Functional interhemispheric asymmetry. See what “Interhemispheric asymmetry” is in other dictionaries.

It is known that the left and right hemispheres of a person have different functions, which, however, are complementary. Asymmetry is a phenomenon that is inherent in the brain not only of humans, but also of animals. Moreover left hemisphere is not a mirror image of the right and vice versa. The hemisphere in which each individual has a speech center is dominant. In the vast majority of cases, this role is played by the verbal-logical left hemisphere.

Connections between hemispheres

There are a few interesting facts about the connections that exist between the two halves of the brain. Firstly, it is always a little larger in size than the right one. Secondly, in the right hemisphere there are long nerve fibers that connect it to the left. The left one, on the contrary, contains a large number of short fibers that create connections in limited areas.
Brain asymmetry is a process that takes an average of ten to fifteen years to develop. Sometimes its speed can be determined by genetic characteristics. It is practically not observed in infants. Asymmetry is an acquired quality. In addition, it has been proven that it is less pronounced in illiterate people. That is, in the process of learning and acquiring new knowledge, the brain becomes more and more asymmetrical. Those who do not pay due attention to education slow down the development of many important functions.

Discovery of asymmetry

Asymmetry is a feature that has always interested scientists. But until a certain point, it remained a mysterious object that could only cause a lot of speculation even among the brightest minds of humanity. The history of the development of this area began with the discovery by Paul Broca of the relationship between human speech and the use of the right or left hand. This happened in 1861, when the scientist discovered that his patient, who suffered from loss of speech, had a lesion in the left

Also, the connection between the two parts is carried out using a special bundle of neurons - the corpus callosum. Thanks to him, they work harmoniously as a single whole. Some seriously ill patients underwent surgery to dissect the corpus callosum. This made it possible to study in more detail the characteristics of the right and left hemispheres.

Split-brain experiments

Functional asymmetry manifests itself in a completely paradoxical way. For example, it turned out that the left hemisphere is responsible for building logical connections and mathematical calculations. It “understands” any complex speech well. on the contrary, it can recognize only the most general connections. When presented with the most ordinary objects - a spoon or a ball of thread - it can assign them to a certain class. The advantage of the right hemisphere is excellent orientation in space. An experiment was carried out: patients with a split brain for medical reasons were asked to assemble a structure according to a drawing with their right hand. At the same time, they made many mistakes. This was due to the fact that the left hemisphere is responsible for right side bodies.

Sperry's experiments

Split-brain studies have also shown that people with damage to the right hemisphere have very poor spatial orientation. Often such patients cannot find their way to the house in which they previously lived for decades.
R. Sperry proved that during dissection the following happens: processes in the two hemispheres of the brain begin to occur independently. It's like two people acting independently of each other different people. According to many scientists, asymmetry is a phenomenon that man acquired during evolution and is its acquisition.

Agnosia in brain damage

Brain asymmetry actually manifests itself most clearly when one of the hemispheres is damaged. For example, injuries to the right hemisphere can lead to various types of so-called agnosia. With this disorder, a person is unable to perceive previously familiar information. For example, there is known face agnosia, in which the patient does not recognize the faces of familiar people. And this despite the fact that memory for other objects in the surrounding world and situation remains absolutely intact.

Two types of thinking

So, asymmetry of the brain involves the division of mental functions into two large spheres - spatial-imaginative thinking and abstract-logical thinking. There are many synonyms for these concepts. For example, the definitions of verbal and nonverbal thinking, as well as discrete and simultaneous, are similar. The right hemisphere is responsible for simultaneous thinking, since it perceives an object in the entirety of its properties. The totality of perception is inaccessible to the logically oriented left hemisphere. It analyzes and studies each object separately.

Analysis and synthesis functions

Brain asymmetry is responsible for the distribution of functions between the two hemispheres. The left hemisphere is responsible for analytical information processing. He is characterized by thinking of the “from particular to general” type, that is, induction. It processes the entire flow of information from the outside world according to a logical principle. The right hemisphere is responsible for such synthesis. In this case, the parts of the perceived object are combined into a whole. Thinking is carried out according to the deductive principle - from the general to the specific. The right hemisphere is responsible for metaphorical, figurative thinking.

Interhemispheric asymmetry: other differences

Perception of current events in chronological order- This is a function of the left hemisphere. For the right, on the contrary, all events seem to occur simultaneously. It is not oriented in time: for it there is only “here and now.”
The left hemisphere is focused on reading patterns, such as information on geographical maps. The right one, on the contrary, is oriented in a specific space, for example, indoors.

There is also a difference between the distribution of emotion control function in the cerebral hemispheres. The left hemisphere is responsible for positive experiences, the right, on the contrary, for negative ones.

Asymmetry in nature

It should be noted that the phenomenon under consideration is characteristic of many natural objects. Interhemispheric asymmetry is not only the prerogative of humans. If symmetry is represented in the structure of molecules and crystals, then asymmetry is in the arrangement of internal organs, the structure of the DNA helix. There is also hair asymmetry.

Research in this area leaves many mysteries. But the progress of science does not stand still. Perhaps the knowledge that now seems obvious will become completely outdated for future scientists. Perhaps scientists of the future will be able to finally unravel all the secrets of the highest product of evolution - the human brain.

Interhemispheric interaction

Interhemispheric asymmetry and interhemispheric interaction- fundamental principles of the functioning of the brain as a paired organ. M. a. is a special case of M. v. At the present stage of studying the work of the brain as a paired organ, the patterns of M. a. have been studied to a greater extent.

Interhemispheric asymmetry- one of the fundamental patterns of brain organization not only in humans, but also in animals. It manifests itself not only in the morphology of the brain, but also in the interhemispheric asymmetry of 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.

Right-hemisphere thinking, which creates a 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 even 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.

The concept of interhemispheric asymmetry

Interhemispheric asymmetry of mental processes is the functional specialization of the cerebral hemispheres: when performing some mental functions, the left hemisphere is dominant, while others are the 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 the mechanisms of the concrete are concentrated in the right hemisphere. imaginative thinking. It was also shown that the left hemisphere is more focused on predicting future states, and the right hemisphere is more focused on interacting with experience and current events.

In the process of individual development, the severity of interhemispheric asymmetry changes - lateralization 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-hemisphere 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 sign operations, and right hemisphere- in figurative.

The brain has two hemispheres, however, this is not a simple duplication of functions, such as in the kidneys or lungs. It turned out that the hemispheres, while performing the same functions - receiving information, processing it and sending commands to the periphery - do it differently. This phenomenon is called functional interhemispheric asymmetry. Studying functional asymmetry cerebral hemispheres began in the mid-19th century on patients with focal brain lesions caused by hemorrhages and traumatic brain injuries. It was found that damage to the left hemisphere cortex in 85% of cases leads to speech impairment, which was first established by Broca; damage to the right hemisphere did not lead to speech impairment. Further studies were carried out on patients who underwent split-brain splitting for health reasons. Such patients could be presented with verbal stimuli (words, formulas) or pictures in the right or left hemisphere. It is clear that there are few such patients, so methods have been developed that make it possible to study the characteristics of the functioning of the hemispheres on the whole brain. The experiments used, for example, unihemispheric anesthesia, which allows one to temporarily turn off one of the hemispheres or present a visual stimulus on the right or left. This allows information to be sent to the right or left hemisphere. The fact is that part of the optic nerve fibers coming from the outer segment of the retina does not cross and remains in its hemisphere, while the other part of the fibers coming from the inner segment goes to the opposite hemisphere (figure). The use of such methods allowed researchers to demonstrate significant differences in the functioning of the hemispheres.

Figure 12Possibility of directing visual stimulus

to the right or left hemisphere of the brain.

It was found that the left hemisphere is involved mainly in analytical processes, it is the basis for logical thinking. The left hemisphere provides speech activity: understanding speech, its construction, working with verbal symbols. Processing of input signals is provided in the left hemisphere sequentially. That's why the left hemisphere is called abstract-logical.

The right hemisphere provides concrete-figurative thinking, distinguishes its non-verbal component (intonation, timbre, volume, emotional coloring of the voice) from the entire flow of speech information. Information entering the right hemisphere is processed simultaneously and holistically. That's why the right hemisphere is called concretely sensual.

Characteristics of the hemispheres

A classification of functional asymmetries is proposed in accordance with the sensory and motor functions of the hemispheres.

Asymmetry of motor activity of the arms, legs, face, right and left half of the body is designated as motor asymmetry.

For example, in right-handed people, the left hand is more resilient than the right to static force; the muscles on the left side of the face are stronger than the right, as a result the left side of the face appears more masculine. Previously it was assumed that the basis of motor asymmetry was the anatomical asymmetry of the motor areas of the cerebral cortex, but now this statement is refuted. The development of motor asymmetry is determined by the activity of the periphery in the early periods of ontogenesis, which leads to microstructural changes at the level of the cerebral cortex. Motor asymmetry appears and increases in childhood, reaches its maximum development in adulthood, and is leveled out in late age. If you begin to retrain a left-handed person in early childhood, then he will be left with a characteristic sensory and mental asymmetry that is different from right-handed people. Motor asymmetry is unstable and can change during the adaptation period.

Asymmetry in the perception of objects is designated as sensory asymmetry.

Sensory asymmetry is a clearer and more constant characteristic of the activity of central systems. This type of asymmetry is preserved and reinforced throughout life. There are asymmetries in the organs of vision, hearing, taste, smell and touch. Information perceived by sensory systems enters the right and left hemispheres, and the dominant one faster, and its processing and storage occurs in the hemisphere adapted to this type of information. In experiments studying the asymmetry of touch, it was found that the pain threshold is higher on the dominant hand, and temperature sensitivity is higher on the non-dominant hand. Tactile asymmetry was detected.

The most pronounced asymmetry in the functioning of the organs of vision and hearing. It is known that the dominant eye is the first to catch an object, so its accommodation occurs faster. The object is perceived by the dominant eye as larger and more contrasting. However, auditory asymmetry is considered a more stable type of sensory asymmetry, since visual asymmetry is leveled out after 30-35 years, and auditory asymmetry after 40-50 years of life.

Distribution of higher nerve functions between the hemispheres (thinking, consciousness, emotions, perception of space and time, speech) – determined like mental asymmetry. It is known that the right hemisphere takes part in the formation of negative emotions: the state of negative emotional stress is manifested by activation of the parietal-temporal region of the right hemisphere.

Physiology studies primarily sensory and motor asymmetries, so determining a personality profile in order to assess the predominance of activity in the right or left hemisphere actually means determining sensorimotor functional asymmetry. It should immediately be noted that sensory and motor asymmetries do not necessarily coincide. A person may have a right-hemisphere or mixed sensory profile and a left-hemisphere motor profile. Nevertheless, we will try to give a general description of people with a predominance of right-hemisphere or left-hemisphere functions. For the first time such a description was given by I.P. Pavlov, who identified exclusively human types based on the predominance of the first or second (speech) signaling systems. If Pavlov’s ingenious research is still weakly confirmed by types of VND; direct correlations between the electrophysiological characteristics of neurons and behavior have not been found (these correlations, most likely, will not be found, because behavior is a complex interaction of all structures of the central nervous system), then his prediction is the selection artists and thinkers found brilliant confirmation in the process of studying functional interhemispheric asymmetry.

"Thinking" type according to I.P. classification Pavlova, with a predominance of the second signaling system.

1. Has a large vocabulary and actively uses it.

2. It is characterized by motor activity.

3. He gravitates toward theory and knows how to predict events.

"Art" type with predominance of the first signaling system

1. Taciturn.

2. Slow

3. Prefers specific types of activities.

4. Able to subtly feel and experience.

5. Prone to contemplation.

According to modern ideas, a person with a predominance of left-hemisphere functions gravitates towards theory, has a large vocabulary and actively uses it, he is characterized by motor activity, determination, and the ability to predict events. “Right-brained” - gravitates towards specific types of activity, is slow, taciturn, but endowed with the ability to subtly feel and experience, prone to contemplation and memories.

A study of functional brain asymmetry in children showed that the initial processing of speech signals is carried out by both hemispheres and the dominance of the left is formed later. If a child who has learned to speak develops damage to the speech zone of the left hemisphere. then he develops aphasia. After about a year, speech is restored, with the speech center moving to the right hemisphere. Such a transfer of functions from the left hemisphere to the right is possible only up to 10 years.

There are fundamentally different points of view on the causes of interhemispheric asymmetry. Adherents of the first believe that interhemispheric asymmetry is characteristic exclusively of humans, and it is based on the movements of the leading hand and the development of speech. The second point of view is based on the experimentally proven existence of interhemispheric asymmetry in animals. Therefore, interhemispheric asymmetry is considered as a general property of the brain. The emergence of the speech center in the left hemisphere is initially associated with its ability to function analytically and evaluate the external world not as a general picture, but in separate fragments. Such a fragment can be a sound and a word. Evidence in favor of this point of view is the presence of asymmetry between the right and left parts of the hypothalamus and medulla oblongata. Let us give just one example indicating that interhemispheric asymmetry is genetic and not related to education.

Scientists at the Japanese National Center for Neuroscience and Psychiatry conducted a magnetic resonance imaging study of the activity of areas of the brain involved in the perception of music. During the experiment, 28 people, including professional musicians, listened to a recording of Bach's Italian Concerto. In all participants, the devices noted excitation of areas of the brain located in the temporal lobe, above the ear canal. But among musicians, activity was noted in the left temporal lobe (yellow area in the figure), and among ordinary listeners, activity was observed in the right. Magnetic resonance scanning has unmistakably separated the professionals from the amateurs.

It has long been established that the left temporal lobe contains the speech center of the brain, which is responsible for verbal behavior. New research shows that in professional musicians, the music processing area overlaps, at least in part, with the language area of ​​the brain. This may mean that for such a person any melody sounds like a “speech”, consisting of significant elements and having its own meaning. Analytical perception distinguishes musicians from mere mortals who perceive music on an emotional level. A professional, therefore, cannot “just listen” to music and “enjoy the sounds,” just as an ordinary person cannot “just read” a book and “enjoy the letters.” So “the language of music”, “musical text” are not metaphors, but unmistakable terms that reflect the specific thinking of musicians and composers.

Very little is still known about the reasons that led to interhemispheric asymmetry and hemispheric specialization. Anatomical differences have been found, but they are so insignificant that they cannot explain the huge difference in the methods of processing information by the right and left hemispheres. Perhaps, today the only convincing basis for interhemispheric asymmetry is the asymmetry in the distribution of mediators and biologically active substances found in animals.

For example, in the left globus pallidus and basal ganglia, more serotonin is produced than in the right ones, and more dopamine is produced in the right amygdala and left striatum than in the opposite structures of the same name. Substances that are characterized by a central activating effect are also distributed asymmetrically in the brain. In rats, there may be more norepinephrine in the amygdala and substantia nigra in the right or left hemisphere, which manifests itself in the individual characteristics of the animals’ behavior. Dopamine in rats is produced significantly more in the left hemisphere, and there are more D-receptors in the same hemisphere. Already in turtles, animals very low in the evolutionary series, an asymmetry in the distribution of opiate receptors has been discovered.

No relationship was found between the level of abilities in general, it does not matter mental or artistic and right or left hemisphere. It has been established that the asymmetry profile determines only the area of ​​interest. Success in any activity, as it turns out, is determined by the speed with which the hemispheres exchange information.

Each person has their own unique palette of feelings and emotions. This determines his individuality and sets him apart from other individuals. From a scientific point of view, asymmetry, which characterizes the distribution of mental acts of activity in the hemispheres, is responsible for such mental originality.

The first assumptions about the different functions of the left and right hemispheres of the brain belong to the twentieth century. Scientists began to conduct experimental experiments on the human brain in order to determine the functional identity of each hemisphere.

Functional asymmetry of the hemispheres, according to most scientists, is an evolutionary breakthrough that indicates a high level of development of the human mind. Functional asymmetry is based on genetic roots, that is, it is prone to hereditary transmission to descendants.

It is formed in close relationship with society, during the social formation of the individual. The dominant hemisphere is considered to be the one whose side is responsible for speech function. According to this theory, the overwhelming number of people have a dominant in the form of the left hemisphere - they are right-handed. Left-handers, accordingly, have the opposite picture, which is reflected in their thinking strategy.

Depending on the dominant hemisphere, all people can be divided into three large categories:

• Left hemisphere about 40 - 42% of the total population
• Right hemisphere from 10 to 20%
• Equihemispheric, having equal development of both hemispheres, about 40%

Right-hemisphere people, also known as left-handers, have always aroused public interest due to their uniqueness. Some peoples preferred to beware of left-handers, putting a negative meaning into this word. In fact, there is no pathology in being left-handed. This does not cause psychological abnormalities, but is individual feature personality.

According to statistics, left-handers more often become writers, journalists, artists, organizers, and left-hemisphere people, otherwise right-handers, become engineers, mathematicians, philosophers, and linguists.

The easiest way to assess the characteristics of brain asymmetry is to compare the development of the right and left hands. People who predominantly use their right hand when writing are right-handed and, accordingly, belong to the left-hemisphere type. Lefties are exactly the opposite. In addition, there are a number of tests that help determine belonging to the type of dominant hemisphere.

One such method is the “Napoleon Pose” or the arm crossing test. People whose right hand is on top of their left forearm when crossing their arms are defined as right-handed, that is, left-hemisphere, otherwise - left-handed, that is, right-hemisphere.

Distribution of functions in the cerebral hemispheres

Each of the hemispheres of the brain has its own direction of functioning, creating, when acting together, a unique and inimitable combination of personality. The predominance of one hemisphere in the functioning of the brain leads to increased personal qualities in one direction or another. Right-hemisphere people are characterized by contemplation, subtle sensitivity and a desire to delve into the jungle of memories.

A person with a predominance of the right hemisphere is often slow and taciturn. And left-hemisphere people show a tendency towards analytical thinking and “iron logic”, they are easily given theoretical knowledge, they have considerable vocabulary, one can often say about such people “they won’t put their words in their pocket.” They are active and purposeful.

The main features that belong to each hemisphere are:

Both hemispheres are connected in their action, providing the personality with a holistic set of qualities, but each of them brings its own bit of uniqueness.

At the beginning of development, in the first years of life, the right hemisphere big brain dominates over the left in functional terms, and the left catches up with it in the second year of life; over time, the hemispheres alternately overtake each other in development. The right and left hemispheres are united by the corpus callosum, which serves as a bridge between them and reaches its final development at the age of 25; in women it is usually larger.

The concept of symmetry in the human body as such is absent. The asymmetry of the hemispheres is closely related to the symmetry of the human face. People's faces are not symmetrical, this is a normal physiological condition. There is a relationship between hemisphere and facial asymmetry.

In left-hemisphere or right-handed people, the nose is most often deviated to the right side, and in right-hemisphere or left-handed people - to the right. left side faces. Raising one eyebrow often belongs to the narrow half of the face, and a crooked smile belongs to the wider half.

Thanks to the asymmetry of the brain, the coordinated work of brain structures is carried out by distributing the functional load between the two hemispheres, combining information and controlling each of the hemispheres over its inherent processes. Due to the fact that each of the brain functions is distributed in relation to both hemispheres, clinical damage to the right or left hemisphere will vary.

This allows us to identify functional asymmetry of the brain as a diagnostic basis for identifying many neurological diseases. Only the unity of the work of both hemispheres, their asymmetrical function, makes it possible to guarantee perfect human life.

IN last years the development of higher mental functions of a person is associated with the level of interhemispheric asymmetry (lateralization) of the brain. According to psychologists, brain lateralization is one of the conditions for normal development, for example, the ability to read or develop articulate speech.

The absence of lateralization is observed in cases of various anomalies in mental development, in particular in schizophrenia, Down's disease, etc.

The most obvious external manifestation of interhemispheric asymmetry is the dominance of a certain hand in the implementation of motor acts - the so-called “right-handedness” and “left-handedness”. However, asymmetry is also manifested in the dominance of not only the hands (“leading hand”), but also the legs, eyes, and ears (respectively, “leading”)*

It has been experimentally shown that in right-handed people the left hemisphere is dominant, while in many left-handed people the right hemisphere is dominant.

Research has shown that these external manifestations of asymmetry often reflect deep natural features of the mechanisms of the human psyche and behavior. They include the specifics of inclinations, temperament, motor activity, extra-introversion, emotionality, methods of self-expression, etc. In this regard, left-handed people are of particular interest.

About left-sided asymmetry

Lefties make up a significant percentage of the population in many countries. According to 1988 data, 25 million Americans are left-handed. In Brazil they make up 10% of the total population. There is now a trend towards an increase in the number of left-handers in the human population. In this regard, initiatives are increasingly emerging to create a subculture for left-handed people, which would make their life easier in the “right-wing” world.

As an analysis of specialized literature shows, there are three points of view when assessing the psychophysical characteristics of left-handed and right-handed individuals. According to one of them, left-handers have lower rates of mental development. The word "right" has an Anglo-Saxon source, meaning "correct", "honest", - "straight"; the word “left” means evil, “dishonest”, “deceitful”.

Marked negative qualities Left-handers: lower level of intelligence, lack of confidence, less ability to learn, greater propensity for drugs and crime.

According to the second point of view, left-handers do not differ from right-handers in the main indicators of higher mental functions. Studies conducted on large samples have shown the absence of any significant differences in academic performance between left-handed and right-handed schoolchildren. However, the arguments are questioned on the grounds that they were carried out under normal conditions, and the specificity of left-handers, according to other sources, manifests itself mainly in unusual situations, for example, in stressful ones.

There is a third point of view: left-handers have higher rates of mental development than right-handers. For example, in Japan, left-handers are especially respected as more skilled craftsmen. Everyone knows the left-handed man from Leskov’s story of the same name, who “shod the flea.” Left-handers are better at solving numerical problems; their special achievements in sports are known: they are the best boxers, fencers, etc. The third point of view is supported by the fact that many talented and brilliant people were left-handed: Michelangelo, Leonardo da Vinci, Joan of Arc, Charlie Chaplin, Maxwell, K . Bakh, I.P. Pavlov, Lewis Carroll and many other outstanding personalities.

What are the characteristics of the mental properties of left-handers? What are the structural features of their brain? How did these features develop during evolution and how do they develop during ontogeny in humans? What is the role of heredity and environment in the formation of interhemispheric asymmetry? These issues will be discussed in subsequent sections.

About the structure of the brain of “right-handers” and “left-handers”

The discovery of morphofunctional asymmetry of the brain itself was made in the clinic. In 1960, the French neurologist P. Broca found that with hemorrhages in the area of ​​the inferior frontal gyrus, and in most patients - in the left hemisphere, the patient loses the ability to pronounce words. This is how the speech motor center (Broca's center) was discovered. Then Wernicke discovered the speech-hearing center in the superior temporal gyrus. Next, the speech-visual center and the writing center were opened. Studies have shown that there is a fairly clear correlation between right-handedness and the localization of the speech motor center in the left hemisphere.

The problem of “right-handedness” - “left-handedness” has long been studied by psychologists, but morphological studies aimed at exploring the structural and functional foundations of this phenomenon have practically begun only in recent years. This is explained by many reasons, in particular, the extremely high individual variability of the brain structure and the great methodological difficulties of studying interhemispheric asymmetry. Studying on sectional material is associated with limited information (or lack thereof) about the “leading” hand. Intravital studies require very complex and expensive equipment, and, in addition, the possibility of obtaining sufficiently representative samples is very limited.

Significant difficulties are also associated with establishing the morphofunctional correlations themselves in such areas as the human psyche.

Nevertheless, there is information in the literature about some features of the structure of the brain in left-handers and right-handers. Thus, it has been shown that in 70% of cases the length of the so-called planum temporale (part of Wernicke's area) is greater in the left hemisphere than in the right. It corresponds percentage"right-handed" in a random sample of people. It is known that the asymmetry of the dimensions of the temporal plane increases with age.

Studying asymmetry in a living person using angiography and computed axial tomography is of significant value. They make it possible to directly compare morphological asymmetry with functional asymmetry (for example, with data on the predominance of activity in one of the hands). These studies showed that the brains of right-handed people have greater anatomical asymmetry than left-handed people. Angiographic studies (the study of blood vessels) show that in most cases the middle cerebral artery, which runs along the Sylvian fissure, has a steeper rise in the right hemisphere and rises higher than in the left. The computer axial tomography method allows you to study brain structures in any section. Using this method, it was established that in “right-handers” the parietal and occipital lobes in the left hemisphere are wider than in “left-handers”. Their frontal lobe is wider in the right hemisphere. The depth of impressions on the inner surface of the skull (endocranes) corresponds to the same patterns.

According to the work of the Brain Institute, in individuals with musical and artistic abilities, the left hemisphere dominates in terms of pronounced apicalization (multiple branching of apical, i.e., apical dendrites) neurons of layer III, horizontal striation of layers IV and V, radiarity of layers VI and VII. The right hemisphere dominates in the number of ultra-small neurons in field 17. In 70-80% of the examined visual field 17 in the right hemisphere was dominant in the width of layers III and V.

Our data on the study of the vascular bed of specifically human cortical areas showed that in speech areas in 75% of cases the left hemisphere dominates in terms of volumetric vascular density.

By comprehensive characterization structural and quantitative characteristics of the hemisphere, including the inferior frontal gyrus, three variants of features and structure can be distinguished, quite clearly different from each other.

The majority (70-80%) of the studied brain specimens are characterized by: 1) left-sided dominance along the arc length of the hemisphere; 2) triangular gyrus of the most complex type with a left-sided dominant complexity; moreover, its apex rests directly on the Sylvian fissure, in which the middle cerebral artery is located; 3) the ascending and horizontal branches of the Sylvian fissure extend directly from it almost at right angles to each other; 4) interhemispheric asymmetry in the pattern of the sulci is clearly expressed.

The second group (6-8%) is characterized by: 1) right-sided dominance along the arc length of the hemisphere; 2) the triangular gyrus has an insufficiently complex structure (2nd or 3rd type of complexity), its apex does not reach the Sylvian fissure; 3) the ascending and horizontal branches form an acute angle and extend from a common stem extending from the Sylvian fissure; 4) interhemispheric asymmetry in the pattern of sulci is not pronounced.

The third group (22% of specimens) combines the characteristics of the first two.

Since the identified groups in their numerical ratio correspond to the data on the quantitative proportions of left-handed and right-handed people in a random sample of people, and also based on the fact that many of the studied criteria have a pronounced functional significance, we can compare these groups with phenotypes: the first group is “right-handed” ", the second - "left-handed", the third - ambidextrous (equal use of both hands).

The state of interhemispheric asymmetry in the process of ontogenesis

Signs of morphological asymmetry of the brain in the speech motor cortex appear very early. Differences between the right and left hemispheres are noticeable already in a 5-month-old fetus. Thus, according to our data, in the region of the inferior frontal gyrus, in most of the cases studied, the ascending branch of the Sylvian fissure first appears in the right hemisphere. During embryonic development, the right hemisphere is slightly ahead of the left. Thus, the insula in the right hemisphere is often more immersed than in the left. The arc lengths of the hemisphere as a whole and the frontal lobe in the right hemisphere are greater than in the left, etc.

Starting from 7 months of the fetal period and up to 2 years of life, according to many indicators, the right hemisphere turns out to be more “advanced” compared to the left. The age of 2-5 years is a turning point, and the left hemisphere becomes dominant.

A similar direction of asymmetry was also noted by employees of the Brain Institute of the Russian Academy of Medical Sciences (works by I.N. Bogolepova and co-workers) in relation to the structural-quantitative relationships of the cytoarchitectonics of fields 44 and 45. It was shown that in terms of the volume of structures, neuron density, width of the cortex, glioperineuronal index, etc. A newborn child has a right-sided asymmetry. Subsequently, the sign of the asymmetry changes, and the value of many indicators becomes greater in the left hemisphere.

The data presented correspond to the observations of psychologists about the early manifestation of functional asymmetry of the brain. It increases during human ontogenesis and decreases in old age.

One of the psychological hypotheses considers the brain of a child under two years old to be functionally split due to the immaturity of the corpus callosum. When manipulating objects in such a child, the formation of engrams occurs in each of the hemispheres, independently. Subsequently, due to the predominant use right hand, the dominant role passes to the left hemisphere.

After two years, the corpus callosum begins to function, and the dominance of the left hemisphere increases. The function of spatial analysis, which was initially localized bilaterally, is displaced to the right hemisphere. Until about four years of age, the right hemisphere “speaks language” as successfully as the left. It is possible that the separation of the hemispheres is very early age would lead to the fact that each hemisphere, separately and independently of the other, would be able to carry out high-order mental functions, similar to those that usually only the left hemisphere possesses in humans.

Our consistent study of the structure of the inferior frontal gyrus in different age periods of pre- and postnatal ontogenesis showed that the development of the left hemisphere, at least in the early stages, proceeds according to an independent program, in comparison with the right hemisphere. Thus, starting from the prenatal period, elements of the “structural features of the future” of the left hemisphere complex of “right-handers” appear in the left hemisphere: a clearly represented inferior frontal sulcus, separating the inferior frontal gyrus from the middle one: the ascending and horizontal branches of the Sylvian sulcus, first extending from the common trunk and dividing the inferior frontal gyrus into triangular, opercular and orbital. IN further development This complex goes in the direction of outstripping the growth rate of the triangular gyrus, which, as it were, “pushes apart” the opercular and orbital gyri, growing between them. Opercularization of the insula in this case occurs mainly due to the triangular gyrus. This gyrus itself takes the shape of an inverted dome with a blunt apex. The ascending and horizontal branches of the Sylvian fissure cover this dome from below, forming a kind of “bowl”.

The described complex is expressed in the inferior frontal gyrus of the left hemisphere in the majority (67-70%) of the studied specimens of the adult brain (right-handed individuals). These data show that, along with the signs noted in the literature (dominance in the left hemisphere of the planum temporale, structural features of the Sylvian fissure), “right-handers” also develop a whole complex of structural and quantitative features in the left inferior frontal gyrus. Its elements are noticeable already in the prenatal period. In single instances it manifests itself at very early stages of postnatal development (in a 4-month-old child), but is fully detected from 2 years of age.

The early appearance of signs of the “left hemisphere” complex in brain ontogenesis indicates a significant role of the genetic factor in the development of right-hand dominance (right-handedness). At the same time, its most intensive formation, accompanied by the subsidence of the island as a result of the “influx” of triangular, opercular and orbital convolutions onto it, takes a period of 2 to 6 years. The final formation with a clear dominance of the triangular gyrus, often acquiring a dome-shaped shape, with the development of the superficial component of the gyri and the emergence of a large-gyral formation occurs in the period from 6 to 10 years.

The presented morphological data correspond to the concept of the role of genetic and environmental factors in the dominance of the right hand (and therefore the left hemisphere), which is discussed below.

On the role of heredity and environment in the formation of interhemispheric brain asymmetry

Three main factors play a role in the formation of morphofunctional interhemispheric asymmetry of the brain: heredity, environment (here, the educational system) and pathology. There is a connection with ecology. Thus, among the population of the North - Eskimos, Chukchi, Koryaks, etc. - the right-hemisphere phenotype is more common (left-handed people are more common). This is probably due to their maximum adaptability to living conditions. Pressure cultural traditions, aimed at the predominant use of the right hand, is weaker in them than in central Russia. Perhaps this is due to their less familiarity with scientific and technological progress and their greater proximity to nature.

A parallel has been noticed between the degree of social pressure in the direction of right-hand dominance and the percentage of left-handed people in the population. Thus, in China the percentage of left-handed people is relatively small (3.5%). Environmental pressure is comparatively stronger in the US, left-handed people make up 11.5%. The pressure of the environment is weakened.

Of the many genetic hypotheses about the inheritance of left-handedness and right-handedness, the Annette hypothesis is of greatest interest. Most people have the gene for right-handedness (“right-sided shift factor” - rs+). If a person has this gene, then he is predisposed to become right-handed with left-hemisphere localization of speech. In the absence of it and the presence of the recessive allele rs, a person can become either right-handed or left-handed, depending on the circumstances, for example, depending on the conditions of embryonic development.

In the human population, there is probably a balanced polymorphism associated with the distribution of the dominant right-shift gene and its recessive allele. The influence of the gene affects not only the preference for one of the hands, but also other types of asymmetries (leg, ear, eye), however, the most objective external assessment of lateralization is the assessment of the leading hand.

The “right shift” gene leads to the development of asymmetry. In early ontogenesis, on the one hand, it inhibits the development of the plenum temporale in the right hemisphere, and on the other hand, the development of the left posterior parietal region. Due to this, the left temporal region receives advantages in phonetic processing processes, and the right posterior parietal region receives advantages in spatial vision processes. Homozygotes for the rs+ gene are distinguished by a particularly strong “right shift”. They will have a pronounced dominance of the right hand and weakened activity of the left, and the function of the right hemisphere in relation to the assessment of spatial relationships will be somewhat inhibited. In general, the rs+ gene has a negative effect on spatial judgment abilities.

Homozygotes for the recessive rs- gene, on the contrary, are distinguished by inhibition of the speech center of the left hemisphere and form a risk group in terms of speech development, especially the phonological aspect.

Heterozygotes for the rs+ gene have the greatest advantages, since they do not have such severe weakness of the left hand and right-hemisphere spatial abilities.

IN psychological literature the “ontogenetic hypothesis of interhemispheric brain asymmetry” was formulated. The origin of asymmetry is determined by five main factors.

1. A lateralizing factor of a non-genetic nature (most likely a weak type of physical influence), under the influence of which the left half of the body, and therefore the left hemisphere of the brain, has some advantages in the speed of embryonic development. The strength of this factor is not very strong.

2. Genetic mechanisms that form a bilateral trait. Manifestations (non-manifestations) of genetic dispersion of asymmetry depend on the characteristics of the phenogenesis of each trait.

3. Penetal environmental influences (stress, stroke, etc.), causing the emergence of an atypical (pathological) interhemispheric organization, in particular, left-handedness.

4. Environmental, systematic (cultural) influences that contribute to the formation of cerebral organization and functional specialization of the cerebral hemispheres. This factor significantly increases the incidence of right-handedness.

5. Environmental stochastic influences, which increase with age and with age-related cerebral pathology and are manifested by a violation of interhemispheric relations. The direction of the asymmetry does not change significantly, but becomes difficult to determine; the absolute value of asymmetry increases.

Psychological testing based on functional brain asymmetry

The concept of an individual asymmetry profile is being developed in the psychological literature. The latter includes the analysis of not just one sign (perhaps the most obvious, but not exhaustive, for example, manual asymmetry), but a whole complex - various criteria for motor and sensory asymmetry (leading hand, leading leg, leading eye, leading ear). In the works of T.A. Dobrokhotova and N.N. Bragina provides methods for determining these criteria. They are decisive in establishing the individual asymmetry profile.

Knowing the features of functional asymmetry in humans, it is possible to identify the hidden, most various shades human character. This assessment can be made using four main tests:

1) interlacing fingers;

2) determining the dominant eye in aiming ability;

3) Napoleon's poses;

4) applause.

Based various combinations signs of asymmetry, 16 mini-portraits of brief generalized psychological characteristics emerge, which are given below. Designations: the first two letters are hand and foot, respectively, the third letter is eye, the fourth is ear.

1. PPPP (“completely right-handed”): only right-wing asymmetries: conservatism, orientation towards generally accepted opinion (stereotype); Such people do not like to conflict, argue, or quarrel.

2. PPPL: the most striking character trait is indecision.

3. PPLP: coquetry, determination, sense of humor, artistry, very contact type of character, more often found in women.

4. PPLL: rare combination; the character is close to the previous one, but softer; there is some contradiction between indecision (left applause) and strength of character; leading eye right.

5. PLPP: analytical mind and gentleness; more common in women; slow addiction, caution in relationships, tolerance and some coldness.

6. PLPL: the rarest combination; defenselessness, exposure different influence; more common in women.

7. DILI: very common combination; emotionality; lack of persistence on major issues; susceptible to male influence, which allows them to adapt to different conditions; happy with friends and easy to get along with people.

8. LPPL: greater than previous types, gentleness of character, naivety.

9. LLPP: friendliness and simplicity; some scattered interests and a tendency to introspection.

10. LLPL: innocence, gentleness, gullibility.

11. LLLP: emotionality, energy and determination.

12. LLLL (“full left-handed”): anti-conservative character type; the ability to look at old things in a new way; the greatest emotionality, individuality, selfishness, stubbornness, sometimes turning into isolation.

13. LPLP: the most strong type character; find it difficult to change their point of view; energetic and persistent in achieving their goals.

14. LPLL: similarity to the character of the previous ones, instability, tendency to introspection; have difficulty finding new friends.

15. PLLP: easy character; know how to avoid conflicts and easily find friends; Hobbies change often.

16. PLLL: impermanence and independence; the desire to do everything yourself.

You can tell about a person’s character traits by performing even one test. If the left finger lies on top of the intertwining of fingers, this indicates emotionality, if the right finger, this indicates an analytical mindset. The right dominant eye speaks of a firm, persistent, more aggressive character, the left - of a soft and compliant character. If in Napoleon's pose the left hand is on top, then the person is capable of coquetry, if the right hand is capable of simplicity and innocence.

On the social and genetic significance in the formation of an individual asymmetry profile

Studies of some physiological characteristics, as well as some properties of higher nervous activity conducted at the Department of Anatomy, Physiology and Valeology of Moscow State Pedagogical University showed that the individual profile of asymmetry in schoolchildren of all age groups and students is formed in the process of postnatal ontogenesis. In Group

of right-handers, complete right-handers account for 22.2%, dominant right-handers - 50%, right-handers with the presence of left-sided dominants - 8%, right-handers in the motor system and left-handers in the sensory system - 8%, and partial ambidextrous - 12%.

In the group of left-handers, complete left-handers make up 6%, dominant - 27%, left-handers with right-sided dominants - 40%, left-handedness in the motor system and right-handedness in the sensory system - 12%, partial ambidextrous - 12%. In general, among older schoolchildren, compared to younger ones, the number of complete right-handers, as well as those with right-sided dominance, increases. So, if at the age of 8-10 years complete right-handers make up 4%, and dominant ones - 12.5%, then from 11 to 18 years old they make up 11% of all subjects, and dominant ones - 33.3%.

In children with more high level the predominance of the right hand has a higher indicator of motor plasticity, i.e. speed of movements, flexibility when switching from one form of motor activity to another. Right-handers are also distinguished by higher rates of processing speed of visual information and a higher level of general activity in the motor and communicative spheres. Left-handers have higher levels of concentration and volume of visual information, higher values ​​of general emotionality with a predominance of negative emotions.

In older schoolchildren, compared to younger ones, the number of combinations of the right leading hand with the right leading eye increases (for schoolchildren aged 8-10 it is 11%, for schoolchildren older than 11-31%). The predominance of right-sided dominance in older age is expressed in both the motor and sensory systems (hand-leg, hand-ear, leg-ear, leg-eye), however, it is most expressed in the hand-eye system. This indicates the special social significance of this system and the importance of the conditions of the social environment in its development.

At the same time, some factors indicate a fairly early formation of the morphofunctional hand-eye system in human embryos. Unlike animals, this is manifested in a special position of the anlage of the future hand - clearly opposite the anlage of the optic cup (Fig. VIII. 1).

From this we can conclude about significant influence and genetic factors on the development of the hand-eye system. Thus, the idea of ​​special ontophylogenetic relationships of a person in connection with his biosocial essence is confirmed. Apparently, some higher mental properties (the ability to improve, the desire to join social progress, etc.) can be transmitted not only according to the laws of social heredity, but also through the genetic program.

The individual asymmetry profile is formed, to a large extent, in the process of individual development, based on brain plasticity. Genetically programmed right-hand dominance is realized under the influence of social factors - training, traditions, upbringing, acting in the direction of the predominant use of the right hand. Strengthening the right-sided dominants indicates a special plasticity of the left hemisphere. It is no coincidence that in its immediate vicinity there are centers of hand movement, as well as speech and oculomotor centers. Numerous variants of the individual asymmetry profile reflect the functional diversity of mental properties of human populations.

Formation of morphofunctional asymmetry of the brain in anthropogenesis

Based on the analysis of ancient Paleolithic images, we can confidently assume that Paleolithic man was most likely ambidextrous; It is also possible that in those days the percentage of left-handed people was higher than that of right-handed people. Among our contemporaries, a high percentage of left-handed people was found among the Australian Aborigines, as well as among the Eskimo hunters.

There is a fairly clear connection between speech and motor asymmetry (lateralization). The left hemisphere is dominant in relation to speech in right-handed people. Some researchers express the opinion that the center of movement of the tongue turned out to be predominantly in the left hemisphere, not because it gradually, in the process of evolution, became more and more connected with symbolism, but because the motor center of speech turned out to be connected with the center of hand movement localized nearby and fingers of the hand. It is believed that the predominantly left-hemispheric localization of the speech center arose in the process of evolution, due to a change in the control centers of the communication system. At the initial stages of the hominization process, the communication system was gestural. At this stage, in the area of ​​the middle frontal gyrus (mainly the left hemisphere) there was a control center for the movements of the right hand. Hand indicated various directions movement, management of a team of people was carried out during relocation, during labor operations, etc.

Subsequently, the vocal muscles and tongue muscles began to be used for communication. And since the area of ​​control of these muscles is located in the brain adjacent to the centers of the hand (also predominantly in the left hemisphere), it was the left hemisphere that became dominant in controlling speech, both oral and written.

Control questions

What hereditary diseases do you know?
What structural features of chromosomes underlie Down syndrome?
What disturbances in cellular interactions in a developing human embryo lead to abnormalities in organ development?
What is the connection between hearing and speech in the occurrence of deaf-muteness?
What is the role of genetic and environmental factors in the development of deaf-muteness?
What are the different points of view on "lefties"?
What are the mental characteristics of left-hemisphere and right-hemisphere people?
What is an individual asymmetry profile?
What are the main criteria for psychological testing based on functional brain asymmetry?