Modern theory of insomnia
Somnologist Mikhail Poluektov – about the features of the structure of the brain and the causes of insomnia
Insomnia is a condition when a person has the ability to sleep normally, but cannot. He cannot fall asleep for a long time, tosses from side to side, all sorts of thoughts come that prevent him from falling asleep, the so–called rumination - obsessive thoughts. And then he falls asleep, may wake up again in the middle of the night and again not be able to sleep, again spends a long time in bed awake. He may wake up early in the morning, when he does not need to get up yet, and also lie awake. That is, the manifestations of insomnia can be very different, but they all relate to the difficulties of either initiating the beginning of sleep or maintaining sleep.
And even if a person seems to have slept for a sufficient amount of time, but in the morning he gets up restless, sleepless, then this is also a manifestation of insomnia, these are complaints about non-restorative sleep. In scientific terms, insomnia is called insomnia (in - ‘inside’; somnus– ‘sleep’), that is, these are the problems that arise inside sleep. And now we have really learned a lot about this condition. How did you imagine before, why does insomnia syndrome develop? The most common idea was that insomnia is just such a whim that a person behaves incorrectly, his behavior is disturbed, that before going to bed he jumps, jumps, gets excited, worries and can't sleep because of it. Indeed, it happens, more often children have such problems, teenagers who flirt on the computer.
But why does an adult, serious, responsible about his health, lie down and can't sleep? Before going to bed, he does nothing so reprehensible. The household theory of insomnia did not answer this question. Another theory of insomnia represented the other extreme, which considered sleep disturbance as a manifestation of a mental illness, that if a person does not sleep, then it means that something is wrong with his psyche: he either has depression or anxiety disorders, and all this will manifest itself in the near future. And therefore, most often, indeed, doctors tried to direct people with insomnia who came to them to complain, to be checked by a psychiatrist just in case. This is also why complaints about insomnia have stopped, and people prefer not to talk about having sleep disorders, because they believe that then it will be regarded either as improper behavior, irresponsible attitude to their sleep, or as a sign of some kind of mental illness.
It turns out, on the one hand, that if you conduct a survey of people in the general population, that is, ask everyone you meet if he has sleep disorders or not, then at least one in ten will say that he has sleep disorders that prevent him from living, he has this insomnia. On the other hand, people with insomnia do not come to doctors and do not complain, do not know who to come to, do not know which doctor can help. And gradually this problem began to rise at a higher, special level. Neurologists, psychiatrists began to gather, discuss whose disease insomnia is, who should treat it. Now there is some mutual understanding that insomnia is still a problem of the central nervous system, a problem that occurs in the brain, which is associated with behavioral disorders, a problem that often coexists with mental illness, but mental illness does not always cause insomnia.
What are the modern ideas, where does insomnia, insomnia come from? In order to understand this, we should return to the theory of sleep. Why at some point in time we can fall asleep, at some point in time we can't fall asleep? It depends on the constant interaction of the two main brain systems. One system is activating, it maintains a sufficient level of wakefulness all the time, there are several centers in the brain that constantly slow down other neurons of the brain, make them work at full strength if it's a day, if you need to constantly solve some tasks during the day. That is, such tonic activation of the central nervous system by activating centers. On the other hand, there are sleep centers that are also not averse to taking control of the brain, and all the time they are ready to take control of the brain, but they are not allowed to do this by the centers of wakefulness, because the centers of wakefulness in the daytime are stronger, because they are also helped by the internal clock that receives information from the retina of the eye. There is a nerve branch that goes directly to the internal clock in the suprachiasmatic nuclei of the hypothalamus and every millisecond conveys information about whether it is day or night, whether there is enough lighting or not.
The internal clock helps the waking systems in the daytime to maintain a sufficient level of activation, at least in humans. There are also nocturnal animals, and they have the opposite. The struggle takes place constantly between the activating and inhibiting centers of the nervous system. When a person goes to bed and if it gets darker outside at this time, the activity of the internal clock decreases, their help to the brain activation centers also decreases, and the sleep centers at some point seize control of the brain. This is ideal.
There are quite a few situations when activating centers are too active. The modern idea of the possibility of developing insomnia suggests that there is a group of people who have an innate feature called hyperarousal – hyperactivation of the brain. In them, this hyperactivity can be traced even during the daytime: not when they can't sleep in the evening, complain of insomnia, and even during the day their brain works too actively. This can be traced, for example, if you do an electroencephalogram in a group of such people, they will have more so-called fast rhythms, beta rhythms on an electroencephalogram than people who do not have insomnia. You can make them a special method of research, which is called transcranial magnetic stimulation. A powerful magnetic field is used there, the motor areas of the brain are stimulated by this magnetic field, and they look at how well these zones cause a motor response – most often by the movement of the thumb.
It turned out that people with insomnia have constant hyperactivation of virtually all areas of the brain, including those that seem to have nothing to do with sleep, which are related to the thumb. This proves the presence of hyperactivation. And according to other indicators, it is actually also proven that with insomnia, everything is too active for these people, that they initially live with increased activation, which helps them during the day, in principle, because they respond better to changes in external circumstances, they can concentrate faster, make the necessary response to some reaction faster, but in the evening, when they go to bed, it starts to bother them, because the activating centers of the brain prevent the sleep centers from taking control in time and returning the body to sleep.
And when a person lies down, tries to fall asleep, he does not succeed because of this hyperactivity. Then secondary mechanisms of insomnia maintenance are already included, and these are various psychological factors. For example, a person goes to bed and gives himself an urgent task to fall asleep: I need to fall asleep urgently so that tomorrow morning I can be cheerful, sleepy. It seems to be nothing special, but when he gives himself such a task, he begins to subconsciously track whether he fell asleep or not. After some time, he can not fall asleep, he begins to worry about the fact that he did not fall asleep. Because of this, his brain activation, which is already high, increases even more, and he can feel sleepiness even less, even to a lesser extent, and the probability of falling asleep decreases even more. A person gets excited, begins to ask himself: "Why don't I fall asleep? I urgently need to fall asleep." And the more he tries to put himself to sleep, the less likely he is to fall asleep.
Academician Vane, one of the initiators of sleep research in Russia, was very fond of the metaphor that sleep is a bird that sits on an open palm, and the faster you try to grab it, the faster it flies away, because the more you strain to grab a dream, the more activating systems are activated and prevent the development of this the inhibition necessary for sleep and entering into sleep. That is, a person drives himself into this state. And gradually this is fixed, and at some point even the habit of not falling asleep or the fear of bed is formed. When a person goes to bed in the evening, he does not think whether he will fall asleep or not, but when he enters the bedroom, gets into a familiar environment, then Pavlov's conditioned reflex works for him: pillow – lack of sleep, like a dog's call (a call means food – the dog has saliva). And here it turns out that he saw his pillow and his body immediately remembered the failures of previous nights when he could not sleep. Accordingly, he automatically develops hyperactivity, which prevents falling asleep. This is one of the most common patterns that explains why insomnia develops.
Now it is believed that there are people with constant hyperactivity, and there are people without hyperactivity, their insomnia develops according to other laws, and it is most often associated with the peculiarities of perception of the time they spend at night in a state of wakefulness. Interestingly, any person at night, when he sleeps, actually does not sleep completely, sometimes he wakes up, and this is normal. And, as it turned out, we wake up not once a night, not twice, but 10-15 times a night, because a person, in order not to lie on his sides, needs to toss and turn in bed from time to time. This is a completely normal phenomenon. And when a person turns over in bed, a short-term awakening for 10-15 minutes is recorded on his electroencephalogram. He wakes up at this time, he can open his eyes at the same time, but he does not remember it the next morning. But there are people who remember it all too well.
It is shown that there is a group of people who complain of sleep disorders, despite the fact that they actually have quite a lot of sleep. For example, now the recommended duration of sleep by the international community is at least seven hours to maintain a sufficient level of vigor, for a sufficient level of health. But if we conduct sleep studies of such a person who complains about sleep, then we will also see that he has 6-6.5 hours of sleep, but he can tell in the morning that he did not sleep at all. Why? His perception of his own dream has been changed. He perfectly remembers those periods of sleep, or rather, those periods of wakefulness when he did not sleep, when he suffered, when he looked at the clock, when he listened to what was happening at the other end of the house, how the neighbors were moving the closet once again in the middle of the night, but he absolutely does not remember when he fell asleep. This is a feature of the perception of time at night.
There is a group of people who develop complaints of insomnia precisely because of this, because they do not know how to count time correctly. They have those periods when they woke up at night, merge in their perception. They wake up in the morning, they are sure that they did not sleep, although in fact this is not true. Maybe they slept a little worse than other people, but they slept enough. This is the so-called phenomenon of pseudoinsomnia. There is a group of people who are unhappy with sleep – unhappy because they do not know how to count time. This is the next cause of insomnia.
Even now, congenital features of the structure of the brain are considered as one of the causes of insomnia. When more complex neurophysiological studies began to be conducted (there is such a study – functional magnetic resonance imaging, which allows you to determine not only the structure of the brain, but also its function, how well certain parts of the brain work, for example, with insomnia and in healthy people (always compared with the control group; the control group - these are healthy people)), it turned out that certain areas of the brain that are involved in the emotional assessment of the situation work worse for people with insomnia. These areas of the brain belong to the oldest zones, and they are called the zones of the orbitofrontal cortex, that is, this is the part of the hemispheres of the large brain that is attached to the eye sockets, hanging over the eye sockets.
It turned out that this is a very important part of the cerebral cortex, since it is just responsible for inhibiting excessively heated hazard assessment centers, let's say. There is a so-called amygdala in the temporal divisions, which we need, among other things, in order to evaluate each stimulus, each impact on the subject of whether it is dangerous for us or not. This amygdala responds in order to instantly assess the sound, the appearance of a new subject, or to assess the danger to us of a certain thought that flashed through our head. And it turned out that with insomnia, this amygdala works too hard, it is always ready to react to a danger that does not even exist, it perceives everything as a threat. Why? Because in patients with insomnia, this part of the brain, the orbitofrontal cortex, is underdeveloped.
One of the most important functions of the orbitofrontal cortex is the inhibition of this untwisted amygdala, so that it does not perceive everything as a danger to the body, the orbitofrontal cortex allows you to slow down in time. And in some people, the orbitofrontal cortex does not have time to slow down the amygdala to the proper extent, the amygdala constantly, both day and night, gives alarm signals. In the daytime, in principle, it does not interfere, because it may even help to be always alert, always react to changes in the situation, the traffic situation, for example. And at night it is absolutely not necessary, at night it is not necessary to react, at night the brain has to deal with its internal affairs, change the ratio of neural weights, it does not need to react to anything. And this amygdala prevents him from reacting, and the symptom complex of insomnia develops again, when a person cannot fall asleep, is on guard all the time, reacts to an insignificant sound all the time.
Indeed, people with such disorders often say that, as soon as night falls, for some reason the neighbors begin to drill, knock, move something there, not because in other houses the neighbors do not knock, do not drill, do not move, but because people with this type of reaction excessive attention to all external stimuli. They even hear what healthy people don't even hear, what's going on at the other end of the house. This is the main theory of insomnia development now – the theory that insomnia is a heterogeneous group of conditions, and some of these conditions are caused by innate features of the nervous system organization. Either these are functional features when hyperactivation is constant, or this is an underdevelopment of the orbitofrontal cortex, or this is psychology, or this is an incorrect assessment of the situation, an incorrect assessment of time.
There are several other phenotypes of insomnia that scientists have not yet reached, a point of view has not been formed. For example, the development of one type of insomnia is associated with insufficient sleep with rem sleep dreams. It turned out that if a person sleeps incorrectly in a fast sleep, then his protection from the stress factor is also violated, the consequence of this is the development of a chronic sleep disorder, while this fast sleep is functioning imperfectly. But this is the topic of the next conversation about the REM sleep function.
About the author: Mikhail Poluektov – Candidate of Medical Sciences, associate professor of the First Sechenov Moscow State Medical University.
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17.01.2017