The size of your pupils during sleep could reveal the memories you relive

The size of your pupils while you sleep could reveal the memories you relive in your dreams.

Sleep, an ally in memory consolidation

While our body rests during sleep, our brain remains in full activity. It sorts and makes sense of the day’s events in light of past experiences. If the way in which these new memories are processed without mixing with old ones has long been the subject of debate, American researchers from Cornell University are shedding new light on the question.

A careful study on mice

The team of researchers equipped mice with cameras to track the movement of their eyes and electrodes to scan their brain activity. They observed them as they learned new tasks during the day and slept at night. They discovered two distinct phases of memory consolidation during non-REM sleep, a crucial phase for the formation of memories.

Two phases of memory consolidation

The first phase corresponds to a reactivation of new memories, accompanied by a contraction of the pupils. The second phase characterizes the reactivation of old memories, with dilation of the pupils. These two phases follow each other quickly. “It’s like new learning, old knowledge, new learning, old knowledge,” says Azahara Oliva, a neuroscientist at Cornell University.

Major implications for research

Ces discoveries represent a major advance in our understanding of how memory works. They could open the way to non-invasive treatments for memory disorders, or to methods to boost memory. Additionally, they fuel thoughts on how our brains and computer systems might forget obsolete information on a large scale, a phenomenon known as catastrophic forgetting in the field of artificial intelligence.