Sleep Disruption Selectively Weakens Reactivated Memories

AbstractA widely accepted view in memory research is that recently stored information can be reactivated during sleep, leading to memory strengthening. Two recent studies have shown this effect can be reversed in participants with highly disrupted sleep. To test whether weakening of reactivated memories can result directly from sleep disruption, in this experiment we varied the intensity of memory reactivation cues, such that some produced sleep arousals. Prior to sleep, participants (local community members) learned the locations of 75 objects, each accompanied by a sound naturally related to that object. Location recall was tested before and after sleep, and a subset of the sounds were presented during sleep. Reactivation with arousal weakened memories, unlike the improvement typically found. We conclude that reactivated memories can be selectively weakened during sleep, and that memory reactivation may strengthen or weaken memories depending on additional factors such as concurrent sleep disruption.Statement of RelevanceThe results of this study have implications for both human health and basic psychology. Sleep disorders like apnea are associated with memory problems; our results suggest a possible mechanism where frequent arousal may disrupt the naturally occurring reactivation of memory in sleep. These results also highlight the importance of avoiding brief sleep disruption for good sleep hygiene. Finally, we raise the possibility that reactivation with sleep disruption could be used therapeutically to weaken distressing memories.Our observation that memories can also be either weakened or strengthened by sleep reactivation has implications for understanding the mechanisms of memory consolidation. In particular, we suggest that sleep memory reactivation may be a reconsolidation-like process with memory restabilization required after reactivation. Our findings also suggest avenues for future experiments; such as using sleep disruption to study the time course of memory reactivation.