Napping Improves Skills, Prevents Burnout
Evidence is mounting that catching a few more minutes of sleep each night or taking a midday nap will enhance information processing and learning.
Recent experiments by Dr. Alan Hobson, Robert Stickgold, Ph.D., and Matthew Walker, Ph.D., show that an afternoon snooze reverses information overload and that a 20 percent overnight improvement in learning a motor skill is traceable to a late stage of sleep that some early risers may be missing. The studies indicate that the brain uses a night's sleep to consolidate the memories of habits, actions and skills acquired throughout the day.
The bottom line: we should stop feeling guilty about taking an afternoon "power nap" or catching a few extra winks the night before an important event, the researchers said.
Stickgold and colleagues found that "burnout," which includes irritation, frustration and poorer performance on a mental task, sets in as a day of training activity wears on. Subjects in the study performed a visual task, reporting the horizontal or vertical orientation of three diagonal bars against a background of horizontal bars in the left corner of a computer screen, the research team explained.
Scores worsened over the course of four practice sessions conducted throughout the day, according to the study results. A 30-minute nap after the second session prevented any further deterioration, while a one-hour nap boosted performance in the third and fourth sessions, the study reported.
To ensure that the burnout was limited to the brain visual system circuits involved in the task, rather than just fatigue, the research team switched the location of the task to the right corner of the screen for the fourth practice session. This time, subjects experienced no burnout and performed about as well as they did in the first session — or after a short nap, team members noted.
The researchers said neural networks in the visual cortex "gradually become saturated with information through repeated testing, preventing further perceptual processing." They suggest the burnout may be the brain's "mechanism for preserving information that has been processed but has not yet been consolidated into memory by sleep."
So how might a nap help? Recordings of the brain and ocular electrical activity monitored during sleep showed that the longer, one-hour naps contained more than four times as much deep, or slow sleep and rapid eye movement (REM) than the half-hour naps. The team traced overnight memory consolidation and improvement on the same perceptual task to amounts of slow wave sleep (SWS) in the first quarter of the night and to REM sleep in the final quarter. Since a nap does not allow adequate time for the early morning REM sleep effect to occur, a slow wave sleep effect is assumed to be the antidote to burnout, they said.
The researchers speculate that sleep may enhance motor skill learning by powerful bursts of synchronous neuronal firing, called spindles. They are thought to promote new neural connections by triggering an influx of calcium into cells of the cortex; an increase in spindles has been found following training on a motor task, the team noted.
The study implies that sleep can help in learning sports, a musical instrument or artistic movement control, according to the researchers.
"All such learning of new actions may require sleep before the maximum benefit of practice is expressed," they said.
In addition, a full night of sleep may prove to be useful because it is important to experience the final two hours of sleep, the team added.
"Life's modern erosion of sleep time could shortchange your brain of some learning potential," said Walker.
The study may also explain why infants sleep so much.
"Their intensity of learning may drive the brain's hunger for large amounts of sleep," Walker said.