Summary: New research identifies the same brain mechanisms that trigger memory reactivation during both wakefulness and sleep.
Source: University of Birmingham
Identical neural mechanisms trigger memory reactivation in both sleep and wakefulness, new research from the University of Birmingham reports.
This study clarifies how the brain ‘replays’ or reactivates memories during sleep, a process that helps consolidate them so they can be retrieved later. While the general importance of sleep for stabilizing memories has long been recognised, the precise neural processes that support this consolidation have remained elusive.
Published in Cell Reports, the research demonstrates in human participants that distinct neural patterns associated with recalling specific memories while awake reappear during subsequent sleep. These findings strengthen the evidence that sleep actively supports memory formation and retention by reinstating the same memory-related brain activity that occurs during wakeful recall.
By revealing these shared mechanisms, the study not only confirms sleep’s beneficial role for memory but also advances our understanding of how memories are formed and maintained. A more detailed picture of these processes may ultimately inform new approaches to diagnosing and treating memory disorders, such as Alzheimer’s disease, and could guide the development of targeted interventions to support memory function.
The research was conducted in collaboration with colleagues at the Donders Institute in the Netherlands and employed a method known as Targeted Memory Reactivation (TMR). TMR is an experimental technique that enhances memory by presenting cues associated with previously learned information while a person sleeps. In this study, participants learned foreign vocabulary before sleep; during their subsequent sleep, sounds associated with that vocabulary were played back to prompt reactivation.
To capture neural activity, researchers recorded electroencephalography (EEG) signals while participants learned and later recalled the vocabulary while awake. The same EEG methods were used to monitor brain activity as the sleeping participants heard the cues. Comparing neural patterns from wakeful recall with patterns recorded during sleep, the team found clear and specific similarities.
Dr Thomas Schreiner of the University of Birmingham’s School of Psychology, who led the study, commented that although wakefulness and sleep appear to be very different states, the brain activity related to memory in each state can be remarkably similar. He emphasised that these results underline the importance of sleep for memory consolidation and for overall well‑being.
Dr Tobias Staudigl of the Donders Institute, co‑lead author of the study, noted that understanding how memories are reactivated across different states may also reveal how memories can be modified. This line of research could have practical applications in therapeutic settings where altering maladaptive memories is desirable.
The study reveals that theta oscillations—a type of rhythmic brain activity—appear to coordinate memory reactivation during both wakefulness and sleep. During non-rapid eye movement (NREM) sleep, the reactivation patterns recurred at a rhythm close to 1 Hz, suggesting coordination by slow oscillatory activity. This slow oscillation likely helps to organize the timing of reactivation events, supporting the consolidation of newly encoded information into longer-term memory storage.
Building on these findings, the research team plans follow-up studies to explore spontaneous memory reactivation during sleep without external cues. Using advanced machine learning methods, they aim to record and decode neural patterns to identify when and where memories are activated naturally, without using an experimental prompt. Such approaches could reveal how the brain prioritises and strengthens certain memories across sleep, and how these processes may change in aging or disease.
Funding: The study was funded by the Swiss National Science Foundation and the European Research Council.
Source: University of Birmingham
Publisher: NeuroscienceNews.com
Image Source: Image noted as public domain.
Original research: “Theta Phase-Coordinated Memory Reactivation Reoccurs in a Slow-Oscillatory Rhythm during NREM Sleep” by Thomas Schreiner, Christian F. Doeller, Ole Jensen, Björn Rasch, and Tobias Staudigl. Published in Cell Reports, October 9, 2018.
University of Birmingham. “Memory brainwaves look the same in sleep and wakefulness.” NeuroscienceNews, 9 October 2018. Original research published in Cell Reports.
Abstract
Theta Phase-Coordinated Memory Reactivation Reoccurs in a Slow-Oscillatory Rhythm during NREM Sleep
Sleep is thought to support memory consolidation by reactivating previously encoded information. To investigate the neural mechanisms that carry reactivation-related mnemonic information, researchers examined whether content-specific memory signatures linked to memory reactivation during wakefulness reappear during subsequent sleep. The study shows that theta oscillations orchestrate memory reactivation in both wakefulness and sleep. During sleep, reactivation patterns re‑emerged autonomously at roughly a 1 Hz rhythm, indicating coordination by slow oscillatory activity during NREM sleep.