Researchers have discovered that during REM sleep some of the structures neurons (dendritic spines) use to make connections are actually pruned. Others are strengthened. These findings underscore the role REM sleep plays in enhancing memory of newly learned information. During this phase of sleep the brain actually selects which spines to eliminate and which to keep, thus enhancing memories.
LifeTip: Sleep on a regular schedule, 7-8 hours per night to maximize the benefits of REM sleep.
Adapted from PositiveChoices.com