Sleep promotes the reproduction of the cells that form myelin, the insulating material found on nerve cell projections in the brain and spinal cord, a new study published in The Journal of Neuroscience found.
The discovery offers further insight into sleep's role in the repair and growth of the brain.
For years, scientists have known that many genes are turned on during sleep that are otherwise remain off. What is unclear, however, is exactly how sleep affects specific cell types, such as oligodendrocytes, which make myelin.
In an effort to unravel this mystery, researchers from the University of Wisconsin measured gene activity in oligodendrocytes from mice that either slept or were forced to stay awake. In doing so, they discovered that genes responsible for promoting myelin formation were turned on during sleep while those genes tied to cell death were turned on when the animals were awake.
Furthermore, additional analysis revealed that the reproduction of the cells that become oligodendrocytes doubled during sleep, and particularly during rapid eye movement.
"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, co-author of the study, said in a statement. "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."
Cirelli further speculates based on the findings that extreme or chronic sleep loss could aggravate symptoms in multiple sclerosis (MS), which is known to damage myelin. For this reason, the researcher said that future experiments may examine any possible links between sleep patterns and the severity of MS symptoms.
In either case, as Mehdi Tafti, a sleep researcher from the University of Lausanne who was not involved in the study, explained, the study's results "hint at how sleep or lack of sleep might repair or damage the brain."