Modern ideas about the localization of function in the cerebral cortex. Dynamic localization of functions in the cerebral cortex Questions for self-control
Morphological bases of dynamic localization of functions in the cortex of the cerebral hemispheres (centers of the cerebral cortex).
Knowledge is of great theoretical importance, as it gives an idea of the nervous regulation of all processes of the body and its adaptation to the environment. It is also of great practical importance for diagnosing lesion sites in the cerebral hemispheres.
Picture of localization of functions in the cerebral cortex associated primarily with the concept of the cortical center. Back in 1874, the Kiev anatomist V. A. Bets made the statement that each part of the cortex differs in structure from other parts of the brain. This laid the foundation for the doctrine of the different qualities of the cerebral cortex - cytoarchitectonics(cytos - cell, architectones - structure). Currently, it has been possible to identify more than 50 different areas of the cortex - cortical cytoarchitectonic fields, each of which differs from the others in the structure and location of the nerve elements. From these fields, designated by numbers, is compiled special map of the human cerebral cortex.
According to I. P. Pavlov, center- this is the brain end of the so-called analyzer. Analyzer- this is a nervous mechanism, the function of which is to decompose the known complexity of the external and internal world into separate elements, that is, to carry out analysis. At the same time, thanks to broad connections with other analyzers, synthesis occurs here, a combination of analyzers with each other and with different activities of the body.
« Analyzer there is a complex nervous mechanism that begins with the external perceptive apparatus and ends in the brain” (I. P. Pavlov). From point of view I. P. Pavlova, think tank, or the cortical end of the analyzer, does not have strictly defined boundaries, but consists of nuclear and scattered parts - theory of nuclei and scattered elements. "Core" represents a detailed and accurate projection in the cortex of all elements of the peripheral receptor and is necessary for the implementation of higher analysis and synthesis. "Scattered elements" are located on the periphery of the core and can be scattered far from it; they carry out simpler and more elementary analysis and synthesis. If the nuclear part is damaged, scattered elements can, to a certain extent, compensate for the lost kernel function, which is of great clinical importance for restoring this function.
Before I.P. Pavlov the motor zone differed in the cortex, or motor centers, precentral gyrus, and sensitive area, or sensitive centers located behind sulcus centralis. I. P. Pavlov showed that the so-called motor area corresponding precentral gyrus, there is, like other zones of the cerebral cortex, a perceptive area (cortical end of the motor analyzer). “The motor area is a receptor area... This establishes the unity of the entire cerebral cortex” (I. P. Pavlov).
- 1) at the beginning of the 19th century. F. Gall suggested that the substrate of various mental “abilities” (honesty, frugality, love, etc.))) are small areas of n. tk. KBPs that grow with the development of these abilities. Gall believed that various abilities have a clear localization in the GM and that they can be determined by the protrusions on the skull, where the brain corresponding to this ability supposedly grows. tk. and begins to bulge, forming a tubercle on the skull.
- 2) In the 40s of the XIX century. Gall is opposed by Flourens, who, based on experiments in the extirpation (removal) of parts of the GM, puts forward the position of equipotentiality (from the Latin equus - “equal”) of the functions of the CBP. In his opinion, the GM is a homogeneous mass that functions as a single integral organ.
- 3) The basis of the modern doctrine of the localization of functions in the CBP was laid by the French scientist P. Broca, who identified the motor center of speech in 1861. Subsequently, the German psychiatrist K. Wernicke in 1873 discovered the center of word deafness (impaired speech understanding).
Since the 70s. The study of clinical observations showed that damage to limited areas of the KBP leads to a predominant loss of well-defined mental functions. This gave rise to the identification of separate areas in the CBP, which began to be considered as nerve centers responsible for certain mental functions.
Having summarized the observations made on the wounded with brain damage during the First World War, in 1934 the German psychiatrist K. Kleist compiled the so-called localization map, in which even the most complex mental functions were correlated with limited areas of the KBP. But the approach of direct localization of complex mental functions in certain areas of the CBP is untenable. An analysis of clinical observations showed that disturbances in such complex mental processes as speech, writing, reading, and counting can occur with lesions of the KBP that are completely different in location. Damage to limited areas of the cerebral cortex, as a rule, leads to disruption of a whole group of mental processes.
4) a new direction has emerged that considers mental processes as a function of the entire GM as a whole (“anti-localizationism”), but it is untenable.
Through the works of I.M. Sechenov, and then I.P. Pavlov - the doctrine of the reflex foundations of mental processes and the reflex laws of the work of the KBP, it led to a radical revision of the concept of “function” - it began to be considered as a set of complex temporary connections. The foundations were laid for new ideas about the dynamic localization of functions in the KBP.
To summarize, we can highlight the main provisions of the theory of systemic dynamic localization of higher mental functions:
- - each mental function is a complex functional system and is provided by the brain as a whole. At the same time, various brain structures make their specific contribution to the implementation of this function;
- - various elements of the functional system can be located in areas of the brain that are sufficiently distant from each other and, if necessary, replace each other;
- - when a certain area of the brain is damaged, a “primary” defect occurs - a violation of a certain physiological principle of operation characteristic of a given brain structure;
- - as a result of damage to a common link included in different functional systems, “secondary” defects may occur.
Currently, the theory of systemic dynamic localization of higher mental functions is the main theory explaining the relationship between the psyche and the brain.
Histological and physiological studies have shown that the KBP is a highly differentiated apparatus. Different areas of the cerebral cortex have different structures. Cortical neurons often turn out to be so specialized that from among them one can distinguish those that respond only to very special stimuli or to very special signs. There are a number of sensory centers located in the cerebral cortex.
Localization in the so-called “projection” zones - cortical fields directly connected by their paths with the underlying sections of the NS and the periphery is firmly established. The functions of the KBP are more complex, phylogenetically younger, and cannot be narrowly localized; Very large areas of the cortex, and even the entire cortex as a whole, are involved in the implementation of complex functions. At the same time, within the CBP there are areas whose damage causes varying degrees, for example, speech disorders, disorders of gnosis and praxia, the topodiagnostic value of which is also significant.
Instead of the idea of the KBP as, to a certain extent, an isolated superstructure above other floors of the NS with narrowly localized areas connected along the surface (association) and with the periphery (projection), I.P. Pavlov created the doctrine of the functional unity of neurons belonging to various parts of the nervous system - from receptors in the periphery to the cerebral cortex - the doctrine of analyzers. What we call the center is the highest, cortical, section of the analyzer. Each analyzer is connected to certain areas of the cerebral cortex
3) The doctrine of the localization of functions in the cerebral cortex developed in the interaction of two opposing concepts - anti-localizationism, or equipontentialism (Flourens, Lashley), which denied the localization of functions in the cortex, and narrow localization psychomorphology, which tried in its extreme versions (Gall ) localize in limited areas of the brain even such mental qualities as honesty, secrecy, love for parents. Of great importance was the discovery by Fritsch and Hitzig in 1870 of areas of the cortex, the irritation of which caused a motor effect. Other researchers have also described areas of the cortex associated with skin sensitivity, vision, and hearing. Clinical neurologists and psychiatrists also testify to the disruption of complex mental processes in focal brain lesions. The foundations of the modern view of the localization of functions in the brain were laid by Pavlov in his doctrine of analyzers and the doctrine of dynamic localization of functions. According to Pavlov, an analyzer is a complex, functionally unified neural ensemble that serves to decompose (analyze) external or internal stimuli into individual elements. It begins with a receptor in the periphery and ends in the cerebral cortex. Cortical centers are the cortical sections of the analyzers. Pavlov showed that cortical representation is not limited to the projection zone of the corresponding conductors, going far beyond its limits, and that the cortical zones of various analyzers overlap each other. The result of Pavlov's research was the doctrine of dynamic localization of functions, suggesting the possibility of the participation of the same nervous structures in providing various functions. Localization of functions means the formation of complex dynamic structures or combinational centers, consisting of a mosaic of excited and inhibited distant points of the nervous system, united in common work in accordance with the nature of the required final result. The doctrine of dynamic localization of functions received its further development in the works of Anokhin, who created the concept of a functional system as a circle of certain physiological manifestations associated with the performance of a specific function. The functional system includes each time in different combinations various central and peripheral structures: cortical and deep nerve centers, pathways, peripheral nerves, executive organs. The same structures can be included in many functional systems, which expresses the dynamism of the localization of functions. I.P. Pavlov believed that individual areas of the cortex have different functional significance. However, there are no strictly defined boundaries between these areas. Cells from one area move into neighboring areas. In the center of these areas there are clusters of the most specialized cells - the so-called analyzer nuclei, and at the periphery there are less specialized cells. It is not strictly defined points that take part in the regulation of body functions, but many nerve elements of the cortex. Analysis and synthesis of incoming impulses and the formation of a response to them are carried out by significantly larger areas of the cortex. According to Pavlov, the center is the brain end of the so-called analyzer. An analyzer is a nervous mechanism, the function of which is to decompose the known complexity of the external and internal world into separate elements, that is, to carry out analysis. At the same time, thanks to broad connections with other analyzers, there is also a synthesis of analyzers with each other and with different activities of the body.
The significance of different areas of the cerebral cortex
brain.
2. Motor functions.
3. Functions of the skin and proprioceptive
sensitivity.
4. Auditory functions.
5. Visual functions.
6. Morphological basis of localization of functions in
cerebral cortex.
Motor analyzer core
Auditory Analyzer Core
Visual analyzer core
Taste Analyzer Core
Skin analyzer core
7. Bioelectrical activity of the brain.
8. Literature.
THE IMPORTANCE OF DIFFERENT AREAS OF THE LARGE CORTAL
HEMISPHERE OF THE BRAIN
Since ancient times, there has been a debate among scientists about the location (localization) of areas of the cerebral cortex associated with various functions of the body. The most diverse and mutually opposing points of view were expressed. Some believed that each function of our body corresponds to a strictly defined point in the cerebral cortex, others denied the presence of any centers; They attributed any reaction to the entire cortex, considering it to be completely unambiguous in functional terms. The method of conditioned reflexes made it possible for I.P. Pavlov to clarify a number of unclear issues and develop a modern point of view.
There is no strictly fractional localization of functions in the cerebral cortex. This follows from experiments on animals, when after the destruction of certain areas of the cortex, for example, the motor analyzer, after a few days the neighboring areas take on the function of the destroyed area and the animal’s movements are restored.
This ability of cortical cells to replace the function of lost areas is associated with the great plasticity of the cerebral cortex.
I.P. Pavlov believed that individual areas of the cortex have different functional significance. However, there are no strictly defined boundaries between these areas. Cells from one area move into neighboring areas.
Figure 1. Scheme of connections between cortical sections and receptors.
1 – spinal cord or medulla oblongata; 2 – diencephalon; 3 – cerebral cortex
In the center of these areas there are clusters of the most specialized cells - the so-called analyzer nuclei, and at the periphery there are less specialized cells.
It is not strictly defined points that take part in the regulation of body functions, but many nerve elements of the cortex.
Analysis and synthesis of incoming impulses and the formation of a response to them are carried out by significantly larger areas of the cortex.
Let's look at some areas that have predominantly one or another meaning. A schematic layout of the locations of these areas is shown in Figure 1.
Motor functions. The cortical section of the motor analyzer is located mainly in the anterior central gyrus, anterior to the central (Rolandic) sulcus. In this area there are nerve cells, the activity of which is associated with all movements of the body.
The processes of large nerve cells located in the deep layers of the cortex descend into the medulla oblongata, where a significant part of them intersect, that is, go to the opposite side. After the transition, they descend along the spinal cord, where the rest of the cord intersects. In the anterior horns of the spinal cord they come into contact with the motor nerve cells located here. Thus, the excitation that arises in the cortex reaches the motor neurons of the anterior horns of the spinal cord and then travels through their fibers to the muscles. Due to the fact that in the medulla oblongata, and partly in the spinal cord, a transition (crossing) of motor pathways to the opposite side occurs, the excitation that arose in the left hemisphere of the brain enters the right half of the body, and impulses from the right hemisphere enter the left half of the body. That is why hemorrhage, injury or any other damage to one of the sides of the cerebral hemispheres entails a violation of the motor activity of the muscles of the opposite half of the body.
Figure 2. Diagram of individual areas of the cerebral cortex.
1 – motor area;
2 – skin area
and proprioceptive sensitivity;
3 – visual area;
4 – auditory area;
5 – taste area;
6 – olfactory area
In the anterior central gyrus, the centers innervating different muscle groups are located so that in the upper part of the motor area there are centers of movement of the lower extremities, then lower is the center of the trunk muscles, even lower is the center of the forelimbs, and, finally, lower than all are the centers of the head muscles.
The centers of different muscle groups are represented unequally and occupy uneven areas.
Functions of cutaneous and proprioceptive sensitivity. The area of cutaneous and proprioceptive sensitivity in humans is located primarily behind the central (Rolandian) sulcus in the posterior central gyrus.
The localization of this area in humans can be established by electrical stimulation of the cerebral cortex during operations. Stimulation of various areas of the cortex and simultaneous questioning of the patient about the sensations that he experiences at the same time make it possible to get a fairly clear idea of the indicated area. The so-called muscle feeling is associated with this same area. Impulses arising in proprioceptors-receptors located in joints, tendons and muscles arrive predominantly in this part of the cortex.
The right hemisphere perceives impulses traveling along centripetal fibers primarily from the left, and the left hemisphere primarily from the right half of the body. This explains the fact that a lesion of, say, the right hemisphere will cause a disturbance of sensitivity predominantly on the left side.
Auditory functions. The auditory area is located in the temporal lobe of the cortex. When the temporal lobes are removed, complex sound perceptions are disrupted, since the ability to analyze and synthesize sound perceptions is impaired.
Visual functions. The visual area is located in the occipital lobe of the cerebral cortex. When the occipital lobes of the brain are removed, the dog experiences vision loss. The animal cannot see and bumps into objects. Only pupillary reflexes are preserved. In humans, a violation of the visual area of one of the hemispheres causes loss of half of the vision in each eye. If the lesion affects the visual area of the left hemisphere, then the functions of the nasal part of the retina of one eye and the temporal part of the retina of the other eye are lost.
This feature of visual damage is due to the fact that the optic nerves partially intersect on the way to the cortex.
Morphological bases of dynamic localization of functions in the cortex of the cerebral hemispheres (centers of the cerebral cortex).
Knowledge of the localization of functions in the cerebral cortex is of great theoretical importance, as it gives an idea of the nervous regulation of all processes of the body and its adaptation to the environment. It is also of great practical importance for diagnosing lesion sites in the cerebral hemispheres.
The idea of the localization of functions in the cerebral cortex is associated primarily with the concept of the cortical center. Back in 1874, the Kiev anatomist V. A. Betz made the statement that each area of the cortex differs in structure from other areas of the brain. This marked the beginning of the doctrine of the different qualities of the cerebral cortex - cytoarchitectonics (cytos - cell, architectones - structure). Currently, it has been possible to identify more than 50 different areas of the cortex - cortical cytoarchitectonic fields, each of which differs from the others in the structure and location of the nerve elements. From these fields, designated by numbers, a special map of the human cerebral cortex is compiled.
P 
About I.P. Pavlov, the center is the brain end of the so-called analyzer. An analyzer is a nervous mechanism, the function of which is to decompose the known complexity of the external and internal world into separate elements, that is, to carry out analysis. At the same time, thanks to broad connections with other analyzers, there is also a synthesis of analyzers with each other and with different activities of the body.
Figure 3. Map of the cytoarchitectonic fields of the human brain (according to the Institute of Medical Sciences of the USSR Academy of Medical Sciences) At the top is the superolateral surface, at the bottom is the medial surface. Explanation in the text.
Currently, the entire cerebral cortex is considered to be a continuous receptive surface. The cortex is a collection of cortical ends of the analyzers. From this point of view, we will consider the topography of the cortical sections of the analyzers, i.e., the most important perceptive areas of the cerebral hemisphere cortex.
First of all, let us consider the cortical ends of the analyzers that perceive stimuli from the internal environment of the body.
1. The core of the motor analyzer, i.e., the analyzer of proprioceptive (kinesthetic) stimulation emanating from bones, joints, skeletal muscles and their tendons, is located in the precentral gyrus (fields 4 and 6) and lobulus paracentralis. This is where motor conditioned reflexes close. I. P. Pavlov explains motor paralysis that occurs when the motor zone is damaged not by damage to motor efferent neurons, but by a violation of the nucleus of the motor analyzer, as a result of which the cortex does not perceive kinesthetic stimulation and movements become impossible. The cells of the motor analyzer nucleus are located in the middle layers of the motor zone cortex. In its deep layers (V, partly VI) lie giant pyramidal cells, which are efferent neurons, which I. P. Pavlov considers as interneurons connecting the cerebral cortex with the subcortical nuclei, nuclei of the cranial nerves and the anterior horns of the spinal cord, i.e. with motor neurons. In the precentral gyrus, the human body, as well as in the posterior gyrus, is projected upside down. In this case, the right motor area is connected with the left half of the body and vice versa, because the pyramidal tracts starting from it intersect partly in the medulla oblongata and partly in the spinal cord. The muscles of the trunk, larynx, and pharynx are influenced by both hemispheres. In addition to the precentral gyrus, proprioceptive impulses (muscular-articular sensitivity) also come to the cortex of the postcentral gyrus.
2. The nucleus of the motor analyzer, which is related to the combined rotation of the head and eyes in the opposite direction, is located in the middle frontal gyrus, in the premotor area (field 8). Such a rotation also occurs upon stimulation of field 17, located in the occipital lobe in the vicinity of the nucleus of the visual analyzer. Since when the muscles of the eye contract, the cerebral cortex (motor analyzer, field 8) always receives not only impulses from the receptors of these muscles, but also impulses from the eye (visual analyzer, field 77), different visual stimuli are always combined with different positions eyes, established by contraction of the muscles of the eyeball.
3. The core of the motor analyzer, through which the synthesis of purposeful complex professional, labor and sports movements occurs, is located in the left (for right-handed people) inferior parietal lobe, in the gyrus supramarginalis (deep layers of field 40). These coordinated movements, formed on the principle of temporary connections and developed by the practice of individual life, are carried out through the connection of the gyrus supramarginalis with the precentral gyrus. When field 40 is damaged, the ability to move in general is preserved, but there is an inability to make purposeful movements, to act - apraxia (praxia - action, practice).
4. The core of the head position and movement analyzer - the static analyzer (vestibular apparatus) in the cerebral cortex has not yet been precisely localized. There is reason to believe that the vestibular apparatus is projected in the same area of the cortex as the cochlea, i.e. in the temporal lobe. Thus, with damage to fields 21 and 20, which lie in the region of the middle and inferior temporal gyri, ataxia is observed, that is, a balance disorder, swaying of the body when standing. This analyzer, which plays a decisive role in human upright posture, is of particular importance for the work of pilots in jet aviation, since the sensitivity of the vestibular system on an airplane is significantly reduced.
5. The core of the analyzer of impulses coming from the viscera and vessels is located in the lower parts of the anterior and posterior central gyri. Centripetal impulses from the viscera, blood vessels, involuntary muscles and glands of the skin enter this section of the cortex, from where centrifugal pathways depart to the subcortical vegetative centers.
In the premotor area (fields 6 and 8), the unification of vegetative functions takes place.
Nerve impulses from the external environment of the body enter the cortical ends of the analyzers of the external world.
1. The core of the auditory analyzer lies in the middle part of the superior temporal gyrus, on the surface facing the insula - fields 41, 42, 52, where the cochlea is projected. Damage leads to deafness.
2. The nucleus of the visual analyzer is located in the occipital lobe - fields 18, 19. On the inner surface of the occipital lobe, along the edges of the sulcus Icarmus, the visual pathway ends in field 77. The retina of the eye is projected here. When the nucleus of the visual analyzer is damaged, blindness occurs. Above field 17 is field 18, when damaged, vision is preserved and only visual memory is lost. Even higher is the field, when damaged, one loses orientation in an unusual environment.
3. The nucleus of the taste analyzer, according to some data, is located in the lower postcentral gyrus, close to the centers of the muscles of the mouth and tongue, according to others - in the immediate vicinity of the cortical end of the olfactory analyzer, which explains the close connection between the olfactory and taste sensations. It has been established that taste disorder occurs when field 43 is affected.
Analyzers of smell, taste and hearing of each hemisphere are connected to the receptors of the corresponding organs on both sides of the body.
4. The nucleus of the skin analyzer (tactile, pain and temperature sensitivity) is located in the postcentral gyrus (fields 7, 2, 3) and in the superior parietal region (fields 5 and 7).
A particular type of skin sensitivity - recognition of objects by touch - stereognosia (stereos - spatial, gnosis - knowledge) is connected with the cortex of the superior parietal lobule (field 7) crosswise: the left hemisphere corresponds to the right hand, the right hemisphere corresponds to the left hand. When the superficial layers of field 7 are damaged, the ability to recognize objects by touch, with eyes closed, is lost.
Bioelectrical activity of the brain.
Abstraction of brain biopotentials - electroencephalography - gives an idea of the level of physiological activity of the brain. In addition to the electroencephalography method - recording bioelectric potentials, the encephaloscopy method is used - recording fluctuations in the brightness of many points of the brain (from 50 to 200).
The electroencephalogram is an integrative spatiotemporal measure of spontaneous electrical activity of the brain. It distinguishes between the amplitude (swing) of oscillations in microvolts and the frequency of oscillations in hertz. In accordance with this, four types of waves are distinguished in the electroencephalogram: -, -, - and -rhythms. The rhythm is characterized by frequencies in the range of 8-15 Hz, with an oscillation amplitude of 50-100 μV. It is recorded only in humans and higher apes in a state of wakefulness, with eyes closed and in the absence of external stimuli. Visual stimuli inhibit the α-rhythm.
In some people with a vivid visual imagination, the rhythm may be completely absent.
An active brain is characterized by (-rhythm. These are electrical waves with an amplitude from 5 to 30 μV and a frequency from 15 to 100 Hz. It is well recorded in the frontal and central regions of the brain. During sleep, the -rhythm appears. It is also observed during negative emotions, painful conditions. Frequency of -rhythm potentials from 4 to 8 Hz, amplitude from 100 to 150 μV. During sleep, -rhythm appears - slow (with a frequency of 0.5-3.5 Hz), high-amplitude (up to 300 μV ) fluctuations in the electrical activity of the brain.
In addition to the types of electrical activity considered, an E-wave (stimulus anticipation wave) and fusiform rhythms are recorded in humans. A wave of anticipation is registered when performing conscious, expected actions. It precedes the appearance of the expected stimulus in all cases, even when it is repeated several times. Apparently, it can be considered as an electroencephalographic correlate of the action acceptor, providing anticipation of the results of the action before its completion. Subjective readiness to respond to a stimulus in a strictly defined way is achieved by a psychological attitude (D. N. Uznadze). Fusiform rhythms of variable amplitude, with a frequency of 14 to 22 Hz, appear during sleep. Various forms of life activity lead to significant changes in the rhythms of bioelectric activity of the brain.
During mental work, the -rhythm increases, while the -rhythm disappears. During muscular work of a static nature, desynchronization of the electrical activity of the brain is observed. Rapid oscillations with low amplitude appear. During dynamic operation, pe-. Periods of desynchronized and synchronized activity are observed, respectively, during periods of work and rest.
The formation of a conditioned reflex is accompanied by desynchronization of brain wave activity.
Wave desynchronization occurs during the transition from sleep to wakefulness. At the same time, spindle-shaped sleep rhythms are replaced by
-rhythm, the electrical activity of the reticular formation increases. Synchronization (waves identical in phase and direction)
characteristic of the braking process. It is most clearly expressed when the reticular formation of the brainstem is turned off. Electroencephalogram waves, according to most researchers, are the result of the summation of inhibitory and excitatory postsynaptic potentials. The electrical activity of the brain is not a simple reflection of metabolic processes in the nervous tissue. It has been established, in particular, that the impulse activity of individual clusters of nerve cells reveals signs of acoustic and semantic codes.
In addition to the specific nuclei of the thalamus, association nuclei arise and develop that have connections with the neocortex and determine the development of the telencephalon. The third source of afferent influences on the cerebral cortex is the hypothalamus, which plays the role of the highest regulatory center of autonomic functions. In mammals, phylogenetically more ancient parts of the anterior hypothalamus are associated with...
The formation of conditioned reflexes becomes difficult, memory processes are disrupted, selectivity of reactions is lost and their excessive strengthening is noted. The cerebrum consists of almost identical halves - the right and left hemispheres, which are connected by the corpus callosum. Commissural fibers connect symmetrical zones of the cortex. However, the cortex of the right and left hemispheres are not symmetrical not only in appearance, but also...
The approach to assessing the mechanisms of work of the higher parts of the brain using conditioned reflexes was so successful that it allowed Pavlov to create a new section of physiology - “Physiology of higher nervous activity,” the science of the mechanisms of work of the cerebral hemispheres. UNCONDITIONED AND CONDITIONED REFLEXES The behavior of animals and humans is a complex system of interconnected...
The problem of localization of functions in the cerebral cortex
The most pronounced form...the attempt to localize individual mental functions in isolated areas of the brain was given by F.A. Gall, whose ideas were very widespread in their time.
Gall was one of the greatest brain anatomists of his time. He was the first to evaluate the role of the gray matter of the cerebral hemispheres and pointed out its relationship to the fibers of the white matter. However, in his interpretation of brain functions, he proceeded entirely from the position of his contemporary “psychology of abilities.” It was he who became the author of the concept according to which each mental ability is based on a specific group of brain cells and the entire cerebral cortex (which he first began to consider as the most important part of the cerebral hemispheres involved in the implementation of mental functions) is a collection of individual “organs”, each of them which is the substrate of a certain mental “ability”.
Those “abilities” that Gall directly associated with individual areas of the cerebral cortex were, as already said, taken in ready-made form by him from contemporary psychology. Therefore, along with such relatively simple functions as visual or auditory memory, orientation in space or a sense of time, the set of “abilities” localized by him in individual areas of the cortex included “procreation instincts,” “love for parents,” and “sociability.” , “courage”, “ambition”, “pliability to education”, etc.
On the one hand, the consideration of the cerebral cortex as a system differing in its functions, proposed by Gall in such a fantastic pre-scientific form, was to a certain extent progressive, since it raised the idea of the possibility of a differentiated approach to the seemingly homogeneous mass of the brain. On the other hand, the ideas of “brain centers” formulated by Hall, in which complex mental functions are localized, in their original fundamental positions turned out to be so strong that they were preserved in the form of psychomorphological ideas of “narrow localizationism” even in a later period, when the study of the cerebral organization of mental processes received a more realistic scientific basis. These ideas determined the approach to the problem of localizing functions in the cerebral cortex for almost a century.
Back in the second half of the 18th century. Gall (1769), without denying that different parts of the brain may be related to different functions, suggested that the brain is a single organ that transforms impressions into mental processes and that it should be considered as "Sensorium sot-ipe", whose parts are equivalent. He saw proof of this position in the fact that one focus can cause a violation of different “faculties” and that the defects caused by this focus can be compensated to a certain extent.
In April 1861, Broca demonstrated at the Paris Anthropological Society the brain of his first patient, who had impaired articulate speech during his lifetime. At autopsy, the patient was found to have a lesion in the posterior third of the inferior frontal gyrus of the left hemisphere. In November of the same year, he repeated a similar demonstration of the brain of a second such patient. This gave him the opportunity to suggest that articulate speech is localized in a clearly limited area of the brain, and that the area he indicated can be considered as a “center for motor images of words.” Based on these observations, Broca made a bold conclusion, which fundamentally continued attempts to directly correlate the complexity
certain psychological functions to limited areas of the brain, namely, that the cells of a given area of the cerebral cortex are a kind of “depot” of images of those movements that make up our articulated speech. Broca ended his report with a pathetic-sounding statement: “From the moment it is shown that the intellectual function is connected with a limited part of the brain, the position that the intellectual functions relate to the whole brain will be rejected and it will become highly probable that each gyrus has its own particular functions.”
Brock's discovery was the impetus for the emergence of a whole series of clinical studies, which not only multiplied the facts he found, but also enriched the position of “localizationists” with a whole series of new observations. A decade after Broca's discovery, Wernicke (1874) described a case in which a lesion in the posterior third of the superior temporal gyrus of the left hemisphere caused a disturbance in speech understanding. Wernicke's conclusion that “sensory images of words” are localized in the zone of the left hemisphere cortex he described, then became firmly established in the literature.
In the two decades following Broca's and Wernicke's discoveries, "centers" such as "visual memory centers" (Bastian, 1869), "writing centers" (Exner, 1881), "concept centers," or "ideation centers" were described. (Broadbent, 1872, 1879; Charcot, 1887; Grasse, 1907) with their connections. Therefore, very soon the map of the human cerebral cortex was filled with numerous diagrams that projected onto the brain substrate the ideas of the associative psychology that was dominant at that time.
1 It should be noted that Jackson’s works, to which A. P. (1913) again drew attention half a century later, GHead(1926) and O.Foerster(1936), were first published in consolidated form only in 1932 (in England), and then in 1958 (in the USA).
Back in the 60s of the last century, the remarkable English neurologist Hughlings Jackson, who first described local epileptic seizures, formulated a number of provisions that sharply contradicted his contemporary ideas of narrow “localizationism.” These principles, which were destined to play a significant role in the further development of neurological thought, were presented by him in his discussion with Broca shortly after the publication of the latter's observations. However, over the following decades they were pushed into the background by the successes of “narrow-localized” views. It was only in the first quarter of the twentieth century that these ideas again received widespread recognition. The facts from which Jackson proceeded did come into conflict with Broca's basic ideas and sharply contradicted the concepts of cellular localization of functions. While studying movement and speech disorders in focal brain lesions, Jackson noted a seemingly paradoxical phenomenon, which was that damage to a certain limited area of the brain never leads to complete loss of function. A patient with a focal lesion of a certain area of the cortex often cannot voluntarily perform the required movement or voluntarily repeat a given word, but is able to do this involuntarily, i.e. reproducing the same movement or uttering the same word in a state of passion or in a habitual utterance.
Based on such facts, Jackson built a general concept of the neurological organization of functions, which differs sharply from classical ideas. In his opinion, each function performed by the central nervous system is not the function of a narrowly limited group of cells that constitute, as it were, a “depot” for this function. The function has a complex “vertical” organization: presented for the first time at the “lowest” (special or stem) level, it is presented for the second time (re-represented) at the “middle” level of the motor (or sensory) parts of the cerebral cortex and for the third time (re-re-represented) - the “highest” level, which Jackson considered to be the level of the frontal regions of the brain. Therefore, according to Jackson, localization of the symptom (loss of one or another function), which is accompanied by damage to a limited area of the central nervous system, cannot in any way be identified with localization of function. The latter may be located in the central nervous system in a much more complex manner and have a completely different cerebral organization.
Jackson's ideas were incorrectly and one-sidedly assessed by his contemporaries. The concept of the complex nature and “vertical” organization of functions, which anticipated the development of science by many decades and received its confirmation only in our days, remained forgotten for a long time. On the contrary, his statements directed against the narrow localization of functions in limited areas of the cerebral cortex, and his indications of the complex “intellectual” or “voluntary” nature of higher psychological processes were after some time taken up by the most idealistic part of researchers, who saw in these provisions a support in the struggle against the materialistic sensationalism of the classics of neurology. Since the 70s of the last century, researchers have appeared
who tried to see the essence of mental processes in complex “symbolic” functions. These researchers contrasted their views with the ideas of narrow localizationism; they considered the basis of mental processes to be the activity of the entire brain as a whole, or they completely refused to talk about their material substrate and limited themselves to pointing out that the mental life of a person is a new, “abstract” type of activity, which is carried out by the brain as an “instrument of the spirit.”
The researchers of this group include Finkelburg (1870), who, in contrast to Broca and Wernicke, interpreted speech as a complex “symbolic” function.
Kussmaul (1885) also took a similar position, denying the idea that the material basis of memory is special “depots” in the cerebral cortex, where images and concepts “sorted into separate shelves” lie. Considering the “symbolic function” to be fundamental to mental life and believing that every complex disorder of the brain leads to “asymbolism,” he wrote: “With a smile we turn away from all naive attempts to find the location of speech in one or another cerebral gyrus.”
If at the end of the 19th century. The voices of researchers calling to reject the sensationalist approach to brain activity and take the position of a difficult-to-localize “symbolic function” remained only isolated, but by the beginning of the 20th century. under the influence of the revival of idealistic philosophy and psychology, they began to intensify and soon became the leading direction in the analysis of higher mental processes.
It was from this time that Bergson (1896) spoke, who tried to substantiate a strongly idealistic approach to the psyche, considering active dynamic schemes as the main driving force of the spirit and contrasting them with the material “memory of the brain.” The psychological studies of the Würzburg school also date back to the very beginning of the century, which put forward the position that abstract thinking is a primary independent process, not reducible to sensory images and speech, and called for a return to Platonism.
These ideas have also penetrated into neuroscience. They came to the fore in the work of the so-called “noetic” school of neurologists and psychologists (P. Marie, 1906 and especially Van Werkom, 1925; Bowman and Grutbaum, 1825, and then Goldstein, 1934, 1942, 1948). Representatives of this school defended the position according to which the main type of mental processes
is “symbolic activity”, realized in “abstract” schemes, and that every brain disease manifests itself not so much in the loss of particular processes, but in a decrease in this “symbolic function” or “abstract attitude”.
Such statements radically changed the tasks that were posed to neurologists in the previous period of development of science. Instead of analyzing the material substrate of individual functions, the task of describing those forms of decrease in “symbolic function” or “abstract behavior” that arose with any brain lesion came to the fore. Research into the brain mechanisms of these disorders has practically receded into the background. Returning again to the position that the brain works as a single whole, and connecting the violation of higher mental processes primarily with the massiveness of the lesion, and not with its topic, these authors enriched the psychological analysis of changes in meaningful activity in local brain lesions; however, they created a significant obstacle to work on a materialistic study of the brain mechanisms of mental processes.
Attempts to translate neurology into the mainstream of an idealistic interpretation of mental disorders met, however, noticeable difficulties. The position of such major neurologists as Monakov (1914, 1928), Head (1926) and, above all, Goldstein (1934, 1942, 1948), who partially or completely joined the “noetic” direction and had to combine the previous established principles in neurology, turned out to be especially difficult. “localizationist” views with new, “anti-localization” views. Each of these neurologists dealt with this difficulty in their own way. Monakov, while remaining the greatest authority on the study of brain structures underlying elementary neurological symptoms, practically abandoned the application of the same principle to deciphering the brain basis of disorders of “symbolic activity,” which he called “asemia.” In his publication together with Mur-g (1928), he came to an openly idealistic explanation of these violations by changes in deep “instincts”. Head, who was firmly established in neurology with his studies of sensitivity, limited his attempts to study complex speech disorders to a description of violations of individual aspects of the speech act, very tentatively comparing them with lesions of large areas of the cerebral cortex. Without giving any neurological explanation for these facts, he turned to the general factor
wakefulness (“vigilance”) as the ultimate explanatory principle.
The most instructive, however, was the position of Goldstein, one of the most prominent neurologists of our time. Adhering to classical views regarding elementary neurological processes, he joined new, “no-ethical” ideas regarding complex human mental processes, highlighting “abstract attitude” and “categorical behavior” as their distinctive features.
Goldstein believed that disruption of this “abstract attitude” or “categorical behavior” occurs with every brain lesion. This statement forced him to take a very unique position in explaining both processes he described - violations of elementary and higher mental functions. Trying to understand the brain mechanisms of these processes, Goldstein identified the “periphery” of the cortex, which allegedly retains the localization principle of its structure, and the “central part” of the cortex, which, unlike the first, is “equipotential” and works on the principle of creating “dynamic structures” that arise on the famous "dynamic background". Lesions of the “periphery of the cortex” lead to disruption of the “means” of mental activity (“Werkzengstdr-ung”), but they leave the “abstract attitude” intact. A lesion of the “central part” of the cortex leads to a profound change in the “abstract attitude” and “categorical behavior”, obeying the “law of mass”: the greater the mass of brain matter covered by this lesion, the more the formation of complex “dynamic structures” is affected and the less differentiated there are relations between “structure” and “background”, which, according to Goldstein, constitute the neurological basis of this complex “categorical behavior”. Taking the position of “gelytaltpsychology” and naturalistically understanding complex forms of human behavior, Goldstein actually repeated the error of Lashley, who tried to turn to elementary ideas about the diffuse and equipotential mass of the brain to explain the most complex forms of intellectual activity. In other words, Goldstein practically combined the classical positions of narrow “localizationism” and new “anti-localizationist” ideas.
Luria A. R. Higher cortical functions of humans. - M. 1962.
A. R. Luria
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Brain
There are projection zones in the cerebral cortex.
Primary projection zone– occupies the central part of the core of the brain analyzer. This is a collection of the most differentiated neurons in which the highest analysis and synthesis of information occurs, and clear and complex sensations arise there. Impulses approach these neurons along a specific impulse transmission pathway in the cerebral cortex (spinothalamic tract).
Secondary projection area
– located around the primary, is part of the nucleus of the brain section of the analyzer and receives impulses from the primary projection zone. Provides complex perception. When this area is damaged, a complex dysfunction occurs.
Tertiary projection zone
– associative – these are multimodal neurons scattered throughout the cerebral cortex. They receive impulses from the associative nuclei of the thalamus and converge impulses of different modalities. Provides connections between various analyzers and plays a role in the formation of conditioned reflexes.
Functions of the cerebral cortex:
perfects the relationship between organs and tissues within the body;
ensures complex relationships between the body and the external environment;
provides processes of thinking and consciousness;
is a substrate of higher nervous activity.
The relationship between the development of fine motor skills and the cognitive sphere
A. R. Luria (1962) believed that higher mental functions as complex functional systems cannot be localized in narrow zones of the cerebral cortex or in isolated cell groups, but must cover complex systems of jointly working zones, each of which contributes to the implementation complex mental processes and which can be located in completely different, sometimes far apart areas of the brain.
Based on the achievements of domestic materialistic physiology (on the works of I. M. Sechenov, I. P. Pavlov, P. K. Anokhin, N. A. Bernshtein,
N.P. Bekhtereva, E.H. Sokolov and other physiologists), mental functions are considered as formations that have a complex reflex basis, determined by external stimuli, or as complex forms of adaptive activity of the body, aimed at solving certain psychological problems.
L.S. Vygotsky formulated a rule according to which damage to a certain area of the brain in early childhood systematically affects higher cortical areas that build above them, while damage to the same area in adulthood affects lower cortical areas that now depend on them. is one of the fundamental provisions introduced into the doctrine of dynamic localization of higher mental functions of Russian psychological science. To illustrate this, we point out that damage to the secondary parts of the visual cortex in early childhood can lead to systemic underdevelopment of higher processes associated with visual thinking, while damage to these same areas in adulthood can cause only partial defects in visual analysis and synthesis, leaving previously formed more complex forms of thinking are preserved.
All data (anatomical, physiological, and clinical) indicate the leading role of the cerebral cortex in the cerebral organization of mental processes. The cerebral cortex (and above all, the neocortex) is the most differentiated part of the brain in structure and function. Currently, the point of view about the important and specific role of not only cortical, but also subcortical structures in mental activity with the leading participation of the cerebral cortex has become generally accepted.
An analytical review of the literature shows that there is an ontogenetic interdependence in the development of fine motor skills and speech
(V.I. Beltyukov; M.M. Koltsova; L.A. Kukuev; L.A. Novikov and others) and that hand movements historically, in the course of human development, had a significant impact on the development of speech function. Comparing the results of experimental studies indicating a close connection between the functions of the hand and speech, based on data from electrophysiological experiments, M.M. Koltsova came to the conclusion that the morphological and functional formation of speech areas occurs under the influence of kinesthetic impulses from the muscles of the hands. The author specifically emphasizes that the influence of impulses from the muscles of the hand is most noticeable in childhood, when the speech motor area is being formed. Systematic exercises for training finger movements have a stimulating effect on the development of speech and are, according to M.M. Koltsova, “a powerful means of increasing the performance of the cerebral cortex.”
Pointing out the importance of studying and improving the motor sphere in children in need of special correctional education, L.S. Vygotsky wrote that, being relatively independent, independent of higher intellectual functions and easily exercised, the motor sphere provides a rich opportunity for compensating for an intellectual defect. The formation of higher types of conscious human activity is always carried out with the support of a number of external auxiliary tools or means.
Many domestic researchers pay attention to the need and pedagogical significance of work on correcting motor skills in children in a complex of correctional and developmental activities (L.Z. Arutyunyan (Andronova); R.D. Babenkov; L.I. Belyakova).
Using electrophysiological methods, it has been established that three types of areas can be distinguished in the cortex in accordance with the functions performed by the cells located in them: sensory areas of the cerebral cortex, associative areas of the cerebral cortex and motor areas of the cerebral cortex. The relationships between these areas allow the cerebral cortex to control and coordinate all voluntary and some involuntary forms of activity, including such higher functions as memory, learning, consciousness and personality traits.
Thus, we can conclude that palm massage, finger exercises and work with a massage ball activate the parts of the brain responsible for thinking, memory, attention and speech (the cognitive sphere of a person).
Based on materials from the book by O.V. Bachina, N.F. Korobova. Finger gymnastics with apparatus (Note 2).
Exercises with a massage ball, 5-7 repetitions:
The ball is held between the palms. The ball is rolled first between the palms, then along the palms towards the fingertips.
The ball is held between the palms. Squeeze and unclench the ball in your palms.
The ball is held between the palms. The ball is rolled clockwise, then counterclockwise.
Ball between palms. “Making a snowball”
Throwing the ball from hand to hand,
Spinning the ball around the hands alternately.
From personal experience I can say that if you alternate exercises, children do them with great pleasure.
Literature
A. R. Luria. Fundamentals of neuropsychology. - M.: Academia, 2002.
Bachina O.V., Korobova N.F. Finger gymnastics with objects. Determining the leading hand and developing writing skills in children 6-8 years old: A practical guide for teachers and parents. – M.: ARKTI, 2006.
Vygotsky L.S. Thinking and speech. Ed. 5, rev. - M.: Labyrinth, 1999.
Krol V. Human psychophysiology. – St. Petersburg: Peter, 2003.
Mukhina V. S. Developmental psychology: phenomenology of development, childhood, adolescence: Textbook for students. universities – 4th ed., stereotype. – M.: Publishing Center "Academy", 1999.
Chomskaya E. D. Kh. Neuropsychology: 4th edition. - St. Petersburg: Peter, 2005.
http://dic.academic.ru/dic.nsf/ruwiki/980358
NOTES
Note 1
Note 2
Finger gymnastics with a pen or pencil
