Abstract

How does the brain safeguard old memories while simultaneously forming new ones? This question has long intrigued neuroscientists, particularly as artificial neural networks continue to grapple with “catastrophic forgetting”—a phenomenon where new learning disrupts previously stored information. A recent study by Chang et al. (2025) offers compelling insights from biology, revealing that distinct microstructures within non-REM (NREM) sleep, reflected in fluctuations in pupil size, may hold the key.