The dream-lag effect: Selective processing of personally significant events during Rapid Eye Movement sleep, but not during Slow Wave Sleep

E Van Rijn,J.-B Eichenlaub,P.A Lewis,M.P Walker,M.G Gaskell,J.E Malinowski,M Blagrove

doi:10.1016/j.nlm.2015.01.009

Abstract

Incorporation of details from waking life events into Rapid Eye Movement (REM) sleep dreams has been found to be highest on the night after, and then 5–7 nights after events (termed, respectively, the day-residue and dream-lag effects). In experiment 1, 44 participants kept a daily log for 10days, reporting major daily activities (MDAs), personally significant events (PSEs), and major concerns (MCs). Dream reports were collected from REM and Slow Wave Sleep (SWS) in the laboratory, or from REM sleep at home. The dream-lag effect was found for the incorporation of PSEs into REM dreams collected at home, but not for MDAs or MCs. No dream-lag effect was found for SWS dreams, or for REM dreams collected in the lab after SWS awakenings earlier in the night. In experiment 2, the 44 participants recorded reports of their spontaneously recalled home dreams over the 10 nights following the instrumental awakenings night, which thus acted as a controlled stimulus with two salience levels, high (sleep lab) and low (home awakenings). The dream-lag effect was found for the incorporation into home dreams of references to the experience of being in the sleep laboratory, but only for participants who had reported concerns beforehand about being in the sleep laboratory. The delayed incorporation of events from daily life into dreams has been proposed to reflect REM sleep-dependent memory consolidation. However, an alternative emotion processing or emotional impact of events account, distinct from memory consolidation, is supported by the finding that SWS dreams do not evidence the dream-lag effect.

Highlights

Rapid-Eye Movement (REM) and non-Rapid Eye Movement (REM) sleep stages Slow Wave Sleep (SWS) and stage 2 sleep (N2), are believed to play a role in the consolidation of memories (e.g., Diekelmann & Born, 2010; Gais & Born, 2004; Smith, 2001)
Home awakenings group Due to technical problems with the equipment, sleep data and dream reports were not collected from 7 participants in the home awakenings group; these participants are not included in the analyses
To divide the home awakenings group into low and high incorporators for the REM sleep analyses, the total number of correspondences for REM dreams divided by the number of REM dreams was calculated for each participant

Summary

Introduction

Rapid-Eye Movement (REM) and non-REM sleep stages Slow Wave Sleep (SWS) and stage 2 sleep (N2), are believed to play a role in the consolidation of memories (e.g., Diekelmann & Born, 2010; Gais & Born, 2004; Smith, 2001). A process of memory triage for consolidation has been proposed (Stickgold & Walker, 2013), in which there is a differential processing of memories based on factors such as salience and future relevance. This discriminatory selection serves multiple forms of memory, such as emotional memory, episodic memory and procedural memory, is facilitated by different sleep stages and by the reactivation of new memories during sleep, and is necessary for rapid and effective adaptation to changes in the environment (Stickgold & Walker, 2013)

Results

Discussion

Conclusion