Reap while you sleep: consolidation of memories differs by how they were sown

Abstract

Newly formed memories are spontaneously reactivated during sleep, leading to their strengthening. This reactivation process can be manipulated by reinstating learning-related stimuli during sleep, a technique termed targeted memory reactivation. Numerous studies have found that delivering cues during sleep improves memory for simple associations, in which one cue reactivates one tested memory. However, real-life memories often live in rich, complex networks of associations. In this review, we will examine recent forays into investigating how targeted sleep reactivation affects memories within complex paradigms, in which one cue can reactivate multiple tested memories. A common theme across studies is that reactivation consequences do not merely depend on whether memories reside in complex arrangements, but on how memories interact with one another during acquisition. We therefore emphasize how intricate study design details that alter the nature of learning and/or participant intentions impact reactivation outcomes. In some cases, complex networks of memories interact harmoniously to bring about mutual memory benefits; in other cases, memories may interact antagonistically and produce selective impairments in retrieval. Ultimately, although this burgeoning area of research has yet to be systematically explored, results suggest that the fate of reactivated stimuli within complex arrangements depends on how they were learned.

Memory consolidation during sleep involves context reinstatement in humans

“…Day-to-day memories are best understood when considering the connections among them, yet these connections are not accounted for in our models of memory processing during sleep. 46 Our demonstration of a role for context in sleep consolidation opens the door for further exploration of how memory interconnections impact consolidation during sleep. More generally, this study underscores the notion that memory processing orchestrated by the sleeping brain is as rich and complex as when we are awake.…”

Memory consolidation during sleep involves context reinstatement in humans

“…Our understanding of how memory representations are reactivated and evolve during sleep is still incomplete. Day-to-day memories are best understood when considering the connections amongst them, yet these connections are not accounted for in our models of memory processing during sleep 46 . Our demonstration of a role for context in sleep consolidation opens the door for further exploration of how memory interconnections impact consolidation during sleep.…”

Spindle-locked ripples mediate memory reactivation during human NREM sleep

“…While we did not explicitly manipulate memory strength, our results seem to be in line with this interpretation, given that the strength of the association between cues and targets might have varied substantially in our data (note that 42 images were associated with each sound/ head orientation in the scalp EEG study; 36 in the iEEG study). Furthermore, participants were not encouraged to integrate memories together, which has been shown to promote benefits in case of multi-target TMR 21,45 . Finally, in an exploratory analysis (see Supplementary Fig.…”