While sleep may be downtime for many parts of your body, it’s a busy time for your brain! In fact, while you’re snoozing, brain waves are working hard to boost your ability to learn.
Of course, it’s common knowledge that you can prevent brain aging effects with daily crossword puzzles, sudoku or other brain games, as well as regular physical exercise. These activities are a great way to help keep your recall and learning skills sharp.
But to help keep your cognitive abilities intact, prioritize sleep (even better brain games and good sleep habits). Why? Here’s what three different medical studies say about how certain sleep brain waves help you hold on to lessons and memories better.
While you sleep, your brain’s making memories
Over the past two decades, the centuries-old theory that sleep plays a role in the formation of memories has been increasingly supported by science.
Researchers at the University of California San Francisco found in 2019 that animal studies showed the same neurons involved in forming the initial memory of a new task or experience are reactivated during sleep to consolidate these memory traces in the brain.
There is also evidence that non-REM sleep stages play a role in consolidating various kinds of memory, including the learning of motor skills.
In humans, researchers have found that time spent in the early stages of non-REM sleep is associated with better learning of a simple piano riff, for instance.
What other studies say about sleep brain waves boosting your ability to learn
Sleep after learning encourages the growth of dendritic spines — the tiny protrusions from brain cells that connect to other brain cells and facilitate the passage of information across synapses — the junctions at which brain cells meet, according to a 2014 published in the journal Science.
Researchers at NYU Langone Medical Center showed that the activity of brain cells during deep sleep (or delta waves sleep), after learning is critical for such growth.
“We’ve known for a long time that sleep plays an important role in learning and memory. If you don’t sleep well you won’t learn well,” says senior investigator Wen-Biao Gan, PhD, professor of neuroscience and physiology and a member of the Skirball Institute of Biomolecular Medicine at NYU Langone Medical Center.
“But what’s the underlying physical mechanism responsible for this phenomenon? Here we’ve shown how sleep helps neurons form very specific connections on dendritic branches that may facilitate long-term memory. We also show how different types of learning form synapses on different branches of the same neurons, suggesting that learning causes very specific structural changes in the brain.”
The findings, in mice, provide important physical evidence in support of the hypothesis that sleep brain waves helps consolidate and strengthen new memories, and show how learning and sleep cause physical changes in the motor cortex, a brain region responsible for voluntary movements.
On the cellular level, sleep is anything but restful: Brain cells that spark as we digest new information during waking hours replay during deep sleep, also known as slow-wave sleep or delta waves sleep, when brain waves slow down and rapid-eye movement, as well as dreaming, stops.
Scientists have long believed that this nocturnal replay helps us form and recall new memories, yet the structural changes underpinning this process have remained poorly understood.
“Now we know that when we learn something new, a neuron will grow new connections on a specific branch,” says Dr. Gan. “Imagine a tree that grows leaves (spines) on one branch but not another branch. When we learn something new, it’s like we’re sprouting leaves on a specific branch.”
A midday nap not only refreshes the mind, but can make you smarter
If you see a teen dozing on the sofa, or a co-worker catching 40 winks in her cubicle, don’t roll your eyes.
Research from the University of California, Berkeley, reported in 2010, showed that an hour’s nap can dramatically boost and restore your brainpower. Indeed, the findings suggest that a biphasic sleep schedule not only refreshes the mind, but can make you smarter.
Conversely, the more hours we spend awake, the more sluggish our minds become, according to the findings. The results support previous data from the same research team that pulling an all-nighter — a common practice at college during midterms and finals –- decreases the ability to cram in new facts by nearly 40 percent, due to a shutdown of brain regions during sleep deprivation.
“Sleep not only rights the wrong of prolonged wakefulness but, at a neurocognitive level, it moves you beyond where you were before you took a nap,” said Matthew Walker, an assistant professor of psychology at UC Berkeley and the lead investigator of these studies.
In the recent UC Berkeley sleep study, 39 healthy young adults were divided into two groups — nap and no-nap. At noon, all the participants were subjected to a rigorous learning task intended to tax the hippocampus, a region of the brain that helps store fact-based memories. Both groups performed at comparable levels.
At 2 pm, the nap group took a 90-minute siesta while the no-nap group stayed awake. Later that day, at 6 pm, participants performed a new round of learning exercises.
Those who remained awake throughout the day became worse at learning. In contrast, those who napped did markedly better and actually improved in their capacity to learn.
These findings reinforce the researchers’ hypothesis that sleep is needed to clear the brain’s short-term memory storage and make room for new information, said Walker.
Since 2007, Walker and other sleep researchers have established that fact-based memories are temporarily stored in the hippocampus before being sent to the brain’s prefrontal cortex, which may have more storage space.
“It’s as though the e-mail inbox in your hippocampus is full and, until you sleep and clear out those fact e-mails, you’re not going to receive any more mail. It’s just going to bounce until you sleep and move it into another folder,” Walker said.
In the latest study, Walker and his team have broken new ground in discovering that this memory-refreshing process occurs when nappers are engaged in a specific stage of sleep.
Electroencephalogram tests, which measure electrical activity in the brain, indicated that this refreshing of memory capacity is related to Stage 2 non-REM sleep, which takes place between deep sleep (non-REM) and the dream state known as Rapid Eye Movement (REM).
Previously, the purpose of this stage was unclear, but the new results offer evidence as to why humans spend at least half their sleeping hours in Stage 2, non-REM, Walker said.
“I can’t imagine Mother Nature would have us spend 50 percent of the night going from one sleep stage to another for no reason,” Walker said. “Sleep is sophisticated. It acts locally to give us what we need.”
