Reactivation during sleep segregates the neural representations of episodic memories

Abstract

Sleep involves the reactivation of recently acquired memories, thereby shaping the neural representations supporting them. An essential feature of episodic memory (i.e., memory for events) is the link between specific elements (e.g., a cake) and the context in which they were embedded (e.g., a birthday party). We investigated how reactivation during sleep impacts item-context binding. Participants (N = 22) formed stories linking together objects in unique contexts. Using functional MRI, we measured the overlap between neural representations for contextually linked objects. During a 90-min nap, some object memories were reactivated by unobtrusively presenting object-specific sounds. Across multiple brain regions, reactivation reduced the overlap between representations of contextually linked memories, promoting object specificity. Furthermore, reactivation reduced the representational overlap between contexts, thereby promoting context specificity. Taken together, data suggest that reactivation during sleep decontextualizes memories. These results inform our understanding of how sleep contributes to interlinked memories embedded in naturalistic contexts and demonstrate that memory reactivation during sleep changes representations of memories within their distinctive contexts.