Sleep—and dream?

To sleep—and to dream? Science is gradually approaching an explanation for one of the eternal mysteries of existence: the phenomenon of sleep. For example, researchers at Harvard Medical Center recently used magnetic resonance imaging to 'peek' into which brain centers are active in a sleeping person. It has been shown that motor skills (e.g., finger movements resembling piano playing) acquired during wakefulness are consolidated during sleep. After sleep, the neural centers controlling learned sequences operate in an 'automatic' mode and are not accompanied by the activity of centers responsible for anxiety.

The journal 'Neurobiology' has presented new data that allow us to consider the human brain as an organ that can be trained. It turns out that with age, the functional specialization of brain regions changes. Continuously working thinking centers subordinate other brain regions and begin to use their resources. As a result, the main activity of our brain can not only be successfully carried out but even improve in old age. By the way, it has been shown again that mental work in mature age correlates with good health (even in those who were not particularly robust in their youth).

But why are dreams needed after all? Why, in addition to the real world to which we adapt, do we need to see an illusory night world? Why nightmares? They reduce our adaptability, draining our mental strength! Why does a sleeping dog chase someone in its dream, twitch its paws, and bark softly? Why does a newborn baby (who has nothing to worry about) spend significantly more time in the rapid eye movement (REM) sleep phase, characterized by dreaming, than an adult? Why does a blind person's sleep consist of auditory and tactile images?

Dreams are a very important part of our lives. Sometimes they flicker somewhere at the periphery of consciousness, and sometimes they strike with their vividness or unexpected wisdom. To explain them, we have to assume that a significant part of the psyche is occupied with generating these night images. The structure of our body, as well as the peculiarities of its functioning, is the result of evolution. How could such a strange feature arise? Why is it needed?

From our point of view, dreaming is part of a mechanism that ensures behavioral flexibility. Behavior is a mechanism for adapting to the environment. Adaptive behavior increases an individual's chances of survival and reproduction, just like the presence of specific structures or functions.

Species are divided into specialists and opportunists. Specialists require refined behavioral patterns that correspond to their characteristic modes of activity. Opportunists, on the other hand, are capable of various types of activities, switching between which depends on the situation. They are characterized by more flexible behavior.

The basis of behavior is the neural networks of the brain. The nature of the connections between neurons determines the class of problems that this network can solve. The connection between neurons can be set in two different ways. The first way is to program the development of precisely the neural network required for species-specific behavior in the inherited program. This method is optimal for specialist species. The second way to obtain the necessary behavioral basis is to tune the neural network with information received from the environment during the process of solving characteristic life tasks.

Let's compare these methods. The rigid method allows obtaining exactly what is needed with a low probability of errors. However, the development and correction of complex behavior through this method requires a long evolutionary path, and the complexity of the resulting networks is limited: the channel for transmitting inherited information has a limited 'bandwidth'.

The second method requires 'tuning' neural networks during a significant part of ontogenesis, which is fraught with many failures. Not a few individuals will die before they develop a perfect mechanism for controlling adaptive behavior. However, when conditions change, new forms of behavior can emerge in evolutionary terms almost instantly, within a single generation. The amount of information coming from the external environment and capable of being reflected in the structure of neural networks is greater than what can be described in an inherited program.

For most species, a certain balance of both mechanisms proves to be optimal: the inherited program determines the basic parameters of the structure of neural networks that control behavior, and fine-tuning is carried out during the use of these networks. For each species, there is its own trade-off between reliability and complexity, speed of formation and flexibility of neural network functioning.

Recent data from the field of neurophysiology have revealed that such 'fine-tuning' is associated with neurogenesis, the proliferation of nerve cells in the hippocampus, their migration through the brain, and their integration into working neural networks. As Elizabeth Gould's research from Princeton University has shown, the rate of increase in the number of neurons in certain centers depends on the intensity of their work. Therefore, out of several 'templates' set by the inherited program, the one used most frequently will receive the best development.

What mechanisms can accelerate the development of adaptive behavior? If it is always tuned during vital interactions, unsuccessful operation of neural networks can lead to the death of the organism. It is best to 'tune' the physiological basis of behavior during training, for example, through play. This is precisely why the phenomenon of play is widespread among mammals. The role of play in refining specific behavioral patterns has long been understood, and after the discovery of neurogenesis, it became clear that it can contribute not only to better organization of neural networks but also to an increase in the number of neurons within them.

However, play is also quite an expensive pleasure. A playful fight can end in injury. While the developing young mammal needs to develop not only its nervous but also its musculoskeletal system, this is justified. But the need for rigid coordination of training both systems can be unfavorable. Moreover, not all functions of the nervous system are related to motor control.

Therefore, 'idle runs' of its working mechanisms can be beneficial for the development of the nervous system. When should they occur? Probably during sleep, when the animal is in a relatively safe place, and the nutrition of its nervous tissue improves. At this moment, the best conditions are created for integrating new neurons into life-important neural networks.

But how to ensure the development during sleep of precisely the centers that are needed? The nervous system has mechanisms that assess the relative importance of certain processes—these are likely what determine the 'themes' for dreams. On the other hand, the importance of some 'sleep' work may be related to recent activities for which there were insufficient specialized control neural networks.

It is clear why the mechanism of dreaming is most active in newborns. But why do dreams of adults manifest in consciousness? Nervous centers need to be developed through activities that are adaptive for them. And when the process is complete, excess data can be removed from consciousness. Perhaps this is why we remember our dreams if we wake up during a dream, and forget them if we manage to transition to normal sleep mode after it.

Thus, we hypothesize that dreaming is a way to complicate neural networks that support behaviors important for wakefulness. It is not entirely clear whether this hypothesis is truly new. The discoverer of neurogenesis, Elizabeth Gould, is currently studying the effects of sleep deprivation on experimental animals, and it can be assumed that she is testing a similar hypothesis. On the other hand, such a viewpoint does not necessarily contradict those previously expressed. For example, according to the Russian-Israeli psychophysiologist Vadim Rotenberg, the function of sleep is to provide exploratory behavior that is insufficiently realized during wakefulness. When the organism cannot find suitable adaptation strategies while awake, dreams help to relieve accumulated tension. This explanation is entirely consistent with ours. Overcoming conflict in dreams helps develop centers necessary for overcoming it while awake!

Processes in the inner world prepare us to solve the problems posed by the large, external world...

While preparing the article, a report was received about facts confirming the hypothesis presented in it. The journal Nature published a study by Japanese scientists led by Tatsuhiro Hisasune from the University of Tokyo, which showed that the theta rhythm generated by the brain during the emotional phase of REM sleep (when vivid dreams occur!) enhances the synthesis of gamma-aminobutyric acid, which stimulates neurogenesis.

“...therefore, the world... must be recognized as related to dreams or even belonging to the same class of things. For the function of the brain, which during sleep, by some magic, generates a completely objective, visual, even tangible world, must participate equally in the creation of the objective world of wakefulness.” Arthur Schopenhauer

Sleep—And Dream? Science is gradually approaching an explanation of one of the eternal mysteries of existence: the phenomenon of sleep. For example, researchers at Harvard Medical Center recently used magnetic resonance imaging to “peek” at which brain centers are active in a sleeping person. It was shown that motor skills (e.g., finger movements resembling piano playing) acquired while awake are consolidated during sleep. After sleep, the work of neural centers that control learned sequences proceeds in an “automatic” mode and is not accompanied by activity of centers responsible for anxiety. The journal *Neurobiology* presented new data allowing us to view the human brain as an organ amenable to training. It turns out that with age the functional specialization of brain regions changes. Tirelessly working centers responsible for thinking subordinate other brain regions and begin to use their resources. As a result, the primary activity of our brain can not only continue successfully but even improve in old age. By the way, it was again shown that mental work in mature age correlates with good health (even among those who were not robust in youth). But why do we need dreams? Why, besides the real world to which we adapt, must we also see an illusory nocturnal world? Why are nightmares needed? They seem to reduce our adaptability by draining mental strength! Why does a sleeping dog chase someone in a dream, twitch its paws and quietly bark? Why does the rapid‑eye‑movement (REM) phase, characterized by dreaming, last much longer in a newborn (who has nothing to worry about) than in an adult? Why does a blind person’s sleep consist of auditory and tactile images? Dreams are a very important part of our lives. Sometimes they flicker at the periphery of consciousness, and sometimes they astonish with their vividness or unexpected wisdom. To explain them, one must assume that a significant portion of the psyche is occupied with generating these nocturnal images. The structure of our body, as well as the features of its functioning, is the result of evolution. How could such a strange trait arise? What is its purpose? From our point of view, dreams are part of a mechanism that provides behavioral flexibility. Behavior is a mechanism of adaptation to the environment. Adaptive behavior increases an individual’s chances of survival and reproduction, just as the presence of specific structures or functions does. Species are divided into specialists and opportunists. Specialists require refined behavioral forms that match their characteristic modes of activity. Opportunists, however, can engage in various activities, switching between them depending on the situation. Their behavior is therefore more flexible. The basis of behavior is the brain’s neural networks. The nature of connections between neurons determines the classes of tasks that a network can solve. Connections between neurons can be established in two different ways. The first consists in programming, in the hereditary program, the development of exactly the neural network needed for a given species‑typical behavior. This method is optimal for specialist species. The second way to obtain the necessary behavioral basis is to tune the neural network with information arriving from the environment during the solution of characteristic life tasks. Let us compare these methods. The hard‑wired approach yields exactly what is needed, with a low error rate. However, the development and refinement of complex behavior by this route requires a long evolutionary path, and the complexity of the resulting networks is limited: the channel for transmitting hereditary information has a limited “bandwidth.” The second method requires “tuning” neural networks throughout a substantial part of ontogeny, which entails many failures. Many individuals will die before a perfect mechanism for controlling adaptive behavior is formed. Yet, when conditions change, new behavioral forms can arise in evolutionary terms almost instantaneously, within a single generation’s lifespan. The amount of information that comes from the external environment and can be reflected in the structure of neural networks exceeds what can be encoded in the hereditary program. For most species, an optimal balance of both mechanisms emerges: the hereditary program determines the main parameters of the nervous networks that govern behavior, while fine‑tuning occurs through the use of these networks. Each species has its own compromise between reliability and complexity, speed of formation and flexibility of network functioning. Recent neurophysiological data have revealed that such “fine‑tuning” is linked to neurogenesis—the proliferation of nerve cells in the hippocampus, their migration through the brain, and integration into functional neural networks. As studies by Elizabeth Good of Princeton University have shown, the rate of increase in neuron numbers in particular centers depends on the intensity of their activity. Thus, of several “templates” set by the hereditary program, the one most frequently used will achieve the best development. What mechanisms can accelerate the acquisition of adaptive behavior? If it is always to be tuned through vital interactions, a malfunctioning neural network can become a cause of organismal death. The best time to “tune” the physiological basis of behavior is during training, for example, play. This explains the widespread occurrence of the play phenomenon among mammals. The role of play in honing specialized behavioral forms has long been understood, and after the discovery of neurogenesis it became clear that play can promote not only better organization of neural networks but also an increase in neuron numbers within them. Nevertheless, play is also a rather costly pleasure. Mock fighting can end in injuries. While a growing mammalian offspring needs to develop not only the nervous but also the musculoskeletal system, this is justified. However, the necessity of tightly coupling the training of both systems may be detrimental. Moreover, not all functions of the nervous system are related to movement control. Thus, “idle runs” of the nervous system’s working mechanisms may be beneficial for its development. When should they occur? Probably during sleep, when the animal is in a relatively safe place and the nourishment of its neural tissue improves. At that moment, conditions are optimal for integrating new neurons into life‑essential neural networks. How can we ensure that during sleep the specific centers needed are developed? The nervous system contains mechanisms that evaluate the relative importance of various processes—these appear to determine the “themes” of dreams. Conversely, the importance of some “sleep‑related” work may be linked to recent activities for which specialized controlling neural networks were lacking. It is clear why maximal dream‑mechanism activity is characteristic of newborns. But why do adult humans experience dreams in consciousness? Neural centers must be trained on activities that are adaptive for them. When the process is complete, surplus data can be removed from consciousness. Perhaps this is why we remember our dreams if we awaken during them, and forget them if we return to ordinary sleep afterward. Thus, we have proposed the hypothesis that dreams are a way to elaborate neural networks that support important waking behavioral forms. It is not entirely clear whether this hypothesis is truly novel. Elizabeth Good, the discoverer of neurogenesis, is currently investigating the effects of sleep deprivation on laboratory animals, and it can be assumed that she is testing a similar idea. On the other hand, this viewpoint does not necessarily contradict earlier ones. For instance, Russian‑Israeli psychophysiologist Vadim Rotenberg has argued that the function of sleep is to provide search behavior insufficiently realized during wakefulness. When the organism cannot find suitable adaptive pathways while awake, dreams help discharge accumulated tension. This explanation fits well with ours. Overcoming conflict in sleep helps develop the centers needed to resolve it in waking life! Internal‑world processes prepare us for solving the tasks posed by the vast external world… During article preparation, a report arrived about facts confirming the presented assumption. *Nature* published a paper by Japanese scientists led by Tatsuhiro Hisatsune of the University of Tokyo, showing that the theta rhythm generated by the brain during the emotional phase of REM sleep (when vivid dreams occur!) enhances the synthesis of gamma‑aminobutyric acid, which stimulates neuron proliferation. “…therefore the world… must be recognized as kin to dreaming or even belonging to the same class of things as it. For the brain function that, during sleep, by some charm creates a completely objective, vivid, even tangible world, must take an equally part in creating the objective waking world.” Arthur Schopenhauer D. Shabanov. Sleep—And Dream? // *Kompyuterrá*, Moscow, 2005. – No. 37 (609). – pp. 56‑57