What senses are active while sleeping?

What senses are active while sleeping?

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During sleep, our body activity decreases. I am wondering on the extent of the lowering of this activity regarding our five senses. Clearly, the sense of touch is still very efficient since shaking a body is the most common way to awake someone, and hearing is also quite unaffacted (most, if not all, alarm clock, rely on this sense). Most deaths due to fire are due to intoxication rather than the burnt of the fire, so it suggests that smell and taste are pretty dimmed during sleep.

My main question: To which extent each sense is dimmed during sleep?

For example,

  1. Can we smell during sleep? I don't remember having been awoken by the smell of something during my life…
  2. Similarly, can we taste? If someone gives me delicious food during my sleep, would I be able to feel its taste and remember this experience?
  3. Can we see? REM are well known but it is a mechanical feature of the sleep. Some people sleep with the eyes opened: what do they see?

Note: This related question tries to explain how senses are dimmed during sleep but not how much they are.

Note 2: I am aware this is person-dependant: any sound would awake my mother (a skill during my nightly escapades) whereas I would not notice a party around me when I am in deep sleep. But there should be some kind of average… It also depends on the phase of sleep; I am mostly interested in deep sleep and REM sleep, but an answer detailing every phase would be awesome.

Note 3: This question is certainly naive in its current form. Please help me to improve it.

The answer is of interest not only in sleep but also the perceptions of patients under anesthesia, comatose states, etc.

Our senses aren't 'dimmed' in sleep. There is no effective way to turn off our senses. The best way to explain what happens in sleep is that at some point (the last point, actually), our cognitive processing of sensations changes. That is, our higher brain functions allow us to ignore certain sensory input. This effect has been most studied in sound perception.

In a sleep study involving sound and EEG/fMRI during all phases of (drug-free) sleep,

The first significant result of this study is that the pattern of brain activation associated with auditory stimulation was strikingly similar in wakefulness and sleep, suggesting that sensory processing occurred in both conditions. However, we found qualitative differences in brain activation associated with auditory processing during sleep compared to wakefulness. The reduced regional activity during sleep, compared to wakefulness, in the left parietal and, bilaterally, in the prefrontal cortex, thalamus, and cingulate gyrus (part of the limbic system) suggests that these areas may be involved in the further processing and perceptual integration of sensory inputs likely to occur during wakefulness only.[1]

Supporting this is evidence that some sounds awaken someone no matter at what stage they are in sleep, for example, young mothers are woken up by their infants' lightest movements[2], and the fact that we respond to our own names in a similar fashion in sleep and in wakefulness, but such responses are not shown for presentation of other first names.[3]

These results suggest that the sleeping brain, during SII and PS, elicits a differential cognitive response to the presentation of the subject's own name, comparable to that occurring during wakefulness, and therefore that the sleeping brain is able to detect and categorize some particular aspects of stimulus significance.[3]

Thus, the results suggest that when subjects were listening to their own name during sleep some brain regions were selectively more responsive than in any other condition… we have demonstrated that the sleeping brain is able to process auditory stimuli. In addition, we postulate the existence of a functional network capable of detecting and facilitating processing of emotionally relevant inputs during sleep.[1]

Our results support the view that PS is not a state of "sensory isolation"; failure to respond to external stimuli during this stage may depend upon mechanisms occurring only after the sensory input has undergone cognitive analysis.[4]

However, as you noted, odors are not good at waking people up.

Some suggest that the human olfactory system during sleep is sufficiently well tuned to ensure arousal to such threatening stimuli as odors associated with smoke from fire. Our results strongly suggest otherwise. The intensity, strength, and noxiousness of the pyridine stimulus elicited behavioral arousal or EEG activation on fewer than half of stage 2 trials, less than one third of REM-sleep trials, and virtually no stage-4- sleep trials. This is a nontrivial lack of response, since pyridine is a component of coal tar and is also used as a herbicide for firewood, and thus is a likely by-product of many real fires. In practical terms, therefore, olfactory awareness in humans is low to absent during sleep, and human olfaction appears insufficiently sensitive and reliable to act as a sentinel system. We further note that auditory arousal threshold is highest in young and sleep-deprived individuals, increasing the likelihood that olfactory processing is even worse for children and sleep-deprived adults.[5]

The methodology in the olfactory study varies quite significantly from the auditory study. Better studies may shed more evidence on why olfactory stimuli are processed differently from other stimuli.

As to what percent? That probably differs from person to person, and I did not search the literature for that.

[1] Auditory Processing across the Sleep-Wake Cycle: Simultaneous EEG and fMRI Monitoring in Humans
[2] Changes in sleep patterns of young women from late pregnancy to postpartum: relationships to their infants' movements
[3] A differential brain response to the subject's own name persist during sleep
[4] Brain Processing of Stimulus Deviance During Slow-Wave and Paradoxical Sleep: A Study of Human Auditory Evoked Responses Using the Oddball Paradigm.
[5] Minimal Olfactory Perception During Sleep: Why Odor Alarms Will Not Work for Humans

Sleep and memory

The relationship between sleep and memory has been studied since at least the early 19th century. Memory, the cognitive process of storing and retrieving past experiences, learning and recognition, [1] is a product of brain plasticity, the structural changes within synapses that create associations between stimuli. Stimuli are encoded within milliseconds however, the long-term maintenance of memories can take additional minutes, days, or even years to fully consolidate and become a stable memory that is accessible (more resistant to change or interference). Therefore, the formation of a specific memory occurs rapidly, but the evolution of a memory is often an ongoing process.

Memory processes have been shown to be stabilized and enhanced (sped up and/or integrated) and memories better consolidated by nocturnal sleep and daytime naps. Certain sleep stages have been demonstrated as improving an individual's memory, though this is task-specific. Generally, declarative memories are believed to be enhanced by slow-wave sleep, while non-declarative memories are enhanced by rapid eye movement (REM) sleep, although there are some inconsistencies among experimental results. The effect of sleep on memory, especially as it pertains to the human brain, is an active field of research in neurology, psychology, and related disciplines.

The nature of sleep

Sleep usually requires the presence of relaxed skeletal muscles and the absence of the overt goal-directed behaviour of which the waking organism is capable. The characteristic posture associated with sleep in humans and in many but not all other animals is that of horizontal repose. The relaxation of the skeletal muscles in that posture and its implication of a more-passive role toward the environment are symptomatic of sleep. Instances of activities such as sleepwalking raise interesting questions about whether the brain is capable of simultaneously being partly asleep and partly awake. In an extreme form of that principle, marine mammals appear to sleep with half the brain remaining responsive, possibly to maintain activities that allow them to surface for air.

Indicative of the decreased sensitivity of the human sleeper to the external environment are the typical closed eyelids (or the functional blindness associated with sleep while the eyes are open) and the presleep activities that include seeking surroundings characterized by reduced or monotonous levels of sensory stimulation. Three additional criteria—reversibility, recurrence, and spontaneity—distinguish sleep from other states. For example, compared with hibernation or coma, sleep is more easily reversible. Although the occurrence of sleep is not perfectly regular under all conditions, it is at least partially predictable from a knowledge of the duration of prior sleep periods and of the intervals between periods of sleep, and, although the onset of sleep may be facilitated by a variety of environmental or chemical means, sleep states are not thought of as being absolutely dependent upon such manipulations.

In experimental studies, sleep has also been defined in terms of physiological variables generally associated with recurring periods of inactivity identified behaviorally as sleep. For example, the typical presence of certain electroencephalogram (EEG) patterns ( brain patterns of electrical activity) with behavioral sleep has led to the designation of such patterns as “signs” of sleep. Conversely, in the absence of such signs (as, for example, in a hypnotic trance), it is believed that true sleep is absent. Such signs as are now employed, however, are not invariably discriminating of the behavioral states of sleep and wakefulness. Advances in the technology of animal experimentation have made it possible to extend the physiological approach from externally measurable manifestations of sleep such as the EEG to the underlying neural (nerve) mechanisms presumably responsible for such manifestations. In addition, computational modeling of EEG signals may be used to obtain information about the brain activities that generate the signals. Such advances may eventually enable scientists to identify the specific structures that mediate sleep and to determine their functional roles in the sleep process.

In addition to the behavioral and physiological criteria already mentioned, subjective experience (in the case of the self) and verbal reports of such experience (in the case of others) are used at the human level to define sleep. Upon being alerted, one may feel or say, “I was asleep just then,” and such judgments ordinarily are accepted as evidence for identifying a pre-arousal state as sleep. Such subjective evidence, however, can be at variance with both behavioral classifications and sleep electrophysiology, raising interesting questions about how to define the true measure of sleep. Is sleep determined by objective or subjective evidence alone, or is it determined by some combination of the two? And what is the best way to measure such evidence?

More generally, problems in defining sleep arise when evidence for one or more of the several criteria of sleep is lacking or when the evidence generated by available criteria is inconsistent. Do all animals sleep? Other mammalian species whose EEG and other physiological correlates are akin to those observed in human sleep demonstrate recurring, spontaneous, and reversible periods of inactivity and decreased critical reactivity. There is general acceptance of the designation of such states as sleep in all mammals and many birds. For lizards, snakes, and closely related reptiles, as well as for fish and insects, however, such criteria are less successfully satisfied, and so the unequivocal identification of sleep becomes more difficult. Bullfrogs (Lithobates catesbeianus), for example, seem not to fulfill sensory threshold criteria of sleep during resting states. Tree frogs (genus Hyla), on the other hand, show diminished sensitivity as they move from a state of behavioral activity to one of rest. Yet, the EEGs of the alert rest of the bullfrog and the sleeplike rest of the tree frog are the same.

Problems in defining sleep may arise from the effects of artificial manipulation. For example, some of the EEG patterns commonly used as signs of sleep can be induced in an otherwise waking organism by the administration of certain drugs.

Other Changes

Your body is busy repairing cells and finishing digestion.

During a good night’s rest, you may not get up to go to the bathroom. That’s because your kidneys make less pee while you sleep.

Growth hormone production surges. Your body makes more thyroid hormones.Levels of cortisol, sometimes called the “stress hormone,” go down when you first fall asleep, then go up again right before you wake up. Levels of melatonin, one of the main chemicals involved in the sleep-wake cycle, do just the opposite: they rise to make you sleepy when the sun sets and ebb at daylight.


American Sleep Association: “What is Sleep?”

Harvard Medical School: “The Characteristics of Sleep.”

National Sleep Foundation: “What Happens When You Sleep?”

Institute of Medicine: “Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem.”

National Sleep Foundation: “Does Your Body Temperature Change While You Sleep?”

National Sleep Foundation: “The Physiology of Sleep – Thermoregulation & Sleep.”

National Sleep Foundation: “Exercise at This Time of Day for Optimal Sleep.”

University of Washington: “What is Sleep . . . and why do we do it?”

National Sleep Foundation: “The Physiology of Sleep – The Respiratory System.”

Dartmouth College: “Chapter 53: The pharynx and larynx.”

National Heart, Lung, and Blood Institute: “What Is Sleep Apnea?”

American Chemical Society: “So Tired in the Morning. The Science of Sleep.”


An unpleasant smell can permeate your dreams and disturb your sleep before you’re sure what’s hit you. A room that smells musty or stale can also prevent you from falling asleep in a natural manner too. Consider using natural scents in the bedroom to freshen the air inside your room like lavender, chamomile, or jasmine plants essential oil air fresheners, or washing bedroom sheets with freshening additives on a weekly basis is also a great idea.

Helpful Hint: If you prefer natural laundry remedies, mix 10 drops of your favorite essential oil into one cup of baking soda and add it to the washer at the beginning or during the pre-wash stage.

How to Improve Your Habits for Healthier Sleep

The amount of sleep required per day varies depending on a person’s age and ranges from up to 18 hours for infants, 9-10 hours for school-age children, to 7-9 hours for adults. Although sleep has drastic importance for our health and well-being, most people don’t receive the recommended requirement per night. A 2016 CDC study found more than 33% of adult Americans received less than 7 hours of sleep a night. Lack of sleep has been associated with higher risks of chronic diseases such as high blood pressure, diabetes, obesity, heart disease, stroke, and mental illness.

In order to improve your sleep habits, you can follow these tips recommended by the NIH. First, follow a regular schedule for daily bedtime. This step will help set your body’s circadian rhythm and make it easier to fall asleep at a regular time. Second, avoid stimulating activities close to bedtime, including those with bright lights and sounds or with exposure to screens. Similarly, avoiding consumption of caffeinated or alcoholic beverages close to bedtime is generally recommended, as these increase hormones that stimulate the body. Finally, exercise for 20 to 30 minutes daily but not fewer than a few hours before bedtime to further promote healthy circadian rhythm patterns.

When you close your eyes and start to drift into non-REM sleep, your brain cells settle down from their daytime activity levels and start firing in a steady, more rhythmic pattern. But when you start to dream, your brain cells fire actively and randomly. In fact, in REM sleep, brain activity looks similar to when you’re awake.

Can you learn in your sleep? Yes, and here's how

Sleep is known to be crucial for learning and memory formation. What’s more, scientists have even managed to pick out specific memories and consolidate them during sleep. However, the exact mechanisms behind this were unknown — until now.

Share on Pinterest We may one day be able to induce brain waves that will enable us to learn in our sleep.

Those among us who grew up with the popular cartoon “Dexter’s Laboratory” might remember the famous episode wherein Dexter’s trying to learn French overnight.

He creates a device that helps him to learn in his sleep by playing French phrases to him.

Of course, since the show is a comedy, Dexter’s record gets stuck on the phrase “Omelette du fromage” and the next day he’s incapable of saying anything else.

This is, of course, a problem that puts him through a series of hilarious situations.

The idea that we can learn in our sleep has captivated the minds of artists and scientists alike the possibility that one day we could all drastically improve our productivity by learning in our sleep is very appealing. But could such a scenario ever become a reality?

New research seems to suggest so, and scientists in general are moving closer to understanding precisely what goes on in the brain when we sleep and how the restful state affects learning and memory formation.

For instance, previous studies have shown that non-rapid eye movement (non-REM) sleep — or dreamless sleep — is crucial for consolidating memories.

It has also been shown that sleep spindles, or sudden spikes in oscillatory brain activity that can be seen on an electroencephalogram (EEG) during the second stage of non-REM sleep, are key for this memory consolidation.

Scientists were also able to specifically target certain memories and reactivate, or strengthen, them by using auditory cues.

However, the mechanism behind such achievements remained mysterious until now. Researchers were also unaware if such mechanisms would help with memorizing new information.

How Sleep Impacts Your Brain

OK, you get it now. Sleep isn’t exactly the blank, no-man’s land that you might’ve thought—and your brain is actually pretty hard at work the entire time. But aside from moving you from one stage of sleep through to the next, what’s actually going on in there?

Get ready—you’re about to find out.

Sleep Helps Your Brain Work Faster And More Accurately

You might already know this intuitively. When you stay up too late or fall behind on sleep, you end up caught in a dense cloud of brain fog. You know, the one that causes you to make mistakes that you know are dumb but can’t seem to avoid, or that makes it harder than usual to figure simple stuff out.

Adequate quality shut-eye helps your brain fire on all cylinders when you’re awake, so you can think and respond faster and with fewer mistakes. Likely, that could be because sleep is an opportunity for the neurons that you’ve been using all day to take a break and repair themselves before you start calling on them again tomorrow. Because everything—even tiny neurons—need to rest at some point.

But after they’ve had a chance to chill, you have an easier time concentrating and remembering stuff. You’ll also be less likely to phone it in when it comes time to solving a tough problem, according to one study

Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source published in the National Library of Medicine.

When City University of New York researchers gave college students a series of math problems after a night of adequate sleep and then again after a night of too-little sleep, the students did equally well after each night. But after not getting enough sleep, students tended to choose less challenging problems.

In other words, they knew that they weren’t as sharp, and tried to avoid failing all together by taking an easier route. Which is fine for an experiment—but probably isn’t the type of behavior that’ll get you the promotion at work.

Sleep Helps You Make Sense Of New Information

Believe it or not, your brain can actually process complex information when you’re sleeping.

Experts have long known that your brain maintains some level of awareness even when your brain is fully engaged in the sleep process. For instance, sleeping people are more likely to respond to their own names or startling sounds like a fire alarm or alarm clock than to other random noises.

But according to mind-blowing research recently published in the journal Current Biology, that’s just the beginning. Researchers asked study participants laying in a dark room to group spoken words into certain categories by pressing a left or right button. Once participants had gotten used to the task so it became automatic, researchers told the participants that they should continue categorizing the words, but that it was okay to fall asleep.

After participants had nodded off, the researchers introduced new words that fell into the same categories as the words that participants heard when they were awake. The crazy thing? Brain monitoring devices showed that even while the participants were snoozing, their brains were using the information they had learned to go through the functions to categorize the words as left or right.

When the participants woke up, they didn’t have any memory of hearing the new words while they were sleeping. In other words, their brains processed all of the new information while the participants were completely unconscious. Which means that, yes, your brain is even learning while you’re sleeping.

Sleep Helps Your Brain Cement Memories

Imagine if every single time you did or experienced something new throughout the day, you had to stop what you were doing to file the experience away in your short- or long-term memory file so you could recall it later when you needed it. Chances are, you’d be spending so much time archiving your life that you’d never actually get anything done.

Thanks to the power of sleep, you don’t have to do that. That’s because snooze time is prime time for your brain to get busy processing memories. As you sleep, your brain works to solidify memories that you formed throughout the day. It also links these new memories to older ones, helping you make connections between different pieces of information to come up with new ideas. (More about that later.)

Remember the stages of sleep we talked about earlier? Stages 1-4, the ones where you aren’t experiencing REM, are key for learning and the memory formation that comes with it. In fact, if you skimp out on non-REM sleep, your ability to learn new information plummets by as much as 40%, say experts at the National Institutes of Health. That’s because sleep deprivation interferes with your hippocampus, the part of your brain that’s responsible for processing memories.

When you’re sleeping, your brain decides what stuff from the day is worth keeping—and what’s worth forgetting about so you can free up space for taking in new information tomorrow.

It makes perfect sense when you think about it. But it’s more than just a theory. More than a century of research shows that sleep improves memory retention—so much so, that the brain can actually be more efficient at consolidating memories while you’re asleep than while you’re awake, wrote German researchers in a 2013 review.

Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source

Unfortunately, the reverse is also true. When your sleep patterns start to change as you get older, so too does your ability to form new memories. Your memory-cementing skills can begin to decline as early as your late thirties, and it only tends to go downhill from there. One study published in the journal Nature Neuroscience found that adults over age 60 had a 70% loss of deep sleep compared to adults ages 18 to 25—and consequently, had a harder time remembering things the next day.

Still, just because you’re getting older doesn’t mean that you’re doomed to a life of total forgetfulness. While some amount of age-related memory decline is unavoidable, getting enough sleep is crucial for making the most of your brain’s memory-consolidating powers. Aim to get seven to eight hours of sleep on most nights—especially on days when you’ve learned important new information.

According to Dr. Josef Parvizi, Associate Professor of Neurology and Neurological Sciences at Stanford University, “the seemingly noisy and disorganized brain activity during sleep has a perfectly unique structure to it,” he added.

During his research he found that populations of cells that were working together during math and memory-related activities, had a coordinated fluctuation of physiological activity during sleep as well, in other words, these cells worked together to complete a task and were paired together during sleep.

“It was almost like they never ceased to be together, almost like a pair of individuals that never depart from each other,” he added. “There is much more going on in sleep than we are able to understand,” said, Parvizi.

Further driving home the point that there is a substantial connection between memory and other activities in your brain while you’re awake and while you’re asleep.

Sleep Helps Your Brain Think More Creatively

On days when you’re running short on sleep, your thoughts probably go on a loop that sounds something like this: “I’m so exhausted. I can’t do this right now. I just want to go home and do nothing.”

When you’ve got a one-track mind for crawling into your bed and getting some much-needed rest and relaxation, you probably aren’t all that concerned about coming up with cool new ideas. Which is one of the reasons why sleep deprivation zaps your ability to be creative.

Of course, there’s way more to it than that. While your brain is busy consolidating memories as you sleep, it’s also forming connections between new ideas and old ones—setting the stage for that all-important light bulb moment.

Research published in the Proceedings of the National Academy of Sciences of the United States of America backs this up. After a night of restful sleep, study participants were 33% more successful at completing tasks that required them to make unusual (read: creative) connections in their brain compared to people who hadn’t slept yet.

Perhaps unsurprisingly, Stage 5 (or REM sleep)—the part of the sleep cycle that involves dreaming—is key to boosting creativity.

One recent study presented at the American Psychological Association’s annual convention found that people who took 90-minute naps featuring REM sleep performed 40% better on word problems that required them to see connections between seemingly unrelated words than people whose naps didn’t feature REM sleep or people who didn’t nap at all. That could be because REM sleep helps your brain “detach” your memory of a word’s meaning and apply the word in another context, say researchers.

Sleep Helps Your Brain Clear Out Harmful Toxins

The word “toxin” gets thrown around a lot these days. And in health-oriented circles, you can find endless solutions that are touted as effective for clearing out toxins in your body. (Juice fasts, activated charcoal, and apple cider vinegar, we’re looking at you.)

For now, it’s up for debate whether any of those things are actually effective. But when it comes to clearing out toxins, one thing that actually has been shown to work is sleep. At the same time that your brain is busy sending out growth hormones, consolidating memories, and forming creativity-boosting connections, it’s also busting out the vacuum to suck up any unwanted dirt and clear it away.

“There is evidence the brain clears out toxic wastes accumulated during the day at night, through convective motion of the fluid that bathes the brain,” according to Dr. John Medina, a developmental molecular biologist and author of the New York Times bestseller Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School. “If you don’t sleep, you won’t get the molecular waste removed,” he added.

Studies conducted on mice back in 2013 found that during sleep, the space between rodents’ brain cells actually expanded, allowing for the brain to sweep away harmful molecules that had built up throughout the day. And not just any harmful molecules—we’re talking about ones that are associated with neurodegenerative diseases like Alzheimer’s and Parkinson’s.

Fast forward to 2015, and we’re learning that the same seems to apply to humans. When University of California-Berkeley researchers used imaging tools to look at the brains of 26 older adults who had not been diagnosed with dementia or sleep problems, they found that people with the highest levels of beta-amyloid—a toxic protein associated with the development of Alzheimer’s and dementia—tended to have the poorest quality sleep. They also performed worse on simple memory tests compared to those who slept better and had lower beta-amyloid levels.

Of course, it’s only one study, and experts still have a lot to learn about how exactly beta-amyloid buildup affects memory. But when it comes to keeping your brain as clean as possible, sleep just might be key.

Sleep Helps Your Brain Regulate Your Appetite

By now, you’ve probably heard that regularly skimping on sleep can lead to weight gain. And while it’s true that most of us are more likely to snack on junk at night, and that being tired could make you more likely to skip your workout, those aren’t the only factors at play.

Just like how sleep prompts the release of growth hormone, snooze time also plays a major role in regulating the hormones that determine whether you feel like eating. Countless studies have shown that lack of sleep prompts your brain to release more ghrelin, the hormone that causes you to feel hungry. At the same time, too little sleep causes your brain to pump out less leptin, the hormone that makes you feel full.

Translation? When you’re zonked, you’re more likely to scarf down everything in sight. In fact, people who are sleep deprived tend to take in about 300 more calories per day compared to their well-rested counterparts.

That adds up to a pound gained in less than two weeks—but some research suggests that the effects could be even more dramatic. One University of Colorado-Boulder study found that just five days of sleep deprivation prompted people to load up on more comforting carbohydrates (hello, mac and cheese!)—and pack on two pounds in the process. (The good news? When subjects got back to healthier sleep patterns, they started making healthier food choices, too.)

To make matters worse, the whole thing ends up turning into a vicious cycle. When you gain weight, you up your risk for running into sleep-stealers like chronic pain, sleep apnea, and even type 2 diabetes. The sleep deprivation makes you feel even more tired, which makes you more likely to make poor food choices and less likely to have enough energy to exercise.

Sleep Helps Your Brain Keep Your Body Looking Good

Seriously, they call it beauty rest for a reason. Sleep is the time that your brain gives the green light for releasing the growth hormone that your body uses to grow new cells and repair damaged tissue.

Of course, your body needs growth hormone to do things like heal wounds or build stronger muscle tissue after a tough workout. But it also uses growth hormone to fight stress and damage caused by the sun and the oxidizing environmental pollutants that we’re all exposed to on a daily basis.

Over time, those things can cause your skin to get dull and wrinkly. And while you can’t keep your skin looking like the way it did when you were 20 forever, logging adequate shuteye can help stave off premature aging by fostering the growth of fresh, healthy cells that keep your skin looking younger, smoother, and more radiant.

And research suggests that you won’t be the only one who can actually tell the difference. In one Journal of Clinical Sleep Medicine study, University of Michigan researchers looked at adults with untreated obstructive sleep apnea who experienced excessive sleepiness.

After just two months of CPAP treatment, the subjects boasted improvements in their facial volume (read: more suppleness and fewer wrinkles) and less redness, while independent raters said that the subjects appeared more youthful and attractive.

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Neurotransmitters and your sleep

Some neurotransmitters help your body recharge while you sleep. They can even help you to remember things that you learned, heard, or saw while you were awake. The neurotransmitter acetylcholine is at its strongest both during REM (rapid eye movement) sleep and while you are awake. It seems to help your brain keep information gathered while you are awake. It then sets that information as you sleep. So if you study or learn new information in the hours before bed, "sleeping on it" can help you remember it.

Other neurotransmitters may work against you as you sleep. Abnormalities with the neurotransmitter dopamine may trigger sleep disorders such as restless legs syndrome.

Even losing just 1 hour of sleep over a few days can have an effect. It can lead to a decrease in performance, mood, and thinking. Getting regular, adequate amounts of sleep is important. It can help you feel awake and refreshed during the day. It can also help you feel relaxed and sleepy at night. This helps make you ready for a long, restful night of sleep.