The main findings from years of numerous and varied sleep studies are as follows. Sleep is not a break in brain activity, it is simply a different state. During sleep, the brain goes through several different phases, or stages, of activity that repeat in approximately one-and-a-half-hour cycles. Sleep consists of two qualities various conditions called slow and fast sleep. They differ in total electrical activity brain (EEG), eye motor activity (EOG), muscle tone and numerous autonomic indicators (heart rate and respiration, electrical activity of the skin, etc.; see Chapter 2).

slow sleep is divided into several stages, identified on the basis of EEG changes (Fig. 13.2) and differing in depth. In the first stage, the main bioelectrical rhythm of wakefulness, the alpha rhythm, disappears. It is replaced by low-amplitude oscillations of various frequencies. This is the stage of drowsiness, falling asleep. In this case, a person may experience dream-like hallucinations. The second stage (shallow sleep) is characterized by the regular appearance of a spindle-shaped rhythm of 14-18 vibrations per second (“sleepy” spindles). With the appearance of the first spindles, consciousness switches off; During pauses between spindles, a person can easily be awakened. The third and fourth stages are combined under the name delta sleep, because during these stages high-amplitude slow waves - delta waves - appear on the EEG. In the third stage, they occupy from 30% to 50% of the entire EEG. In the fourth stage, delta waves occupy more than 50% of the entire EEG. This is the most deep stage sleep here highest threshold awakenings, the most powerful disconnection from the outside world. When waking up at this stage, a person has difficulty finding his bearings and compresses time to the greatest extent (underestimates the duration of the previous sleep). Delta sleep predominates in the first half of the night. At the same time, muscle tone decreases, breathing and pulse become regular and slow, body temperature decreases (by an average of 0.5°), eye movements are absent, and a spontaneous galvanic skin reaction can be recorded.

REM sleep- the most last stage in the sleep cycle. It is characterized by fast, low-amplitude EEG rhythms, making it similar to the waking EEG. Cerebral blood flow increases, and against the background of deep muscle relaxation, powerful activation of autonomics is observed. In addition to the tonic components of the REM sleep stage, phasic components are identified - rapid movements of the eyeballs with closed eyelids (REM, or REM-rapid eye movements), muscle twitching in separate groups muscles, sudden changes heart rate (from tachycardia to bradycardia) and breathing (a series of frequent inhalations and exhalations, then a pause), episodic rises and falls blood pressure, erection of the penis in men and clitoris in women. The awakening threshold ranges from high to low. It is at this stage that most of memorable dreams. Synonyms for REM sleep are paradoxical (the activated nature of the EEG with complete muscle atonia), REM, or REM sleep, rhombencephalic (due to the localization of regulatory mechanisms).

The entire night's sleep consists of 4-5 cycles, each of which begins with the first stages of slow sleep and ends with REM sleep. Each cycle lasts about 90-100 minutes. In the first two cycles, delta sleep predominates; episodes of REM sleep are relatively short. In the last cycles, REM sleep predominates, and delta sleep is sharply reduced and may be absent (Fig. 13.2). Unlike many animals, humans do not wake up after each sleep cycle. The structure of sleep in healthy people is more or less similar - stage 1 takes up 5-10% of sleep, stage 2 - 40-50%, delta sleep - 20-25%, REM sleep - 17-25%.

Rice. 13.2. Sleep phases:

EEG during different stages of sleep (top). Changes in sleep depth throughout the night, lengthening periods of REM sleep (bottom) [after Bloom et al., 1988]

Thus, every night we dream 4-5 times, and “looking at” dreams takes a total of 1 to 2 hours. People who claim that they dream very rarely simply do not wake up in the dreaming phase. The intensity of the dreams themselves, the degree of their unusualness and emotional richness may vary, but the fact of their regular occurrence during sleep is beyond doubt.

The idea, widespread in the past, that sleep is necessary for the “rest” of brain neurons and is characterized by a decrease in their activity, has not been confirmed by studies of non-ironal activity. During sleep, in general, there is no decrease in the average frequency of neuronal activity compared to the state of quiet wakefulness. In REM sleep, spontaneous neuronal activity can be higher than in intense wakefulness. In slow-wave sleep and rapid eye movement sleep, the activity of different neurons is organized differently (see Chapter 8).

In addition to electrophysiological ones, certain stages of sleep are characterized by certain hormonal changes. Thus, during delta sleep, the secretion of growth hormone, which stimulates tissue metabolism, is increased. During REM sleep, the secretion of hormones from the adrenal cortex is increased, which increases during wakefulness under stress. The intensity of energy metabolism in the brain tissue during slow-wave sleep is almost the same as in a state of quiet wakefulness, and during REM sleep it is much higher.

Thus, it can be argued that the brain is active during sleep, although this activity is qualitatively different than during wakefulness, and in different stages sleep has its own specifics.

Sleep in onto- and phytogenesis

During ontogenesis, the sleep-wake ratio changes. Thus, in newborns, the state of wakefulness constitutes only a small part of the day, and a significant part of sleep is occupied by REM sleep. As you grow older, the total amount of sleep decreases, the ratio of phases within the sleep cycle changes - REM sleep decreases and relatively increases slow sleep By the age of 14, the sleep cycle reaches 90 minutes. In an adult, as already mentioned, REM sleep takes up about 1/4 of the total sleep time. IN old age there is a decrease total number sleep, while both slow and fast sleep are reduced. After 75 years, neurotic insomnia is often observed - slow-wave sleep is reduced, sleep becomes intermittent, and sleep cycles are disrupted.

Alternating periods of activity and rest occur in all living beings; Perhaps periods of rest are analogues of slow-wave sleep. In one form or another, sleep is observed in all vertebrates. But sleep, consisting of several cycles, within which the stages of slow and fast sleep unfold, is characteristic only of warm-blooded animals. In its organization, the sleep of mammals and birds does not differ from human sleep, although slow-wave sleep in animals is less differentiated, the percentage of slow and fast sleep varies in different animals, and sleep cycles are usually shorter. “A short, intense life goes hand in hand with long sleep and a short sleep cycle" [Borbeli, 1989, p. 97]. In a rat, the sleep cycle lasts 12 minutes, in a dog - 30 minutes, in an elephant - about 2 hours. Peculiarities of sleep organization are related to the ecology of animals.

In birds, periods of REM sleep are very short - at the same time, due to complete muscle atonia, the head drops and the wings fall. If a bird sits on a branch, then as the tone of the leg muscles decreases, the toes contract, and the bird can sleep without falling from the branch.

The sleep of ungulates is also associated with their way of life - gregariousness, fear of predators - and has the character of “ragged” sleep (after each sleep cycle the animal raises its head and looks around, so at each this moment some individuals are necessarily awake). The nature of plant foods requires prolonged chewing, and the superficial stages of sleep occur in ruminants during chewing.

Burrowing mammals have a well-defined cyclicity, they sleep a lot, and REM sleep takes up to 1/3 of the total sleep time. Many of them are characterized by seasonal hibernation. It is characterized by loss of the ability to thermoregulate, a sharp decrease in the amount breathing movements and heart rate, a drop in the overall level of metabolism. Some large mammals (bears, raccoons, and partly badgers) experience seasonal sleep, or facultative hibernation. In this case, body temperature, the number of respiratory movements and the general level of metabolic phenomena decrease slightly. If external conditions change, such sleep can easily be interrupted.

The sleep patterns of marine mammals are also related to their ecology. For each act of breathing, both during sleep and during wakefulness, they must float to the surface to point their nostrils into the air. Depending on the lifestyle arose different shapes adaptation. Thus, during electrophysiological recording of sleep in dolphins, L. Mukhametov discovered the phenomenon of “unihemispheric” sleep - delta waves arose only in one hemisphere (alternately in the right or left). At the same time, in the other hemisphere the EEG pattern corresponded to the superficial stages of slow-wave sleep or wakefulness. EEG corresponding to the superficial stages of slow-wave sleep could be observed in both hemispheres simultaneously; No signs of REM sleep could be detected. The same “one-hemisphere” slow-wave sleep appears in the so-called eared seals (seals and sea lions) when they are in the pool and cannot go to land. When they sleep on land, in both hemispheres they have an EEG characteristic of normal slow-wave sleep; Many episodes of REM sleep are recorded.

In seals and sea lions, which spend only part of their lives in water, their entire sleep cycle develops during the respiratory pause. They “breathe out” well by doing several deep breaths, and dive. In 15-20 minutes, the stages of slow sleep and rapid sleep change, and they emerge for the next “breathing”.

Thus, sleep is vital for highly organized animals. At the same time, the sleep characteristics of various animals reflect its adaptive nature to living conditions and environmental factors.

Need for sleep

Many people would like to sleep less, since sleep, in their opinion, is time lost from life. Others, on the contrary, would like to sleep more because they do not feel well enough.

“We are chronically sleep deprived”; "Should we sleep more?" are the titles of two articles recently published in the journal Sleep, reflecting polarized attitudes to the issue of sleep duration. One of the common maxims in sleep medicine is that our modern society severely lacks sleep, and this affects the state of the person and the environment, being to a large extent the cause of accidents and disasters. This point of view is supported by numerous studies showing negative effects lack of sleep on the mood of the subjects and their performance of psychomotor tasks. Using various psychological tests It has been shown that if the duration of night sleep is reduced by 1.3-1.5 hours, this affects the state of alertness during the day. Recent studies on the required duration of sleep have shown that the average sleep requirement among young people is 8.5 hours per night. A night's sleep duration of 7.2-7.4 hours is insufficient, and sleeping less than 6.5 hours for a long time can undermine health. Another point of view is that most people do not have chronic sleep deprivation, but they may sleep more, just as we eat and drink more. physiological needs. This is based on significant individual variations in sleep needs, as well as the fact that after long periods of sleep, improvements in daytime alertness are minimal, and fatigue is successfully eliminated by short breaks from work.

The effect of “accumulation of sleep deprivation” completely disappears after the first 10-hour period of “restorative” sleep. Therefore, chronic lack of sleep on weekdays and oversleeping on weekend mornings are interrelated phenomena. Nevertheless, the statement of the Committee “Disasters, Sleep and Public Policy” created in the USA emphasizes that even a slight chronic lack of sleep for 1-2 hours is fraught with serious disruptions in work if it constantly requires high level concentration and attention [Kovalzon, 1989].

Sleep deprivation

Experiments with deprivation (artificial sleep deprivation) suggest that the body has a special need for delta sleep and REM sleep. After prolonged sleep deprivation, the main effect is an increase in delta sleep. Thus, after 200 hours of continuous wakefulness, the percentage of delta sleep in the first 9 hours of recording recovery sleep increased 2 times compared to the norm, and the duration of REM sleep increased by 57%. Deprivation of less than 100 hours did not cause an increase in the duration of REM sleep on the first recovery night. As the total amount of sleep decreases, the duration of delta sleep does not change or even increases, and the duration of REM sleep decreases.

In order to study the role of individual sleep phases, methods have been developed to selectively prevent their occurrence. To suppress delta sleep, the “stimulation” method is used - when delta waves appear on the EEG, sound signals of such intensity are given to ensure a transition to more superficial stages of sleep. At the same time, the subjects develop a feeling of weakness, fatigue, memory deteriorates and attention decreases. Research by V. Rotenberg shows that the feeling of being overwhelmed and increased fatigue, especially increasing in the afternoon, in patients with neurosis is due to a chronic deficit of delta sleep [Rotenberg, 1984].

To exclude REM sleep, a person or animal is woken up at the first signs of this sleep phase - the appearance of rapid eye movements and a drop in muscle tone. REM sleep deprivation in animals is usually carried out according to the method proposed by M. Jouvet. The animal (most often rats are used in these experiments) is placed on a small area surrounded by water and adapts to sleep on it. But at the very beginning of each episode of REM sleep, as soon as the animal’s muscle tone drops, it collapses into cold water and immediately wakes up. As a result, the animal can be deprived of the REM sleep phase for many days without significantly disrupting slow-wave sleep. After such deprivation, the animals showed increased excitability, aggressiveness, and motor restlessness, i.e., symptoms of severe stress. In order to separate the effect of REM sleep deprivation from the effect of stress (a hopeless situation of being in a limited area with inevitable falls into the water), V. Kovalzon developed a method of REM sleep deprivation without stress - irritation of the activating reticular formation of the brain stem with weak impulses electric current, awakening the animal upon the onset of REM sleep.

At the same time, the rats were in a spacious experimental cage, during periods of wakefulness they drank, ate, played normally, and they had no symptoms of stress - their fur was shiny, their weight did not decrease. The duration of REM sleep was reduced by 3 times while slow-wave sleep was maintained. Despite the absence of any behavioral symptoms of REM sleep deprivation, the number of attempts to transition to REM sleep increased day by day, and the awakening threshold increased.

With selective deprivation of REM sleep, a person's need for it increases, although no mental disorders can be detected. However, in the first experiments with REM sleep deprivation in humans (conducted by V. Dement on three subjects continuously for several days), significant changes in the psyche were discovered - increased irritability, absent-mindedness, the appearance of hallucinations and delusional ideas. It later turned out that these subjects were not completely healthy. When studies were carried out on healthy subjects, it turned out that REM sleep deprivation “not only does not lead to mental disorders, but also has no effect on health at all.” mental state- does not change mood, does not impair task performance, does not affect memory or performance. The more comfortable the conditions were during the period of deprivation, the more carefully the experimenters ensured that all the needs of the subjects were met, the more exciting and varied the pastime was during the study period, the less the effect of deprivation affected” [Rotenberg, Arshavsky, 1984, p. 86].

When the results of REM sleep deprivation began to be analyzed individually, due to personal characteristics subjects, certain differences were found. Thus, R. Cartwright and colleagues found that REM sleep deprivation causes various changes in the psyche and behavior depending on the initial mental status. Anxious subjects responded to deprivation with a significant increase in anxiety; they tried to immediately compensate for the interrupted REM sleep. Subjects of the other type did not have significant behavioral disturbances, and a compensatory increase in REM sleep was detected on the recovery night. Finally, the third type did not show behavioral disturbances, did not attempt to immediately compensate for REM sleep or increase REM sleep on the recovery night, but when awakening before the first manifestations of REM sleep, they gave detailed reports of dreams. Obviously, their dreams took place in slow-wave sleep, and this replaced their need for REM sleep.

The importance of REM sleep for health was shown by E. Hartmann, identifying two extreme groups among healthy subjects - “long sleepers” (who wellness you need at least 9 hours of sleep), and “short sleepers” (6 hours of sleep is enough). In terms of sleep structure, these people differed mainly in the duration of REM sleep - for long sleepers it took almost twice as long. When analyzing their mental characteristics, it turned out that, compared to short sleepers, they were emotionally less stable - they took all problems to heart, were characterized by restlessness, anxiety and mood swings. One got the impression that in their dreams they were escaping the difficulties of life, i.e. “they went to bed as neurotics and woke up as healthy people.” Hartmann suggested that this recovery of mental health from evening to morning is determined by the high presence of REM sleep in their nightly sleep. By interviewing healthy people whose sleep duration was not constant throughout their lives, Hartmann found that a reduction in sleep usually occurs during periods when a person feels good, works with interest and is free from anxiety. The need for sleep increases when insoluble problems arise, mood and performance decrease.

Dreams

Dreams have long amazed and worried people. In ancient times, dreams were seen as “the gateway to another world”; It was believed that through dreams contact with other worlds could occur. For a long time people have tried to induce dreams using certain ritual formulations; similar formulations are found even in texts dating back to around the 3rd millennium BC. e. Already the first civilizations of the Middle East, Egypt, India and China left some records about dreams and methods of inducing them. For example, a special prayer of the ancient Assyrians is known for inducing good dreams and getting rid of unpleasant ones [Garfield, 1994]. The ancient world was full of beliefs in dreams, and in Ancient Greece dreams played a leading role even in the development of laws. "Great importance was acquired" prophetic dreams”, predicting the development of future events. However, Aristotle already taught that dreams are not the “language of the gods” or the “journey of the soul,” but phenomena arising from the very essence of the human spirit, which are the result of the special activity of the human brain, especially his senses. In his treatise “On Dreams and Their Interpretation,” Aristotle tried to understand the very nature of dreams (see [Anokhin, 1945]). The attention of ancient thinkers was focused mainly on questions about the origin of dreams and the ability to predict events. These same questions concern people today.

The results of numerous studies suggest that one of the main functions of dreams is emotional stabilization [Rotenberg, 1984]. This is well stated by Roberts [cit. from: Borbeli, p. 53]: “A person deprived of the ability to dream will, after a while, fall into madness, for a mass of unformed, fragmentary thoughts and superficial impressions will accumulate in his brain and suppress those thoughts that should be completely preserved in memory.” For the first time, systematic research into the role of dreams was undertaken by the founder of psychoanalysis, Z. Freud. Considering dreams as special and very important language brain, he noted that dreams are the product of our own mental activity and at the same time the completed dream strikes us as something external to us. In his work “The Interpretation of Dreams” 3. Freud showed that dreams contain not only a clear, obvious meaning that can be stated in a retelling, but also a hidden, implicit one that cannot be immediately realized or understood. To understand this second meaning, it is necessary Additional Information about the identity of the one who saw this dream. Based on this, using the method of “free associations,” the psychoanalyst leads the patient to the awareness of repressed desires hidden in the dream, which relieves emotional tension.

Modern psychotherapists and psychoanalysts came to the conclusion that dreams can be controlled. An example is the attitude towards dreams in the Sinoan tribe in Malaysia, where each member of the tribe knows how to destroy nightmares [Garfield, 1994]. The Shinoi teach their children to perceive dreams as an important part of personality formation and have managed to organize their lives in such a way that they do not have mental illness.

A powerful impetus for the experimental study of dreams was the discovery of REM sleep and its connection with dreams. It became possible to receive reports on dreams immediately after their completion. It was discovered, to the surprise of those who thought that they did not dream or dreamed very rarely, that every person dreams several times a night. The question of the duration of dreams was also resolved experimentally. It turned out that the subjective duration of dreams corresponds to the objective duration of the REM sleep period. A subject awakened at the beginning of a period of REM sleep reports a short dream, and one awakened at the end reports a long one. After very long episodes of REM sleep (30-50 minutes), subjects reported unusually long dreams. Interestingly, reports of the content of these dreams were no longer than when subjects were awakened as early as 15 minutes after the onset of REM sleep. Apparently, dreams begin to be forgotten despite the continuation of a long episode of REM sleep. Numerous experiments indicate that the content of dreams correlates with the characteristics of the phasic components of REM sleep. It has been shown that the degree of emotional coloring of dreams is associated with the frequency of heart contractions and respiration, the degree of vasoconstriction and the severity of electrical activity of the skin in last minutes REM sleep before waking up.

Apparently, animals also have dreams during REM sleep - this is evidenced by M. Jouvet’s experiments with the destruction of the nuclei of the blue spot (locus coeruleus) in cats, which ensures the suppression of muscle tone in the REM sleep phase. A sleeping animal with a destroyed blue spot rose to its paws with the onset of REM sleep. eyes closed, sniffed, scratched the floor of the cell, made sudden jumps, as if chasing an enemy or escaping from danger. These data, as well as the results of numerous laboratory studies of sleep in humans, allow us to consider REM sleep physiological basis dreams.

However, it is a simplification to consider REM sleep as the only phase of sleep with dreams, since subjects also report dreaming when awakening from slow-wave sleep. But reports of dreams in REM sleep are more vivid, more complex, fantastical, and more emotionally charged compared to dreams in slow-wave sleep, where rational and realistic elements, similar to waking thinking, predominate. The main difference lies in their duration - dreams in REM sleep are longer. Apparently, this explains the fact that when waking up from REM sleep, dreams are better remembered.

A phenomenon, in a certain sense opposite to dreams, is somnambulism (sleepwalking, or sleepwalking). Laboratory research showed that somnambulism occurs against the background of delta sleep; The severity and duration of the attack varies significantly. In the mildest case, a person can sit up in bed, mutter something and fall asleep again - in such cases, the EEG shows a picture of deep delta sleep. In other cases, the somnambulist gets up, walks, can get dressed and leave the house (in this case, the eyes are usually open, the face is mask-like); a somnambulist can give monosyllabic answers to simple questions - in such cases, signs of drowsiness or even wakefulness appear on the EEG. In the morning, the somnambulist does not remember anything about what happened to him at night. In contrast to dreams, with their world saturated with bright colors and events with complete muscle atony, somnambulism is characterized by twilight state consciousness (which is not recorded in memory at all) while maintaining the ability to move as if awake. The existence of two extreme phenomena (dreams and somnambulism) indicates that sleep is a whole set of different states, among which there is a deep immersion in the inner world and a demonstration of external activity.

Is physiological process, in which a person (as well as mammals, fish, birds and some insects) is in a state radically different from the waking state. This condition characterized by altered consciousness, decreased level brain activity and reactions to external stimuli. Natural sleep is significantly different from such similar states as coma, suspended animation, fainting, sleep under the influence of hypnosis and lethargic sleep. Along with sleep in the usual sense of the word (i.e. sleep at night), certain cultures allow the existence of the so-called daytime rest or siesta. Short-term nap is part of the traditions of many peoples. According to the results of ongoing research, regular afternoon naps can significantly reduce (by almost 40%) the risk of a heart attack. In a word, sleep is the most important element of human life and, at the suggestion of researchers, since 2008, every 3rd Friday of the first month of spring is celebrated as Sleep Day.

Basic functions of sleep

Thanks to sleep, the body receives the necessary rest. During sleep, the brain processes the information accumulated during the day. The so-called slow sleep allows you to better assimilate the studied material and consolidate it in memory. REM sleep provides the ability to simulate upcoming events at the subconscious level. Important function sleep is also the restoration of the human immune system by activating the activity of T-lymphocytes that resist viral infections and fight colds.

Physiology of the sleep process

Healthy sleep can last from 4 to 8 hours. However, these indicators are quite subjective, since the duration of sleep depends on physical fatigue person. A significant amount of work done during the day may require a longer night's rest. Normal sleep is cyclical and required to the human body at least once a day. Sleep cycles are called circadian rhythms. Every 24 hours, circadian rhythms are redefined. The most important factor during sleep, illumination is considered. The concentration of photodependent proteins in the body depends on its natural cycle. Usually, circadian cycle correlates with the length of daylight hours. Just before sleep sets in, a person feels drowsy and brain activity decreases, and a change in consciousness is also noted. In addition, a person who is in a sleepy state experiences a decrease in sensory sensitivity, a decrease in heart rate, yawning, and also a decrease in the secretory function of the lacrimal and salivary glands. Another physiological feature of sleep is a process called “vegetative storm”, i.e. when various forms of arrhythmias are observed, an increase or decrease in blood pressure, increased blood supply to the brain and secretion of the adrenal glands, erection of the clitoris and penis.

Structure of the sleep process

Any sleep is divided into several stages, which are repeated with a certain pattern throughout the night (naturally, provided that the daily schedule is absolutely normal). Each stage of sleep directly depends on the activity of one or another brain structure. The first stage of sleep is slow-wave sleep (Non-REM). The duration of Non-REM sleep is 5 to 10 minutes. This is followed by the second stage, lasting approximately 20 minutes. Over the next 30-45 minutes, another 3 and 4 stages of sleep are observed. Next, the person again falls into the second stage of slow-wave sleep, at the end of which rapid REM sleep occurs (episode 1). This is approximately 5 minutes. All of the above stages are the first sleep cycle, which lasts from 90 to 100 minutes. After this, the cycle repeats again, but at the same time the stages of slow-wave sleep are reduced, and REM sleep, on the contrary, increases. Typically, the last sleep cycle ends with an episode of REM sleep, lasting in some cases about 1 hour. A full sleep includes 5 complete cycles. The sequence in which one stage of the sleep cycle follows another, as well as the duration of each cycle, is usually presented in the form of a hypnogram. The sleep cycle is regulated by certain areas of the cerebral cortex, as well as the locus coeruleus, located in its trunk.

What is slow wave sleep?

NREM sleep (also called orthodox sleep) lasts 80 to 90 minutes and occurs immediately after a person falls asleep. The formation and development of slow sleep is ensured by the anterior parts of the hypothalamus, raphe nuclei, nonspecific nuclei of the thalamus and middle part bridge (the so-called Moruzzi brake center). At the first stage of slow-wave sleep, the alpha rhythm decreases, transforming into slow low-amplitude theta rhythms, equal in amplitude to the alpha rhythm or exceeding it. The person is in a state of drowsiness (half-asleep), and dream-like hallucinations are observed. Muscle activity decreases, heart rate and breathing decrease, metabolic processes slow down, and the eyeballs move slowly. At this stage of sleep, solutions to problems that seem unsolvable during wakefulness are intuitively formed. By at least, the illusion of their existence may arise. The first stage of slow-wave sleep may also include hypnogogic jerks.

In the second stage of Non-REM sleep (this is usually light and shallow sleep), a further reduction in muscle activity occurs, the heart rate slows down, body temperature drops, and the eyes become motionless. The second stage is approximately up to 55% of the total sleep time. The first episode of the second stage lasts approximately 20 minutes. The electroencephalogram shows at this moment the predominant theta rhythms and the emerging sigma rhythms (the so-called “sleep spindles”), which are essentially rapid alpha rhythms. At the moment of the appearance of sigma rhythms, consciousness turns off. However, during pauses between sigma rhythms, which occur at a frequency of 2 to 5 times per minute, a person can be easily awakened.

At the third stage of slow-wave sleep, the total number of delta rhythms is no more than 50%. At the fourth stage this figure exceeds 50%. The fourth stage is slow and deep sleep. Quite often stages III and IV are combined and called delta sleep. It is extremely difficult to wake a person during delta sleep. Dreams usually appear at this stage (up to 80%). A person may begin to talk, sleepwalking is possible, nightmares may occur and enuresis may develop. At the same time, a person usually does not remember any of the above. The third stage lasts from 5 to 8% of the total sleep time, and the fourth stage takes from 10 to 15% of the entire sleep period. The first four stages of slow-wave sleep in a normal person last from 75 to 80% of the total duration of this physiological process. According to the researchers, Non-REM sleep provides complete restoration of the energy expended during the day. In addition, the slow-wave sleep phase allows you to record conscious memories of a declarative nature in your memory.

What is REM sleep?

Rapid eye movement sleep is also called REM sleep, paradoxical sleep, or rapid wave sleep. In addition, the generally accepted name is the REM (rapid eye movement) stage. The REM stage lasts 10 to 15 minutes and follows non-REM sleep. REM sleep was discovered in 1953. The centers responsible for REM sleep are: the superior colliculus and the reticular formation of the midbrain, the locus coeruleus, as well as the nuclei (vestibular) medulla oblongata. If you look at the electroencephalogram at this moment, you can see quite active fluctuations in electrical activity, the values ​​of which are as close as possible to beta waves. During REM sleep, the electrical activity of the brain is almost identical to the waking state. However, at this stage the person is completely motionless, since his muscle tone is zero. At the same time, the eyeballs actively move under closed eyelids, moving quickly with a certain periodicity. If you wake up a person in the REM stage, there is a 90% chance that he will report an exciting and vivid dream.

As noted above, the electroencephalogram of REM sleep reflects the activation of brain activity and is more reminiscent of the EEG of the first stage of sleep. The first episode of the REM stage lasts from 5 to 10 minutes and occurs 70-90 minutes after the person falls asleep. Throughout the entire sleep period, the duration of subsequent episodes of REM sleep becomes increasingly longer. The final episode of REM sleep can last up to 1 hour. The duration of REM sleep in a healthy adult is approximately 20-25% of the total sleep time. From one cycle to the next, the REM sleep phase becomes longer and longer, and the depth of sleep, on the contrary, decreases. Disturbances of slow-wave sleep are not as severe for the psyche as interruption of the REM phase. If any part of REM sleep is interrupted, it must be replenished in one of the subsequent cycles. Experiments conducted on mice have proven the detrimental effect of the missing REM phase on these mammals. After 40 days, the mouse deprived of REM sleep died, while the rodents deprived of slow-wave sleep continued to live.

There is a hypothesis that during the REM phase, the human brain works to organize the information received during the day. Another theory is that REM sleep is especially important for newborns, providing neural stimulation that promotes the formation and development of the nervous system.

Sleep duration

Duration normal sleep can vary from 6 to 8 hours per day. However, this does not exclude large deviations in one direction or another (4-10 hours). If sleep disturbances are observed, then its duration can be equal to several minutes or several days. When the duration of sleep is less than 5 hours, this is considered a violation of its structure, which can lead to the development of insomnia. If you deprive a person of sleep, then within a few days his consciousness will lose clarity of perception, an irresistible urge to sleep will appear, and “dips” into the so-called borderline state between sleep and wakefulness will be observed.

Dreams

Along with the corresponding physiological process, the word “sleep” also means a sequence of images that arise in the REM sleep phase and, in some cases, are remembered by a person. A dream is formed in the consciousness of a sleeping person, consisting of a variety of subjectively perceived tactile, visual, auditory and other images. Usually the person who is dreaming is not aware that he is in a dream state. As a result, the dream is perceived by him as an objective reality. An interesting type of dreams are lucid dreams, in which a person understands that he is dreaming and therefore can control the development of the plot in the dream. It is believed that dreams are inherent in the REM sleep phase, which occurs once every 90-120 minutes. This phase is characterized by rapid movement of the eyeballs, increased heart rate and breathing, stimulation of the pons, as well as short-term relaxation of skeletal muscles. According to the results of recent research, dreams may also be characteristic of the slow-wave sleep phase. At the same time, they are less emotional and do not last as long as REM dreams.

Sleep pathologies

All kinds of sleep disorders are quite common. For example, the cause of insomnia (insomnia) can be psychosis, depression, neurosis, epilepsy, encephalitis and other diseases. Apnea is a breathing disorder of a sleeping person, the causes of which can be mechanical or psychogenic in nature. Parasomnias such as sleepwalking, nightmares, epilepsy and teeth grinding are formed and develop on the basis of neurosis. Pathologies such as lethargic sleep, narcolepsy and sleep paralysis are among the most severe disorders sleep. In case of any alarming factors associated with obvious deviations in the structure of sleep, you should seek help from a specialist.

Pharmacological hypnotics

Sleep regulation using pharmacological agents must be carried out under the supervision of a physician. Along with this, it should be remembered that long-term use sleeping pills reduces the effectiveness of the latter. Relatively recently, the group of sedatives even included drugs - morphine and opium. Barbiturates have also been used as sleeping pills for quite a long time. Melatonin is considered one of the most progressive drugs at the moment. No less effective treatment Insomnia is helped by taking magnesium supplements, which improve sleep and promote the production of melatonin.

Sleep Study

According to prominent researchers of the past and present, sleep plays a more important role for the human body than food. In the second half of the 20th century, technologies for recording the activity of muscles (EMG), brain (EEG) and eyes (EOG) were developed, after which it was possible to formulate ideas about the structure of sleep and its nature, which no one has yet refuted .

The whole dream is divided into two fundamentally various types- This is slow sleep and rapid sleep. In turn, slow-wave sleep is divided into 4 phases. It turns out that there are only 5 different phases of sleep.

slow sleep

It is also called the dormancy stage. It is characterized by thinking and experiencing problems that arise during the day. The brain, by inertia, tries to find a solution to the problems it was working on while awake. A person can see images that implement a solution to a problem.

There is a further decrease in muscle activity, pulse and breathing slow down. The brain gradually stops working. This stage is characterized by short bursts of auditory sensitivity. Several times a minute a person is in a state where it is very easy to wake him up.

Is transitional. The difference between stages three and four of sleep is the number of delta oscillations. But we will not delve into such details.

Characterized by the deepest sleep. It is considered the most important, since at this time the brain receives the most complete rest and restores its performance. In the fourth stage of sleep, it is difficult to wake a person. Cases of talking in a dream or sleepwalking occur precisely in this phase.
The first two phases are considered shallow slow-wave sleep, and the second two are considered deep sleep. NREM sleep is also called orthodox sleep or non-REM sleep.

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Rapid eye movement sleep (REM sleep)

This stage is also called REM sleep (from the English rapid eye movements, which means “rapid eye movements”). As you may have guessed, REM sleep is characterized by accelerated movements of the eyeballs under closed eyelids - this is the first fundamental difference from slow sleep.

The second difference is that in the REM sleep phase the brain does not rest at all, but on the contrary, it is activated. The heart rate also increases, but the large muscles are completely relaxed.

And the most interesting thing is that in the REM sleep phase it is most difficult to wake a person, although his state is closest to the state of wakefulness. That's why REM sleep is also called paradoxical sleep.
The purpose of REM sleep is not entirely clear. There are several assumptions about this:

1. During the REM sleep stage, the brain sorts out the information received.
2. The brain analyzes conditions environment, in which the organism is located and develops an adaptation strategy. Indirect confirmation of this judgment is the fact that in newborns REM sleep is 50%, in adults - 20-25%, in older people - 15%.

But there is one fact that does not cause controversy - the most vivid dreams come to us in REM sleep! In other stages, dreams are also present, but they are blurred and we remember them very poorly. Scientists also say that you will only remember a dream well if you wake up in the REM phase.

Sequence of sleep stages

Sleep begins with phase 1, which lasts approximately 10 minutes. Then the 2nd, 3rd, and 4th phases follow sequentially. Then in the reverse order - 3rd, 2nd and the REM sleep phase begins. Together they form a cycle that repeats 4-5 times a night.

This changes the duration different phases from cycle to cycle. In the first cycle, REM sleep is very short, longer time occupies deep slow-wave sleep. But in the last cycles there may be no deep sleep at all. Typically one cycle is 90-100 minutes.

Now comes the fun part. Your well-being depends on what phase of sleep you wake up in. The worst place to wake up is deep sleep. When you wake up from a deep sleep, you will feel groggy.

It is best to wake up after the end of the REM sleep phase, that is, at the beginning of the first or second phase. Waking up from REM sleep is not recommended.
Now you probably have a question about how to make sure you wake up in the right phase.

I will express only one thought on this matter. As already mentioned, it is quite difficult to wake a person in the deep sleep stage. So if your sleep is interrupted in a natural way, and not the sound of an alarm clock, then you are most likely to wake up in the right phase.

Now a little about the importance of fast and slow sleep. Some scientists say that REM sleep is a relic of the past, supposedly a person does not need it, just like the appendix.

The following facts are cited in support of this statement:

If you forcibly limit the duration of sleep, then the duration of the deep phase of sleep practically does not change; the brain primarily reduces the duration of REM sleep.

But this only proves that deep sleep is more important than fast sleep - no more!

Experiments have been conducted where people were completely deprived of REM sleep for two weeks. However, their health did not deteriorate in any way.

Two weeks is not that long, considering that some people can live that long without sleep at all.

But other scientists conducted experiments on rats. As a result, after 40 days without REM sleep, the rats died.

The sleep process is a very little studied phenomenon. In the future, sleep scientists will have to find answers to many controversial questions.
Well, we need to take care of our sleep and lead a healthy lifestyle!

NREM and REM sleep

NREM and REM sleep are different in their bioelectrical activity brain

Recording brain biocurrents in the form of an electroencephalogram (EEG) gives a peculiar pattern characteristic of various conditions. During slow-wave sleep, the EEG shows

slow waves of large amplitude, followed by fast rhythms during REM sleep. Differences between sleep stages are not limited to EEG data.

slow sleep

During slow sleep, breathing and pulse become less frequent, muscles relax, and during this period the so-called physical activity person.

REM sleep

During the REM sleep phase, breathing rate and heart rate increase, motor activity increases, and movements are clearly visible behind closed eyelids. eyeball. These so-called rapid eye movements - characteristic feature this phase, hence another name for it: REM in its first letters English words Rapid eye movements. At this moment, the sleeper dreams. An interesting fact has been established: waking up a sleeper during REM sleep, despite signs of more superficial sleep, increased breathing and heart rate, and EEG rhythm, is much more difficult than during slow-wave sleep. Therefore, the REM sleep phase is also called paradoxical sleep (respectively, slow-wave sleep is orthodox).

REM sleep never occurs immediately - it is recorded only after a certain duration of the slow-wave sleep phase. REM sleep is very important for a person’s mental state. When volunteers' sleep patterns were studied and they were awakened for 3-4 nights in a row before the onset of the REM phase, they began to experience mental disorders, despite the overall sufficient duration of sleep.

Night sleep

Typically, nighttime sleep consists of a strict alternation of 4-6 completed cycles, each of which begins with slow sleep and ends with REM sleep. The normal duration of any cycle is from 60 to 90 minutes, but if at the beginning of the night REM sleep lasts only a few minutes, then by the morning its duration is about half an hour. In this case, it is necessary to combine these cycles, characterized by different ratios of sleep phases, with a certain hormonal level and temperature rhythm, changing from evening to morning. This is why certain hours of the day are so important for sleep. And it is no coincidence that the dream daytime, as a rule, does not give the same refreshing effect as night.

Another interesting point is that every healthy person dreams, but only those who wake up in the first 15 minutes after REM sleep remember them. It turned out that those who have a good memory dream. The brighter and more imaginative the dreams, the better sleep. According to some scientists, one of the reasons for this is that during sleep, information received during the day may be actively processed. Thus, in the slow-wave sleep phase, information received during the day is processed, and in the REM sleep phase, which is characterized by dreams with the inclusion of fantastic unreal components, both protection from external stimuli and mental activity are carried out.

REM sleep plays a significant role in the process of learning and memorizing various information. Thus, among students actively studying foreign language, we can identify a group of young people who memorize new words very quickly and correctly. Unlike students with poor memorization ability, they have a longer duration of REM sleep.

We now know that nighttime sleep is a complex physiological process that includes up to five cycles of rapid and slow-wave sleep. But more recently, in the 19th century, sleep was perceived by scientists as a phenomenon closed to study, in contrast to the waking state, which can be measured and observed.

You can evaluate the sleeping position, measure his physical indicators: pulse, blood pressure, breathing rate, body temperature. But how to evaluate the fundamental processes of sleep itself?

First experiments were based on the awakening of the subject, that is, on the intrusion into the sleep process.

However, through these studies, the understanding has been gained that sleep occurs in successive stages.

Köllschütter, a German physiologist, established in the 19th century that sleep is deepest in the first hours, and later becomes more superficial.

A breakthrough in the history of sleep research was the discovery of electrical waves that originate in the brain and can be recorded.

Scientists have the opportunity to observe, record and study phenomena that occur in a person’s sleep using an electroencephalogram.

Thanks to numerous studies, it has been established:

State of the autonomic nervous system different in both stages.

In slow-wave sleep, we grow faster: the growth hormone produced by the pituitary gland is produced more actively in this phase.

Dreams are of different nature.

IN fast phase– dream pictures are action-packed, brightly and emotionally colored, in slow ones – the dream plot is calm or completely absent.

Awakening.

If you wake a person in the middle of REM sleep, he will get up much easier and will feel much better than as a result of waking up in the slow phase.

Even if you've had enough time to sleep and you expect to feel a surge of strength and vigor, this will not happen if you wake up unsuccessfully at the beginning or in the middle of the slow-wave sleep cycle. In such a situation, you can hear: “Did you get up on the wrong foot?”

Apparently the cause of this condition is incomplete neurochemical processes that take place in slow-wave sleep.

When you fall asleep, breathing becomes less frequent and louder, but less deep.

It slows down even more and becomes irregular in delta sleep.

Breathing in REM sleep is sometimes slow, sometimes rapid, sometimes - this is how we react to the events of the dream we are watching.

Brain temperature decreases in slow-wave sleep, and in fast sleep, due to increased blood flow and active metabolism, it rises and sometimes exceeds the temperature during wakefulness.

Despite numerous differences, the stages of slow and fast sleep have a chemical, physiological, functional interdependence and belong to a single balanced system.