Pupil Size Reveals Memories Relived During Dreams: Study

A new study by Cornell University, published in the journal Nature, has discovered that pupil size during sleep may reveal which memories are being relived in dreams. Using advanced eye-tracking technology and EEG analysis, scientists studied mice that were taught new tasks like navigating a maze during the day and observed their sleep patterns at night. The researchers found two distinct phases during NREM (Non-Rapid Eye Movement) sleep. In one phase, pupils contracted, indicating replay of newly learned memories. In another phase, pupils dilated, suggesting the processing of older memories. These phases alternated throughout sleep.

Azahara Oliva, a neuroscientist at Cornell, explained that the brain alternates between "new learning" and "old knowledge," ensuring that new memories are integrated without overwriting old ones. This balance prevents the loss of previous memories while allowing continuous learning. The study also highlighted how the brain avoids "catastrophic forgetting," a challenge in both biological and artificial neural networks. The findings could lead to advancements in memory enhancement techniques and better learning methods, with researchers hopeful about similar studies in humans.