For most people, the dominant hemisphere is. Sex differences in brain asymmetry. Hypotheses. Interhemispheric asymmetry: other differences.

06.05.2019

The concept of “functional interhemispheric asymmetry of the brain,” according to the psychological dictionary (1999), means a characteristic of the distribution of mental functions between the left and right hemispheres of the brain and comes from the Greek word asymmetria - disproportion. This characteristic characteristic only of man. Moreover, in full accordance with the general symmetry of the human body, each hemisphere is an almost exact mirror image of the other. Control of the basic movements of the human body and its sensory functions, as mentioned above, is evenly distributed between the two hemispheres of the brain. left hemisphere controls right side body, right hemisphere - left (Springer S., Deitch G., 1983; Bragina N.N., Dobrokhotova T.A., 1988; Kotik B.S., 1992; Wilson P.A., 1996; Danilova N.N., 1998). But the left and right brains are not identical in their capabilities and organization, despite the physical asymmetry. Complex human mental functions are asymmetrically distributed between the left and right brain.

Initial empirical studies are aimed at establishing whether cognitive impairment in psychopathy is associated with hemispheric lateralization for language stimuli. Numerous clinicians have noted that the current behavior of psychopathic subjects often strongly contradicts their verbal messages, leading to the assumption that the disorder is associated with abnormalities in language. Further research has shown that such anomalies are more common when these individuals must perform tasks involving semantic processing.

The question of interhemispheric asymmetry of the brain was first raised in 1836 by Mark Dax at a meeting of the medical society in Montpellier (France). He hypothesized that each half of the brain controls its own special functions and speech is controlled by the left hemisphere. Jackson also believed that each half of the brain controls its own specific functions. He believed that the right hemisphere is occupied with visual perception outside world, and the left hemisphere predominantly controls speech and related processes. Regarding sound speech, the right hemisphere, according to Jackson, can produce only such verbal forms that, as it were, are not broken into parts, but entirely serve as automatically pronounced designations for the whole situation. Testing and clarification of this hypothesis became possible only recently, thanks to the material accumulated during neurosurgical operations on the brain, in particular during dissection of the two hemispheres of the brain. Results from split-brain studies confirm that the left hemisphere is primarily responsible for language and speech, while the right hemisphere controls skills related to visual and spatial experience. In addition, some differences were found in the way the hemispheres process information. The left hemisphere processes it analytically and sequentially, while the right hemisphere processes it simultaneously and holistically. In addition, the left hemisphere is superior to the right when the task involves identifying few clear details, while the right hemisphere dominates when interpreting elements in a complex configuration. It was also found that the interaction of the hemispheres is normally reciprocal, that is, when processing information in one hemisphere, the other is somewhat inhibited for this time and to some extent the intensity and clarity of the manifestations of its functions decreases (Ivanov V.V., 1978; Bloom F. , Leyzerson A., Hofstadter L., 1988; Granovskaya R.M., Bereznaya I.Ya., 1991;

A well-known clinical feature found in psychopaths is the unexpected use of language. Cleckley, cited by Raine, O Brien, Smiley and Scerbo, described this characteristic: their language is persuasive, free and misleading, and also shows a curious dissociation between what they say about themselves and how they become, They present pathological lies, good intelligence, but very low insight.

The applicant, cited by Raine, O Brien, Smiley and Scerbo, found that in the interviews it was not psychopathic subjects that were driving fewer hands than psychopathic subjects, and that they presented many more gestures and actions during the conversation But exalted. The applicant, cited by Raine, O Brien, Smiley, and Scerbo, suggested that the evidence explaining differences in verbal processing may reflect weak lateralization of linguistic processes in psychopaths. This interpretation was given by a verbal dichotic auditory task administered to a psychopathic adult.

At present, the problem of functional interhemispheric asymmetry of the human brain has acquired a broad interdisciplinary character. It attracts psychologists, physiologists, teachers, neurologists, geneticists, linguists, sociologists, and philosophers. The development of this problem is proceeding in two main directions. The first direction is associated with the study of the influence of the type of interhemispheric brain asymmetry on the effectiveness of learning (Suvorova V.V., 1976; Springer S., Deych, 1983; Khomskaya E.D., 1992; Urzova Yu.A., 1995, etc.). The second direction involves studying the characteristics of the dynamics of interhemispheric asymmetry of the brain when performing any activity (Ermakov P.N., 1988; Bloom F., Leiserson A., Hofstadter L., 1988; Kotik B.S., 1992; Dikaya L.A. ., 1996, etc.).

The prisoners were given 22 essays from three pairs of one syllabic word, which were presented in a dichotomous manner. During execution, no differences were found at all. When this was reversed from one ear to the other, it did not reduce auditory asymmetry in psychopaths.

One possible explanation for previous findings of abnormal linguistic processing in psychopaths is that they are less lateralized to verbal processes. In this line of research, psychopaths and non-psychopaths used dichotic auditory tasks that consisted of vocal-consonant pairs of stimuli aligned according to their temporal properties. This particular task was chosen because it had advantages over the standard dichotic listening procedure used by Hare and McHerson.

Despite the fact that all areas of the brain are equally involved in the functioning of the brain, the literature also says that at the same time, they can be differently associated with the so-called “focus of consciousness”, with the physiological mechanisms of awareness of the “I” (Teplov B.M., 1961; N. Herrmann, 1988; Sandomirsky M.E., 1995; Vasilyeva V.N., Ramazanova A.P., Bogomaz S.A., 1996; Gulenko V.V., Tyshchenko V. .P., 1997). According to the authors listed above, the dominance in the process of conscious processing of information of certain zones of the cortex, taking into account their hemispheric affiliation, leaves an imprint on the personal and typological characteristics of a person. This is also confirmed by the statements of Sandomirsky M.E. (1995) in his work. He believed that the profile functional asymmetry hemispheres, characteristic of right-handers, when the left hemisphere is dominant, in left-handers the asymmetry profile is inverted. Thus, as mentioned above, interhemispheric asymmetry is the basis primarily for such typological characteristics as rationality/irrationality. Persons in whom the left hemisphere plays a leading role in the process of reflection of reality by the brain are thus classified as rational psychological types, while the right hemisphere is classified as irrational. As for extraversion and introversion, they are also associated with interhemispheric asymmetry and are determined by the intensity of information exchange between the hemispheres (Sandomirsky M.E., 1995): high intensity is characteristic of extroverts, low - for introverts. Due to the described differences in the methods of processing information by the left and right hemispheres, it is generally accepted that these methods complement each other. Accordingly, in the process of functioning of consciousness, the hemispheres partially duplicate each other, processing the same pieces of information in different ways. At the same time, the interhemispheric exchange of information, or rather the exchange of the results of the work of the hemispheres and their unification, or superposition, gives consciousness a holistic, adequate and full picture reality. If information exchange between the hemispheres occurs frequently and in small portions, at the level of intermediate results of information processing, this corresponds to an outward focus of consciousness (extraversion). In the same case, when this exchange occurs rarely and in large portions, at the level of ready-made results of information processing, this corresponds to the turning of consciousness inward (introversion).

If psychopaths have reduced speech lateralization, they should demonstrate a reduction in auditory asymmetry in the task. The second goal of this study was to evaluate whether the findings for adult psychopaths can be generalized to psychopathic adolescents. Hare and McPherson found that reduced asymmetry in psychopaths may be a function of individual differences in the degree of stimulus suppression along the ipsilateral auditory pathways rather than differences in language lateralization. The results show that these subjects show a reduction in auditory asymmetry in psychopaths, indicating that psychopaths are less lateralized for linguistic processes.

So, we see that such functions as extraversion / introversion and rationality / irrationality is associated with the specifics of the organization of interhemispheric interaction and is considered as interhemispheric functions. In relation to the connection of socionic functions with hemispheric asymmetry, this creates the following scheme for localizing a person’s personal-typological characteristics, where N and T are left-hemispheric functions; S and F - right hemisphere functions; T and S are functions of the left hemisphere, and N and F are functions of the right:

From the paradigm that oral dichotic listening has little effect on the direction of attention to the ear, reduced asymmetry is unlikely to be caused by selective attention to the left ear. It is said that instead of having less lateralization for language processes, psychopaths have, on the one hand, left hemisphere dysfunction or have a deficit in interhemispheric transfer, this is just a hypothesis.

The data are, however, consistent with the notion that linguistic processes are less lateralized in the left hemisphere in psychopaths and perhaps receive more cortical representation in the right hemisphere than in non-psychopaths. This effect does not appear to be modality specific; The same reduction in hemispheric asymmetry was recently found in the visual modality in psychopaths.

Divisions of the cerebral cortex

Cerebral hemispheres

Left hemisphere

(rational)

Right hemisphere

(irrational)

Front

(precentral)

Posterior (postcentral)

The precise interpretation of how lateralization of linguistic processes is reduced has not yet been determined. Reduced asymmetries in the language of psychopaths may reflect the reduced role of language in mediating and regulating behavior in the psychopath and that they are less likely to use cognitive and behavioral strategies to rely on sequential operations and verbal impairments of the left hemisphere. We can only speculate for now, but it is reasonable to work with hypotheses to explain the reduced auditory asymmetry in psychopaths.

If this proposition is true, one would predict that reduced linguistic asymmetry is particularly associated with those traits that reflect language features psychopaths. Another dichotic listening study concluded that psychopathy may be associated with poor lateralization of language function and that psychopaths may have lower left hemisphere resources for language processing than normal individuals.

Logic (T)

Ethics (F)

Intuition (N)

Sensory (S)

In the above diagram, the functions that K.E. Jung described how rational - thinking (logic) and feeling (ethics) - belong to the rational (dominant) hemisphere, and irrational - intuition and sensation (sensory) - respectively to the irrational hemisphere (subdominant). With regard to the physiological role of individual cortical zones, the most “transparent” seems to be their connection with socionic functions for the precentral parts of the cortex. The anterior sections of the left hemisphere - in right-handed people - are directly connected with verbal-logical thinking, and the symmetrical sections of the right hemisphere - with abstract non-verbal (intuitive) thinking. In relation to the posterior parts of the cortex, it is necessary to take into account, first of all, the closest connection of the corresponding area of the right hemisphere with sensations coming from internal organs, non-verbalized emotional reactions and visual-objective mechanisms of thinking. The posterior parts of the cortex of the left hemisphere are also associated with external afferentation and emotional reactions, but are more accessible to verbalization due to the anatomical proximity of the speech zones. The corresponding verbal description and verbally mediated awareness of emotions puts them in close connection with ethical and moral categories. In combination with the modeling mental functions of the frontal cortex, the activity of the postcentral region of the left hemisphere can be a catalyst for the processes of interpersonal communication, providing the underlying mechanisms of empathy. Accordingly, such socionic functions as logic, ethics, intuition, sensory, associated with the specific organization of interhemispheric interaction, are considered as intrahemispheric functions.

The experiment was conducted using a split-field procedure, which has been used to study the brain organization of language processes in psychopaths. Subjects had to decide whether a particular noun presented tachychoscopically together, right visual field or left visual field, equaled the “pretrial task” or was salient in a specific category or an abstract category. There were no differences between groups during the reaction period. Non-criminal low psychopathy groups had more errors in the right visual field than in the left visual field.

Thus, the two hemispheres do have specialized functions, but in the intact brain they work together to produce a person's adaptability and extraordinary problem-solving abilities. Due to the particular interest in the functions of the different hemispheres, some neuroscientists have asked whether there are some anatomical or physiological differences between the hemispheres that would explain their specialization. Until recently, it was believed that the two hemispheres were anatomically identical. However, studies conducted in lately, have shown that there are marked anatomical differences between the hemispheres. For example, the data indicate that in approximately 70% of cases the planum temporale in the left hemisphere is larger than in the right hemisphere. Also, many studies have found a number of other manifestations of asymmetry, most of which correlate with functional right- or left-handedness (Bogen J.E., 1969; Bloom F., Leiserson A., Hofstadter L., 1988).

This shows the expected benefits with semantic categorization with the correct field of view. While the opposite happened with the High Psychopathy group. Another study, in a similar vein, suggests that psychopaths may be poor at processing information in the left hemisphere; 26 psychopathic and 46 non-psychopathic prisoners were asked to perform a divided attention task in which a lateralized stimulus appeared in the left and right monitoring visual fields.

The cards were presented first in the correct visual field to induce activation of the left hemisphere, a procedure that was performed in the same manner in the left visual field to provoke the same level of activation from both hemispheres. Psychopaths were less accurate than non-psychopaths when activating the left hemisphere. Thus, performance deficits in psychopaths were specific and explained by asymmetrical left hemisphere conditions.

It is known from sources that the thought process itself always requires the participation of both hemispheres and includes several successive stages: when the left dominates, the results of mental activity achieved by this moment can be verbalized and realized; when the right dominates, the thought process, developing immanently, cannot be consciously verbalized. And only when the left dominates again, there is a feeling of suddenness of the result obtained, its disconnection from the states immediately preceding its receipt, unconsciousness, at the preparatory stages, at intermediate operations. In such cases, it is usually believed that the solution was found intuitively, and feedback indicates that an intuitive solution was obtained and is closed through the emerging emotional sensations (Bogoyavlenskaya D.V., 1983).

Brain structures associated with violence. The traditional violence-based theory of left hemisphere dysfunction advocates structural damage in the hemisphere, through neuropsychological tests, over other brain damage. A more recent, subtle, and potentially more plausible theory of violence relates to the fact that these people have less lateral discourse processes.

Nachon argues that left hemisphere dysfunction predisposes to criminal behavior by disrupting the normal control that the left hemisphere exerts on impulsive behavior. There are some problems with this theory: first, the mechanisms of differential electrical conduction in each hand are confusing because the brain connections for these functions are not clearly established. For this reason, it is difficult to draw conclusions about hemispheric laterality in this sense. Second, although Nachon attributes the concept of impulsivity as a mediator between left hemisphere dysfunction and violence, none of these studies have validated this concept using measures of impulsivity.

But, nevertheless, in accordance with the dominance of one or another cerebral hemisphere, there are four main types of thinking, which (Torrence E.P., 1990):

an approach with predominant activity of the left hemisphere (left-sided) in which logical analysis plays the main role. A person with this cognitive type prefers to use a logical-verbal approach and specific tasks;

Third, dichotic listening data are used to support global left hemisphere deficits, but this is not easy to interpret. For example, Naxon argues that the left ear overcomes dichotic tone tasks in violent aggressors, while other researchers have viewed this as a common function for nonverbal material.

Despite these criticisms, the concept of global hemispheric dysfunction remains as a possible theory of violence but needs further research. The empirical evidence for this hypothesis is based on a large number of neuropsychological studies, typically involving aggressive and violent subjects. Research shows 76% of this type of dysfunction in criminals is located in the frontal and temporal regions of the brain. Of these, 79% showed left lateral late abnormalities.

a right-brain-dominant (right-brain) approach that is characterized by a predominant use of intuition.

a mixed approach in which, depending on the situation, the left or right “brain” is used. The relatively weak relationship between the hemispheres suggests that such a person has transitions from a right-sided thinking strategy to a left-sided strategy, or vice versa.

Similar locations of dominant left temporal lobe activity have been found in violent adolescents. Structural abnormalities in the psychopathic brain. Some authors suggest that psychopathy is associated with abnormalities in the semantic processing of linguistic information. Functional magnetic resonance was used to characterize the neural architecture underlying lexical-semantic processes in criminal psychopathic individuals and compared with controls. Participants performed a lexical decision task across blocks of linguistic stimuli interspersed with a break in the baseline condition.

a combined strategy in which right-sided and left-sided approaches are combined. Such a person uses both hemispheres simultaneously.

Scientists have conducted a large number of studies on the phenomenon of functional interhemispheric asymmetry of the brain and discovered a variety of sensory and motor asymmetries (Auriol B., 1985; Valière-Monaud M., Roth G., Ribo J., 1978; Springer S., Deutsch G. , 1983; Bragina N.N., Dobrokhotova T.A., 1988; Torrens E.P., 1990; Talanov V.L., 1990;

In each block, the stimuli were: Concrete words and pseudopalabras. Consistent with the hypothesis, psychopathic individuals relative to control subjects showed poorer performance for abstract word processing. Analyzes support the prediction that psychopaths do not show proper neuronal differentiation between concrete and abstract stimuli in the temporal gyrus and right peripheral cortex.

Another study of hippocampal structural asymmetry in unsuccessful psychotics left the ground that structural abnormalities and hippocampal function associated with higher aggressive psychopathic populations are known. The volume of the left and right hippocampus was studied using magnetic resonance imaging, using 23 control subjects, 16 unsuccessful psychopaths and 12 successful psychopaths within the community.

Motor asymmetry, according to Bragina N.N. and Dobrokhotova T.A. (1988), is a set of signs of inequality in the functions of the arms, legs, halves of the body and face in the formation of general motor behavior and its expressiveness.

The functional asymmetries of the hands are diverse: for the vast majority of the world's population, the right hand is superior to the left in strength, and the hands are also unequal in accuracy and speed of movements made in different directions. Thus, the accuracy of movements of the right hand decreases when the body moves to the right, and the left - when the body moves to the left (Rosen A., 1970). The movements of the leading hand are dosed, controlled, and realized more accurately.

Unsuccessful psychotics showed exaggerated structural asymmetry of the hippocampus, due to successful psychotics and control subjects located in the anterior region of the hippocampus. This effect could not be explained by environmental or diagnostic issues and represents the first image of brain analysis of psychopaths with and without success.

The search for brain structures and functioning began to show significant neurobiological weaknesses in groups of antisocial and aggressive psychopaths. Although most of these studies involve the prefrontal cortex, there is growing interest in the role of temporal limbic structures, such as hippocampal mediation, in antisocial and psychopathic behavior. At the general level of the temporal cortex, abnormal functions have been found in strong, antisocial psychopathic groups using magnetic resonance imaging, single-shot photoemission tomography, and positional emission tomography.

When considering the functional asymmetry of the legs, we get: the legs are not exactly equal in size and length. The left leg is “relatively more often larger than the right,” but the relative number of people with a predominance of the left leg over the right is less than with a predominance of the right arm over the left - 50-60%. “And the leg is not so conspicuous on the upper limbs division of labor”; and “equal-legged” should be more frequent than “equal-armed” (Brandt A.U., 1927). The fact that the legs are unequal in strength depends on the lifestyle. The leading leg is considered more maneuverable.

Most people are characterized by a combination of right-handedness with the left leading leg (Zhedenev V.N., 1962), although the opinion was also expressed about the more frequent dominance of the arm and leg of one side (Annet M., 1972).

According to Bragina N.N. and Dobrokhotova T.A. (1988), sensory asymmetry is a set of signs of functional inequality of the right and left parts of the sensory organs.

Studies of functional asymmetry of vision have shown that 90% of information is perceived through the eyes (Lindgren N., 1962; Bragina N.N. and Dobrokhotova T.A., 1988). IN binocular vision according to G.A. Litinsky (1929), the visual impressions of each eye do not have the same strength and quality, “the impressionability of one of the eyes outweighs and this prevalence is more often on the right eye.” In addition, differences in visual acuity and color perception were identified (Ivanov V.V., 1978). The aiming ability and localization of an object in space are also different, most often the right eye predominates. The fields of view are also different (Bragina N.N., Dobrokhotova T.A., 1988).

When studying the characteristics of functional hearing asymmetry, differences in hearing acuity were established: better sensitivity of the left ear (Valière-Monaud M., Roth G., Ribo J., 1978; Neimark M.T., 1954).

The combination of dominance of certain motor and sensory asymmetries constitutes the profile of lateral organization (Bragina N.N., Dobrokhotova T.A., 1988). In the practical part of this work, all of the above listed sensory and motor asymmetries were identified in the subjects, and thereby the profile of lateral organization characteristic of each group was identified.

Gender differences were also discovered when considering data obtained from a study of functional asymmetry of the brain in men and women (Springer S., Deitch G., 1983). According to Springer S. and Deutsch G., women outperform men in a wide range of skills requiring the use of language, and men outperform women in solving problems that are spatial in nature. Women's language and spatial abilities are more bilateral than men's.

Thus, having analyzed the works devoted to the problem of functional asymmetry of the brain, all the features of the cerebral hemispheres can be summarized in the table:

Summarizing the analysis of the literature on functional interhemispheric asymmetry, we see that functional interhemispheric asymmetry can be represented in the form of two main paradigms: lateralization of mental functions (memory, emotions, speech, thinking) and lateralization of the method of information processing ( Auriol B., 1985; Plotnikov V.V., Vyazovan V., 1986; Rotenberg V.T., 1937; Moskovichiute L.I., Golod V.I., 1989). And the interaction of the hemispheres is cyclical: the dominance of one is replaced by the dominance of the other. The cycle can be repeated many times, which ensures the gradual inclusion of qualitatively different strategies of the hemispheres in processing incoming information. Due to the combination of motor and sensory asymmetries, different profiles of lateral organization can be determined.

N. Defois

P.S. This article, revised and edited, was included in the book: Natalya Defois "The influence of meditative training on the level and channels of empathy"

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Interhemispheric asymmetry

1. The concept of interhemispheric asymmetry

Interhemispheric asymmetry(other gr b- - “without” and uhmmefsib- “proportionality”) is one of the fundamental patterns of organization of the brain not only of humans, but also of animals. Manifests itself not only in brain morphology, but also in interhemispheric asymmetry mental processes.

As part of the ongoing research, the main attention is paid to the connection between hemispheric asymmetry and mental cognitive processes and the influence of lesions of individual structures and areas of the brain on the course of these processes.

Two types of thinking are associated with the functions of the left and right hemispheres in humans - abstract-logical and spatial-figurative. These types of thinking have a number of synonyms.

According to V. Rotenberg:

· Verbal and non-verbal (since abstract-logical thinking of the left hemisphere, unlike imaginative thinking the right hemisphere is based on the ability to produce speech);

· Analytical and synthetic (since using logical thinking in the left hemisphere the analysis of objects and phenomena is carried out, while imaginative thinking in the right hemisphere ensures the integrity of perception);

· Discrete and simultaneous (since with the help of logical thinking the left hemisphere carries out a number of sequential operations, while with the help of imaginative thinking the right hemisphere acquires the ability to simultaneously perceive and evaluate an object).

The right hemisphere, which creates specific spatial-imagery context, has been shown to be critical for creativity. Thus, with organic damage to the left hemisphere of the brain in artists and musicians, their artistic abilities practically do not suffer, and sometimes the level of aesthetic expressiveness of creativity increases, but damage to the right hemisphere can lead to a complete loss of the ability to create.

At the same time, the issues of the relationship between the leading hand and the leading speech hemisphere, the connection of interhemispheric asymmetry with the emotional sphere and such mental cognitive processes as memory and imagination still remain unclear.

Interhemispheric asymmetry of mental processes - functional specialization of the cerebral hemispheres: when performing some mental functions, the left hemisphere is dominant, while others - right. More than a century of history of anatomical, morphofunctional, biochemical, neurophysiological and psychophysiological studies of asymmetry cerebral hemispheres the human brain indicates the existence of a special principle for the construction and implementation of such important brain functions as perception, attention, memory, thinking and speech.

It is currently believed that the left hemisphere in right-handed people plays a predominant role in expressive and impressive speech, reading, writing, verbal memory and verbal thinking. The right hemisphere acts as the leading hemisphere for non-speech, for example, musical ear, visual-spatial orientation, non-verbal memory, criticality. The mechanisms of the abstract are concentrated in the left hemisphere, and in the right - specific figurative thinking. It has also been shown that the left hemisphere to a greater extent is focused on predicting future states, and the right - to interact with experience and with current events. In the process of individual development, the severity of interhemispheric asymmetry changes - lateritization of brain functions occurs.

Recent studies indicate that interhemispheric asymmetry makes a significant contribution to the manifestation of high human intelligence. Moreover, within certain limits, there is interchangeability of the cerebral hemispheres. It is important to note that a specific type of hemispheric response is not formed at birth. In the early stages of ontogenesis, most children exhibit a figurative, right-hemispheric type of response, and only at a certain age (usually from 10 to 14 years) does one or another phenotype, predominantly characteristic of a given population, become established (Arshavsky V.). This is also confirmed by the data that illiterate people have less functional asymmetry of the brain than literate people.

The asymmetry also intensifies during the learning process: the left hemisphere specializes in symbolic operations, and the right hemisphere in figurative ones.

2. Brief history studying the problem

asymmetry interhemispheric split brain

· In 1836, the doctor Mark made a presentation at a meeting of the medical society. He found signs of damage to the left hemisphere in patients with speech loss. He was unable to identify any cases of speech loss due to damage to the right hemisphere.

· 1844: A. Vagan attracted public attention by writing “A Treatise on the Duality of the Brain.” He considered man to be a dual being. “Discordance in the work of the two hemispheres leads to insanity” (at that time, each hemisphere was considered a separate brain; the idea of asymmetry had not yet arisen).

· In the middle of the 19th century, there was a rapid development of aphasiology (the science of speech disorders). Franz Gall's idea: different functions are controlled by different areas of the brain. George Boillot associated left-hemisphere aphasia with right-handedness in most people.

· 1861: Auburtin repeated Gall's assertion that the center controlling speech was located in the frontal lobes of the brain. A few months later, Paul Broca formed a rule linking left-handedness with the representation of speech in the right hemisphere. Ten years after Broca's observations, the concept known today as the concept of hemispheric dominance had become the main point of view on interhemispheric relationships. In the same year, Paul Broca examined a patient with severe speech impairment - the patient understood, but did not say anything. The observed left hemisphere was destroyed, frontal lobe responsible for speech - motor aphasia. Brock believed he had discovered the speech center.

· 1869: J. Jackson formulated the idea of the leading hemisphere “For the most important and the most important processes there must be one leading party”...

· 1874: German psychiatrist Carl Wernicke was the first to document another type of aphasia - sensory aphasia. This was the opposite of Broca's case: the patient could speak, but did not understand anything.

3. Modern ideas about interhemispheric asymmetry

Currently, the problem of interhemispheric asymmetry of the brain is studied primarily as a problem of the functional specificity of the hemispheres, that is, as a problem of the specificity of the contribution that each hemisphere makes to any mental function. These ideas are based on the neuropsychological theory of the brain organization of higher mental functions, formulated by Luria A.R. (1969, 1973, etc.)

Thus, interhemispheric asymmetry is not global, but partial in nature: the right and left hemispheres take different in nature and unequal in importance participation in the implementation of mental functions. It is also important to note that in different systems the nature of functional asymmetry may be different.

The results of studies by various authors indicate that there are anatomical differences between the right and left hemispheres of the brain (Khomskaya U.D., 2005).

4. Explanations of the causes

Evolutionary theory asymmetry

A unified theory explaining from an evolutionary point of view many aspects of interhemispheric functional asymmetry in animals and humans was proposed by V.A. Geodakyan in 1993. According to the theory, lateral asymmetry arises as a result of the asynchronous evolution of the cerebral hemispheres and the sides of the body controlled by them.

Explanation from an ethological point of view

Ethology considers the emergence and development of interhemispheric asymmetry to be a consequence of natural selection: it was found in dolphins and birds (from parrots to canaries), and it is very likely that its occurrence was associated with speech activity and group interaction. But, as V. Dolnik notes, it was not possible to draw the “border between mind and non-mind” based on the asymmetry of the hemispheres.

5. The main functions of the hemispheres and the connection between them

Logistics and pattern recognition

The ability to speak, analyze, detail, and abstract is provided by the left hemisphere of the brain. It works sequentially, building chains, algorithms, operating with a fact, detail, symbol, sign, and is responsible for the abstract-logical component in thinking.

The right hemisphere is able to perceive information as a whole, work through many channels at once and, in conditions of lack of information, reconstruct the whole from its parts. It is customary to correlate with the work of the right hemisphere creative possibilities, intuition, ethics, ability to adapt. The right hemisphere provides the perception of reality in all its diversity and complexity, in general with all its constituent elements. Thus, the logic of the left hemisphere without the right one will be flawed.

Color recognition

A number of studies have shown that there are differences in the functions of the cerebral hemispheres in color perception: the cerebral hemispheres are asymmetrical in the perception and designation of colors.

The right one provides verbal coding of primary colors using simple high-frequency names (blue, red). Characteristics here are minimal latent periods of names and exact correspondence of names to the physical characteristics of primary colors. In general, the right hemisphere is responsible for the formation of rigid connections between an object and a color, a color and a word, a word and a complex color image objective world.

The left hemisphere provides verbal coding of colors using relatively rare in language, special and subject-related names. When the left hemisphere is depressed, color names such as orange, terracotta, cherry, etc. disappear from the lexicon. sea wave etc.

Organization of speech

Each hemisphere forms its own principles of speech organization:

1. The right forms the integrity of the semantic content, provides empirical and figurative (metaphorical) thinking, creates associations based on visual and sensory ideas about the subject; the left hemisphere provides theoretical thinking, grammatical formulation of statements and characterization of the properties of objects;

2. The formation of the structure of a person’s lexicon occurs through the summation of different layers of vocabulary: the right hemisphere is based on a figurative representation of the objective world, the left hemisphere is based on precise, literally perceived designations, “words-concepts”.

90% of the adult population has localization of speech functions in the left hemisphere, more than 95% of right-handers and about 70% of left-handers have localization of speech in the left hemisphere. People whose language functions are concentrated in the right hemisphere retain phonemic and semantic abilities, but have deficits in syntactic abilities.

People with damage to the right hemisphere have greater difficulty grasping meaning from the context of a phrase, understanding metaphors or humor, following the meaning of a perceived conversation, etc. The right hemisphere is associated with the semantic characteristics of speech.

6. Syndromesplitbrain"

Since interhemispheric interaction serves as the basis for the implementation of higher mental functions, disruption of this interaction in adults can lead to the formation of the “split brain” syndrome.

This syndrome manifests itself in disturbances of sensory, speech, motor and constructive-spatial functions. Violations that occurred in early age, can be partially compensated.

7. The connection between brain asymmetry and gender

Brain asymmetry is closely related to gender. Among children who are left-handed, who stutter, who are cross-eyed, who are dyslexic, who are neurotic, who suffer from urinary and fecal incontinence, there are about five boys for every girl. It is known that there is a certain relationship between these phenomena, and they are all closely related to brain asymmetry. For example, when forcibly retraining left-handed children to write right hand they often develop the listed anomalies, mental retardation, psychosis, and speech defects. Ideas about sex differences in brain function are based primarily on the results of clinical and behavioral studies. When the left hemisphere is damaged as a result of hemorrhage, tumor, or surgical removal of part of the temporal lobe for epilepsy, the deficit in verbal functions in men is much greater than in women. Similar damage to the right hemisphere also leads to greater deficits in nonverbal functions in men compared to women. Aphasia due to damage to the left hemisphere occurs in men three times more often than in women, and is more severe. Therefore, it was concluded that women's language and spatial abilities are represented more symmetrically than men's.

Psychological sexual dimorphism - different abilities and inclinations of men and women, different professional suitability and preferences, different learning ability and intelligence - can be associated with both sex differences in the lateralization of the brain and with social factors. For example, in terms of verbal abilities: speech in general, speed and fluency of speech, spelling, reading skills, short-term memory, conformity of thinking in all age groups higher levels in women. Women have a much better developed sense of smell and less atrophy with age. Men have more developed spatial-visual abilities. In men, much more often than in women, an advantage is also found for the right ear during dichotic listening and the left hand for right-handed people during tactile recognition of objects using the digaptic method. Sexual dimorphism was discovered in the ratio of the lengths of the left and right temporal planes. Sex differences have been noted in anatomical, clinical, dichotic, tachistoscopic, electrophysiological and psychological studies of the hemispheres.

Currently, the vast majority of authors support the view that brain asymmetry is more clearly expressed in men. For example, Levy believes that the female brain is similar to the brain of a left-handed man, that is, it is characterized by reduced hemispheric asymmetry. In a large critical review specifically examining sex differences in brain asymmetry, McGlone concluded that “there is an impressive body of evidence to suggest that the male brain may be more asymmetrically organized than the female brain in both verbal and nonverbal functioning.” . These tendencies are rarely observed in childhood, but are often significant in adulthood.” Witelson studied tactile recognition of objects with the left and right hands in 200 right-handed children and came to the conclusion that boys already have a right-hemisphere specialization at the age of six, and girls show bilateral representation until the age of 13. This and a number of other studies allow us to conclude that brain asymmetry increases during ontogenesis. The debate is mainly about the age of completion of lateralization. Some believe that it ends during puberty, when the ability, being in an appropriate environment, to master a new language and speak it without an accent is lost. Others say that this happens around the age of five, and still others believe that asymmetry begins even earlier, and that the brain of a newborn is no different in the degree of asymmetry from the brain of an adult. The last point of view can be discarded, since it is impossible to talk about asymmetry of the brain function of a newborn when there are no functions themselves, but only their rudiments.

Sex differences in brain asymmetry. Hypotheses

Several hypotheses have been proposed to explain sex differences. Weiber suggested that they are associated not with gender, as such, but with different rates of development of men and women. This interpretation can explain best case scenario, sexual dimorphism in children and adolescents, but not in adults. Levy suggested that social factors underlie sex differences: men hunted and led migrations, which led to better development of their spatial abilities, and women's verbal superiority was due to the fact that they raised children, which requires verbal communication.

Existing interpretations associate sexual dimorphism in brain asymmetry mainly with purely human or social factors. However, more and more evidence is accumulating indicating that not only brain asymmetry, but also sexual dimorphism in it, is common among animals. For example, there are reports of a greater degree of brain asymmetry in males compared to females in rats, cats, and cetaceans.

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