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 the outcomes of sleep reactivation. 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 reactivation during sleep does not act holistically on object memory

“…The consolidation trajectory hypothesis, by Antony & Schechtman (2023), posits that sleep serves to reinforce goals formed during learning, such that if interconnected elements of a complex memory are learned harmoniously, they will be jointly promoted during sleep; if they are learned antagonistically, they will be pitted against each other during sleep 62 . One prior TMR study demonstrated that generating specific competitive dynamics during pre-nap learning modulated the impacts of reactivation 63 .…”

Semantic relatedness proactively benefits learning, memory, and interdependence across episodes

“…The preceding results accord well with the qualitative results from our prior study examining retroactive effects (with a few exceptions, which we cover more extensively in the Discussion). One conclusion from these converging results could be that relatedness benefits memories in the retroactive and proactive case for similar reasons, namely that by virtue of increasing the likelihood of looking back and associating new learning with existing memories, it helps the connected memories survive due to being embedded in an integrated memory structure (Antony & Schechtman, 2023;Lee & Chen, 2022;Schlichting et al, 2015;Trabasso & Sperry, 1985). Our results here and earlier, as well as those from other recent studies showing that memory updating benefits from variables that improve contact between the past and present (e.g., Kemp et al, 2023;Wahlheim et al, 2020Wahlheim et al, , 2023Wahlheim & Zacks, 2019), support this idea.…”