Dream Sleep Could Recast Our Memories

REM and deep sleep might affect our recollections in differing ways, according to a fresh study.(Image credit: PeopleImages/Getty Images)

The quantity of REM sleep you experience could shape which components of your memories are preserved, a novel research of the brain indicates.

Prior investigations have revealed that slumber aids in strengthening our recollections, but understanding how it influences the elements of these recollections has been more difficult. Now, a study released Oct. 1 in the journal Communications Biology implies that time invested in different sleep phases could sway this characteristic of memory storage.

The sleep phase is separated into four segments: a solitary phase of rapid eye movement (REM) and three non-REM segments, incorporating “deep sleep,” distinguished by sluggish brainwaves. To evaluate how these sleep phases affect our memories, researchers requested 32 healthy young participants to learn 96 word-image combinations — such as a verb related to a visual of an animal or plant — while their neural activity was documented with an electroencephalogram (EEG), which keeps track of brainwaves spreading over the brain’s surface.

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The participants were then observed with EEG as they dozed overnight, and their recall was assessed the following morning. The researchers contrasted the pre- and post-sleep brain activity utilizing a method termed representational similarity analysis. These data authorized the scientists to concentrate both on comprehensive recollections linked to precise images — such as a photo of a beagle — and on broader, categorical recollections, encompassing all the animal images, as an illustration.

“Via EEG, we had the ability to monitor how cerebral activity associated with recollections altered from prior to following sleep,” Jing Liu, the study’s primary author and a research assistant professor at The Hong Kong Polytechnic University, stated to Live Science via email.

The team discovered a tendency: Brainwaves correlated with the individual images attenuated subsequent to sleep, whereas the more general category signals remained constant.

The alteration was more marked when REM composed a greater portion of someone’s overall sleep duration, as opposed to deep sleep. Liu elucidated that this tendency hints that REM sleep might facilitate the brain’s connection of new recollections with existing knowledge, whereas slow-wave sleep supports the maintenance of those recollections in their initial, more intricate version.

“Even when individuals recalled the identical elements after waking, the brain patterns behind those recollections had altered,” she contributed. This implies sleep not only reinforces recollections but also potentially rearranges how they’re depicted within the brain, with REM and slow-wave sleep each playing differing roles.

In conjunction, these outcomes supplement proof that memory consolidation — the brain’s operation of stabilizing and reorganizing new recollections — entails both preservation and transformation. As opposed to retaining recollections of occurrences precisely as they transpired, the brain might subtly restructure them throughout sleep, balancing precision with generalization. The distinction, the researchers highlighted, could aid in clarifying how knowledge systems in the brain evolve as time passes.

Nonetheless, this tendency doesn’t necessarily denote that deep sleep and REM sleep function antagonistically. In its place, the two segments bolster distinct aspects of remembering, Dr. George Dragoi, a professor of psychiatry and neuroscience at Yale University with no involvement in the study, conveyed to Live Science via email.

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He appended that adhering to regular sleep patterns could promote these processes, as superior sleep quality is extensively associated with beneficial cognitive performance. “Lengthier REM durations might encourage the form of memory transformation this study underscores,” he proposed.

Liu, however, advised that the outcomes display correlations, not causation.

“[EEG] obstructs our precise identification of the brain regions activating these alterations,” she voiced, adding that joining EEG with recordings obtained directly from electrodes positioned within the cranium could clarify the circuitry underpinning the impact. She further denoted upcoming studies that could attempt to reactivate particular recollections throughout sleep — for instance, by reiterating sounds or prompts correlated with prior learning — or disrupt certain sleep phases to observe whether that shifts how flexibly individuals can employ their knowledge.

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Anirban MukhopadhyayLive Science Contributor

Anirban Mukhopadhyay is an independent science journalist. He holds a PhD in genetics and a master’s in computational biology and drug design. He regularly writes for The Hindu and has contributed to The Wire Science, where he conveys complex biomedical research to the public in accessible language. Beyond science writing, he enjoys creating and reading fiction that blends myth, memory, and melancholy into surreal tales exploring grief, identity, and the quiet magic of self-discovery. In his free time, he loves long walks with his dog and motorcycling across The Himalayas.

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