The memory sources of dreams: serial awakenings across sleep stages and time of night.
Claudia Picard-Deland, Karen R Konkoly, Rachel Raider, Ken A Paller, Tore Nielsen, Wilfred R Pigeon, Michelle Carr
Sleep April 12, 2023 DOI: 10.1093/sleep/zsac292 (opens in new tab) via PubMed
Summary
AI-generated from the abstractDreams incorporate memories from waking life, but this incorporation varies across the night. Twenty healthy adults were awakened repeatedly during early, middle, and late sleep stages (N1, N2, N3, REM) to collect dream reports. Recent memories appeared more often in N1 and REM dreams than in other stages. Distant memories from over a week ago, semantic memories, and anticipated future events remained stable across sleep stages. However, across the night, the balance shifted: late-night dreams in all stages contained fewer recent and more remote memories than earlier dreams. Dreams also repeated similar themes across the night. These results suggest that dream content may reflect sleep-dependent memory consolidation processes.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 20 |
| Population | Healthy participants (11 female; mean age 24.1 ± 5.7 years) |
| Duration | One night in the laboratory with approximately 12 awakenings across early, middle, and late sleep periods |
| Topics | Dreaming |
| Keywords | Nrem sleep Episodic memory Memory sources Semantic memory |
| Key finding | Recent memory sources were more frequent in N1 and REM dreams than in other stages, and the proportion of recent versus distant memories changed across the night independently of sleep stage, with late-night dreams containing fewer recent and more remote memories. |
Abstract
Memories of waking-life events are incorporated into dreams, but their incorporation is not uniform across a night of sleep. This study aimed to elucidate ways in which such memory sources vary by sleep stage and time of night. Twenty healthy participants (11 F; 24.1 ± 5.7 years) spent a night in the laboratory and were awakened for dream collection approximately 12 times spread across early, middle, and late periods of sleep, while covering all stages of sleep (N1, N2, N3, REM). In the morning, participants identified and dated associated memories of waking-life events for each dream report, when possible. The incorporation of recent memory sources in dreams was more frequent in N1 and REM than in other sleep stages. The incorporation of distant memories from over a week ago, semantic memories not traceable to a single event, and anticipated future events remained stable throughout sleep. In contrast, the relative proportions of recent versus distant memory sources changed across the night, independently of sleep stage, with late-night dreams in all stages having relatively less recent and more remote memory sources than dreams earlier in the night. Qualitatively, dreams tended to repeat similar themes across the night and in different sleep stages. The present findings clarify the temporal course of memory incorporations in dreams, highlighting a specific connection between time of night and the temporal remoteness of memories. We discuss how dream content may, at least in part, reflect the mechanisms of sleep-dependent memory consolidation.