Evidence is mounting that sleep – even a nap – appears to enhance information processing and learning. New experiments by NIMH grantee Alan Hobson, M.D., Robert Stickgold, Ph.D., and colleagues at Harvard University show that a midday snooze reverses information overload and that a 20 percent overnight improvement in learning a motor skill is largely traceable to a late stage of sleep that some early risers might be missing. Overall, their studies suggest that the brain uses a night’s sleep to consolidate the memories of habits, actions and skills learned during the day.
Reporting in the July, 2002 Nature Neuroscience, Sara Mednick, Ph.D., Stickgold and colleagues demonstrate that “burnout” – irritation, frustration and poorer performance on a mental task — sets in as a day of training wears on. Subjects performed a visual task, reporting the horizontal or vertical orientation of three diagonal bars against a background of horizontal bars in the lower left corner of a computer screen. Their scores on the task worsened over the course of four daily practice sessions. Allowing subjects a 30-minute nap after the second session prevented any further deterioration, while a 1-hour nap actually boosted performance in the third and fourth sessions back to morning levels.
Recordings of brain and ocular electrical activity monitored while napping revealed that the longer 1-hour naps contained more than four times as much deep, or slow wave sleep and rapid eye movement (REM) sleep than the half-hour naps.
