RESEARCH / NEUROSCIENCE
Your brain has a night shift, too.
How research in mice reveals a possible way the brain keeps old and new memories apart.
Sleep is doing more than switching off
A 2025 study in Nature explored how the brain revisits memories without muddling new information with older experiences. Researchers recorded hippocampal activity and tracked pupil size in sleeping mice. During non-REM sleep, smaller pupils tended to accompany replay of newer memories; larger pupils accompanied older ones.
What happened when researchers interrupted it?
The team used light to disrupt neural activity during specific sleep states. Interrupting activity during the small-pupil state impaired retention of newly learned information, while previously learned information was spared. The findings suggest that non-REM sleep contains distinct substates that help organise memory replay.
The part to keep in perspective
This was research in mice, not a trial of revision techniques in medical students. It does not tell us how many hours a particular person needs, or prove that a specific bedtime improves exam results. Its appeal is the mechanism: a sleeping brain may be carefully separating yesterday’s learning from what it already knows.
Read the sources
Original FOMO editorial summary. Source dates are shown above; this is not a breaking-news report or individual medical advice.