Replay began as a striking observation: neural activity patterns associated with movement through a space could reappear when an animal was asleep. The brain seemed to run a compressed echo of experience.
The Filing-Cabinet Model Is Too Small
Memory consolidation is real, but sleep is unlikely to be only storage. Some experiments suggest replay can include paths not actually taken, as if the brain is evaluating alternatives.
Why Translation Is Hard
Rodent studies can record from many neurons with precise timing. Human studies often rely on imaging or scalp recordings with coarser resolution. The concepts travel, but the evidence changes shape.
The Practical Takeaway
Sleep is not passive. It is an active biological state in which memory, emotion, and prediction may be reorganized.
