Link between deep sleep and visual learning

A relationship has been observed between deep sleep and the ability of the brain to learn specific tasks. Researchers at Harvard-affiliated Brigham and Women’s Hospital (BWH) have now shown that the processes that regulates deep sleep may affect visual learning. These results are published in the March 12 issue of the Journal of Neuroscience.

“These findings show that deep sleep is important for visual learning and possibly the ability of the brain to learn new tasks,” said Daniel Aeschbach, researcher in the Division of Sleep Medicine at BWH and lead author of the study.

Deep sleep, also called slow-wave sleep, is a period of non-rapid-eye-movement sleep when very large brain waves, called slow waves, can be observed in the EEG, which is a recording of the brain waves.  Slow waves are thought to reflect the need for sleep, but their exact function is unknown.  Researchers sought to determine the function of these waves in visual learning.

Aeschbach and colleagues trained healthy subjects on a visual learning task in which they were required to determine on a computer screen the orientation of a few dashes that were embedded in a field of horizontal dashes.  Subjects were tested on their accuracy of performing this task before and after they had slept for a period of four hours. One group of subjects slept normally, with no interruptions, and their visual skill in performing the task improved after sleep.

In another group, researchers suppressed the occurrence of slow waves by playing targeted acoustic tones while subjects were asleep. The tones did not wake the subjects, but prevented them from slipping into deep sleep as monitored on the EEG.  This group was also tested in the visual task after sleep, and their skill did not improve.

Researchers suggest that these findings could have clinical implications for conditions like depression and insomnia, as well as aging, which are associated with learning deficits and also a reduction of deep sleep.

This research was funded by awards from the National Alliance for Research on Schizophrenia and Depression, the Milton Fund of Harvard University, and the National Institutes of Health.