While you sleep, your brain may strengthen the memories you made during the day.

That's according to a study due to be presented on May 2 in Boston at the American Academy of Neurology's 59th annual meeting.

The researchers -- who included Jeffrey Ellenbogen, MD, a neurologist and fellow in sleep research at Harvard Medical School -- studied 48 healthy adults aged 18 to 30.

Ellenbogen's team split participants into four groups. Participants in all four groups memorized word pairs.

One group was tested on the word pairs at the end of the day. Another group took the same test the following morning, after sleeping at home. Their test scores were similar.

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Distracting the Mind

The remaining two groups got an extra challenge. Right before the test, they saw another set of word pairs that was very similar to the word pairs they had memorized.

Those participants were tested on both sets of word pairs. The point was to see whether their memory was distracted by the new set of word pairs.

The students who slept at home before the tests performed best. They correctly identified about three-quarters of the word pairs.

In comparison, the students who took the test before going home for the evening correctly identified about one-third of the word pairs

"This is the first study to show that sleep protects memories from interference," Ellenbogen says in an American Academy of Neurology news release.

"These results provide important insights into how the sleeping brain interacts with memories: It appears to strengthen them," he says. "Perhaps, then, sleep disorders might worsen memory problems seen in dementia."

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This article was reviewed by Louise Chang, MD.

SOURCES: American Academy of Neurology's 59th Annual Meeting, Boston, April 28-May 5, 2007. News release, American Academy of Neurology.