A well-rested brain remembers things better, but why? In a recent study, psychiatrist Giulio Tononi at the University of Wisconsin—Madison and his colleagues found evidence that sleep actively cements the connections between brain cells that allow us to learn new skills.

In the study, 11 volunteers learned to play a simple game that required them to move a cursor between different locations on a computer screen. Prior research had shown that playing this game activates an area called the right posterior parietal cortex, which lies behind and above the right ear.

A week later, the participants in the study played the same game just before going to sleep. Unknown to them, the scientists made the task more difficult by slightly skewing the location of the target area. The players were able to compensate for the change and learn how to reach the target accurately.

As the gamers slept, the scientists used electroencephalogram (EEG) recordings to tune in on a distinctive type of electrical rhythm that occurs in the brain during sleep. Called slow wave activity (SWA), it represents the synchronized firing of large numbers of brain cells. The EEGs showed increased SWA in right posterior parietal cortex. People who showed the greatest increase in SWA demonstrated the most skill in later rounds of the game.

The study is exciting because it essentially catches the brain in the act of learning. It suggests that as we sleep, SWA helps to strengthen connections made between individual brain cells during our waking hours.  This provides insight into the role that sleep plays in transforming experience (in this case, playing the computer game) into a form of long-term memory (greater skill at manipulating the computer cursor).

Further Reading:

"Local Sleep And Learning," by Reto Huber, PhD, and others. (Nature, July 1, 2004, Volume 430, pp. 78-81.)