Instead of a preface. It is not by chance that we publish this article on a website addressed to psychologists and psychotherapists. The author of this article is a biologist by education, a psychotherapist by occupation. Gestalt therapy offers us work "at the junction" of the mental and physical, and the data about the brain and the fact that nerve cells are regenerating are extremely optimistic. There is evidence from German researchers that after psychotherapy, the performance of the brain as a biological object improves. Maybe here is finally the desired objective proof of the effectiveness of psychotherapy? Elena Petrova (October 5, 2006)
I apologize in advance to my brothers in science, and sisters, too, for the hasty conclusions and unrestrained imagination, which is by no means characteristic of a strict scientific mind. I can say in my defense that fantasies extend only to the interpretation of facts, and I undertake to state the facts themselves accurately, clearly and with references.
The first doubts about the dogma "nerve cells do not recover" were voiced in 1965 (Josef Altman, Gopal Das). About 20 years later, newly formed neurons were found in the higher vocal center of canaries (Fernando Notterbohm, Steven Goldman, cited in 1) during a period when males were learning new elements of singing. In the 90s, articles appeared on the formation of new neurons in the olfactory bulb in mice during pregnancy (cited from 1). There is a lot of data on the appearance of new nerve cells in the rat hippocampus (5, 2, 6, 8). In humans, the formation of new neurons in the hippocampus is less pronounced than in rodents (3). There is evidence that the volume of the hippocampus is reduced in patients with depressive disorders (9, 3). Diseases and disorders (animal models) such as hyperactivity (11), schizophrenia (8),epilepsy (4) in the light of new data on neurogenesis in the adult brain. Many works are devoted to the study of factors that enhance or suppress the formation of new neurons in the adult brain, the search for brain regions where this process takes place, and the study of substances that affect it. I want to emphasize that all these works were done on animals (birds, rodents, monkeys), there is not a lot of data on the human brain. Nevertheless, most researchers tend to extrapolate (with reservations) the discoveries made in animals to the human brain.that all these works were done on animals (birds, rodents, monkeys), there is not a lot of data on the human brain. Nevertheless, most researchers tend to extrapolate (with reservations) the discoveries made in animals to the human brain.that all these works were done on animals (birds, rodents, monkeys), there is not a lot of data on the human brain. Nevertheless, most researchers tend to extrapolate (with reservations) the discoveries made in animals to the human brain.
What is neurogenesis?
Neurogenesis is the process of forming new neurons. In the adult brain, there are clusters of cells that do not perform any function - they are not engaged in the exchange and processing of information, nor the maintenance of neurons - but they are capable of dividing throughout the life of an animal or a person. These cells are called progenitor cells. After division, one daughter cell remains in place, grows and divides again, and the second migrates and integrates into the already existing networks of neurons, becoming mature after a while. Not all newly formed neurons survive. It is known that a nerve cell dies if it does not establish a connection with its target cell (a neuron that is not involved in the exchange of information disappears).
The survival rate increases under the influence of several factors. The division of the precursor cell takes approximately 2 hours. The newly generated neurons are functionally integrated into the network within 1 month, they are smaller than mature (the cell body size is smaller, the branching of processes (dendrites) is also smaller) and finally mature after 4 months (10). Under the influence of factors triggering neurogenesis, cells are actively dividing within 24 hours, and then within 7 days the process dies out (6).
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Areas of the brain where neurogenesis is found
Neurogenesis in the adult brain is found only in a few strictly defined areas. One of them is the subventricular zone - the area lining the lateral walls of the lateral ventricles of the brain from the inside (data obtained on rats). During the development of mammals (embryonic stage), neurons are formed from the layer of cells lining the ventricles (ventricular zones), then the divided cells migrate to different areas, forming all the structures of the brain. The subventricular zone is located below the ventricular (cited in 7) and contains cells that can divide in the adult brain. Neurogenesis in this zone is initiated by pregnancy (mice and rats). In rodents, sense of smell is critical for recognizing and rearing young. By the time of birth, in the female's olfactory bulb (the area of the brain that receives information from the receptors in the nose;is activated in response to odors) new cells appear that migrate from the subventricular zone. These cells integrate into existing networks and develop into mature neurons (7, 12).
Another area of the adult brain, where there are clusters of "forever young", capable of cell division, is the hippocampus (a paired subcortical formation located deep in the temporal lobes; it borders on the lower part of the lateral ventricles). The functions of the hippocampus are complex and extremely interesting. This area receives information from the cerebral cortex, which came from the outside world. For example: sensation of wind on the skin (tactile zone of the cerebral cortex), rustling of leaves (auditory zone), play of light and shadow (visual), smell (olfactory bulb) … - such information in an integrated form comes to the hippocampus. However, he is unlikely to be very aroused in response to the described situation. It is believed that the hippocampus reacts to novelty: the more unusual the information, the higher its activity.
Further, the hippocampus sends out its excitement throughout the brain, creating local foci of activation, thereby facilitating information processing (13). In experiments on rats, it was found that in animals constantly receiving new toys, the survival of newly born cells is higher than in controls (rats without any toys) (6). At the same time, hippocampal neurogenesis is reduced in rats living in isolation (8). In addition, it is believed that the hippocampus contains neural systems that regulate memorization and learning (13). It is known that memory is organized in the brain in the following way: for each "piece" of information (for example, the taste of lemon), a completely specific part of the brain is responsible, and a holistic reaction (to the letters "v-k-y-s n-a ") is carried out with the interaction of many sites located in different areas. It is assumedthat the hippocampus acts as a regulator of this interaction (13). Apparently, this regulation is mediated by neurogenesis. In training experiments on rats, it was found that learning is accompanied by the appearance of new neurons in the hippocampus (2, 1, 6, 3).
And finally, the hippocampus is involved in the process of motivation and regulation of the level of activity of the body. The cells of the hippocampus are capable of producing the correct, regular theta rhythm (4-7 Hz). In infants from 3-4 months of age, the presentation of a new stimulus leads to an increase in the severity and amplitude of theta-range waves; in adults, theta-rhythm occurs in situations requiring mobilization. The intensity of the theta rhythm correlates well with such personality manifestations as aggressiveness, incontinence, intolerance, and suspicion. An increase in the theta rhythm of the hippocampus in animals correlates with high emotional stress such as fear, aggression, and pronounced food, drinking and sexual needs (13). K. T., both in animals and in humans, an increase in the frequency of theta rhythm is associated with mobilization before the action, with spontaneous behavior, with the intensity of actions.
Thus, the theta rhythm generated by the hippocampus is responsible for the level of activity in the body. If the brain evaluates the external environment as threatening, the activity can be destructive (accompanied by anger, hatred, the desire to destroy or destroy) or it can be aimed at avoiding danger. Activity can be exploratory (reaction to safe novelty). Activity can be aimed at satisfying any other urgent need. Apparently, this activity, regulated by the theta rhythm of the hippocampus, is aggression in the understanding of gestalt therapists. Then the work of recovery (in the case of postsynaptic syndrome and depression) and maintenance of the client's aggression is filled with new meaning: as a result, the brain's ability to neurogenesis of the hippocampus is restored. The formation of new neurons in the hippocampus is suppressed if the animal is helpless in the face of an imminent threat or is in a state of chronic stress (7, 5, 9). Apparently, the suppression of activity is expressed at the brain level in the weakening of hippocampal neurogenesis. The process is restored by spontaneous physical activity (in rats it was running in a "squirrel" wheel) (5, 11, 3, 6, 1). Moreover, "running" rats learn better (11).
I must note that rats in vivariums are kept in cages, where they especially have nowhere to move. The squirrel wheel gives them the opportunity to get closer to their natural way of life. Perhaps for people, movement itself is not as important as the natural life for us - following our own needs, along with obedience to rules and duty. However, this is nothing more than a fantasy, it is extremely difficult to confirm it experimentally by counting the number of newly generated neurons in a person living in accordance with his nature. And the fact that movement is life, the life of new neurons, has been confirmed.
So, the hippocampus is a zone in the temporal region of the brain; neurogenesis occurs in the hippocampus of the adult brain; hippocampal cells generate theta rhythm, which is responsible for the level of activity of the body; The hippocampus is involved in the following brain functions:
- the integration of sensory information and its distribution throughout the brain; the answer to novelty;
- learning and memorization;
- motivation and regulation of the activity of the whole organism;
- regulation of mood.
If we consider the brain as a system consisting of interacting elements, then the hippocampus may be the organizer of the interaction of various elements of the brain (for example, it organizes the connection between the perception of events in the external world and
emotional assessment of these events). Then, in the case of a lack of existing connections (when faced with something new or learning something new), the hippocampus organizes new connections between the elements of the brain, generating new cells. Probably, the same function of organizing new interactions between already existing elements is performed by new neurons in the olfactory bulb of pregnant mice.
In humans, I would like to assume that the subjective experience of insight at the level of the brain corresponds to the incorporation of new nerve cells into the existing networks of the hippocampus - the formation of a hitherto non-existent connection between long-existing elements. Gestalt psychologists call this phenomenon the "aha-effect" that occurs at the moment of contacting in the contact cycle. And then the whole cycle of contact is the initiation or maintenance of neurogenesis in the brain.
Another area of the brain where new neurons are generated is the substantia nigra (4), located in the midbrain. This area activates the cerebral cortex, imparting emotional coloring to some behavioral responses. In addition, the substantia nigra is responsible for the coordination and initiation of complex movements.
And finally, the supreme vocal center of songbirds, where dividing cells were first discovered in the adult brain.
The male canary sings complex songs during the breeding season and learns new song elements every year. During the non-breeding period, they sing less, their songs are less perfect, and their vocal center decreases in volume. But when it comes time to embellish their song again, the vocal center increases with the addition of new neurons.
Striped finches, on the other hand, learn one song as a teenager and never change it. Their brains reflect this difference: finches only add large numbers of neurons to the vocal center during adolescence. In one experiment, they selectively destroyed neurons in the vocal center of finches and found that new neurons migrated there, apparently replacing the dead. The song noticeably "degraded" with a decrease in neurons, but some elements of the song recovered with the addition of neurons (cited by 1).
Brain injuries (bruises, wounds) initiate neurogenesis in the hippocampus in animals (4). It can be assumed that the area destroyed as a result of trauma is restored by migrating neurons, as described in the experiment with the vocal center of a finch. But I have not come across data to support this assumption. However, inflammatory processes in brain tissues are accompanied by suppression of neurogenesis. Inflammation is the response of the immune system to foreign particles or microorganisms, accompanied by the destruction of everything foreign. The brain is isolated from the immune system by a special barrier. However, there are cells that play the role of "destroyers" - microglial cells. They release N2O (laughing gas), which is neurotoxic (4). Thus, trauma initiates neurogenesis and inflammation suppresses it. Obviouslythat the rate of recovery will be determined by a combination of these two factors.
Substances affecting neurogenesis
The division of progenitor cells in the hippocampus is suppressed by glucocorticoids (substances of the adrenaline group) (3, 9, 7). The adrenaline system of the brain reacts in response to a threat from the external environment, is activated when developing reactions with negative (painful) reinforcement (13). Interestingly, opiates, acting on the adrenaline system, also suppress neurogenesis (3). Thus, a threatening situation suppresses the process of the appearance of new neurons.
A decrease in the level of serotonin (one of the brain mediators) is accompanied by a decrease in the intensity of neurogenesis in the hippocampus, but does not affect this process in the subventricular zone (8, 7). Serotonin, in contrast to substances of the adrenaline group, facilitates the development and storage of skills based on positive (nutritional) reinforcement and negatively affects the development of defensive reactions (13). In addition, there is evidence that serotonin is responsible for the experience of pleasure and satisfaction (14).
Another mediator, dopamine, has a similar effect on the appearance of new neurons: a decrease in dopamine levels is accompanied by a decrease in the intensity of neurogenesis in the hippocampus (8). The richest in dopamine is the substantia nigra (see above). Disturbances in this zone lead to a deep disorder of stereotyped motor activity, its coordination and initiation - Parkinson's disease (14). Perhaps the painful manifestations are associated with any changes in the generation of dopamine neurons in the substantia nigra and / or neurogenesis in the hippocampus.
Among the substances that enhance neurogenesis in the hippocampus, the main role is assigned to various growth factors (substances that stimulate the functions of neurons, support their survival, inducing the growth of axons and dendrites in the direction of target cells). Exercise (experiments with "running" rats, see above) increases the peripheral level of one of these growth factors, then the level of this factor in the hippocampus increases, after which the progenitor cells begin to divide more actively (3).
Glutamate is another neurotransmitter (the main excitatory neurotransmitter in the brain); in the cerebral cortex and hippocampus, with the participation of this mediator, the processes of learning and memorization take place (13). This substance also increases the rate of neurogenesis (8) by initiating division of progenitor cells (3).
One of the physiological and biochemical manifestations of schizophrenia is the hyperactivity of the dopaminergic system.
A significantly increased level of dopamine was also revealed in the temporal lobe of the brain (in this area the hippocampus is located).
A number of morphological changes in the same area were also noted - an increase in the volume of the lateral ventricles, thinning of the parahippocampal cortex, etc. A significant weakening of the glutamatergic system in the frontal cortex was noted (excitation from the hippocampus comes to this area) (cited by 13). A rat model of schizophrenia demonstrates a significant weakening of neurogenesis in the hippocampus (8).
In depression, the volume of the hippocampus is also reduced. Antidepressants initiate neurogenesis in the hippocampus (3, 5) without affecting the division of progenitor cells in the subventricular zone (9).
Prolactin is a sex hormone. It has been shown in rodents that an increase in this hormone is a signal for lactation. It is this hormone that initiates neurogenesis in the subventricular zone of mice during pregnancy (1, 7). In humans, an increase in plasma prolactin levels enhances orgasm (12).
Conclusion
So, in the adult brain, the process of the appearance of new neurons is underway. Neurogenesis was found in the subventricular zone (from there, cells migrate to the olfactory bulb), in the hippocampus, in the substantia nigra, in the higher vocal center of birds. This process is enhanced by learning; in conditions where the animal is placed in an enriched environment; in conditions where the animal has the opportunity for voluntary physical movement; during pregnancy; with brain injuries. The process is weakened by exposure to a threat, in isolation, under the influence of opiates, with inflammation in the brain tissues.
All the data presented are approximately 5 years old. For those who want more recent information, I suggest the keywords: adult brain, neurogenesis.
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Author: Olga Ilyunina