Localization of functions in the cerebral cortex. Morphological basis of the dynamic localization of functions in the cortex of the cerebral hemispheres (centers of the cerebral cortex) Neuroglial cells play a role
Spatial localization of functions in the cerebral cortex
A. A. Vinokurov, V. I. Guzhov, I.O. Marchenko, M.A. Savin Novosibirsk State Technical University
Abstract: The article provides an overview of modern ideas about the localization of functions in the cerebral cortex from the point of view of its structure.
Key words: brain, cerebral cortex, contex cerebi, neocortex, neocortex, cytoarchitectonics, functional map of the cerebral cortex, localization of functions in the cerebral cortex, sensorimotor center, taste analysis center, auditory center, vestibular center.
Introduction
People have always been interested in the nature of complex human behavior: thinking, memory mechanisms, mental processes, creative abilities. In ancient times, these issues were dealt with by representatives of various religions, priests, and philosophers. By the end of the 18th century. scientists have tried to solve this problem from the point of view of the structure of the brain.
Franz Joseph Gall was the first to try to prove that all human mental functions are determined by the structure of the brain. In addition, Gall formulated the doctrine of localization of functions and proposed to determine character inclinations and human individuality by bumps on the surface of the skull. The idea was ridiculed, and Gall's real merits were forgotten. At the beginning of the 19th century. The theory of M. Flourens was popular. He believed that the human cerebral cortex has no functional specialization and argued about the equality of all parts of the cerebral cortex. In 1861, Brock established a relationship between damage to the posterior third of the inferior frontal gyrus of the left hemisphere and a violation of articulate speech. Subsequently, Brock and Warnicke continued to deepen the idea of localization of functions and obtained some facts proving this idea. The discovery that the cerebral cortex has
highly differentiated structure and that strictly differentiated effects can be caused from its individual sections have become firmly established in science.
Currently, there are many methods for studying the structure and functional state of the brain. New directions of research are also being developed.
Researchers from the Jülich Research Center and the Montreal Neurological Institute have created the first high-resolution 3D digital model of the brain and called it BigBrain. Using high-tech cutting, the researchers cut the human brain into 7,404 thin slices, each about the thickness of plastic film.
Next, the researchers stained the sheets to increase contrast, photographed each sheet with a flatbed scanner (with a resolution of 13 thousand by 11 thousand pixels.), and then used the computing power of supercomputers from seven centers in Canada to digitally stitch together the images (using about 100,000 computer processors). The researchers analyzed about one terabyte of images. The result is the most detailed atlas of the brain yet (Fig. 1).
Rice. 1. - 3-0 Atlas of the Human Brain (bigbrain.loris.ca) Such an anatomical atlas not only simplifies the work of neurologists and neurosurgeons, but also provides an opportunity to understand how the brain processes and perceives information.
Digital reconstruction of the human brain allows us to see it at the level of individual cells: its resolution is 20 microns. In total, during the painstaking work on which scientists spent 10 years, 80 billion neurons were recorded. Attempts are currently being made to build a brain model with a resolution of 1 micrometer. This model will be able to reflect the morphology of the brain at the subcellular level.
The US has announced $130 million for a project to map the human brain to help find treatments for disorders such as Alzheimer's disease. Some of the biggest investors in brain research include the Wellcome Trust, which invests £80 million in the field each year. The European Union is ready to allocate a billion euros to develop a model of the human brain using computer technology.
This article discusses modern ideas about the localization of functions in the cerebral cortex from the point of view of its structure. Information about the functional fields of the human brain was obtained in various studies, for example, by comparing local destruction of areas of the cortex with observed deviations in behavior, direct stimulation of the cortex with microelectrodes, positron emission tomography and other methods described in.
Global brain structure
The brain - the highest organ of the nervous system - as an anatomical and functional formation can be conditionally divided into several levels (Fig. 2), each of which carries out its own functions.
Level I - the cerebral cortex - carries out higher control of sensory and motor functions, primary control of complex cognitive processes.
Level II - the basal nuclei of the cerebral hemispheres - controls involuntary movements and regulates muscle tone.
Level III - hippocampus, pituitary gland, hypothalamus, cingulate gyrus, amygdala - primarily controls emotional reactions and states, as well as endocrine regulation.
Level IV (lowest) - the reticular formation and other structures of the brain stem - controls vegetative processes.
As an anatomical formation, the large brain (cerebrum) consists of two hemispheres - right and left (hemisphererum cerebri dextrum et sinistrum).
Each hemisphere has five lobes (Fig. 3, Fig. 4):
1) frontal (lobus frontalis);
2) parietal (lobus parietalis);
3) occipital (lobus occipitalis);
4) temporal (lobus temporalis);
5) insular, islet (lobus insularis, insule).
Rice. 2. - Lobes of the cerebral hemispheres All data (anatomical, physiological, and clinical) indicate the leading role of the cerebral cortex in the cerebral organization of mental processes. The cerebral cortex is
the most differentiated region of the brain in structure and function.
The cerebral cortex (contex cerebi) is divided into the following structural elements:
Ancient (paleocortex);
Old (archicortex);
Middle (mesocortex);
New (neocortex).
In humans, the neocortex is the most complex in structure; its length makes up 96% of the entire surface of the hemispheres, so we will consider it specifically.
All areas of the neocortex are built according to the same principle. The most typical human cortex is a six-layer neocortex, but the number of layers varies in different parts of the brain. Each layer differs in thickness, structure of neurons and their organization.
Cytoarchitectonic fields
The human cerebral cortex is heterogeneous even within the same hemisphere and has a different cellular composition (Fig. 3).
Rice. 3. - Diagram of the neural and cytoarchitectonic structure of some areas of the cerebral cortex.
This made it possible to identify uniformly organized centers in it - cytoarchitectonic fields.
Cytoarchitectonics is a science that studies the structural features of the cerebral cortex relating to cells. Studies the distinctive features of various formations of the cortex regarding the general nature of the cellular structure: the size and shape of cellular elements, their distribution in words, the density of their arrangement throughout the entire diameter of the cortex and in its individual layers, the width of the cortex and its layers, their division into sublayers, the presence of those or other special cellular forms in one layer or another, the distribution of cells in the vertical direction.
Given that the brain differs between men and women, between different races, ethnic groups, and even within the same family, the location, size and presence of cytoarchitectonic fields will vary from person to person.
Therefore, the images shown in Figure 4 demonstrating cytoarchitectonic fields are approximate.
Rice. 4. - Map of cytoarchitectonic fields of the human brain (Brain Institute): a - outer lateral surface; b - inner side surface; c - front surface; g - rear surface; d - upper
surface; e - bottom surface; g - one of the typical options for the location of fields on the supratemporal surface.
The numbers indicate cytoarchitectonic fields of different structures. The boundaries of cytoarchitectonic fields coincide with functionally specialized areas of the neocortex, therefore cytoarchitectonic maps of the brain reflect the representation of various sensory organs, motor and associative centers.
Information about human functional fields was obtained in various studies, by comparing local destruction of areas of the cortex with observed deviations in behavior, direct stimulation of the cortex with microelectrodes, positron emission tomography and other methods described in.
At present, the relationships between cytoarchitectonic fields and their functions have not been fully identified. Let's look at what we've learned.
Functional centers of the frontal region
Let's consider the organization of sensorimotor centers (Fig. 5) in fields 4 and 6, which are part of the precentral gyrus of the frontal lobe of the brain.
Rice. 5. - Sensorimotor centers of the human brain (according to various authors).
Between the blue and red lines lie the motor centers of the cortex, and between the red and green lines lie the sensorimotor centers.
Sensorimotor centers of the human brain, marked in Figure 5: 1 - root of the tongue; 2 - larynx; 3 - palate; 4 - lower jaw; 5 - tongue; 6 - lower part of the face; 7 - upper part of the face; 8 - neck; 9 - fingers; 10 - brush; 11 - arm from shoulder to hand; 12 - shoulder; 13 - blade; 14 - chest; 15 - belly; 16 - lower leg; 17 - knee; 18 - thigh; 19 - toes; 20 - big toe; 21 - four toes; 22 - foot; 23 - face; 24 - pharynx.
Let's consider the organization of sensorimotor centers (Fig. 6) in fields 8, 9, 44, 45, 46, included in the frontal areas of the brain (Fig. 4).
Rice. 6. - Sensorimotor centers of the frontal region of the human brain (according to
Sensorimotor centers of the human brain, marked in Figure 13.
1) motor speech field, or Broca’s area (field 44, 45);
2) field of control over coordinated movements (field 46);
3) coordination of eye movements (field 8);
4) the object tracking field and the eye movement control center associated with attention (46);
5) tone of the limbs on the opposite side of the body (field 8);
6) combined body rotation (field 8)
7) control over eye and head movements in the opposite direction, head statics (field 8).
Precentral areas responsible for complex voluntary movements are integrated with specialized motor fields. With the help of these fields complex coordinated movements are carried out
eyes, head, hands and whole body. This is why in the human neocortex there are no sharp cytoarchitectonic boundaries between the precentral and frontal regions.
Broca's area (areas 44 and 45) is a kind of superstructure over the motor and sensory fields located around the central sulcus. The size of these fields is not constant and can vary several times between individuals.
We have described in detail the main functional centers of the frontal region. Now let's briefly look at the functions of other areas of the cerebral cortex.
The insular region is responsible for receiving and analyzing taste sensations, and also consciously controls the eating process.
The temporal region is responsible for hearing and analyzing received sounds, and is also responsible for the vestibular apparatus.
The parietal region, like the frontal region, makes up a significant part of the cerebral hemispheres. The function of the parietal lobe is associated with the perception and analysis of sensory stimuli and spatial orientation.
The occipital region is associated with the perception and processing of visual information, the organization of complex processes of visual perception.
Conclusion
The global structure of the brain is presented. A review of modern ideas on the localization of functions in the cerebral cortex is presented. It has been shown that the localization of functions coincides with the localization of various structural elements of the brain. Note that due to the large variability of the brain, the presented data have
close character. Each person's functional areas will be different in size and slightly different in location.
At the moment, there are many different kinds of “gaps” in understanding the organization of the brain and the functions of its various sections. The problem of localizing functions in the cerebral cortex has not been completely resolved. Therefore, the enormous attention of researchers to studying the structure and building a model of the brain is justified.
Literature
1. Luria A. R. Higher human cortical functions and their disorders in local brain lesions. Moscow: Moscow University Publishing House, 19b2. 42b p.
2. Guzhov V.I., Vinokurov A.A. Methods for studying the structure and functional state of the brain // Automation and software engineering. 2G14. No. 3 (9). S. SG-SS.
3. Catherine Amunts, Claude Lepage, Louis Borgeat, Hartmut Mohlberg, Timo Dickscheid, Marc-Étienne Rousseau, Sebastian Bludau, Pierre-Louis Bazin, Lindsay B. Lewis, Ana-Maria Oros-Peusquens, Nadim J. Shah, Thomas Lippert, Karl Zilles, Alan C. Evans. REPORT BigBrain: An Ultrahigh-Resolution 3D Human Brain Model. DOI: 10.1126/science.1235381. Science 21 June 2G13: Vol. 34G no. b139. pp.1472-1475.
4. Belik D.V., Dmitriev N.A., Pustovoy S.A. Study of ways of audio-color-visual stimulation of brain memory fields in the post-stroke period // Current problems of electronic instrumentation (APEP-2G14): tr. 12th international Conf., Novosibirsk, October 2-4. 2G14: in 7 volumes. -Novosibirsk: NSTU Publishing House, 2G14. pp. 12G-124.
5. M. Hallett. Transcranial magnetic stimulation and the human brain. Nature 4G6. 2GGG. pp. 147-15G.
6. Fedotov A. A. Measuring transducer of evoked auditory potentials of bioelectrical activity of the brain // Engineering Bulletin of the Don, 2012, No. 4 URL: ivdon.ru/ru/magazine/archive/n4p1y2012/1107.
7. Minyaeva N.R. Evoked brain activity during the perception of Kaniz figures // Engineering Bulletin of the Don, 2012, No. 4 URL: ivdon.ru/magazine/archive/n4p1y2012/1131.
8. Kuo C-C, Luu P, Morgan KK, Dow M, Davey C. Localizing Movement-Related Primary Sensorimotor Cortices with Multi-Band EEG Frequency Changes and Functional MRI. PLoS ONE 9(11): e112103. 2014. p. 14
9. Savelyev S.V. The emergence of the human brain. M: VEDI, 2010. 324 p.: ill.
10. Khomskaya E. D. Neuropsychology: 4th edition. St. Petersburg: Peter, 2005. 496 pp.: ill.
1. Lurija A.R. Vysshie korkovye funkcii cheloveka i ih narushenija pri lokal"nyh porazhenijah mozga. Moscow: "Izdatel"stvo Moskovskogo universiteta", 1962. 426 p.
2. Guzhov V.I., Vinokurov A.A. Automatics and Program Engineering. 2014. No. 3 (9). pp. 80-88.
3. Catherine Amunts, Claude Lepage, Louis Borgeat, Hartmut Mohlberg, Timo Dickscheid, Marc-Etienne Rousseau, Sebastian Bludau, Pierre-Louis Bazin, Lindsay B. Lewis, Ana-Maria Oros-Peusquens, Nadim J. Shah, Thomas Lippert, Karl Zilles, Alan C. Evans. DOI: 10.1126/science.1235381. Science 21 June 2013: Vol. 340 no. 6139. pp.1472-1475.
4. Belik D.V., Dmitriev N.A., Pustovoj S.A. Aktual"nye problemy jelektronnogo priborostroenija (APJeP-2014): tr. 12 mezhdunar. konf.,
Novosibirsk, 2-4 okt. 2014: v 7 t. - Novosibirsk: Izd-vo NGTU, 2014. pp. 120124.
5. M. Hallett. Nature 406. 2000. pp. 147-150.
6. Fedotov A.A. Inzenernyj vestnik Dona (Rus), 2012, No. 4 URL: ivdon.ru/ru/magazine/archive/n4p1y2012/1107.
7. Minjaeva N.R. Inzenernyj vestnik Dona (Rus), 2012, No. 4 URL: ivdon.ru/magazine/archive/n4p1y2012/1131.
8. Kuo C-C, Luu P, Morgan KK, Dow M, Davey C. PLoS ONE 9(11): e112103. 2014. p. 14
9. Savel "ev S.V. Vozniknovenie mozga cheloveka. M: VEDI, 2010. 324 p.: il.
10. Homskaja E.D. Nejropsihologija: 4th edition. SPb.: Piter, 2005. 496 p: il.
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 in 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...
Morphological basis of dynamic localization of function in the cerebral hemisphere cortex (cerebral cortex centers)
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 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 marked the beginning of the doctrine of the different qualities of the cerebral cortex - cytoarchitectonics (cytos - cell, architectones - structure). Research by Brodmann, Economo and employees of the Moscow Brain Institute, headed by S. A. Sarkisov, was able 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; there is also a division of the cortex into more than 200 fields (U. Vogt and O. Vogt, 1919). From these fields, designated by numbers, a special “map” of the human cerebral cortex is compiled (Fig. 299).
According to 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, synthesis occurs here, a combination of analyzers with each other and with different activities of the body. “The analyzer is a complex nervous mechanism, starting with the external perceptive apparatus and ending in the brain” (I. P. Pavlov. Selected works, p. 193). From the point of view of I.P. Pavlov, think tank, or cortical end of the analyzer, does not have strictly defined boundaries, but consists of a nuclear and scattered part - the theory of the nucleus and scattered elements. The "core" represents a detailed and precise projection in the cortex of all the elements of the peripheral receptor and is necessary for the implementation of higher analysis and synthesis. " Trace elements"are located on the periphery of the nucleus and can be scattered far from it; simpler and more elementary analysis and synthesis are carried out in them. When the nuclear part is damaged, scattered elements can to a certain extent compensate for the lost function of the nucleus, which is of great clinical importance for restoring this function.
Before I.P. Pavlov, the cortex was distinguished by the motor zone, or motor centers, the anterior central gyrus and the sensitive zone, or sensory centers, located behind the sulcus centralis Rolandi. I.P. Pavlov showed that the so-called motor zone, corresponding to the anterior central gyrus, 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).
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 main perceptive areas of the cerebral hemisphere cortex.
First of all, let's consider cortical ends of internal analyzers(see Fig. 289, 299).
1. , i.e., the analyzer of proprioceptive (kinesthetic) irritations emanating from bones, joints, skeletal muscles and their tendons, is located in the anterior central 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 nucleus, the motor analyzer, are located in the middle layers of the motor zone cortex. In its deep layers (5th, partly and 6th) lie giant Betz pyramidal cells, which are efferent neurons, which I. P. Pavlov considers as interneurons connecting the cerebral cortex with the subcortical ganglia, nuclei of the brain nerves and anterior horns spinal cord, i.e. with motor neurons. In the anterior central gyrus, the human body, as well as in the posterior one, 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 anterior central gyrus, proprioceptive impulses (muscular-articular sensitivity) also come to the cortex of the posterior central gyrus.
2. Motor analyzer core related to combined rotation of the head and eyes in the opposite direction, 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 eye muscles contract, the cerebral cortex (motor analyzer, field 8) always receives not only impulses from the receptors of these muscles, but also impulses from the retina (visual analyzer, field 17), different visual stimuli are always combined with different eye positions, established by contraction of the muscles of the eyeball.
3. Motor analyzer core, through which synthesis occurs targeted combined movements, is located in the left (for right-handed people) inferior parietal lobule, in the gyrus supramarginalis (deep layers of area 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 anterior central 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 is a static analyzer (vestibular apparatus)- not yet precisely localized in the cerebral cortex. 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, i.e., 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 rocket aviation, since the sensitivity of the vestibular system on an airplane is significantly reduced.
5. Pulse Analyzer Core, coming from viscera and vessels(autonomic functions), located in the lower parts of the anterior and posterior central gyri (V.N. Chernigovsky). Centripetal impulses from the viscera, blood vessels, smooth muscles and glands of the skin enter this section of the cortex, from where centrifugal paths emanate to the subcortical vegetative centers.
In the premotor area (fields 6 and 8), the unification of vegetative and animal functions takes place. However, one should not assume that only this area of the cortex influences the activity of the viscera. They are influenced by the state of the entire cerebral cortex.
Nerve impulses from the external environment of the body enter the cortical ends of external world analyzers.
1. Auditory Analyzer Core 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 cortical deafness.
2. Visual analyzer core located in the occipital lobe - fields 17, 18, 19. On the inner surface of the occipital lobe, along the edges of the sulcus calcarinus, the visual pathway ends in field 17. Here the retina of the eye is projected, and the visual analyzer of each hemisphere is connected with the visual fields and the corresponding halves of the retina of both eyes (for example, the left hemisphere is connected with the lateral half of the left eye and the medial half of the right). 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 field 19, when damaged, you lose orientation in an unusual environment.
3. Nucleus of the olfactory analyzer located in the phylogenetically most ancient part of the cerebral cortex, within the base of the olfactory brain - uncus, partly the horn of Ammon (field 11) (see Fig. 299, fields A and B).
4. Taste Analyzer Core, according to some data, is located in the lower part of the posterior central gyrus, close to the centers of the muscles of the mouth and tongue, according to others - in the uncus, in the immediate vicinity of the cortical end of the olfactory analyzer, which explains the close connection between olfactory and taste sensations. It has been established that taste disorder occurs when field 43 is damaged (V. M. Bekhterev).
Analyzers of smell, taste and hearing of each hemisphere are connected to the receptors of the corresponding organs on both sides of the body.
5. Skin analyzer core(touch, pain and temperature sensitivity) is located in the posterior central gyrus (fields 1, 2, 3) and in the cortex of the superior parietal region (fields 5 and 7). In this case, the body is projected upside down in the posterior central gyrus, so that in its upper part there is a projection of the receptors of the lower extremities, and in the lower part there is a projection of the receptors of the head. Since in animals the receptors for general sensitivity are especially developed at the head end of the body, in the area of the mouth, which plays a huge role in capturing food, humans have retained a strong development of mouth receptors. In this regard, the region of the latter occupies an enormously large area in the cortex of the posterior central gyrus. At the same time, in connection with the development of the hand as an organ of labor, touch receptors in the skin of the hand sharply increased in humans, which also became an organ of touch. Accordingly, the areas of the cortex related to the receptors of the upper limb are sharply superior to the area of the lower limb. Therefore, if in the posterior central gyrus you draw the figure of a person with his head down (to the base of the skull) and feet up (to the upper edge of the hemisphere), then you need to draw a huge face with an incongruously large mouth, a large hand, especially a hand with a thumb that is sharply larger than the rest, a small body and a small leg. Each posterior central gyrus is connected to the opposite part of the body due to the intersection of sensory conductors in the spinal cord and partly in the medulla oblongata.
A particular type of skin sensitivity is recognizing objects by touch, stereognosia(stereos - spatial, gnosis - knowledge) - is connected with a section of 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.
The described cortical ends of the analyzers are located in certain areas of the cerebral cortex, which, thus, represents “a grandiose mosaic, a grandiose signaling board” (I.P. Pavlov). Thanks to analyzers, signals from the external and internal environment of the body fall onto this “board”. These signals, according to I.P. Pavlov, constitute first signaling system reality, manifested in the form of concrete visual thinking (sensations and complexes of sensations - perceptions). The first signaling system is also present in animals. But “in the developing animal world, during the human phase, there was an extraordinary increase in the mechanisms of nervous activity. For an animal, reality is signaled almost exclusively only by irritations and their traces in the cerebral hemispheres, directly arriving in special cells of the visual, auditory and other receptors of the body. This is what we have in ourselves both impressions, sensations and ideas from the surrounding external environment, both natural and from our social one, excluding the word, audible and visible. This is the first signal system, common to us with animals. But the word made up the second, specifically our signal system system of reality, being the signal of the first signals... it was the word that made us human" (I. P. Pavlov).
Thus, I.P. Pavlov distinguishes two cortical systems: the first and second signal systems of reality, from which the first signal system first arose (it is also present in animals), and then the second - it is found only in humans and is a verbal system. Second signaling system- this is human thinking, which is always verbal, for language is the material shell of thinking. Language is “...the immediate reality of thought” (K. Marx and F. Engels. Works, ed. 2, 1955, p. 448).
Through very long repetition, temporary connections were formed between certain signals (audible sounds and visible signs) and movements of the lips, tongue, and muscles of the larynx, on the one hand, and with real stimuli or ideas about them, on the other (from V.N. Tonkov). So, on the basis of the first signaling system, a second one arose.
Reflecting this process of phylogenesis, in human ontogenesis the first signaling system is first established, and then the second. For the second signaling system to begin to function, the child needs to communicate with other people and acquire oral and written language skills, which takes a number of years. If a child is born deaf or loses his hearing before he begins to speak, then the ability of oral speech inherent in him is not used and the child remains mute, although he can pronounce sounds. In the same way, if a person is not taught to read and write, then he will forever remain illiterate. All this indicates the decisive influence of the environment on the development of the second signaling system. The latter is associated with the activity of the entire cerebral cortex, but some areas of it play a special role in speech. These areas of the cortex are the cores of speech analyzers.
Therefore, to understand the anatomical substrate of the second signaling system, it is necessary, in addition to knowledge of the structure of the cerebral cortex as a whole, to also take into account cortical ends of speech analyzers(Fig. 300).
1. Since speech was a means of communication between people in the process of their joint work activity, motor speech analyzers developed in close proximity to the core of the general motor analyzer.
Motor speech articulation analyzer(speech motor analyzer) is located in the posterior part of the inferior frontal gyrus (gyrus Broca, area 44), in close proximity to the lower part of the motor area. It analyzes the irritations coming from the muscles involved in the creation of oral speech. This function is associated with the motor analyzer of the muscles of the lips, tongue and larynx, located in the lower part of the anterior central gyrus, which explains the proximity of the speech motor analyzer to the motor analyzer of these muscles. When field 44 is damaged, the ability to make simple movements of the speech muscles, scream and even sing is retained, but the ability to pronounce words is lost - motor aphasia (phase - speech). In front of field 44 is field 45, which relates to speech and singing. When it is affected, vocal amusia occurs - the inability to sing, compose musical phrases, as well as agrammatism (E.K. Sepp) - the inability to compose sentences from words.
2. Since the development of oral speech is associated with the organ of hearing, in close proximity to the sound analyzer it has developed auditory speech analyzer. Its nucleus is located in the posterior part of the superior temporal gyrus, in the depth of the lateral sulcus (area 42, or Wernicke's center). Thanks to the auditory analyzer, various combinations of sounds are perceived by a person as words that mean various objects and phenomena and become their signals (second signals). With its help, a person controls his own speech and understands someone else’s. When it is damaged, the ability to hear sounds is preserved, but the ability to understand words is lost - word deafness, or sensory aphasia. When area 22 (the middle third of the superior temporal gyrus) is damaged, musical deafness occurs: the patient does not know motives, and musical sounds are perceived by him as random noise.
3. At a higher stage of development, humanity learned not only to speak, but also to write. Written speech requires certain hand movements when drawing letters or other characters, which is associated with the motor analyzer (general). That's why motor analyzer of written speech located in the posterior part of the middle frontal gyrus, near the zone of the anterior central gyrus (motor zone). The activity of this analyzer is connected with the analyzer of learned hand movements necessary for writing (field 40 in the inferior parietal lobule). If field 40 is damaged, all types of movement are preserved, but the ability to make subtle movements necessary for drawing letters, words and other signs (agraphia) is lost.
4. Since the development of written speech is also connected with the organ of vision, a visual written speech analyzer, which is naturally associated in the sulcus calcarfnus, where the general visual analyzer is located. The visual analyzer of written speech is located in the inferior parietal lobule, with the gyrus angularis (field 39). If area 39 is damaged, vision is preserved, but the ability to read (alexia), that is, to analyze written letters and compose words and phrases from them, is lost.
All speech analyzers are formed in both hemispheres, but develop only on one side (for right-handers - on the left, for left-handers - on the right) and are functionally asymmetrical. This connection between the motor analyzer of the hand (organ of labor) and speech analyzers is explained by the close connection between work and speech, which had a decisive influence on the development of the brain.
"...Work, and then with it articulate speech..." led to the development of the brain. (K. Marx and F. Engels. Works, ed. 2, vol. 20, p. 490). This connection is also used for medicinal purposes. When the speech motor analyzer is damaged, the elementary motor ability of the speech muscles is preserved, but the ability to speak is lost (motor aphasia). In these cases, it is sometimes possible to restore speech by long-term exercise of the left hand (in right-handed people), the work of which favors the development of the rudimentary right-sided nucleus of the speech motor analyzer.
Analyzers of oral and written speech perceive verbal signals (as I. P. Pavlov says - signal signals, or second signals), which constitutes the second signal system of reality, manifested in the form of abstract abstract thinking (general ideas, concepts, conclusions, generalizations), which characteristic only of man. However, the morphological basis of the second signal system is not only made up of these analyzers. Since the speech function is phylogenetically the youngest, it is also the least localized. It is inherent in the entire cortex. Since the cortex grows along the periphery, the most superficial layers of the cortex are related to the second signaling system. These layers consist of a large number of nerve cells (100 billion) with short processes, thanks to which the possibility of unlimited closure function and broad associations is created, which is the essence of the activity of the second signaling system. In this case, the second signaling system does not function separately from the first, but in close connection with it, or rather on its basis, since the second signals can arise only in the presence of the first. “The basic laws established in the work of the first signaling system should also govern the second, because this is the work of the same nervous tissue” (I. P. Pavlov. Selected works, pp. 238-239).
I. P. Pavlov’s doctrine of two signal systems provides a materialistic explanation of human mental activity and forms the natural science basis of V. I. Lenin’s theory of reflection. According to this theory, the objective real world, which exists independently of our consciousness, is reflected in our consciousness in the form of subjective images.
Sensation is a subjective image of the objective world. “Sensation is the transformation of the energy of external stimulation into a fact of consciousness” (V.I. Lenin).
At the receptor, external stimulation, such as light energy, is converted into a nervous process, which becomes a sensation in the cerebral cortex.
The same quantity and quality of energy, in this case light, will cause a sensation of green color (subjective image) in the cerebral cortex in healthy people, and a sensation of red color in a person with color blindness (due to the different structure of the retina).
Consequently, light energy is an objective reality, and color is a subjective image, its reflection in our consciousness, depending on the structure of the sense organ (eye).
This means that from the point of view of Lenin’s theory of reflection, the brain can be characterized as an organ for reflecting reality.
After all that has been said about the structure of the central nervous system, it can be noted human signs of brain structure, i.e., specific structural features that distinguish humans from animals (Fig. 301, 302).
1. Predominance of the brain over the spinal cord. Thus, in carnivores (for example, a cat) the brain is 4 times heavier than the spinal cord, in primates (for example, macaques) - 8 times, and in humans - 45 times (the weight of the spinal cord is 30 g, the brain - 1500 g) . According to Ranke, the spinal cord by weight makes up 22-48% of the weight of the brain in mammals, 5-6% in a gorilla, and only 2% in humans.
2. Brain weight. In terms of the absolute weight of the brain, a person does not take first place, since large animals have a brain heavier than a person’s (1500 g): a dolphin - 1800 g, an elephant - 5200 g, a whale - 7000 g. To reveal the true relationship of brain weight to body weight, recently they began to determine the “square brain index” (Ya. Ya. Roginsky), i.e., the product of the absolute weight of the brain and the relative one. This index made it possible to distinguish man from the entire animal world.
Thus, in rodents it is 0.19, in carnivores - 1.14, in cetaceans (dolphin) - 6.27, in apes - 7.35, in elephants - 9.82 and, finally, in humans - 32. 0.
3. The predominance of the cloak over the brain stem, i.e., the new brain (neencephalon) over the old brain (paleencephalon).
4. The highest development of the frontal lobe of the cerebrum. According to Brodmann, the frontal lobes account for approximately 8-12% of the total surface area of the hemispheres in lower monkeys, 16% in anthropoid monkeys, and 30% in humans.
5. The predominance of the new cortex of the cerebral hemispheres over the old one (see Fig. 301).
6. The predominance of the cortex over the “subcortex”, which in humans reaches maximum figures: the cortex, according to Dalgert, makes up 53.7% of the total brain volume, and the basal ganglia - only 3.7%.
7. Furrows and convolutions. The furrows and convolutions increase the area of the gray matter cortex, so the more developed the cerebral cortex, the greater the folding of the brain. An increase in folding is achieved by the greater development of small grooves of the third category, the depth of the grooves and their asymmetrical arrangement. No animal has such a large number of grooves and convolutions at the same time, so deep and asymmetrical, as in humans.
8. The presence of a second signaling system, the anatomical substrate of which is the most superficial layers of the cerebral cortex.
To summarize the above, we can say that the specific features of the structure of the human brain, which distinguish it from the brain of the most highly developed animals, are the maximum predominance of the young parts of the central nervous system over the old ones: the brain - over the spinal cord, the cloak - over the trunk, the new cortex - over the old, superficial layers of the cerebral cortex - above the deep ones.
Motor cortex areas. Movements occur when the cortex is stimulated in the area of the precentral gyrus. The area that controls the movements of the hand, tongue, and facial muscles is especially large.
Sensory cortex: somatic (skin) Human sensitivity, feelings of touch, pressure, cold and heat are projected into the postcentral gyrus. In the upper part there is a projection of the skin sensitivity of the legs and torso, lower - the arms and even lower - the head. Proprioceptive sensitivity (muscle feeling) projects to the postcentral and precentral gyri . Visual area cortex is located in the occipital lobe. Auditory zone The cortex is located in the temporal lobes of the cerebral hemispheres. Olfactory zone The cortex is located at the base of the brain. Projection taste analyzer , localized in the area of the mouth and tongue of the postcentral gyrus .
Association areas of the cortex. The neurons of these areas are not connected either to the sense organs or to the muscles; they communicate between different areas of the cortex, integrating, combining all impulses entering the cortex into integral acts of learning (reading, speech, writing), logical thinking, memory and providing the possibility of expedient behavior reactions. These areas include the frontal and parietal lobes of the cerebral cortex, which receive information from the association nuclei of the thalamus.
Lateral ventricles(right and left) are cavities of the telencephalon, lie below the level of the corpus callosum in both hemispheres and communicate through the interventricular foramina with the third ventricle. They are irregular in shape and consist of anterior, posterior and lower horns and a central part connecting them.
Topic 17. Basal ganglia
The basal ganglia of the telencephalon are accumulations of gray matter within the hemispheres. These include striatum (striatum), consisting of caudate and lenticular nuclei interconnected. The lentiform nucleus is divided into two parts: located outside shell and lying inside pale ball. The caudate nucleus and putamen are united into neostriatum. They are subcortical motor centers. Outside the lenticular nucleus there is a thin plate of gray matter - the fence. In the anterior part of the temporal lobe lies amygdala. Between the basal ganglia and the thalamus there are layers of white matter, the internal, external and outermost capsules. Conducting pathways pass through the internal capsule.
Topic 1. Limbic system
The telencephalon contains the formations that make up the limbic system: the cingulate gyrus, hippocampus, mammillary bodies, anterior thalamus, amygdala, fornix, septum pellucida, hypothalamus. They are involved in maintaining the constancy of the internal environment of the body, regulating autonomic function and forming emotions and motivations. This system is otherwise called the “visceral brain.” Information from internal organs comes here. When the limbic cortex is irritated, autonomic functions change: blood pressure, breathing, movements of the digestive tract, tone of the uterus and bladder.
Topic 19. Liquid media of the central nervous system: circulatory and liquor systems.Blood-brain barrier.
Blood supply The brain is carried out by the left and right internal carotid and branches of the vertebral arteries. Formed at the base of the brain arterial circle(Circle of Willis), which provides favorable conditions for blood circulation in the brain. The left and right anterior, middle and posterior cerebral arteries pass from the arterial circle to the hemispheres. Blood from the capillaries collects in the venous vessels and flows from the brain into the sinuses of the dura mater.
Liquor system of the brain. The brain and spinal cord are washed by cerebrospinal fluid (CSF), which protects the brain from mechanical damage, maintains intracranial pressure, and takes part in the transport of substances from the blood to brain tissue. From the lateral ventricles, cerebrospinal fluid flows through the foramen of Monro into the third ventricle and then through the aqueduct into the fourth ventricle. From it, the cerebrospinal fluid passes into the spinal canal and into the subarachnoid space.
Blood-brain barrier. Between neurons and blood in the brain there is a so-called blood-brain barrier, which ensures the selective flow of substances from the blood to nerve cells. This barrier performs a protective function, as it ensures the constancy of the cerebrospinal fluid. It consists of astrocytes, endothelial cells of capillaries, epithelial cells of the choroid plexuses of the brain.
Seminar topics
1. The role of spinal and cranial nerves in the perception of sensory information
2. The role of the telencephalon in the perception of signals from the external and internal environment
3. The main stages of the evolution of the central nervous system and ontogenesis of the nervous system
4. Brain diseases
5. Brain aging
Tasks for independent work
1. Draw a frontal section of the spinal cord with all the symbols known to you.
2. Draw a sagittal section of the brain indicating all its parts.
3. Draw a sagittal section of the spinal cord and brain, indicating all the cavities of the brain.
4. Draw a sagittal section of the brain with all the structures known to you.
Questions for self-control
1. Define the basic concepts of the anatomy of the central nervous system:
The concept of the nervous system;
Central and peripheral nervous system;
Somatic and autonomic nervous system;
Axes and planes in anatomy.
2. What is the main structural unit of the nervous system?
3. Name the main structural elements of a nerve cell.
4. Give a classification of nerve cell processes.
5. List the sizes and shapes of neurons. Tell us about the use of microscopic technology.
6. Tell us about the nucleus of a nerve cell.
7. What are the main structural elements of neuroplasm?
8. Tell us about the nerve cell membrane.
9. What are the main structural elements of a synapse?
10. What is the importance of mediators in the nervous system?
11. What are the main types of glia in the nervous system?
12. What is the role of the myelin sheath of the nerve fiber for conducting nerve impulses?
13. Name the types of nervous system in phylogeny.
14. List the structural features of the reticular nervous system.
15. List the structural features of the nodal nervous system.
16. List the structural features of the tubular nervous system.
17. Expand the principle of bilateral symmetry in the structure of the nervous system.
18. Expand the principle of cephalization in the development of the nervous system.
19. Describe the structure of the nervous system of coelenterates.
20. What is the structure of the nervous system of annelids?
21. What is the structure of the nervous system of mollusks?
22. What is the structure of the nervous system of insects?
23. What is the structure of the nervous system of vertebrates?
24. Give a comparative description of the structure of the nervous system of lower and higher vertebrates.
25. Describe the formation of the neural tube from the ectoderm.
26. Describe the stage of three brain vesicles.
27. Describe the stage of five brain vesicles.
28. The main parts of the central nervous system in a newborn.
29. Reflex principle of the structure of the nervous system.
30. What is the general structure of the spinal cord?
31. Describe the segments of the spinal cord.
32. What is the purpose of the anterior and posterior roots of the spinal cord?
33. Segmental apparatus of the spinal cord. What is the organization of the spinal reflex?
34. What is the structure of the gray matter of the spinal cord?
35. What is the structure of the white matter of the spinal cord?
36. Describe the commissural and suprasegmental apparatus of the spinal cord.
37. What is the role of the ascending tracts of the spinal cord in the central nervous system?
38. What is the role of the descending tracts of the spinal cord in the central nervous system?
39. What are spinal nodes?
40. What are the consequences of spinal cord injuries?
41. Describe the development of the spinal cord in ontogenesis.
42. What are the structural features of the main membranes of the central nervous system?
43. Describe the reflex principle of the organization of the central nervous system.
44. Name the main parts of the rhombencephalon.
45. Describe the dorsal surface of the medulla oblongata.
46. Describe the ventral surface of the medulla oblongata.
47. What are the functions of the main nuclei of the medulla oblongata?
48. What are the functions of the respiratory and vasomotor centers of the medulla oblongata?
49. What is the general structure of the fourth ventricle, the cavity of the rhombencephalon?
50. Name the structural features and functions of the cranial nerves.
51. List the characteristics of the sensory, motor and autonomic nuclei of the cranial nerves.
52. What is the purpose of the bulbar parasympathetic center of the brain?
53. What are the consequences of bulbar disorders?
54. What is the general structure of the bridge?
55. List the nuclei of the cranial nerves lying at the level of the pons.
56. What reflexes in the central nervous system correspond to the auditory and vestibular nuclei of the pons?
57. Explain the ascending and descending paths of the bridge.
58. What are the functions of the lateral and medial lemniscal tracts?
59. What is the purpose of the reticular formation of the brain stem in the central nervous system?
60. What is the role of the blue spot in the organization of brain functions. What is the noradrenergic system of the brain?
61. What is the role of the raphe nuclei in the central nervous system. What is the serotonergic system of the brain?
62. What is the general structure of the cerebellum. What are its functions in the central nervous system?
63. List the evolutionary formations of the cerebellum.
64. What are the connections of the cerebellum with other parts of the central nervous system. Anterior, middle and posterior cerebellar peduncles?
65. Cerebellar cortex. Tree of life of the cerebellum.
66. Describe the cellular structure of the cerebellar cortex.
67. What is the role of the subcortical nuclei of the cerebellum in the central nervous system?
68. What are the consequences of cerebellar disorders?
69. What is the role of the cerebellum in organizing movements?
70. Name the main functions in the central nervous system of the midbrain. What is the Sylvian aqueduct?
71. What is the structure of the roof of the midbrain. Anterior and posterior tubercles of the quadrigeminal and their purpose?
72. What is the purpose of the main tire cores?
73. What is the purpose of the mesencephalic parasympathetic center?
74. What is the periaqueductal gray matter needed for? Reveal the features of the organization of the pain system in the central nervous system.
75. What are the red nuclei of the midbrain. Define decerebrate rigidity?
76. Black nucleus and ventral tegmental area. What is the role of the brain's dopaminergic system in the central nervous system?
77. Descending and ascending pathways of the midbrain. Pyramidal and extrapyramidal systems of the central nervous system.
78. What is the structure and purpose of the cerebral peduncles?
79. What is the purpose of the dorsal and ventral chiasm of the midbrain?
80. Describe the general structure of the diencephalon and its main functions. What is the location of the third ventricle?
81. Name the main parts of the thalamic brain.
82. Describe the structure and functions of the thalamus.
83. Describe the structure and functions of the suprathalamic region.
84. Describe the structure and functions of the post-thalamic region.
85. What is the role of the hypothalamus in organizing the functions of the central nervous system?
86. Neurohumoral function of the brain. Epiphysis and pituitary gland, their location and purpose.
87. What is the role of the Peipets circle in the organization of adaptive behavior.
88. Hippocampus, its structure and functions.
89. Cingulate cortex, its structure and functions.
90. The amygdala complex, its structure and functions.
91. Emotional-motivational sphere and its brain support.
92. What are the “reward” and “punishment” systems of the brain? Self-irritation reaction.
93. Neurochemical organization of the brain’s reinforcing systems.
94. What are the consequences of damage to individual formations of the limbic system? Animal studies.
95. Describe the general structure of the telencephalon. What is its role in ensuring adaptive behavior in humans and animals?
96. Name the main functions of the striatum.
97. Evolutionary formations of the striatum.
98. Caudate nucleus, its location and purpose. Nigrostriatal system of the brain.
99. Ventral striatum, its structure and functions. Mesolimbic system of the brain.
100. General structure of the cerebral hemispheres (lobes, sulci, gyri).
101. Dorsolateral surface of the cerebral cortex.
102. Medial and basal surfaces of the cerebral cortex.
103. What is the role of interhemispheric asymmetry in the organization of adaptive behavior. Corpus callosum.
104. Cytoarchitecture of the cerebral cortex (cortical layers and Brodmann areas).
105. Evolutionary formations of the cerebral cortex (new cortex, old cortex, ancient cortex) and their functions.
106. Projection and associative areas of the cerebral cortex and their purpose.
107. Speech-sensory and speech-motor centers of the cerebral cortex.
108. Sensomotor cortex, its localization. Projections of the human body in the sensorimotor cortex.
109. Visual, auditory, olfactory, gustatory cortical projections.
110. Basics of topical diagnostics for damage to areas of the cerebral cortex.
111. Frontal and parietal cortex and their role in ensuring adaptive activity of the brain.
1.1. From the history of the doctrine of localization of HMF
The idea that different parts of the brain have different specializations, that is, they do not function in the same way, arose a long time ago, long before the emergence of neuropsychology as a scientific discipline. First of all, it is associated with the name of the French neurologist Franz Gall (F. Gaal), who was the first to suggest that the monotonous-looking mass of the brain consists of many organs. G. Head, who wrote a work that traced the history of scientific thought over the course of a century (from the mid-19th to the mid-20th centuries), provides interesting information about how F. Gall developed this opinion.
As a child, F. Gall grew up and studied with a boy who found learning much easier. If it was necessary to learn something by heart, this boy and some other students at school were significantly ahead of him in many subjects, but at the same time lagged behind him in written work. F. Gall noticed that these students with a good memory for oral texts have large “bull's eyes” and bumps above the brow ridges. On this basis, he associated the ability to easily learn by heart with a good memory for words and came to the conclusion that this ability is located in that part of the brain that is located behind the orbits. This is how the idea arose that memory for words is located in the frontal lobes of the brain. All his life he paid attention to the structure of the skull of different people and associated certain abilities they had with its features. On the basis of these views, a whole field of knowledge arose - phrenology (from Greek - “soul”), containing instructions on how to determine the character and abilities of a person by the shape of the skull. F. Gall began to be called the founder of phrenology, which was considered, and continues to be considered, a dubious area of scientific research. F. Gall's views were considered so dangerous to religion and morals that his lectures were prohibited by the Kaiser's own letter. However, F. Gall's phrenological ideas, no matter how they are assessed, played a big role. They started the idea of the presence of specialized sections in the human brain, each of which performs its own specific function. This no longer allowed us to consider the brain as a single homogeneous mass.
By the 60s of the 19th century, the situation in neurological science was tense to the limit. Questions about the localization of function in the brain have been raised in scientific debates on all occasions. Despite the work of F. Gall and his followers, the main question remained the question of whether the brain functions as one whole or whether it consists of many organs and centers operating more or less independently of each other. The most pressing problem was speech localization. It was a common belief that speech was the responsibility of frontdepartments brain
F. Gall believed that other HMFs also have a certain cerebral localization. Thus, he distinguished the memory of things, places, names, grammatical categories and located them in different areas of the brain. As will be shown below, these views were progressive and were largely confirmed later. F. Gall's opinion that abilities higher in the hierarchy have the same delineated localization in any part of the brain turned out to be untenable. It turned out that such psychological qualities as “courage”, “sociability”, “love for parents”, “ambition”, “instinct of procreation”, etc., are not located in “separate organs” of the brain, as F. Gall claimed.
Nevertheless, the idea of localization received powerful development. In August 1861, the French neurologist Paul Broca, at a meeting of the Anthropological Society of Paris, reported his famous case, which proved that damage to a separate brain zone, i.e. localized lesions can destroy functions such as speech, causing a loss of speech called aphasia. At the autopsy of the skull of P. Broca's patient, Lebran, whom he had been observing for 17 years, destruction of a large area of the left hemisphere of the brain, covering mainly the speech motor area, was discovered. Based on the fact that speech movements were the most affected, this area began to be considered the center motor speech, and aphasia resulting from its defeat, motor aphasia.
10 years after P. Broca's report, at a meeting of the same Society, German neurologist Karl Wernice presented another case of local brain damage, also in a patient with aphasia. Patient K. Wernicke, although confusedly, could speak himself, but practically did not understand the speech of other people. In this patient, the lesion covered most of the temporal lobes of the left hemisphere. K. Wernicke gave this form of aphasia the name sensory, and the affected area of the brain - the center of sensory speech, and designated the aphasia arising as a result of its damage as sensory. Thus, the doctrine of the localization of HMF was significantly advanced.
Soon others were added to the centers of motor and sensory speech. Interest in the issue of local brain lesions has increased in many countries. The localizationist ideas of F. Gall received an even more powerful sound, and a fascination with centers began in science, which led, as G. Head aptly put it, to the construction of diagrams and diagrams. The brain became divided into many areas, reflecting the ideas of that time about the varied functional specialization of brain areas. The famous patchwork map of the brain appeared, where to the character traits localized by F. Gall were added many more, including acquired, addictions, for example, to this or that food, to this or that music, etc. Thus, the idea of localizing a function was taken to the point of absurdity (Fig. 9 cm. color on). Naturally, serious objections arose from contemporaries who believed that the brain could not function so “fractionally.” These scientists, who formed the opposition to narrow localizationists, were called antilocalizationists. The most prominent representative of this trend was the French scientist Pierre Marie (P. Man). He believed that the functional specialization of the brain cannot be so narrow and that the actual speech area is only the left temporal lobe.
Some scientists took an intermediate position. Their prominent representative was H. Jackson. In his opinion, each complexly organized function is represented in the brain at three levels: 1) lower (stem or spinal); 2) middle (in the motor or sensory parts of the cerebral cortex); 3) higher (frontal lobes of the brain). These ideas are still relevant today, although with some clarifications, which will be discussed below. X. Jackson famously said that localize function and localize lesion- Not same. This means that as a result of brain damage in one place, dysfunction in another may result, and this no longer coincided with the ideas of narrow localizationism.
1.2. Modern ideas about the localization of VMF (the idea of dynamic localization of VMF)
The accumulated experience in the field of the consequences of local brain lesions served as the basis for the emergence of the theory of the systemic structure of speech function and its dynamic localization in the brain, which put an end to the debate between localizationists and antilocalizationists that had lasted more than a century. This theory was created by the works of domestic neurologists and neurophysiologists N.A. Bernstein, P.I. Anokhin, A.I. Ukhtomsky, psychologist L.S. Vygotsky, the founder of neuropsychology A.R. Luria et al.
Term "dynamic" in relation to localization is due to the fact that, according to the ideas of these scientists, the same brain area can be included in a variety of different ensembles of brain regions, i.e. dynamically change your position and role. When performing one function, it functions together with some zones, and when performing another, with others, like colored glass in a children's toy. kaleidoscope: the pieces of glass are the same, but the image is different - depending on changes in their combination. In each specific ensemble of brain zones involved in the implementation of a function, the role of each of them is specific (rice.I).
This ability of nervous structures to be involved in different ways in different functions is a vivid embodiment of the biological principle of economy, which makes it possible to make this or that type of mental activity the most optimal way to implement it.
Despite this complexity of the brain organization of the HMF, much more is now known about what functional specialization different areas of the brain have, which is reflected in special brain maps.
The zones indicated in them are the result of research not only within the framework of neuropsychology, but also much older scientific research.
Outstanding Russian neurophysiologist P.K. Anokhin defines each functional system as a specific complex, a set of afferent signaling, “which, through action acceptors, directs the execution of its function.”
^ DYNAMIC LOCALIZATION OF HIGHER PSYCHIC FUNCTIONS
Rice. I
Legend: D - right hemisphere, S - left hemisphere, F - frontal lobe, O - occipital lobe, T - temporal lobe.
PC. Anokhin revealed the most important regularity of higher nervous activity, namely that external afferent stimuli entering the central nervous system spread throughout it not linear, as was previously believed, and enter into subtle interactionsviya with other afferent excitations. These “associations” can be replenished with new connections, enriched by them. Activities as a whole are changing. It is the unification of afferentations that is an indispensable condition for decision making.
Thus, afferent synthesis as a mechanism of higher mental activity by P.K. Anokhin attached paramount importance. Finally, one cannot help but dwell on the fact that he introduced into science the concept of “reverse afferentation”, i.e. a mechanism that informs about the results of the action performed so that the body evaluates them. Currently, this idea has developed into a whole scientific and practical direction of medicine called biofeedback (biofeedback).
A huge contribution to the understanding of the localization of HMF was made by the teachings of A.R. Luria about the brain organization of the HMF, which was the result of scientific and practical work with a colossal number of cranial wounds in practically healthy young people who were “suffered” by the Second World War. This tragedy made it possible to see exactly where the brain was damaged and to record which function was “lost.” The isolated findings of the classics of neurology (P. Broca, K. Wernicke, etc.) were confirmed that there are local HMFs or their fragments, i.e. those that can be carried out not at the expense of the entire brain, but of any specific area of it. The results obtained brought our country to the forefront in the world in this field, allowing us to create, as already mentioned, a new scientific discipline - neuropsychology.
L.S. Vygotsky emphasized that the problem of the brain organization of the HMF is not limited to identifying those zones that implement them. Each HMF is essentially the center of two functions: 1) specific, associated with the type of mental activity assigned to it; 2) non-specific, making this area capable of participating in any type of activity. A specific function is never carried out by any one area of the brain, but is the result of its integration with other areas of the brain. Thus, any function is related to the activity of the brain, like a figure to a background. At the same time, L.S. Vygotsky emphasized that the integrative essence of functions does not at all contradict their differentiation. On the contrary, he believed, differentiation and integration not only do not exclude each other, but rather presuppose one another and, in a certain respect, go in parallel.
Other important features of the ideas about the localization of HMF by L.S. Vygotsky believed: 1) variability of interfunctional connections and relationships; 2) the presence of complex dynamic systems in which a number of elementary functions are integrated; 3) a generalized reflection of reality in consciousness. He believed that all these three conditions reflect the universal law of philosophy, which states that the dialectical leap is not only the transition from inanimate to animate matter, but also from sensation to thinking the degree of automation of the method of performing an action by L.S. Vygotsky considered it to be conditioned by the hierarchical level at which the function is carried out.
Finally, L.S.’s conviction should be considered fundamentally important. Vygotsky’s idea is that “development comes from the bottom up, and decay comes from the top down.” This catchphrase by L.S. Vygotsky reaches such a level of generalization when the thought becomes practically undeniable. As a child develops, he comprehends the world from simple to complex. In case of loss (decay) of function, a person returns to more basic knowledge, skills and abilities, which serve as the basis for compensation processes.
From the ideas of L.S. Vygotsky’s discussion of the laws of development and decay directly follows from the following proposition: equally localized lesions lead to completely different consequences in a child and an adult. In developmental disorders associated with any brain damage, the area closest to the affected one is affected first, and in an adult, i.e. when a function disintegrates, on the contrary, the nearest inferior, and the nearest superior, suffers relatively less.
The concept of local HMFs was largely developed by N.P. Bekhtereva, who developed the concepts of flexible and rigid parts of the brain systems. To the hard links of N.P. Bekhtereva included most of the areas of regulation of vital internal organs (cardiovascular, respiratory and other systems), the second - the area of analysis of signals from the external (and partly internal) world, depending on the conditions in which a person is located. N.P. Bekhtereva found that changing conditions leads to significant changes in the functioning of brain structures that provide one or another function, and most importantly, which areas of the brain are turned off or included in activity. These data showed that the localization of the HMF can change not only from age indicators, when some links seem to die off, while others are connected, or from the individual characteristics of the brain organization of mental activity, but also from the conditions in which the activity takes place. From here, in addition, far-reaching conclusions follow about the observance of the necessary conditions for upbringing, training and human life in general, as well as about the selection of optimal conditions for the occurrence of these processes.
French scientists J. de Ajuriaguerra and X. Ekaen draw attention to the fact that the value of the clinical concept of localization is extremely great, but only if we take into account that different functions are localized differently. Anatomical, physiological and clinical data allow us to establish that the localization of certain functions is somatotopy(coincide with the projection in the brain of a dysfunctional part of the body). These include the areas of analyzers, as well as various types of gnosis, praxis, including oral-articulatory. Some types of such functions (for example, body diagram) vary significantly in structure and localization depending on the location of the lesion within the zone of their implementation or depending on the individual organization of brain activity in different patients. This is evidenced by differences in the structure of the defect in their lesions.
According to J. de Ajuriaguerre and X. Ekaen, X. Jackson’s position on the positive and negative symptoms of HMF disorder is fundamentally important. Negative means loss of function, and positive means the release of lower-lying zones, which before the breakdown were under the control of higher ones. To this, J. de Ajuriaguerra and X. Ekaen add that the release of underlying areas of the brain and corresponding functions is associated with an imbalance between the type of response to external stimuli by the lower and upper areas of the brain.
Speaking about the problem of localization, one cannot fail to take into account the fact that brain lesions of different etiology (vascular, tumor or traumatic) cause differences in the symptom complex of developing disorders.
^ Questions on the topic “Teaching about localization”:
What idea about the brain representation of the HMF was introduced by the works of classics of neurology (P. Broca, K. Wermce, etc.)?
What do the terms “localizationism” and “anti-localizationism” mean?
What does the term “dynamic localization of VMF” mean?
What are the main provisions of L.S. Vygotsky about the localization of HMFs, their structure, development and decay?
What material was used to create the teachings of A. R. Luria?
Chapter 2. Structure of the brain
2.1. General ideas about the brain
In order to consider modern ideas not only about the psychological structure of human HMF, but also their brain organization, it is advisable to turn to modern ideas about the brain as a whole.
The human brain is the upper part of the central nervous system (CNS). Between it and the lower part of the central nervous system (spinal cord) there is no boundary that would be expressed anatomically. The end of the spinal cord and the beginning of the brain is the upper cervical vertebra. From this it is clear what an important role the state of each part of the central nervous system plays for the functioning of the entire nervous system. In particular, the fact that its “nervous axis” (brain and spinal cord) is united determines the dependence of the functioning of the brain on the state of the spinal cord, especially in childhood. This, in turn, indicates that educational measures to strengthen the spinal column in the earliest period of life, as well as to develop correct posture in the future, are necessary.
The different parts of the brain are not the same in hierarchy. In neuropsychology, their anatomical division into blocks is accepted, the teaching of which was developed by A.R. Luria. Each of them is composed of different brain structures, which will be discussed below.
The main part, the largest in terms of occupied area, is the cerebral cortex (Fig. 1, 2, color on). It has: a) surface folds, which are designated as furrows; b) deep folds, designated as cracks; c) convex ridges on the surface of the brain - convolutions.
Fissures divide the brain into lobes (Fig. 2, color on). The convolutions divide the lobes into even more functionally differentiated areas.
The basic units of the nervous system are nervouscells - neurons (Fig. 9 cm. color. on). Like other cells in our body, a neuron contains a body with a centrally located nucleus and processes called neuritis. Some of the neurites transmit nerve impulses to other cells, others receive them. The transmitting processes are long. These are Receiver axons - short. These are dendrites. Each cell has one axon and many dendrites.
Neurons make up the gray matter of the brain. They are extremely diverse in form and functionality. Their processes, axons that transmit information, are the white matter of the brain. Axons are myelinated, i.e. covered with fatty myelin, which increases the speed of transmission of nerve impulses. The axons are reliably protected by glial cells, mitochondria, which are supporting cells that form the white fatty (myelin) layer - glia. Glia are not continuous. It has interceptions called nodes of Ranvier. They facilitate the passage of nerve impulses from cell to cell. The same role is played by vesicles (neuromidiators) located at the endings of axons. Glial cells do not conduct nerve impulses. Some of them nourish neurons, others protect against microorganisms, and others regulate the flow of cerebrospinal fluid.
The cell body also contains other structures that provide vital functions. The most important of these are ribosomes (Nissl bodies). Ribosomes are in the form of granules. They synthesize proteins without which the cell cannot survive.
Despite the complexity of the cellular structure of the brain, the laws of its functioning have been largely studied and are of extreme interest.
The Spanish scientist Santiago Ramon y Cajal gave a surprisingly poetic description of the brain in terms of its constituent nerve cells. “The garden of neurology,” he wrote, “presents to the researcher an exciting, incomparable spectacle. In him all my aesthetic feelings found complete satisfaction. Like an entomologist pursuing brightly colored butterflies, I hunted in a colorful garden of gray matter with their delicate, elegant forms, mysterious butterflies of the soul, the beating of whose wings, perhaps once upon a time - who knows? - will clarify the secret of spiritual life.”
The brain of a newborn child has 12 billion neurons and 50 billion glial cells, an adult has 150 billion neurons (according to I.A. Skvortsov). If you stretch them into a chain, or rather, into a bridge, then you can travel across it to the Moon and back.
The size of each cell is extremely small, but the range of their differences in this characteristic is quite large: from 5 to 150 microns. Throughout life, a person loses a certain number of cells, but in comparison with their total number, the losses are negligible (approximately 4 billion neurons). If quite recently it was believed that nerve cells do not recover, now this truth has ceased to be absolute. Neuroscientist S. Weiss from Canada in 1998 expressed the opinion, based on his research, that neurons can recover. True, the mechanism of such restoration does not occur in all people and not under all conditions. The reasons for this continue to be clarified, but the very fact that this is possible is extremely sensational.
Before the secrets of the maturation and functioning of nerve cells were discovered, it was believed that nerves were empty (hollow) tubes. Streams of gases or liquids move along them. Isaac Newton was the first to move away from these ideas, declaring that the transmission of a nerve impulse is carried out by a vibrating ethereal medium. However, the Italian researcher Luigi Galvani came even closer to the true state of affairs. In the scientific world, as well as outside it, the incident is well known, which helped him discover the bioelectric nature of the functioning of the nervous system.
This refers to the detached leg of a frog that has just been dissected, which accidentally came under the influence of an electric current and began to contract (twitch). Thus, the foundations were laid for the most important science about the brain today - neurophysiology, which studies the electrical biopotentials of the brain.
It is widely known that nerve cells are combined into networks, which are also called nerve circuits. Each neuron has approximately 7 thousand such circuits. Information is transmitted along circuits from cell to cell. The place of exchange is the junction of the axon (long process of a cell) of one cell and the dendrite (short process) of another cell. A neuron transmits excitation to another neuron through one or many points of contact (synapses) - (Fig. 10, color on). When an impulse reaches a synaptic node, a special chemical is released - a neurotransmitter. It fills the synaptic cleft and propagates the nerve impulse over a considerable distance. The more synapses, the more capacious the brain “computer” in terms of memory. Each nerve cell receives impulses from many hundreds, even thousands of neurons.
According to the concepts of neurophysiology, the speed of electric current flow through nerve wires is equal to the speed of a propeller plane - 60-100 m/s. Typically, the distance from synapse to synapse is 1.5-2 m. A nerve impulse overcomes it in 1/100 of a second. Consciousness does not have time to record this time. The speed of thought is thus higher than the speed of light. This is reflected in many folklore sources. Let us remember, for example, the princess who, testing a good fellow, asks him riddles, and in particular this one: “What is the fastest thing in the world?” (meaning thought as an answer).
Nerve cells do not divide like other cells in the body, so when damaged they most often die.
Despite the fact that the nerve impulse is electrical in nature, communication between neurons is ensured by chemical processes. For this purpose, the brain contains biochemical substances - neurotransmitters and neuromodulators. The moment the electrical signal reaches the synapse, the corresponding transmitters are released. They, like a vehicle, deliver a signal to another neuron. These neurotransmitters then break down. However, the process of transmitting nerve impulses does not end there, because nerve cells located behind the synapse are activated, and a postsynaptic potential arises. It generates an impulse that moves to another synapse, and the process described above is repeated thousands and thousands of times. This allows you to perceive and process a colossal amount of information.
Many publications on neurology and neurophysiology note that the most complex brain activity is ensured, in essence, by simple means. Some of the authors note that this simplicity reflects the universal law of “achieving great complexity through repeated transformations of simple elements” (E. Goldberg). Similarly, many words in a language are made up of a limited number of speech sounds and letters of the alphabet, countless musical melodies are made up of a small number of notes, the genetic codes of millions of people are provided by a finite number of genes, etc.
2.2. Anatomical and functional differentiation of the brain
2.2.1. Cortical fields
According to prevailing ideas, the cerebral cortex has six main layers, each of which consists of nerve cells of different shapes and sizes. This anatomical fact, however, is not as important for understanding neuropsychological phenomena as the functional differentiation of the cortex into three main types of fields - primary, secondarynal and tertiary (Fig. 8, color on). They differ from each other in hierarchy. The most elementary are the primary ones, the more complex in structure and functioning are the secondary ones, and finally, the most complex in terms of these characteristics are the tertiary fields.
The fields of each level have their own numbering, which is indicated on the cytoarchitectonic maps of the brain. The most common of these is the Brodmann map. (Fig. 6, color on).
Primary fields - these are the “cortical ends of the analyzers” and, as already reported above, they function naturally, innately. Their localization depends on which analyzer they belong to.
Primary fields located in frontal lobe(to the central gyrus), namely fields 10, 11, 47, are configured for the preparation and execution of motor acts related to the physical Level.
Primary fields auditory The analyzer is located mainly on the inner surface of the temporal lobes of the brain (fields 41, 42), kinesthetic (sensitive in general) near the central (Rolland) sulcus, in the parietal lobe (fields 3, 1 and 2).
Primary sensitive(tactile) fields are characterized by the fact that they are projection zones in relation to certain parts of the body: the upper sections receive sensory signals (sensations) from the lower extremities (legs), the middle ones process sensations from the upper extremities, and the lower ones from the face, including parts of the speech apparatus (tongue, lips, larynx, diaphragm). In addition, the lower parts of the parietal projection zone receive sensations from some internal organs. The algorithm of body projections in the anterior block of the brain is the same as in the posterior one. They are also projection, but in relation not to sensitive (kinesthetic), but to motor functions. The main difference between projection zones and others is that the size of one or another part of the body is determined not by anatomical, but by functional significance.
Primary brain cells in the earliest ontogenesis function in isolation from each other, like separate worlds in the Cosmos. So, the child recognizes the mother's voice, but does not recognize her face if she is silent. Particularly often, the separation of auditory and visual impressions at the level of sensations is observed in relation to the father's face, which infants see less often than the mother's face. The literature describes cases when a child, seeing his father’s face bent over him, begins to cry loudly in fear until he speaks. Gradually, information connections (associations) are established between the primary fields of the cerebral cortex. Thanks to them, the experience of sensations accumulates, i.e. elementary knowledge about reality appears. For example, the baby “learns” that sucking on the breast or bottle satisfies hunger.
2.2.2. Modality-specific cortex
Primary fields are homogeneous in cellular composition, so they are designated as modal-specific. The olfactory fields contain only olfactory nerve cells, the auditory fields - only auditory ones, etc. Despite the universality of the physiological and biochemical mechanisms that ensure the functioning of the brain, its various parts function differently, i.e.have different functional specializations, representing different modalities.
Secondary fields are also modality-specific, although less homogeneous than primary ones. The cells of the predominant modality are interspersed with cells of other modalities. Tertiary being zones of overlap, they contain not only cells of hollow modalities, but also their entire zones. Based on this, they are designated as multimodal or supramodal. Thanks to the functioning, the most complex HMFs are realized, and in particular, certain speech components. Modally specific brain structures make their own and, what is especially important, a total contribution to them.
Secondary and tertiary fields of the cortex, unlike primary ones, have features of functioning depending on latepalization, those. location in one or the other hemisphere of the brain. For example, the temporal lobes of different hemispheres, belonging to the same, namely, auditory modality, perform different “work”. The temporal lobe of the right hemisphere is responsible for processing non-speech noise (produced by nature, including “animal voices” and human voices, objects, including musical instruments, and music itself, which can be considered the highest type of non-speech noise). The temporal lobe of the left hemisphere processes speech signals. In addition to the differences in the specialization of the temporal lobes of the brain, which belong to different hemispheres, one can also see here the principle of “protection” of the most important functions, so characteristic of nature, and even more so, such an important and necessary for any person as speech.
Differences in the functional specificity of primary, secondary and tertiary fields also determine differences in their ability to replace each other (compensate) in the case of pathology. The destruction of primary fields is not reparable, i.e. Lost physical hearing, vision, smell, etc. are not restored. Most recently, this position has been revised in connection with the study of the regenerating role of so-called stem cells. The functions of damaged secondary fields are subject to compensation, carried out by connecting other, “healthy” brain systems and restructuring the way they operate. The functions of the affected tertiary fields are compensated relatively easily due to multimodality, which allows one to rely on a powerful system of associations stored in each of them and between them. It is necessary, however, to remember that in this case, age thresholds and the time when restoration measures are started are important. The most favorable is early age and timely initiation of therapeutic corrective and restorative measures.
Functionally, all three types of cortical fields are related to each other vertically: the functions of the primary ones, the functions of the secondary ones are built on top of them, and the tertiary functions are built on top of the secondary ones. However, anatomically they are not located in this way, i.e. on top of each other. Primary fields form the core of one or another analytical zone, which in neuropsychology is called modalities. Secondary fields are located further from the core, i.e. shifted to the periphery of the zone, and tertiary - even further. The sizes of fields different in hierarchy are proportional to the proximity to the nucleus: primary ones occupy the smallest area, secondary ones occupy the largest area, and tertiary ones occupy the largest area. As a result, the latter overlap each other, forming so-called “overlap” zones. These include, for example, the most important zone for the HMF - the temporo-parietal-occipital zone (temporahs - temple; panetahs - crown; oxipitahs - back of the head).
The auditory, visual and tactile cortex takes the greatest part in the implementation of higher mental functions.
The auditory zone belongs to the sensory (perceptive) cortex of the brain. Its main department is, as A.R. points out. Luria, Temple area left hemisphere. It includes sections of different hierarchies, which determines the complexity of its structural and functional organization. The most significant of them is nuclear the zone of the auditory analyzer, which provides physical hearing (fields 41, 42), is the primary fields of the auditory cortex. Further from the core is located peripheral zone department (tertiary field 22). Following them is the region middle temple, border with the parietal and occipital regions (tertiary field 21 and partially with tertiary field 37). Middle temporal(extranuclear) sections of the temporal lobe are represented by the tertiary cortex and are more complexly organized. They, according to neuropsychology, are responsible for the perception of not individual sounds of speech and words, but their series, and are closely connected by numerous associative fibers with the visual cortex, which determines its participation in the realization of words. In the area of the 37th field there is also a small area of overlap (overlapping of the temporal and occipital cortex).
According to E.P. Kok, presented in her monograph “Visual Agnosia,” written back in 1967, this area is most suitable for mastering and further mastering the word. E. P. Kok emphasizes that a word is the unity of the visual image of an object and its “sound shell”, and, therefore, the presence of the auditory and visual cortex in the same area of the brain contributes to the development of strong figurative-verbal associations.
The word and its visual image become firmly united.
The stronger this “adhesion” is, the more reliably the word is stored in memory and, on the contrary, the weaker it is, the easier the word is forgotten (word amnesia).
A.R. Luria writes that auditory perception includes the analysis and synthesis of signals reaching the subject already at the first stages of their arrival.
It follows from this that the process of speech perception is based not only on physical hearing, but also on the ability to analyze what is heard. The functions of such analysis are attributed primarily to the secondary temporal area 22, located in the superior temporal region.
It is responsible for the discrete perception of speech sounds, including, which is fundamentally important, and for isolating from them acoustic images of signal (meaning-distinguishing) features, called phonemic.
It is also recognized that the phonemic system of a language is formed with the direct participation of the articulatory apparatus, due to which acoustic-articulatory connections are developed and strengthened.
In addition to the actual cortical level of the auditory zone, there is a basal auditory area 20 and a medial (“deep”) temple. This part of the brain is part of the so-called “Peipetz circle” (hippocampus - nuclei of the visual thalamus - septum and mamillary bodies - hypothalamus).
The medial parts of the temple are closely connected with nonspecific formations of the limbic-reticular complex (the part of the brain that regulates the tone of the cortex) - (Fig. 12, color on).
This composition of the medial temple determines its most important feature - the ability to regulate the state of activity of the cerebral cortex as a whole, processes of neurodynamics, the autonomic sphere, and within the framework of higher mental activity - emotions, consciousness and memory.
^ Visual cortex
The primary visual cortex extends bilaterally along the calcarine sulcus on the medial surface of the occipital lobe and extends to the conversion surface of the occipital pole. Nuclear zone visual cortex is the primary cortical field 17. The secondary cortical fields (18, 19) make up a wide visual sphere. In relation to the principle of functioning of this zone, the same revision of the principles of the Reflex Theory of Sensations, which was mentioned when highlighting the functional specialization of the temporal (auditory) cortex, is relevant. As a result of this revision, visual perception began to be seen not as a passive process, but as an active action
The main difference between the activity of the visual, as well as the cutaneous-kinesthetic, parietal cortex, is that the signals it perceives are not arranged in sequential rows, but are combined into simultaneous groups. This ensures complex visual differentiation, suggesting the ability to identify subtle optical signs. With focal lesions of this area occurs often encountered in clinical practice optical agnosia. Back in 1898 E Lessauer(E Lissauer) designated it as “apperceptive mental blindness” and noted that patients suffering from it do not recognize visual images of even familiar objects, although they can recognize them by touch. Subsequently, optical visual agnosia was studied in detail and described by E. P. Kok, L. S. Tsvetkova and others, who showed its connection with amnestic aphasia
In the parieto-occipital cortex, the highest in the hierarchy, which is the region where the central ends of the visual and tactile analyzers are connected (“overlap zones”), environmental stimuli are combined into “simultaneous syntheses”, allowing one to simultaneously perceive complex images, for example, plot pictures. According to neuropsychology, damage to this area leads to disorders simultaneous visual gnosis and systemically determined semantic aphasia.
^ Tactile cortex
Synthesis of tactile signals is carried out parietal parts of the cerebral cortex, similar to how the parieto-occipital region carries out optical perception Nuclear zone this analyzer is the area of the posterior central gyrus Primary fields tactile cortex provides skin-kinesthetic sensitivity at the physical level (field 3) Secondary oke fields(2, 1, 5, 7) are specialized in complex differentiation of tactile signals (stereognosis). Thanks to them, it is possible to recognize objects by touch.
^ Motor cortex
The motor “analyzer” is understood as consisting of two jointly working parts of the cerebral cortex (postcentral and precentral). Together they make up sensorimotory region of the cortex.
The postcentral cortex, or, otherwise, the inferior parietal cortex, along with the primary fields (10, 11, 47), receives tactile signals and processes them into tactile sensations, including speech
At the level of secondary fields (2, 1, 5, 7) it ensures the implementation of individual postures - kinesthesia of the body, limbs, speech apparatus
Within front block of the brain of the left hemisphere for speech function the most significant is the anterior central gyrus - premotor cortex at the level of secondary fields (6, 8) It ensures the implementation of various motor acts, which are a series of sequential movements and are called dynamic or, otherwise, efferent, practicalSisa It, in turn, constitutes the second, in addition to the afferent, voluntary motor unit. It is important that the premotor cortex is capable of not only building, but also remembering motor sequences (kinetic melodies), without which, within the framework of speech activity, it would be impossible to smoothly pronounce words and phrases.
At the level of tertiary field 45, the motor cortex provides the ability to create programs for various types of activities. Due to this area, standard programs of mastered actions are operated, including speech ones, for example, syntactic models of sentences.
Below is a table of brain field numbers at various levels (according to Brodmann)
table 2
| ^ Range mod | Auditory | Visual | Tactile | "Motor" |
||||||||
| Cortex field type | I | II | III | I | II | III | I | II | III | I | II | III |
| № Fields | 41, | 22. | 21, | 17. | 18, | - | 3 | 2,1, | 39, | 10, 11,47. | 6,8. | 45. |
