The first study found that the medial prefrontal cortex, a brain region responsible for retrieval of distant memories, was also found to replay the day's events during sleep. Scientists observed the brain activity of rats while they ran on a track and afterward while they slept. While they were active the brain cells were sending electrical signals in specific patterns over time.
When the rats were sleeping, the researchers found that the same patterns were being observed but at seven times the speed observed during activity. The study suggests that the medial prefrontal cortex's fast-forward replay of the day%u2019s memories during sleep could be evidence that our brains can process information much faster when we're not busy with tasks.
The second study suggests that, in order to ensure memory consolidation is unhindered, our brains might have mechanisms that inhibit the formation of new memories as we approach bedtime. Scientists conducted experiments on zebrafish that were trained to perform a task during the day, when melatonin levels are low, and during night when levels are at their peak.
They found the fish had trouble performing the following day if the training was done during the night or if the fish were administered a dose of melatonin during the day. Although human memories are more complex than a zebrafish, the basic application of melatonin still applies on a basic level.