Fri Jan 03 01:41:42 UTC 2025: ## Pupil Size During Sleep Reveals Memory Replay: Cornell Study
**ITHACA, NY** – A groundbreaking study published in *Nature* reveals a previously unknown link between pupil dilation and memory processing during sleep. Researchers at Cornell University used advanced eye-tracking technology and EEG to monitor the sleep patterns of mice, observing that pupil size fluctuates during non-rapid eye movement (NREM) sleep, correlating with memory replay.
During NREM sleep, the mice exhibited two distinct substages. Pupil constriction was associated with the replay of newly acquired memories (like navigating a maze), while pupil dilation suggested the processing or reliving of previously learned experiences. These phases occurred in rapid succession, creating a pattern described as “new learning, old knowledge, new learning, old knowledge.”
Neuroscientist Azahara Oliva explained that this “fluctuation” throughout sleep helps answer a long-standing question: how does the brain form new memories without erasing old ones? The study suggests the brain uses these distinct sleep substages to multiplex cognitive processes, preventing “catastrophic forgetting” – the loss of old memories when acquiring new ones.
This discovery offers potential breakthroughs in several fields. The ability of the brain to separate new and old memory processing during sleep could inform the development of new memory enhancement techniques in humans and potentially improve the design of artificial intelligence systems, preventing them from losing previously learned information when learning new tasks. The researchers hope to replicate these findings in human subjects in the future.
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