The study, released in the July 3 edition of Neuron, involved teaching people to type a sequence of keys on a computer keyboard as quickly and accurately as possible. They were trained for 12 minutes and were able to become relatively good at the task. The group trained in the morning and then re-tested 12 hours later were able to improve their performance by about two percent. The performance of those trained in the evening and re-tested 12 hours later, after a good night's sleep, improved far more significantly - an average of 20 percent improvement in their performance. In addition, the research showed the amount of improved performance was directly correlated with the amount of Stage 2 (a stage of non-rapid eye movement or NREM) sleep an individual was able to receive, particularly late in the night.
"This is the part of a good night's sleep that many people will cut short by getting up early in the morning," said Matter Walker, Harvard Medical School clinical fellow in psychiatry and senior author of the paper. "Motor skill learning is maximized when we get a full night's sleep. You could say that modern life's erosion of sleep time is seriously short changing your brain of valuable learning potential."
A full night of normal sleep is characterized by a progression through an orderly succession of sleep states and stages. In a healthy adult, the first cycle is always initiated by going from wakefulness to NREM sleep. The first REM period follows the first period of non-REM sleep to complete the first sleep cycle. The two sleep states continue to alternate throughout the night with an average cycle period of about 90 minutes. A full night of normal human sleep will usually consist of four to six NREM/REM sleep cycles. Stage 2 sleep represents about 50 percent of a full night's sleep.
"This is the phenomenon of a pianist or a gymnast working on a passage or a routine that they cannot master after hours of practice and finally giving up in frustration. If they set it aside and return to their task the next day, they are able to get through the routine the first time through," Walker said. "Our research demonstrates that after a certain time, further practice may not make someone perfect at a motor task, but rather a good night's sleep could be the key to perfection."
Improvement in motor skill performance is known to continue for at least 24 hours after training. This research provides evidence that a night of sleep results in a 20 percent increase in motor speed without loss of accuracy, while an equivalent period of time awake does not provide a significant benefit to performance.
"These findings have important implications for learning real-life motor skills such as those involved with sports, learning a musical instrument or dance." Walker said. "In order for an individual to learn new things, they may require a good night's sleep before the maximum benefit of the time they spend practicing is realized."
This also may help to explain why infants sleep so much. "Their intensity of learning new skills and information may drive the brain's hunger for large amounts of sleep," said Walker.
This study was supported by funds from the National Science Foundation and National Institute of Health.
Harvard Medical School has more than 5,000 full time faculty working in eight academic departments based at the School's Boston quadrangle or in one of 47 academic departments at 17 affiliated teaching hospitals and research institutes. Those HMS affiliated institutions include:
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Massachusetts Eye and Ear Infirmary
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Massachusetts General Hospital
Massachusetts Mental Health Center
Center for Blood Research
Mount Auburn Hospital
Dana-Farber Cancer Institute'
Schepens Eye Research Institute
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