of faces with emotionally negative and neutral scenes and then either suppressed or retrieved the scenes when presented with the faces as reminder cues. They then took a nap monitored with polysomnography (nap group) or remained awake for an equivalent period of time in the laboratory (wake group). Before and after the delay, emotional responses to the negative and neutral scenes were evaluated using self-report, skin conductance responses (SCRs) and heart rate deceleration (HRD) to index changes in emotional affect that were attributable to memory suppression and/or sleep-associated consolidation. Memory suppression had no impact on self-reported emotion, SCRs or HRD in either the nap or wake group. However, subjective emotional responses decreased significantly more after sleep than wake. These findings support a role for sleep-associated consolidation in reducing the affective salience of emotional memories.