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It is widely known that adequate amounts of high-quality sleep are essential to good physical, mental, and cognitive health, but exactly how sleep contributes to the various aspects of health remains unknown. A large body of evidence suggests that deep sleep, also known as slow-wave sleep, is particularly important for cognitive health, a topic discussed by Department faculty members in a review recently published in the journal Trends in Neurosciences.

“Our review pulls together a lot of the individual pieces of evidence showing how brain activity during slow-wave sleep, termed slow-wave activity (SWA), is related to cognitive health and points out novel methods that we might use to enhance slow-wave sleep and improve cognitive health,” said lead author Kristine Wilckens, PhD, Assistant Professor of Psychiatry.

Slow-wave sleep difficulties are prevalent among many disorders of cognition such as mild cognitive impairment, dementia, and schizophrenia. In addition, both sleep quality and cognition worsen with normal aging, so it’s possible that changes in sleep help to account for changes in cognition that are observed in older adults. 

“Sleep troubles generally receive far less attention than the learning and memory difficulties experienced by neuropsychiatric patients. We discuss a number of noninvasive and easily implemented ways to improve slow-wave sleep, which could potentially help offset some of the cognitive difficulties these patients are experiencing,” said co-author Fabio Ferrarelli, MD, PhD, Assistant Professor of Psychiatry.

The new review explores both nighttime and daytime strategies to enhance cognition through improving deep sleep. One possibility for slow-wave sleep enhancement the researchers suggest is to play acoustic tones in a specific pattern that mimics SWA during sleep. These tones “teach” the brain to fire in a similar pattern, leading to enhanced slow-wave sleep. Evidence suggests that using this approach overnight helps older individuals retain certain types of memories during sleep.

Another way to enhance SWA is by engaging in physical exercise during the day. Exercise increases energy metabolism, which generates heat in the body. The brain responds to heat by activating neurons that lead to SWA. “Exercise is widely known to be beneficial for memory and cognitive function, so we propose in the review that slow-wave sleep could be one of several mechanisms through which exercise enhances cognitive function,” said Dr. Wilckens.

A third approach detailed in the review is to stimulate specific areas of the brain important for cognition directly, using electrical or magnetic stimulation techniques, which lead to enhanced SWA in those regions. The researchers are currently using transcranial magnetic stimulation to improve slow-wave sleep and cognition in patients with mild cognitive impairment.

“It’s really exciting that we are now starting to use novel techniques to enhance cognition by improving deep sleep. This research stands to improve the quality of life of millions of adults who struggle with both sleep problems and cognitive challenges,” said the review’s co-author Daniel Buysse, MD, UPMC Endowed Chair in Sleep Medicine and Professor of Psychiatry and Clinical and Translational Science.

Slow-Wave Activity Enhancement to Improve Cognition
Wilckens KA, Ferrarelli F, Walker MP, Buysse DJ
Trends in Neurosciences, 2018 41(7): 470-482