Psychologists Reveal How Sleep Boosts Learning

Sunday, August 2, 2020 - 10:30
Sleep

Psychologists of the Department of Cognitive, Linguistic, and Psychological Sciences at Brown University in Providence, RI, have provided important clues that could help resolve the debate over the relative contributions of rapid eye movement (REM) sleep, which is when most dreaming occurs, and non-REM sleep, which is mostly dreamless.

Based on the study, their experiment, which focuses on visual learning, suggests that rather than one stage being more important than the other for learning new skills, both play essential and complementary neurochemical processing roles, Medical News Today reports.

Researchers discovered that while non-REM sleep enhances our performance of newly acquired skills by restoring flexibility, REM sleep stabilizes those improvements, and prevents them from being overwritten by subsequent learning.

“I hope this helps people realize that both non-REM sleep and REM sleep are important for learning,” says corresponding author Yuka Sasaki, a professor of Cognitive, Linguistic, and Psychological Sciences at Brown.

Most REM sleep occurs in the final hours of sleep, so the finding reinforces the importance of not cutting short these later stages.

Learning during the day involves forming new synapses, which are the electrical connections between nerve cells, and the strengthening of existing synapses through repeated use.

While we sleep, the brain appears to streamline its operations to work more efficiently. According to a leading hypothesis, it does this by reactivating synapses that have been strengthened during the day, and then indiscriminately ‘downscales’ or weakens them all.

This restores flexibility, or plasticity, to the brain’s local connections and wider networks, to improve overall performance.

At the same time, during sleep, the brain must also stabilize key synapses to prevent what was learned the previous day from being eliminated by new learning experiences.

To investigate when each of these processes occurs during sleep, the scientists gave volunteers a standard visual learning task. This involved identifying letters and the orientation of lines that pop up on a screen in two different tasks: one before sleep and one after sleep.

When the scientists analyzed their results, they found that plasticity increased during non-REM sleep, which correlated with improved task performance after sleep.

Interestingly, plasticity increased during non-REM sleep even for the volunteers without any tasks to learn, which suggests there was an overall streamlining process going on in the brain.

Later in the sleep session, the plasticity of those in the learning task fell to below waking levels during REM sleep. This fall correlated with stabilization of the previous day’s learning: it appeared to prevent any performance gains from being lost.

In other words, the REM stage may make learning before sleep more resilient to interference from subsequent learning.

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