A stage of sleep – reflected in the size of our pupils – is important to committing recent memories to the brain, which could be manipulated to improve cognitive function and even identify issues with being able to recall newer experiences when awake.

They found new memories replayed and consolidated when the pupil was contracted during a substage of sleep. When the pupil was dilated, the brain appeared to replay older memories. The brain’s ability to separate these two sleep substages is crucial in preventing “catastrophic forgetting”,

Scientists uncover how pupil size changes during sleep help the brain boost memories. This could revolutionize memory improvement techniques