New Reason To "Sleep On It": Study Shows Importance Of Sleep To Memory Consolidation And Task Performance

"Our research shows that you need sleep that first night if you want to improve on a task," says Robert Stickgold, Harvard Medical School assistant professor of psychiatry at the Massachusetts Mental Health Center.

The study, which appears in the December Nature Neuroscience, adds a critical piece to a growing body of work by Stickgold and others showing that sleep is necessary for learning (see http://www.med.harvard.edu/publications/Focus/Oct27_2000/index.html).

Previously, Stickgold and his colleagues found that people who learned a particular task did not improve their performance when tested later the same day but did improve after a night of sleep.

To see whether the night of sleep actually caused the improvement, Stickgold trained 24 subjects in the same visual discrimination task, which consisted of identifying the orientation of three diagonal bars flashed for a sixtieth of a second on the lower left quadrant of a computer screen full of horizontal stripes. Half of the subjects went to sleep that night while the other half were kept awake until the second night of the study. Both groups were allowed to sleep on the second and third nights. On the fourth day, both groups were tested on the visual discrimination task. Those who slept the first night identified the correct orientation of the diagonal bars much more rapidly than they had the first day. The other group showed no improvement, despite the two nights of catch-up sleep.

"We think that getting that first night's sleep starts the process of memory consolidation," says Stickgold. "It seems that memories normally wash out of the brain unless some process nails them down. My suspicion is that sleep is one of those things that does the nailing down."

Support for this research was provided by the National Institutes of Health and The Network on Mind-Body Interactions, a multidisciplinary research network sponsored by the John D. and Catherine T. MacArthur Foundation. Begun a decade ago, the Mind-Body Network (http://www.mindbody.org) has been committed to discovering the biological mechanisms by which the social world and mental processes affect physical health.