Science of sleep: part 2

The second part of the article reveals the amazing secrets of what is happening in your brain after you close your eyes and fly away to the country of dreams (and about what happens if you do not do this).

4. Dreams

Ah, dreams are the most intriguing, mysterious and interesting part of the sleep process. What do we know about them? Yes, you guessed right - not enough to be completely sure of anything.

Let us immediately discard Freud with his “subconscious desires” (we have a scientific blog) and proceed directly to the facts. Some researchers believe that there is a connection between the newly created memory, their consolidation and the formation of dreams. One hypothesis says that when the elements of a new memory appear in a dream, it becomes easier for the brain to write them down, since they are reproduced in their original state (as if you perceive the memories again). There are studies showing that in the morning, after people had dreamed of something recently learned, they better cope with the memories on this score than those who did not dream of it.

And although we still can not determine which parts of the brain are responsible for creating dreams, in a couple of recent studies, scientists have made some progress in determining which part of the brain makes us dream. It turns out that the parietal-occipital region, working on the creation of mental images and processing all your sensations during the day, is actively working at night to create dreams. And if you enjoy your night adventures (hmm, it sounds somehow wrong), you need to take very much care of this site - studies show that its damage leads to loss of dreams. Moreover, scientists have even determined which parts of the brain are activated at the time when you are dreaming about something specific. They came up with five rude categories (thoughts and sensations, speech, faces, movements, space) and found that when people dream of something from a certain category, the part of the brain that is responsible for it while waking is much more active than others and behaves in a dream . This means that the "perception" of certain information activates the same parts of the brain, regardless of whether they are real or dreamed.


Yesterday I dreamed that a hamburger is eating me

5. What can go wrong?

Like everything else in life, sleep can deteriorate - and in many ways. It may be intermittent insomnia, familiar to all of us, or it may be an incurable disease “ fatal familial insomnia, ” which completely prevents a person from falling asleep, as a result of which he experiences hallucinations, dementia and death. Yes, scary. But let's start with something easier.

There is insomnia (insomnia) - when you cannot fall asleep, hypersomnia - when you sleep too much, parasomnia - when you demonstrate abnormal behavior during sleep, and other conditions (for example, sleep apnea , when you have problems during sleep) with breath).

Insomnia can cause a whole car of factors - you can get nervous before the exam, constantly returning to some stupid cue thrown five years ago (or be exposed to the side effect of an existing illness). However, sometimes the brain simply sabotages your sleep - studies show that people with primary insomnia (that is, not associated with other states) may suffer from a lack of the GABA neurotransmitter working as a “brake fluid” of the brain. It has been shown that adults with chronic insomnia 30% less GABA than the average in the population. As a result, the brain is unable to drown out waking up its signals, and remains hyperactive. Moreover, it was found that these patients also have problems with brain relatedness — with connections from and to the thalamus , a part of the brain that controls many functions — consciousness, sleep, and wakefulness. It is not yet clear whether breaking the link is the cause or effect of insomnia, but at least this fact sheds some light on this mysterious disease.


Red: white matter areas whose integrity is impaired in patients with primary insomnia

Hypersomnia, on the contrary, constantly drives you to sleep. Narcolepsy , a disease in which a person feels excessively sleepy and uncontrollably falls asleep during the day, is the main example of hypersomnia. It was found that people with narcolepsy have a lack of orexins . Orexins are chemical compounds produced in the hypothalamus, signaling the brain stem, the site that keeps us awake so that it continues to keep us awake. Therefore, when these orexins die for some reason (mainly for autoimmune), it becomes difficult for a person to stay awake for a long time, because the brain does not receive signals that it should remain active.


Number of orexin-producing neurons in a healthy person (left) and in narcoleptic (right)

The list of parasomnies includes such things as somnambulism , nightmare or even sexomnia (although the latter is often referred to as somnambulism). In a 2012 study, it was found that 29.2% of Americans at least once in their lives experienced somnambulism . It usually occurs during deep sleep in the 4th phase (this is the phase after a forced awakening from which you feel depressed). And although most of these episodes are harmless, sometimes somnambulism can get serious (you can recall the characteristic case of Kenneth Parks , who, while in a dream, left the house, got into the car, drove 23 km to the house of his mother-in-law and father-in-law, killed them, and then drove to the police station). Research suggests that such episodes may occur due to the fact that more primitive parts of our brain (the limbic system ) involved in the formation of emotions and complex motility remain awake, while more complex parts of the brain that control rational thinking and memory, sleep. The brain is stuck in an indefinite state between sleep and reality, and is governed by an archaic system aimed at survival, since normal control mechanisms are still asleep.


The man who killed the mother-in-law and father-in-law during the attack of somnambulism

Finally, look at what happens to the brain if a person does not get enough sleep. We all know that sleep deprivation is not good - a person feels bad, starts to forget everything, breaks down on people and works on autopilot. But what does it do with your brain?


Sleep deprivation is a one-way ticket to a temporary psychosis.

More recently, scientists have found that 24 hours without sleep cause symptoms similar to schizophrenia: people lack attention and concentration, are unable to filter incoming sensory information, which leads to overloading of the senses. It also reported a change in the sense of time and smell, and some people even said that they had the feeling that they could read minds.

Recently, one of the studies was honored with noisy lighting in the press headlines, which sounded something like “The brain eats itself with a lack of sleep!” between brain cells (synapses) develop excessive activity in the brain of sleep deprived mice. Astrocytes, cells that eliminate superfluous synapses, were active in only 5% of brain cells from a well-sleeping mouse. In mice with sleep deprivation, this number increased to 13%. In addition, astrocytes from a mouse that had not slept started not only to carefully remove synapses to update brain connections, but actually to eat them in the process of phagocytosis (from the Greek word φαγεν, meaning “to devour”). However, no matter how awful it sounds (and how sensational headlines sound like “the brain eats itself!”), Scientists say that the strongest, oldest and most used synapses were eaten. Therefore, in a sense, it looks like getting rid of old furniture. The researchers did not consider this something catastrophic. Another result was more disturbing. Microglia , a type of cell that cleans out old and worn cells (also using phagocytosis), also began to behave hyperactively after chronic sleep deprivation. And this is not very good, since the hyperactivation of microglia was associated with various neurodegenerative diseases like Alzheimer's. It has also been shown that a sleep disorder makes people more vulnerable to dementia - so perhaps there is a connection between them.

Another study found that sleep deprivation leads to a slower response to external events - due to the slower transfer rate between neurons. Therefore, in essence, brain cells get too tired and simply cannot transmit information at normal high speed, which leads to cognitive failures and slows down the reaction rate. Instead of walking at the speed of a hare, as after a normal 8-hour sleep, thoughts creep like turtles. Moral of the story: go to sleep. Check out today with Netflix and Facebook.


I have not slept for 83 consecutive hours, but I'm fine.

6. So how much sleep do we need and how to sleep correctly?

We all heard about the magic figure - 8 hours of sleep. Eight hours for the most soothing sleep, eight hours for the alignment of the chakras, eight hours then, eight hours it. But is it really? Apparently, articles arguing with the 8-hour idea, and offering new opinions about the optimal duration of sleep, occur more often than I manage to sleep properly. So where is the truth?

Although there is no answer to the minute, scientists still agree on some estimates. Of course, there are people sleeping a little, thanks to a rare genetic mutation that can fully rest after a very short sleep (4-5 hours), and to which the general rules do not apply. However, most people are not so lucky, and for an ordinary person a good estimate would be 7-8 hours. There are studies that study the connection between sleep and things like cardiovascular diseases ( 1 , 2 , 3 ), obesity , depression, and mortality rates ( 1 , 2 , 3 ), showing that this connection is similar to the U-shaped curve. , and the smallest manifestations of these diseases occur at around 7-8 hours. Moreover, the American Academy of Healing Sleep ( AASM ) and the National Sleep Foundation released their recommendations, and both agree that you need to sleep for 7-8 hours (AASM mysteriously writes about "7 hours or more", and mentions that , which lasts more than 9 hours, may also have its drawbacks). And excessive sleep is really unfavorable: in one study it was shown that abuse of sleep increases the risk of dementia , some studies have shown that too much sleep (and lack of sleep) can lead to deterioration of cognitive functions and impaired memory , while others found that inflammatory processes are stronger manifest in people sleeping for more than 8 hours.


Dependence of risks on the duration of sleep: upper left - total mortality, right - cardiovascular diseases, lower left - coronary insufficiency, right - stroke. Lower risk values ​​are around 7-8 hours of sleep.

By this criterion, it turns out that the Western community is constantly playing around with sleep deprivation — some polls say that 35% of adults in the US and three-quarters of Britons sleep less than 7 hours. This is rather regrettable because, as we remember, lack of sleep can severely undermine your health. In addition, it is estimated that only in the United States alone, sleep deprivation costs the economy billions of dollars through loss of efficiency and quality of work. Therefore, it is important to plan your day so that you can sleep at least 7 hours almost every day. I know, I know, this is very annoying, considering that the average adult needs about 30 hours a day just to do all the housework, all the work, participate in social life, relax, and the fifth and tenth ... But in the long run It is very important not to deprive our body of precious time for sleep and recovery.

You may ask: is it possible to catch up with the lost time of sleep? Maybe I just sleep for 12 hours at the weekend: will it help my body to forget all those awful sleepless nights during the week? Unfortunately, this does not work. In one study , it was found that attempts to catch up on lost time on a weekend after a week of sleep deprivation only increase drowsiness and inflammatory processes. Impaired cognitive function (concentration and attention), which occurs due to sleep deprivation, does not go away after a long sleep at the weekend. That is, sleep in bed or sleep after a lack of sleep will not work - it does not help to return concentration and attention. It is necessary to sleep an appropriate amount of time every night.


In 2017, 12% of Britons sleep less than five hours a day. This is 7% more than in 2013.

How to sleep better?

As we learned from the last part, the blue light is not our friend. It means that the bedtime procedure should include the refusal of all devices for an hour or two before bed, and you do not need to use these devices in bed in order not to associate rest with work or with the flow of information (do not need to type text on a laptop while lying bed). At least you need to download the f.lux application, which reduces the screen brightness before bedtime and eliminates the blue color from the picture.

Another method of going to bed is relaxation. It has been proven that meditation with awareness [mindfulness] (meaning simply concentrating on one's breathing, body sensations, perception of the environment, and tracking thoughts instead of dragging them) helps people who suffer from insomnia and improves the quality of sleep (not to mention the rest of the benefits for health) ( 1 , 2 , 3 , 4 , 5 , 6 ). Just concentrating on your breathing for 10 minutes instead of looking at funny pictures can do a lot. Your mind relaxes and stops frantically thinking about the to-do list for tomorrow or remembering the disgraceful situations of a bygone day. Personally, I use the app 10% Happier App [10% happier] and I can not rejoice at it.

Another intuitive thing that helps you fall asleep is to avoid caffeine before bedtime. And I mean, after lunch. One study found that caffeine consumption, even 6 hours before bedtime, reduces sleep by one hour. Therefore, to make sure that caffeine does not interfere with your sleep, you must drink it no later than 7-8 hours before sleep. Another study found that caffeine is able to delay the course of your internal hours, and reduce the time to sleep due to the fact that you are awake longer. This is another reminder that you should not drink coffee in the afternoon. As a result, the method of using your daily drug that does not harm your sleep is: gradually reduce the amount of caffeine during the day, and drink the last cup no later than 14.



Finally, the cool atmosphere in the bedroom is important (here you can insert an awkward joke about sex). Scientists advise that the optimum temperature for sleep should be between 18 ° and 21 ° C ( 1 , 2 , 3 , 4 ). A few hours before bedtime, our body temperature begins to decrease — and a slight decrease in the temperature in the bedroom helps to induce sleep. In one study , it was found that an increase in skin temperature of just 0.4 ° C (which allows the body to radiate more heat) leads to deeper sleep and reduces the number of awakenings. Some studies have shown that impaired thermoregulation (and too high a body temperature during sleep) is associated with certain types of insomnia.

Now you have a pretty good idea of ​​how to take as much as possible from sleep, what are the undesirable effects of a three-hour sleep after a sleepless night, and that some dude killed people during a sleepwalking attack. Good night and wait for a new news block on neuroscience soon!