ISLAMABAD: Two distinct sleep stages appear to play vital, complementary roles in learning: one stage enhances overall performance, while the other stabilizes what we learned the previous day.
\nScientists have long known that a good night\u2019s sleep works wonders for our ability to learn new skills.
\nWhat has been less clear is the role of different sleep stages. In particular, there has been controversy over the relative contributions of rapid eye movement (REM) sleep, which is when most dreaming occurs, and non-REM sleep, which is mostly dreamless.
\nTheir experiment \u2014 which focuses on visual learning \u2014 suggests that rather than one stage being more important than the other for learning new skills, both play essential and complementary neurochemical processing roles.
\nThey found 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.
\n\u201cI hope this helps people realize that both non-REM sleep and REM sleep are important for learning,\u201d says corresponding author Yuka Sasaki, a professor of Cognitive, Linguistic, and Psychological Sciences at Brown.
\nMost REM sleep occurs in the final hours of sleep, so the finding reinforces the importance of not cutting short these later stages.
\n\u201cWhen people sleep at night, there are many sleep cycles. REM sleep appears at least three, four, five 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\u2019t shorten our sleep.\u201d
\nPsychologists have previously identified two distinct benefits of sleep for learning.
\nThe first benefit, which they call \u201coffline performance gains,\u201d means the learning acquired before sleep is enhanced after sleep, without any additional training.
\nThe second benefit, called \u201cresilience to interference,\u201d protects the skills learned before sleep from being disrupted or overwritten by subsequent learning after awaking.
\nTo reap both benefits, there is a trade-off between flexibility and stability.
\nLearning during the day involves forming new synapses, which are the electrical connections between nerve cells, and the strengthening of existing synapses through repeated use.
\nWhile 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 \u2018downscales\u2019 or weakens them all.
\nThis restores flexibility, or plasticity, to the brain\u2019s local connections and wider networks, to improve overall performance.
\nAt 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.
\nTo 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.
\nThe letters and lines were displayed against a fixed background of horizontal lines for one group of volunteers, and vertical lines for another group.
\nParticipants were then allowed to sleep for 90 minutes with their heads inside an MRI scanner.
\nAfter awakening, they were given 30 minutes to fully wake up before performing the same task, but with the opposite orientation of background lines.
\nPrevious research has shown that switching the orientation of background lines interferes with performance gains on this learning task.
\nA third group of volunteers was not given any learning task before or after sleep.
\nThe researchers used electrodes glued to subjects\u2019 eyelids and scalps to detect when they entered different sleep stages.
\nThey also used a technique called magnetic resonance spectroscopy to measure the relative concentrations of two neurotransmitters \u2014 glutamate and gamma aminobutyric acid (GABA) \u2014 in the parts of their brains that process visual information.
\nGlutamate transmits excitatory signals in the brain, whereas GABA transmits inhibitory signals. Neuroscientists believe that when glutamate concentrations are high relative to GABA, it reflects an increase in neural plasticity, whereas the opposite indicates an increase in stabilization.
\nWhen the scientists analyzed their results, they found that plasticity increased during non-REM sleep, which correlated with improved task performance after sleep.
\nInterestingly, 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.
\nLater 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\u2019s learning: it appeared to prevent any performance gains from being lost.
\nIn other words, the REM stage may make learning before sleep more resilient to interference from subsequent learning.
\nUnlike non-REM sleep, the sharp fall in plasticity during REM sleep was only seen among the volunteers with a task to learn.
\nThis suggests that the stabilization that occurred during REM sleep was focused exclusively on synapses involved in learning this task.
\nAmong participants who did not manage to get any REM sleep during their 90 minutes in the scanner, improvements in performance from their nap failed to materialize.
\nOverall, the results suggest both sleep stages are essential for learning new things. While our brains are \u201coffline,\u201d non-REM sleep improves performance on freshly learned tasks, but without REM sleep to stabilize the memories, these gains will be lost.
\nThe study focuses on a particular part of the brain and involved only one kind of learning task. Sasaki and her team hope to investigate whether the same principles apply to learning in general.
\nIn addition, they want to explore the role of sleep when rewards are provided to motivate learning.
\n\u201cPreviously, we showed that rewards enhance visual learning through sleep, so we would like to understand how that works,\u201d she says. \u201cIt is ambitious, but maybe we could expand this research to other types of learning so we could better remember and develop better motor learning, visual skills, and creativity.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
ISLAMABAD: Two distinct sleep stages appear to play vital, complementary roles in learning: one stage enhances overall performance, while the other stabilizes what we learned the previous day. Scientists have long known that a good night\u2019s sleep works wonders for our ability to learn new skills. What has been less clear is the role of […]<\/p>\n","protected":false},"author":1,"featured_media":4201,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[35],"class_list":["post-4200","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-health","tag-35","entry"],"yoast_head":"\n