All functions of our body are regulated by the brain. Functionally and structurally, the left and right hemispheres are different from each other. This is the interhemispheric asymmetry of the brain. This is the rule of how the brain works not only in humans, but also in animals.
This asymmetry is also called functional. Functional interhemispheric asymmetry of the brain is the most important physiological and psychological feature brain.
Lateralization according to the emotional system was found to exist for only some components of these circuits, in particular activation of the prefrontal cortex. Thus, it is expected that the right prefrontal cortex will be directly involved in the braking system, and the left one - in the approach system. This means that subjects with a right-sided activation asymmetry in the tonic pre-frontal cortex tend to experience more intense negative emotions compared to its left-sided counterpart.
In addition, people with pre-tonic right frontal cortex more active are predisposed to be more sensitive to threatening stimuli, inhibiting their behavior and experiencing more Negative influence. There is converging evidence on the consequences of different patterns of brain asymmetries for affectivity.
This asymmetry is not congenital and is formed before 10-15 years. She has her own age characteristics and is implemented differently in different parts of the brain. This process is called lateralization.
Features of the right and left hemispheres
Particular attention in the study of the brain is paid to the relationship between hemispheric asymmetry and mental processes. Interhemispheric asymmetry of mental processes is the ability of the brain to carry out one type of mental function main role the right hemisphere, the other - the left.
Emotional regulation and affective style. There is evidence of processes that occur during the regulation of negative emotions. Laboratory studies have shown that emotional regulation occurs simultaneously with control of the prefrontal cortex? Activation of the amygdala. Specifically, voluntary reductions in negative emotions are associated with changes in neuronal activity in the amygdala.
In other areas of development, various consequences of regulation have been identified in “efficiency,” depending on levels of tonic activity in the prefrontal cortex. Specifically, subjects with asymmetric right frontal tone activation experience difficulty regulating negative emotions compared to its left asymmetric counterpart. In other words, the time required for negative affect to recover is related to differences in prefrontal asymmetries, where subjects with right asymmetries are more difficult to complete with negative emotions as soon as it started.
The study of speech showed that verbal characteristics are under the control of the left hemisphere, and voice intonations and timbre are under the control of the right. Also left hemisphere is responsible for strengthening conditioned reflexes and for defining goals, sequential processing of information using the analytical method.
The processes of inhibition and disinhibition are fundamental for adaptation. Sometimes approach behavior can be selectively blocked by the presence of keys or the expectation of punishment. The psychopath's main failure is that there is no inhibition in situations where both reward and punishment are possible and, when this happens, psychopaths seem to focus on the possibilities of reward and punishment to ignore. This may be due to a lack of guilt or remorse.
Psychopathology: Linguistic and emotional processing. Psychopathy is a behavioral socially disruptive disorder defined by a constellation of love, interpersonal characteristics and including self-centeredness, impulsivity, irresponsibility, shallow emotionality, loss of guilt, loss of empathy and regret, pathological lying, manipulation and persistent disruption social norms.
Psychopathy is a complex personality disorder of unknown etiology. For many years, research on psychopathy has focused on characterizing and elucidating the role of emotional processes in the disorder. Overall, these studies have shown that psychopaths have difficulty understanding the input and connotative aspects of emotional stimuli. Abnormal emotional and affective processing.
For language processing, it tends to be higher in the left hemisphere, and especially for emotional processing of negative emotions, it tends to be higher in the right hemisphere. There are studies that, in line with the above, suggest that psychopathy is associated with abnormal processing of verbal affective material.
Functional asymmetry of the brain is very indicative of visual perception: the left hemisphere perceives the image in detail, separately analyzing color, size, etc.; the right one, on the contrary, evaluates the image as a whole.
The motor difference is manifested in the fact that the work of the muscles of the arms, legs, body, for example, with right side responds to the area of the cortex of the left hemisphere. And only certain facial muscles are under the control of both hemispheres.
These measures were taken in response to a range of words written with affective meanings, compared to neutral words and nonsense words. The results support predictions that psychopaths exhibit less behavior between neutral and emotional words than non-psychopaths.
Accumulating empirical evidence supports Cleckley's view that emotional deficits underlie psychopathy. Compared to non-psychopaths, psychopaths showed decreased autonomic reactivity to various situations that cause fear and anxiety, such as no shock during exposure to an unpleasant slide, and refusal to show typical picture differential response to words with and without emotional content.
Connections between the hemispheres and their properties
At the moment, the problem of interhemispheric asymmetry and interhemispheric interaction is one of the most important in natural science. This issue was first raised by Hippocrates, and in the 19th century a sufficient number of facts were collected confirming interhemispheric differences.
In this study, when negative emotional material was processed, psychopaths, compared to non-psychopaths, were less dependent on right-hemisphere-based emotional connotative processes and more on left-hemisphere-based denotative language processes.
A double-sided tachistoscope was used in this study to examine side faces and emotional processing of negative and neutral words in psychopaths and non-psychopaths. He predicted that psychopaths depend more than non-psychopaths in the right hemisphere on decoding strategies that emphasize the emotional connotative meaning of stimuli. Instead, they had to rely more on linguistic decoding through left-hemisphere strategies.
Now this question is studied in terms of the relevance of the participation of each cerebral hemisphere in the implementation of mental functions. The participation of each of them in performing different functions is not total, but partial. It has been revealed that the cerebral hemispheres take unequal in type and unequal in importance participation in the implementation of mental functions.
Two tasks were prepared with similar tachoscopes. The accuracy and reaction time of prisoners' responses were measured by asking them which of two stimuli presented bilaterally was the dominant stimulus. Differences in lateral processing between the two groups occurred in the word task but not in the face task, providing partial support for the experimental hypotheses. Psychopaths also showed broad emotional sensitivity lower than non-psychopaths on the lesion intensity dimension.
Psychopaths, on the other hand, did not show a significant advantage according to visual field. The right hemisphere appears to be specialized for processing the emotional meaning of linguistic stimuli. Additionally, psychopaths differ from non-psychopaths in failing to demonstrate advantages in the left visual field when processing words with emotional content.
Sensory lateralization is as follows: one sense organ (paired) responds more strongly to stimulation. Thus, the dominant eye has better vision, the ear has more acute hearing, etc.
The results of this experiment indicate that psychopaths cannot demonstrate this pattern. The hypothesis that negative emotional faces created a weaker left visual field advantage for psychopaths than for non-psychopaths was not supported. Data suggested that abnormal processing of emotional material in psychopaths may be limited to the linguistic domain. They showed fewer emotional reactions in affect intensity than non-psychopaths. This is due to the aforementioned characteristics of loss of attachment and flat emotionality.
Thus, individuals who are typical of the left hemisphere are distinguished by rationality, logic, and thoroughness. In turn, right-hemisphere people are characterized by inconsistency and lack of inclination to analysis.
The following properties can be distinguished functional asymmetry:
- Dominance. Zones of one hemisphere are activated at the time of certain activity. This is a stable characteristic.
- Switchability. If the state of the body changes, then the activation of the hemisphere also changes.
- Plastic. Some features explained by asymmetry change and become fixed under the influence of certain factors.
Thanks to latest works in this area it was also revealed that in certain areas of activity the asymmetry between the hemispheres is stationary. But sometimes its dynamism manifests itself when lateralization occurs over a long period of time.
Abnormal lateral processing of language in psychopaths has been interpreted as indicating that psychopaths are less lateralized in the left hemisphere for processing linguistic stimuli. The results indicate that a task in which non-psychopaths showed advantages in the correct hemisphere for processing emotional language also showed poorer lateral performance.
Psychopaths' failure to demonstrate superiority in the right hemisphere task provides some preliminary evidence that the emotional quality of preferential-mental stimuli decoded by the right hemisphere may be less prominent in psychopaths.
The main interhemispheric differences were noticed by the scientist R. Sperry. To treat epilepsy, he developed an operation to dissect the corpus callosum. Thus, it became possible to study the work of the brain hemispheres in some isolation from each other.
Another study on lateralization in emotion processing in psychopaths has been developed. Known method dichotic listening was used to study hemispheric asymmetry, based on the principle that auditory input to either ear is more strongly represented in the contralateral hemisphere due to the greater gain and predominance of auditory projections against the sides. Asymmetrical performance indicates greater processing efficiency in the opposite hemisphere for more accurate listening. Based on abnormal linguistic and emotional functioning, psychopaths are expected to show less hemispheric specialization than non-psychopaths to recognize word tones and emotions.
These patients' temperament did not change, but phenomenal disorders were identified that were a consequence of the operation.
Contrary to what was expected, psychopathic people had an advantage when listening to text cards correctly. Looking at the comparison group, it shows that there is no evidence of decreased laterality for the word cards. The results do not support the hypothesis that psychopaths demonstrate Latin lateralization.
In contrast, psychopaths showed a smaller advantage in left listening than controls for detecting cards with emotional stimuli. The accentuated, reduced laterality in psychopaths on tasks with emotional stimuli reflects normal performance by left listeners but superior performance compared to controls. In addition to their reduced asymmetry, emotional processing in psychopaths is more efficient in the right hemisphere than in the left hemisphere, and, like controls, they showed advantages in the left ear.
For example, when a patient was asked to assemble a structure according to the diagram right hand, it was noted a large number of inaccuracies. This happened because the left hemisphere is interconnected with the right side of the body. Thus, it was discovered that the cerebral hemispheres are a single organ, and only with their interaction does the brain function correctly.
Thus, psychopaths have normal efficiency for processing maps with emotional stimuli in the left ear, but are more efficient than normal for emotional maps presented in the right ear. Psychopaths' good performance on emotional tasks may be surprising given their characteristics of information processing deficits. However, their high accuracy is consistent with the literature, which shows that psychopaths do not differ from controls when asked about emotional content.
There is a lot of literature that explains the difference between a psychopath's ability to recognize emotions and the use of this information. The process is one thing and the use of it is another, and there are theories about emotional processing that explain this. The normal ability of psychopaths to detect emotions in card tests is consistent with clinical observations, theoretical models, and previous empirical evidence.
Relationship between brain development and gender
Currently, there are observations confirming the connection between a person’s gender and the speed at which the brain matures. By the time they are born, the left hemisphere is the most developed in girls, and the right in boys. This difference is explained by the connection between hemispheric asymmetry and hormones.
Abnormal linguistic processing in psychopaths. There are many studies that show that abnormal language processing may be associated with abnormal lateralization of the brain, and psychopathic subjects have been found to have deficits in left hemisphere functioning. Let's look at some experiments that show empirical evidence of this.
For most right-handed people, language is processed more efficiently in the left hemisphere of the brain than in the right hemisphere. Left hemisphere specialization is accomplished in superior linguistic processing of stimuli presented unilaterally on the left side, opposite the right hemisphere. Psychopaths, however, often do not demonstrate left hemisphere superiority for language processing.
This is partly the reason why girls begin to speak and read earlier than boys, and they usually do it better.
Numerous studies show that men's brains are more asymmetrical in their organization than women's; Also, in the stronger half of humanity, a predominance of the left hemisphere over the right is more common.
Thanks to research, it has become clear that when there are defects in the left hemisphere (trauma, tumor, surgery), men’s verbal function suffers much more often than women. This just proves the symmetry of the female brain in comparison with the male one.
Psychological differences by gender are also closely related to unequal lateralization. Speech, its speed and fluency, literacy - here women are ahead of men. But the abilities for geometry, geography, chess, and invention are, as a rule, higher among men.
Research into hemispheric differences continues to this day. It is possible that current knowledge will become irrelevant and outdated in the future, and scientists will finally comprehend all the secrets of the brain. And the most important advice
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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 series 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 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 emotional sphere and so mental cognitive processes like memory and imagination.
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 abstract thinking are concentrated in the left hemisphere, and the mechanisms of concrete figurative thinking are concentrated in the right hemisphere. It has also been shown that the left hemisphere to a greater extent is focused on predicting future states, and the right one is focused on interaction with experience and with 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-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.
Brief history of studying the problem
- In 1836, physician Mark Dax 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 “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 mid-19th century century, the rapid development of aphasiology (the science of speech disorders) was noted. 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 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. Broca believed that he had discovered the center of speech.
- 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 Karl 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.
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 a 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 E. D., 2005).
Explanations of the causes
Evolutionary theory of asymmetry
A unified theory that explains 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 brain hemispheres and the sides of the body controlled by them.
Explanation from an ethological point of view
The main functions of the hemispheres and the connection between them
Logic 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.
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 its entirety of 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). This is characterized by minimal latent periods of names and exact matching of names physical characteristics 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 the 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 and so on.
Organization of speech
Each hemisphere forms its own principles of speech organization:
- the right forms the integrity of 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;
- the formation of the structure of a person’s lexicon occurs due to the summation of different layers of vocabulary: the right hemisphere relies on a figurative representation of the objective world, the left hemisphere relies 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 speech 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.
Split brain syndrome
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.
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 left-handed children are forcibly retrained to write with their 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 during 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 brain lateralization and 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 the 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 sex differences are based on social factors: men hunted and led migrations, which led to better development of their spatial abilities, and the verbal superiority of women was due to the fact that they raised children, and this requires verbal communication.