During sleep, the brain appears to firm up memories of newly acquired information, report Jeffrey Ellenbogen, M.D., and colleagues in Current Biology's July 11 edition.
Ellenbogen is a sleep research fellow at Harvard Medical School in Boston. His study included 48 adults, aged 18 to 39, who were healthy and had no sleep problems.
At the researchers' lab, participants learned 20 word pairs that included two randomly chosen two-syllable nouns, such as "blanket" and "village."
Half of the participants learned the word pairs at 9 p.m. Afterward, they went home, slept for an average of seven hours, and returned to the lab for a 9 a.m. test on the word pairs.
For comparison, the other participants learned the word pairs at 9 a.m. and took the follow-up test 12 hours later, with no napping in between.
Better Test Scores With Sleep
The group that slept before the exam scored 13% better on the follow-up test than the no-sleep group, the study shows.
Half the participants in each group got an extra challenge. Right before the word test, they were shown another set of word pairs that weren't covered on the exam. Their task: Ignore the new word pairs when they took the test.
Once again, the sleep group scored best. Their test scores were 58% better than those who hadn't slept before the exam.
Ellenbogen and colleagues repeated the test with 12 more participants, doubling the time frame to 24 hours. The results held.
Sleep may help consolidate memories and make those memories resist interference, the researchers write.
SOURCES:: Ellenbogen, J. Current Biology, July 11, 2006; Vol. 16: pp. 1290-1294. News release, Cell Press.
By Miranda Hitti
Reviewed by Louise Chang, M.D.
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