University of Arizona in Tucson researchers have found that the brain’s ability to store or consolidate memories (“replaying” and filing away events while we sleep) is impaired in old age.

The researchers recorded the activity in the hippocampuses of rats while they repeatedly navigated tracks and mazes in search of food. The exact patterns seen in young animals as they completed the exercises played back as they slept; but in older animals the sequences were garbled. Older rats whose nighttime patterns most resembled their waking sequences performed better in memory and learning exercises than the other older rats.

Neurons in the hippocampus (a midbrain region responsible for short-term and episodic memory of places and people as well as emotions linked to specific events) reactivate the same patterns during sleep that they displayed when initially recording activities. This repeated replay copies that information into the neocortex, the outermost layer of the brain where long-term memory storage takes place.

The researchers are investigating drugs that might correct deficits in memory replay.