Slow wave sleep facilitates spontaneous retrieval in prospective memory

Abstract

Study objectives: Previous studies have shown that sleep benefits prospective memory by facilitating spontaneous retrieval processes. Here, we investigated the sleep features supporting such a benefit.

Methods: Forty-nine young adults (mean age ± SD: 22.06 ± 1.71 years; 18 males) encoded intentions comprising four related (phone-unplug earphones) and four unrelated (mirror-close the book) cue-action pairs. They were instructed to remember to perform these actions in response to cue words presented during a semantic categorization task 12 h later. The retention interval involved either a period of wakefulness (09:30-21:30; n = 24) or overnight sleep with polysomnographic monitoring (21:30-09:30; n = 25).

Results: We found a significant Group × Relatedness interaction for prospective memory accuracy (F = 8.35, p < 0.01). The sleep group successfully executed a significantly higher percentage of related intentions compared to the wake group (mean ± standard error of the mean (SEM): 94.00 ± 2.61% vs 66.67 ± 6.84%, p < 0.001). This benefit for related intentions was associated with longer post-learning slow wave sleep (r = 0.46, p < 0.05). In contrast, the percentage of unrelated intentions successfully executed did not differ between groups (82.00 ± 5.10% vs 72.92 ± 6.88%, p = 0.29).

Conclusion: Slow wave sleep after memory encoding may strengthen the preexisting associations between semantically related cues and actions, thereby facilitating subsequent spontaneous retrieval processes.

Keywords: memory consolidation; prospective memory; slow wave sleep; spontaneous retrieval; strategic monitoring.