New Insight on How Sleeping well Boosts Brain Power
Memory and learning, focus and decision making, impulse control and emotional regulation, cognitive flexibility, insight and creativity—sleep has a direct impact on these elements of cognition and many more.
We’re constantly learning more about how sleeping well improves cognitive capabilities and protects against neurodegenerative disease—and about the risks to cognitive health from poor sleep.
Here are some recent, fascinating, relevant-to-your-daily-life insights that science has delivered about the relationship between sleep and cognition. They reveal in new and important ways how prioritizing sleep can have direct, immediate benefits for your cognitive health, productivity, and emotional well being.
For memory recall, high-quality sleep is essential
Some important new research from scientists at Northwestern University underscores the power of sleep to boost memory—and offers a glimpse of the technology that could someday be available to enhance sleep’s memory-enhancing impact.
Researchers investigated the effects of sleep on memory recall, and found that a couple of factors together significantly improved ability to remember recently learned information:
- The reactivation of recently acquired memories during sleep (more on what this means in a minute)
- Sustained high-quality deep, or slow-wave, sleep
The study offers a clear view into how sleep directly enhances memory recall—and gives a blueprint for how to improve memory, by making sure to get ample, uninterrupted time in slow wave sleep.
Scientists gave two dozen young adults (between ages 18-31) 80 photographs of faces with names to memorize. The participants were told the pictures were of students in two hypothetical classes: a Latin American history class and a Japanese history class. Scientists tested baseline recall by showing participants the photographs again and asking them to identify them by name.
Participants then took a nap in a sleep lab, while having brain activity monitored by EEG. When participants entered the deep phases of non-REM sleep (aka slow-wave sleep) scientists “reactivated” selected memories from the face-name pairings by playing some of the names over a speaker (accompanied by music associated with the classes that the people in photographs were said to belong to).
After participants woke from their naps, they were tested again on their ability to recall names associated with faces in the same batch of 80 pictures. Scientists found that memory recall was significantly stronger for the face-name pairs that had been reactivated during the slow-wave sleep phase of participants’ naps.
They also discovered that the quality of slow-wave sleep was critical to the improved recall. To benefit from the enhancement in memory recall from reactivation, participants needed to experience a period of uninterrupted slow-wave sleep.
This is the first study to demonstrate that this technique—known as targeted memory reactivation (TMR)—can improve face-name memory recall. And, and the study scientists note, there are potential future applications for TMR as a tool that might one day be available to help us boost our memories.
The most important takeaway is one that you can put into practice today. That’s the importance of ample, high-quality deep sleep in facilitating memory. Sleep that’s restless and frequently interrupted—whether by the presence of sleep disorders such as sleep apnea and insomnia, by stress or illness, by a sleep environment that doesn’t promote sound rest, or by poorly-timed use of stimulants like caffeine and alcohol—can interfere with brain’s ability to process new information into memory and consolidate those memories for future recall. And there is abundant, growing evidence that poor sleep increases our long-term risks for neurodegenerative diseases, including Alzheimer’s disease.
Staying rested enough to linger briefly in light sleep can unleash bursts of creativity
We’ve all probably had the experience of finding inspiration and insight after waking from sleep. Stories of artists and thinkers tapping into the creative powers of sleep are common. Paul McCartney woke up with an early version of the melody for “Yesterday” in his head. Both Salvador Dali and Thomas Edison had the same trick for harnessing sleep’s creativity-unlocking powers: they lay down for a nap holding an object that would fall from their hands just as they fell asleep, at which point they’d be startled awake–and proceed directly to their work.
New research from French sleep scientists incorporated this creativity hack of Dali and Edison’s into an a really clever, interesting investigation of the role of sleep in boosting creative thinking. The scientists specifically examined the hazy, mixed-consciousness stage of N1 sleep—the lightest of all the sleep stages—on creative problem solving. And they found it to be a rich, productive source of creativity.
A lot of sleep research on creativity has focused on the roles of deep, slow-wave sleep and REM sleep—and studies have shown these sleep stages help the brain make creative leaps. The lightest stage of sleep, when the brain veers between waking consciousness and sleep, has barely been studied in relation to creative thinking.
To investigate the capacity of N1 sleep to spur creative insight, scientists gave 103 study participants a series of math problems, along with a set of instructions for solving all the problems in a two-step method. The participants were instructed to solve the problems as fast as possible.
At the same time, scientists held back a “hidden rule” that would allow participants to skip the two-step method—a secret shortcut for solving the problems.
Participants were given several tries to solve the problems. (A few—16 out of the 103–identified the hidden rule right away. These individuals were removed from the study’s later analysis.) Next, they were given a 20-minute break and asked to relax, recline, and close their eyes in a dark room. Throughout the 20-minute rest, their brain activity was monitored. Like Dali and Edison, participants held an object in their hands (in this case, it was a water bottle) so they’d be awakened when they drifted into sleep.
After the rest period, they were again given the math problems to solve.
Researchers found that participants who spent at least 15 seconds in N1 sleep were almost 3 times as likely to identify the hidden rule than participants who stayed awake for the entire rest period. And the N1 sleepers were nearly six times as likely to spot the hidden rule as participants spent at least 30 seconds in N2 sleep–a slightly deeper stage of slight sleep—before being awakened by the falling water bottle.
This is a fascinating pinpointing of what the scientists call the “creative sweet spot” of very light sleep, when the brain is perhaps asleep enough to undertake a different and freer sort of creative thinking but awake enough to retain and apply the insights.
This study also speaks powerfully to the productivity gains to be found in well-timed naps (with or without a water bottle in hand), and to the power of maintaining balanced rest in daily life. To achieve these creative bursts, participants needed to be tired enough to be able to fall asleep AND rested enough that they didn’t skip right through the lightest stage of sleep and miss out on the sweet spot that N1 sleep offers.
Here’s what to know about the power of napping—and how to harness it.
And here are some actionable steps you can take to reduce your sleep debt.
Small reductions in overnight sleep generate big boosts in daytime anxiety
We talk a lot about the changes to mood that come with not getting enough sleep, and from sleep that is restless and poor quality. When we don’t get enough rest on a consistent basis, we’re significantly more likely to be emotionally reactive, to experience symptoms of anxiety and depression, and meet clinical thresholds for anxiety disorders and clinical depression. In turn, mood problems can interfere with our ability to sleep soundly, setting up a difficult cycle that negatively affects both sleep and mood.
For all the evidence of a close connection between sleep and anxiety, there is still a lot that’s not known about how sleep triggers anxiety—and how sleeping well can ease anxiousness.
Recent research from scientists at the University of California, Berkeley, showed for the first time that sleep amounts directly affect anxiety levels by compromising activity in a region of the brain that handles high-level cognitive functions. Using MRI technology, researchers found that sleep deprivation led to a significant drop in activity in the medial prefrontal cortex, which plays a major role in regulating and controlling emotions, and managing emotional reactivity. (This area of the brain handles a broad range of complex cognitive functions beyond emotional control, including several aspects of memory processing, decision making, attention and our ability to form habits.)
In the laboratory phase of their study, scientists learned that a single night of full sleep deprivation led to a 27% increase in anxiety levels, compared to getting a full night of sleep. Among the participants in the sleep lab study, a night of total sleep deprivation generated anxiety levels beyond the clinical measurement of an anxiety disorder for 50% of non-sleepers.
In another phase of their research, scientists conducted two studies that gathered data about the day-to-day relationship between sleep and anxiety through online reports. They found that smaller, modest degrees of sleep loss generated significant spikes in next-day anxiety.
Researchers also found that greater amounts of slow-wave sleep—the deep sleep that becomes more plentiful with a full night of high-quality rest—reduced next-day anxiety.
When we experience a full night of high-quality sleep, we power our brain’s emotional regulation center, which works to keep emotional reactivity and anxiety in check. Carving out the time and creating the conditions for consistently abundant and restful sleep has a direct and immediate effect on our mood and emotional stability and control.
Your nightly rest is critical to your day-to-day cognitive functioning and to your long-term cognitive health. There’s no better investment in a healthy brain than a habit of consistently sleeping well.
Sweet Dreams,
Michael J. Breus, PhD, DABSM
The Sleep Doctor
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