Dreaming and its Mechanisms in REM and NREM Sleep
The Science of Sleep November 1, 2025 DOI: 10.1093/med/9781605352978.005.0001 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Review Peer reviewed |
|---|---|
| Topics | Dreaming |
| Key findings | The appendix reviews evidence that dreams are reported during lighter NREM sleep as well as REM sleep, and that debates persist over whether REM-related dreams are more fantastic and irrational and whether recall length and complexity differ by stage. It argues that conclusions depend on subjective reports and inferences about timing, and that pre-awakening neural activity and sleep inertia may affect dream memory and report content. It also reviews evidence that dream-production systems are dissociable from those producing REM sleep's objective features, and discusses lucid dreaming and its associated neural activity. |
Abstract
This appendix reviews evidence that dreams are reported to occur during lighter stages of NREM sleep as well as during REM sleep. It reviews debates about whether REM-related dreams are more fantastic and irrational than NREM-related dreams, and whether the length and complexity of dream recall differs between sleep stages. Determining whether there are sleep stage-related differences in the nature of dreams relies on participants’ subjective self-reports, and on inferences about when dream experiences occur relative to when people are awakened to report their dreams. Different patterns of neural activity during REM and NREM sleep before awakening may affect the probability of successfully storing and/or retrieving a memory of the subjective experience, and therefore of reporting dream content. In addition, factors like the extent of sleep inertia (and its neural correlates) after awakening from different sleep stages may affect the content and complexity of dream reports. This appendix also reviews the patterns of neural activity associated with dream production and evidence that the systems involved in this process are dissociable from those producing the objective features that define REM sleep. Finally, this appendix discusses the nature of lucid dreaming and the patterns of neural activity that are associated with this experience. Lucid dreams are those in which people report that they are aware of being in a dream state and are able to exert varying degrees of control over the dream content.