Sleep reactivation did not boost suppression-induced forgetting

Eitan Schechtman,Ken A Paller,Eunbi Kwon,Brianna J Wilson,Anna Lampe,Michael C Anderson

doi:10.1038/s41598-020-80671-w

Eitan Schechtman, Ken A Paller + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-80671-w

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Abstract

Sleep's role in memory consolidation is widely acknowledged, but its role in weakening memories is still debated. Memory weakening is evolutionary beneficial and makes an integral contribution to cognition. We sought evidence on whether sleep-based memory reactivation can facilitate memory suppression. Participants learned pairs of associable words (e.g., DIET–CREAM) and were then exposed to hint words (e.g., DIET) and instructed to either recall (“think”) or suppress (“no-think”) the corresponding target words (e.g., CREAM). As expected, suppression impaired retention when tested immediately after a 90-min nap. To test if reactivation could selectively enhance memory suppression during sleep, we unobtrusively presented one of two sounds conveying suppression instructions during sleep, followed by hint words. Results showed that targeted memory reactivation did not enhance suppression-induced forgetting. Although not predicted, post-hoc analyses revealed that sleep cues strengthened memory, but only for suppressed pairs that were weakly encoded before sleep. The results leave open the question of whether memory suppression can be augmented during sleep, but suggest strategies for future studies manipulating memory suppression during sleep. Additionally, our findings support the notion that sleep reactivation is particularly beneficial for weakly encoded information, which may be prioritized for consolidation.

Highlights

Sleep’s role in memory consolidation is widely acknowledged, but its role in weakening memories is still debated
The active systems consolidation hypothesis suggests that declarative memories are selectively reactivated during non-rapid-eye-movement sleep (NREM) and that this process shapes and stabilizes cortical representations based on hippocampal–cortical interactions[4]
Participants learn to associate a set of hint words (e.g., “Diet”) with target words (e.g., “Cream”)

Summary

Introduction

Sleep’s role in memory consolidation is widely acknowledged, but its role in weakening memories is still debated. Results showed that targeted memory reactivation did not enhance suppression-induced forgetting. Sleep-based consolidation supports declarative memories (concerning facts and events; e.g.,1), as well as nondeclarative memories (which include skill learning and implicit learning; e.g.,2,3). The active systems consolidation hypothesis suggests that declarative memories are selectively reactivated during non-rapid-eye-movement sleep (NREM) and that this process shapes and stabilizes cortical representations based on hippocampal–cortical interactions[4]. The neural trace supporting selective memory suppression, established during wake, may itself be reactivated and cemented during sleep, just as other nondeclarative products of learning (e.g., motor skills[3], perceptual skills2) benefit from offline processing. Studies exploring the long term effects of TNT manipulations have yielded conflicting results, with most reports suggesting that suppression-induced forgetting is diminished with time[11,12], and only one showing longlasting effects[13]. Studies exploring the effects of sleep on motivated forgetting using other

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