Both REM and non-REM sleep are important for visual learning, according to new research published in Nature Neuroscience

There has been a debate over the roles of REM and non-REM sleep in visual learning, according to a press release. Although sleep is universally accepted as being beneficial for the mind and body, disagreement persists regarding how sleep is good, according to the researchers. 

For the study, young adults were trained to identify a letter and the orientation of a set of lines on a textured background in 2 different tasks. One task was before sleep and the other was after sleep. 

Researchers then analyzed the participants’ brain waves while they were sleeping, according to the press release. They also measured the concentration of glutamate, an excitatory neurotransmitter, and gammaminobutyric acid, an inhibitory neurotransmitter. Researchers also performed an analysis on participants who did not participate in the visual learning tasks.

The study, which was conducted by Brown University, found that during non-REM sleep, the visual areas of participants’ brains showed an excitation and inhibition balance suggestive of increased plasticity. It was also found in the participants who did not take part in the visual learning tasks. 

This finding suggests it occurs even in the absence of learning, according to the press release; however, participants who only underwent non-REM sleep did not exhibit any performance gain. 

Those who underwent both REM and non-REM sleep exhibited significant performance gains for both tasks. According to the press release, researchers found that REM sleep is necessary to reap the benefits of the increased plasticity they exhibit during non-REM sleep.  

"I hope this helps people realize that both non-REM sleep and REM sleep are important for learning…When people sleep at night, there are many sleep cycles. REM sleep appears at least 3, 4, 5 times, and especially in the later part of the night. We want to have lots of REM sleep to help us remember more robustly, so we shouldn't shorten our sleep," Yuka Sasaki, PhD, corresponding author and professor of Cognitive, Linguistic and Psychological Sciences at Brown University, said in the press release. 

The next step is to see whether the findings can be generalized for other types of learning, according to the press release. Researchers would also like to combine this research with previous findings on visual perceptual learning and reward.  

Reference:
Study helps to settle debate on roles of REM and non-REM sleep in visual learning (News Release), Providence, RI, July 20, 2020, EurekAlert!, Accessed July 21, 2020