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Sleep May Be Essential for Learning and Forgetting

Sleep May Be Essential for Learning and Forgetting

Why do people and other animals sicken and die if they are deprived of sleep? What is it about sleep that makes it so essential?

A new study, published in Science, shows evidence that in fact humans sleep to forget some of the things they learn each day — maintaining the brain’s “plasticity,” its ability to change and adapt.

The investigation is a follow-up on the “synaptic homeostasis hypothesis” (SHY) posited by psychiatrists Drs. Chiara Cirelli and Giulio Tononi of the Wisconsin Center for Sleep and Consciousness. The research offers direct visual proof of SHY via electron-microscope pictures from inside the brains of mice. The visuals suggest what happens in our own brain every day.

The pictures showed that our synapses — the junctions between nerve cells — grow strong and large during the stimulation of daytime, then shrink by nearly 20 percent while we sleep, creating room for more growth and learning the next day.

In the study, a large team of researchers sectioned the brains of mice, and then using a scanning electron microscope they photographed, reconstructed, and analyzed two areas of cerebral cortex. Investigators were able to reconstruct 6,920 synapses and measure their size.

The team deliberately did not know whether they were analyzing the brain cells of a well-rested mouse or one that had been awake. When they finally “broke the code” and correlated the measurements with the amount of sleep the mice had during the six to eight hours before the image was taken, they found that a few hours of sleep led on average to an 18 percent decrease in the size of the synapses.

These changes occurred in both areas of the cerebral cortex and were proportional to the size of the synapses. The study has been bolstered by a companion Johns Hopkins University study that analyzed brain proteins, also confirming SHY’s prediction that the purpose of sleep is to scale back synapses.

Source: University of Wisconsin-Madison/EurekAlert

Sleep May Be Essential for Learning and Forgetting

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2018). Sleep May Be Essential for Learning and Forgetting. Psych Central. Retrieved on December 1, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 20 Feb 2018)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
Published on Psych All rights reserved.