Researchers from the University of Wisconsin, Madison, found that sleep increases the process by which certain cells, known as oligodendrocytes, form myelin. Myelin is the insulation on nerve cells in the brain and spinal cord that allows electrical impulses to move rapidly from one cell to another.
In conducting the study, published in the September 4 issue of the Journal of Neuroscience, the researchers examined the myelin-forming cells of mice that slept, as well as those of mice that were deprived of sleep.
Genes activated during sleep
Genes that promote the production of this insulation were activated during sleep, the researchers found. Meanwhile, the genes linked to cell death and the cellular stress response were activated among the mice that were forced to stay awake.
"These findings hint at how sleep or lack of sleep might repair or damage the brain," Mehdi Tafti, a sleep researcher at the University of Lausanne in Switzerland, who was not involved with this study, said in a journal news release.
The study authors also found that the reproduction of the cells that go on to become oligodendrocytes doubles during sleep. This is particularly true during rapid eye movement (REM), which is the phase of sleep associated with dreaming.
"For a long time, sleep researchers focused on how the activity of nerve cells differs when animals are awake versus when they are asleep," Dr Chiara Cirelli, from the University of Wisconsin, Madison, said in the news release. "Now it is clear that the way other supporting cells in the nervous system operate also changes significantly depending on whether the animal is asleep or awake."
The study findings suggest that extreme or chronic sleep loss could worsen some symptoms of multiple sclerosis, a disease that damages myelin, the researchers said. Future studies may look for a possible link between sleep patterns and severity of multiple sclerosis symptoms, they added.
Scientists caution, however, that research in animals often fails to provide similar findings in humans.
The U.S. National Institute of Neurological Disorders and Stroke has more about sleep.