Getting the right amount of restful, uninterrupted sleep offers many benefits, many of which are obvious and well documented. The science of sleep is still a growth industry, and we have a long way to go before this aspect of living is strongly understood.

Most scientists have believed the proper amount of sleep improves memory and learning skills. A new study, a joint project between U.S. and Chinese researchers from Peking University Shenzhen Graduate School and New York University's Skirball Institute of Biomolecular Medicine, effectively discovers the underlying ways in which sleep helps the brain form and store memories. The study was published in Science magazine.

"We've known for a long time that sleep plays an important role in learning and memory," said senior investigator Wen-Biao Gan, a professor at the Skirball Institute. "If you don't sleep well, you don't learn well."

Using the latest technology in microscopy and with the aid of a few mice, scientists were able to track real-time changes in mouse memory during sleep and during waking hours. Fifteen mice were trained for one hour to walk forwards and backwards on top of a rotating rod. After this exercise, some of the mice were allowed to sleep for seven hours, others were kept awake.

It was observed the brains of the mice that were allowed to catch their beauty rest formed significantly more connections between neurons. This indicated that learning and memory formation was occurring far more easily and effectively than in the mice that were not allowed to sleep.

Some of the sleeping mice deliberately had their sleep disrupted. These mice did not fare as well as the mice whose sleep was uninterrupted.

This implies memory formation occurs overwhelmingly during deep or slow-wave sleep, a phase during which the brain replays activity from the day's affairs. Scientists also observed physical changes in the brain during this stage of sleep in which dendritic spine growth (dendritic spines are tiny offshoots which grow from neuron branches) occurs, with the new dendrites connecting with other neurons to pass information on that helps build an inventory of memories. The sleep-deprived mice sprouted far fewer dendritic spines.

"Finding out sleep promotes new connections between neurons is new. Nobody knew this before," said Wen-Biao Gan.

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