by Neuroscientist Dr. Allison Brager
Every year, the top sleep scientists in the world, including myself, gather to discuss recent discoveries in the world of sleep, with REM sleep being one of the most popular topics.
Despite many unknowns and unknowables in the field of sleep, as scientists, we can agree that there is one type of sleep that helps us to maximize creativity, learning, and information retention.
What type of sleep is this?
In fact, I even had the opportunity to sit down and hear about the trials and tribulations of discovering REM sleep from the original discoverer of REM sleep himself: Dr. William C. Dement (Stanford University).
We talked about many topics, such as:
REM sleep stands for "rapid eye movement sleep". This is what Dr. William Dement (and his fellow researchers) decided to call REM sleep when they discovered it in 1953 at the University of Chicago when they noticed that their research participants had vigorously flickering eyelids at random intervals throughout the night.
After careful study, this team discovered that REM sleep is characterized by a highly active brain, aggressive eye movements (that will often drive dream content), and a nearly paralyzed body.
These characteristics of REM sleep are why REM sleep is called 'paradoxical sleep'. It's like putting your brain on the gas and your body on the brake at the same time.
During REM sleep, nearly every skeletal muscle of your body is paralyzed. The only muscles that aren't frozen are the ones important for basic survival, this includes your:
•Ocular eye muscles (to initiate rapid eye movements)
•Auditory muscles (for hearing)
•The diaphragm (for breathing).
Otherwise, all of your body’s other musculature are limp, thanks to signals traveling from the brain and along the spinal cord. Clearly, this state is reversible. After every REM episode, the brain briefly enters a state of wake (whether you are consciously aware of it or not), which in return, re-activates your muscles.
How long is a REM sleep cycle?Each cycle of human sleep is 90 minutes. During that 90 minute cycle, we transition from non-REM sleep (typically deep non-REM sleep) to REM sleep to a brief state of being awake (typically subconsciously). As the night progresses, our non-REM sleep episodes within our 90 minute cycle get shorter, and our REM sleep episodes get longer.
Simply put, the longer you sleep, the more deep REM sleep you will get.
REM sleep is only 10-15% of our total nightly sleep. This means that we only spend 15-20 minutes in REM sleep per cycle! This is why you want to get as many hours of sleep as you can so that you get more REM cycles.
REM sleep is also the only state of sleep where you dream. Some dreams seem to last the entire night. This is especially true if you are sleep-deprived. As sleep scientists, we still know very little about how dreams occur (and the meaning behind them). We have had recent breakthroughs in decoding dream content, but most importantly, it has been our discoveries about the function of REM sleep that has been most impactful on human health and performance.
How our brains piece together narratives in what appears to be cinematographic films (i.e. dreams) is still a mystery but we are one step closer to decoding dream content. A few years ago, a group of Japanese researchers recorded brain activity of sleepers who volunteered to sleep and have their brains scanned by means of functional magnetic resonance imaging (fMRI).
After matching verbal reports of dream content with key words, the researchers later interviewed the volunteers while they were lying in an fMRI. Recall of key words from dream reports would activate some areas of the brain, particularly those involved with how we process visual information, and not others (see Horikawa et al. 2013, Science for more information).
Why is it that you can remember how to ride a bike and never forget, but can't remember what you ate for dinner the day before?
The answer is...
REM sleep keeps the necessary information and filters out the unnecessary information so that your brain doesn’t have to waste time trying to process everything.
The 'seahorse' structure of the brain, appropriately named the hippocampus (hippocampi being Greek for sea horse), helps us remember information, retain information, and recall information. The more we access this information and repeat this information, the more the hippocampus will retain this information.
Thus, there is biological evidence behind the old adage that "practice makes perfect". But practice will not be perfect, if you deprive yourself of REM sleep. Sleep researchers know this by means of having volunteers remember information before they sleep and waking them up throughout the night just as they enter REM sleep. After years of study, there is a strong relationship between the inability to remember information and a lack of REM sleep.
REM sleep is helpful not just for remembering encyclopedic knowledge, but also for prioritizing the integration and retention of muscle knowledge. Learning to ride a bike as a child is a skill. Learning to Olympic snatch as an adult is a skill. In fact, there is a direct correlation between learning new skill in real-time and the amount of REM sleep in real-time.
In general, when we learn a new skill, we tend to require more REM sleep at night, which assists and enhances the learning of new skills. To no surprise, being deprived of REM sleep, deprives your mind from integrating and retaining new skills.
This is why REM sleep is so important for those who have intensive jobs where you take in a lot of information (whether physical or mental).
More REM Sleep = Increased Retention = Better Performance.
"How to Win Friends and Influence People," by the late Dale Carnegie is one of the best selling books in the world. It was written in the early 20th century, but still has real-life relevance in today's age of technology.
What does this book have to do with REM sleep? Carnegie's book talks about how to be emotionally balanced. This is the ultimate key to success in life according to Dale Carnegie. REM sleep acts out our frustrations, feelings, and fights for us: while we dream. It is not a coincidence that a traumatic and emotionally troubling time in one's life coincides with more REM sleep (as studied in the lab).
Why would this be? The act of sleeping, in and of itself, is meant to protect us from danger and help us conserve energy. REM sleep acts to preserve us from mental danger, which we know from the study of psychiatric conditions. REM sleep can help individuals suffering from PTSD cope with stress through dreaming, and a lack of REM sleep can be correlated with poorly coping with stress in real life.
Why is this so?
REM sleep helps to fine-tune the emotional centers of the brain, making sure nerve cells are communicating properly and, hopefully, with increased frequency. There is a direct line of feedback between emotional controller of the brain and REM controller of the brain. In fact, in healthy folks, taking a nap can further refine and sharpen the link between the emotional and REM controllers of the brain.
This knowledge bomb was discovered through studies in which volunteers were asked to study emotionally-charging faces before a nap. Those that were lucky enough to nap (based on their group assignment) felt the negative faces were less threatening after a nap. As expected, everything went south if the volunteers were sleep-deprived. The bottom line is you can become more emotionally balanced with a nap (during an optimal time [see below])!
On paper, REM sleep is rapid-eye movement sleep and non-REM sleep is well, non-rapid-eye movement sleep. As we now know, REM sleep is more for mental restoration while non-REM sleep is more for physical restoration. We cycle in and out of non-REM and REM sleep throughout the night, restoring and preserving our physical and mental health in the process!
If you’d like to learn more about non-REM sleep and it’s physically restorative benefits, you can read my more in-depth article here.
Getting more REM sleep isn't difficult. Here, I offer two strategies for getting more REM sleep at night:
• Stay Cool At Night. As our body’s temperature drops, the body’s desire to be in REM sleep rises. Sleep in a cool room. Or, better yet, sleep naked. Clothing provides insulation, and insulation makes us sweat. You can't get quality sleep if you are sweating.You can read more sleep tips here.
• Stay Away From Light When You Sleep. When REM sleep occurs, it is internally controlled by your biological clock. We are day-active creatures and need to sleep at night. If we sleep during the day, our clocks can’t - and quite frankly will never - really be re-programmed to optimize REM sleep.
Thriving in low light at night essentially helps to strengthen the biological clock's schedule of wanting to sleep throughout the night with zero (brain-induced) interruptions and being active during the day.
• Take Magnesium: Most people are magnesium-deficient and need to supplement. In fact, research shows that half of the US population is deficient (source). Magnesium helps to maintain and fine-tune the functioning of the nervous system. This helps to positively impact REM sleep since coordinating an active brain in a paralyzed body during REM sleep are directly controlled by the nervous system.
The second means of maximizing REM sleep involves an understanding of when to sleep during the day and during the night in order to maximize time in REM sleep.
• Go To Bed Before 11:00pm: As I just mentioned, our body’s temperature rises and falls throughout the day and throughout the night and the lower our body temperatures, the more our bodies want to spend in REM sleep. We hit a nighttime low in body temperature between 3:00 - 5:00am that for the most is unchangeable, even in shift workers. It took thousands of years od living by sunrise and sunset for us to develop a daily rhythm of core body temperature, and our body’s rhythm has yet to change with just a hundred years of modern electricity.
This being said, going to bed before midnight can help us capitalize on non-REM sleep throughout the first half of the night, and capitalize on REM sleep during the second half.
• Nap Around 3:00PM: Our body temperature may be the lowest between 3:00 - 5:00am during the early morning, but it also reaches a daytime low between 3:00 - 4:00pm. During this time, our body not only wants to sleep, but if we do happen to take a power nap, most of the nap will be saturated with REM sleep due to the lowering in body temperature. Take advantage of this REM sleep boost!
To conclude, the science behind REM sleep is ever-progressing. REM sleep is more than just pieced together, outrageously weird narratives, and what appear to be cinematographic films every night (i.e. dreams).
REM sleep helps us remember and retain vital information. It refreshes your brain. It also helps to keep us from lashing out at co-workers, family, and strangers and helps to keep life as blissful as possible.
REM sleep is the overlooked but most powerful edge for mental restoration.
Dr. Allison Brager is a neuroscientist specializing in the physiology and genetics of sleep and performance. She is author of Meathead: Unraveling the Athletic Brain, which debunks the myth of the "dumb jock" and serves as a manual for optimizing athletic performance through neuroscience. Outside of the laboratory, she is a former college athlete, Crossfit Games team athlete, and is still active in track and field: pole vault and hurdles.
Other Resources for Optimizing Sleep:
1. My book, “Meathead: Unraveling the Athletic Brain” describes several "neurohackers" for bettering athletic performance through science.
2. Podcast on How to 10x Your Sleep.
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