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Distinct substates of NREM sleep organize replay of recent and older experiences, helping the brain consolidate memories while limiting interference.
We thank Hongyu Chang for sharing the research, the thinking behind the discovery, and the challenges and decisions that shaped the work with the Biolà community.
PAPERS & REFERENCES
NatureEVENT MATERIALS
On January 19, 2025, at 8:30 AM Beijing Time, Biolà hosted the 5th issue of the Bioneer First-Author Forum, featuring Hongyu Chang, a PhD candidate at Cornell University. As the first author of the study, Chang presented ‘Sleep Microstructure Organizes Memory Replay,’ published in Nature in 2025.
Memory consolidation requires the brain to stabilize newly acquired information while preserving previously stored memories, raising the question of how these processes avoid interfering with one another. Combining simultaneous electrophysiology, closed-loop optogenetics, and pupillometry in freely behaving and sleeping mice, Chang and colleagues found that hippocampal replay was organized by distinct substates of non-rapid eye movement (NREM) sleep: recent experiences were preferentially replayed during contracted-pupil substates, whereas older memories were preferentially replayed during dilated-pupil substates. Selectively disrupting sharp-wave ripples during these respective substates impaired recent or remote memory, revealing a temporal organization of sleep that may allow the brain to consolidate different memories while minimizing interference.
We sincerely thank Hongyu Chang for sharing the findings and scientific story behind this work with the Biolà community, and for discussing how the microstructure of sleep may support continuous memory consolidation.
Citation: Chang, H., Tang, W., Wulf, A. M., Nyasulu, T., Wolf, M. E., Fernandez-Ruiz, A., & Oliva, A. (2025). Sleep microstructure organizes memory replay. Nature. https://doi.org/10.1038/s41586-024-08340-w