motor areas of the cortex. Movements occur when the cortex is stimulated in the region of the precentral gyrus. Especially large is the zone that controls the movements of the hand, tongue, and mimic muscles.
Sensory areas of the 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, below - the arms and even lower - the head. proprioceptive sensitivity (muscular feeling) is projected into the postcentral and precentral gyrus . visual area the cortex is located in the occipital lobe. Hearing 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 region of the mouth and tongue of the postcentral gyrus .
association areas of the cortex. The neurons of these areas are not connected either with the sense organs or with 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 an expedient reaction of behavior. These areas include the frontal and parietal lobes of the cortex. big brain, which receive information from the associative nuclei of the thalamus.
Lateral ventricles(right and left) are the cavities of the telencephalon, lie below the level of the corpus callosum in both hemispheres and communicate through the interventricular openings 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 nuclei
The basal nuclei 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. Caudate nucleus and putamen unite to form neostriatum. They are subcortical motor centers. Outside of the lenticular nucleus is a thin plate of gray matter - a fence. In the anterior temporal lobe lies amygdala. Between the basal nuclei and the thalamus are layers of white matter, the inner, outer and outermost capsules. Pathways pass through the inner capsule.
Topic 1. Limbic system
In the final brain there are formations that make up the limbic system: cingulate gyrus, hippocampus, mammillary bodies, anterior thalamus, amygdala, fornix, transparent septum, hypothalamus. They are involved in maintaining the constancy of the internal environment of the body, the regulation of autonomic function and the formation of emotions and motivations. This system is otherwise called the "visceral brain". This is where information comes from internal organs. 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 CNS: circulatory and cerebrospinal fluid 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 the blood circulation of the brain. The left and right anterior, middle and posterior cerebral arteries pass from the arterial circle to the hemispheres. Blood from the capillaries is collected 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 with 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 the brain tissues. 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 plexus of the brain.
Seminar Topics
1. The role of the 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. Main stages of the evolution of the CNS and ontogenesis nervous system
4. Diseases of the brain
5. brain aging
Tasks for independent work
1. Draw a frontal section of the spinal cord with all the symbols you know.
2. Draw a sagittal section of the brain with the designations of all its departments.
3. Draw a sagittal section of the spinal cord and brain with labels for all brain cavities.
4. Draw a sagittal section of the brain with labels for all structures known to you.
Questions for self-control
1. Give definitions of 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 the processes of a nerve cell.
5. List the sizes and shapes of neurons. Describe the use of microscopic techniques.
6. Tell us about the nucleus of a nerve cell.
7. What are the main structural elements of the neuroplasm?
8. Tell us about the sheath of the nerve cell.
9. What are the main structural elements of the synapse?
10. What is the significance 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 the conduction of the nerve impulse?
13. Name the types of the nervous system in phylogenesis.
14. List the features of the structure of the network 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 comparative characteristic structures 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 the three brain bubbles.
27. Describe the stage of the five brain bubbles.
28. The main divisions 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 CNS?
38. What is the role of the descending tracts of the spinal cord in the CNS?
39. What are spinal nodes?
40. What are the consequences of spinal cord injuries?
41. Describe the development of the spinal cord in ontogeny.
42. What are the structural features of the main membranes of the CNS?
43. Describe reflex principle organizations of the CNS.
44. Name the main parts of the rhomboid brain.
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 rhomboid brain?
50. Name the features of the structure and function 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 CNS correspond to the auditory, vestibular nuclei of the pons?
57. Tell about the ascending and descending paths of the bridge.
58. What are the functions of the lateral and medial lemniscal pathways?
59. What is the purpose of the reticular formation of the brain stem in the CNS?
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 CNS?
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. The 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 CNS?
68. What are the consequences of cerebellar disorders?
69. What is the role of the cerebellum in the organization of 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 quadrigemina and their purpose?
72. What is the purpose of the main cores of the tire?
73. What is the purpose of the mesencephalic parasympathetic center?
74. What is the need for periaqueductal gray matter. Expand the features of the organization of the pain system in the CNS.
75. What are the red nuclei of the midbrain. What is the definition of decerebrate rigidity?
76. Black nucleus and ventral region of the tegmentum. What is the role of the dopaminergic system of the brain in the CNS?
77. Descending and ascending pathways of the midbrain. Pyramidal and extrapyramidal systems of the CNS.
78. What is the structure and purpose of the legs of the brain?
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 zathalamic 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. Belt cortex, its structure and functions.
90. Almond-shaped complex, its structure and functions.
91. Emotional and motivational sphere and its brain support.
92. What are the "reward" and "punishment" systems of the brain? Self-irritation reaction.
93. Neurochemical organization of brain reinforcement systems.
94. What are the consequences of damage to individual formations of the limbic system? Animal research.
95. Describe the general structure of the telencephalon. What is its role in ensuring the adaptive behavior of 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, gyrus).
101. Dorso-lateral 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. Calloused body.
104. Cytoarchitecture of the cerebral cortex (layers of the cortex and Brodmann fields).
105. Evolutionary formations of the cerebral cortex (new cortex, old cortex, ancient cortex) and their functions.
106. Projective and associative areas of the cerebral cortex and their purpose.
107. Speech-sensory and speech-motor centers of the cerebral cortex.
108. Sensorimotor cortex, its localization. projections human body in the sensorimotor cortex.
109. Visual, auditory, olfactory, gustatory cortical projections.
110. Fundamentals of topical diagnosis in case of damage to areas of the cerebral cortex.
111. Frontal and parietal cortex and their role in ensuring the adaptive activity of the brain.
Morphological bases dynamic localization functions in the cerebral cortex (centers of the cerebral cortex)
Knowledge of the localization of functions in the cerebral cortex is of great theoretical importance, since it gives an idea of the nervous regulation of all body processes and its adaptation to the environment. It is also of great practical importance for diagnosing lesions in the cerebral hemispheres.
The idea of the localization of a function in the cerebral cortex is associated primarily with the concept of the cortical center. Back in 1874, the Kievan anatomist V. A. Betz made the statement that each section of the cortex differs in structure from other sections of the brain. This was the beginning of the doctrine of the heterogeneity of the cerebral cortex - cytoarchitectonics (cytos - cell, architectones - system). The studies of Brodman, Economo and employees of the Moscow Institute of the Brain, led by S. A. Sarkisov, managed to identify more than 50 different sections of the cortex - cortical cyto-architectonic fields, each of which differs from the others in the structure and location of nerve elements; there is also a division of the cortex into more than 200 fields. From these fields, designated by numbers, a special “map” of the human cerebral cortex was compiled (Fig. 299).
According to IP Pavlov, the center is the brain end of the so-called analyzer. The analyzer is a nervous mechanism whose function is to decompose the known complexity of the external and internal world into separate elements, i.e., to perform analysis. At the same time, thanks to extensive connections with other analyzers, synthesis also takes place here, a combination of analyzers with each other and with various activities of the organism. "The analyzer is a complex nervous mechanism that begins with an external perceiving apparatus and ends in the brain." From the point of view of I. P. Pavlov, the brain center, or the cortical end of the analyzer, does not have strictly defined boundaries, but consists of a nuclear and diffuse part - the theory of the nucleus and scattered elements. The "nucleus" represents a detailed and accurate projection in the cortex of all elements of the peripheral receptor and is necessary for the implementation of higher analysis and synthesis. "Scattered elements" are located on the periphery of the nucleus and can be scattered far from it; they carry out a simpler and more elementary analysis and synthesis. 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 the restoration of this function.
Before I.P. Pavlov, the cortex distinguished between the motor zone, or motor centers, the anterior central gyrus and the sensory zone, or sensory centers located behind the sulcus centralis Rolandi. IP Pavlov showed that the so-called motor zone, corresponding to the anterior central gyrus, is, like other zones of the cerebral cortex, a perceiving area (the cortical end of the motor analyzer). "The motor area is the receptor area ... This establishes the unity of the entire cortex of the hemispheres."
At present, the entire cerebral cortex is regarded as a continuous perceiving 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 perceiving areas of the cortex of the cerebral hemispheres.
Let us first consider the cortical ends of internal analyzers.
1. The core of the motor analyzer, i.e., the analyzer of proprioceptive (kinesthetic) stimuli emanating from bones, joints, skeletal muscles and their tendons, is located in the anterior central gyrus (fields 4 and 6) and lobulus paracentralis. Here motor conditioned reflexes are closed. 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 core of the motor analyzer, as a result of which the cortex does not perceive kinesthetic stimuli and movements become impossible. The cells of the nucleus of the motor analyzer are laid down in the middle layers of the cortex of the motor zone. In its deep layers (5th, partly also 6th) lie Betz's giant pyramidal cells, which are efferent neurons, which I.P. Pavlov considers as intercalary neurons connecting the cerebral cortex with the subcortical nodes, the nuclei of the head nerves and the 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. At the same time, the right motor area is connected with the left half of the body and vice versa, because the pyramidal paths starting from it intersect partly in the medulla oblongata, and partly in the spinal cord. .The muscles of the trunk, larynx, pharynx are under the influence of both hemispheres. In addition to the anterior central gyrus, proprioceptive impulses (muscle-articular sensitivity) also come to the cortex of the posterior central gyrus.
2. The core of the motor analyzer, which is related to the combined rotation of the head and eyes in the opposite direction, is placed in the middle frontal gyrus, in the premotor region (field 8). Such a turn also occurs when field 17 is stimulated, 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 retina (visual analyzer, field 17), various visual stimuli are always combined with a different position of the eyes, established contraction of the muscles of the eyeball.
3. The core of the motor analyzer, through which the synthesis of purposeful combined movements takes place, is placed in the left (in right-handers) lower parietal lobule, 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 anterior central gyrus. With the defeat of field 40, 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 analyzer of the position and movement of the head - the static analyzer (vestibular apparatus) - has not yet been exactly 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. So, with the defeat of fields 21 and 20, which lie in the region of the middle and lower temporal gyri, ataxia is observed, that is, an imbalance, swaying of the body when standing. This analyzer, which plays a decisive role in human upright walking, is of particular importance for the work of pilots in rocket aviation, since the sensitivity vestibular apparatus on the plane is significantly reduced.
5. The core of the analyzer of impulses coming from the viscera and blood vessels (vegetative functions) is located in the lower sections of the anterior and posterior central gyri. Centripetal impulses from the viscera, blood vessels, smooth muscles and glands of the skin enter this section of the cortex, from where the centrifugal paths proceed to the subcortical vegetative centers.
In the premotor region (fields 6 and 8), the vegetative and animal functions are combined. However, it should not be considered that only this area of the cortex affects the activity of the viscera. They are influenced by the state of the entire cerebral cortex.
Nerve impulses from the external environment of the organism enter the cortical ends of the analyzers of the external world.
1. The nucleus 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 cortical deafness.
2. The core of the visual analyzer is 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 path ends in field 17. The retina of the eye is projected here, and the visual analyzer of each hemisphere is associated with the fields of view and the corresponding halves of the retina of both eyes (for example, the left hemisphere is associated with the lateral half of the left eye and the medial right). When the nucleus of the visual analyzer is damaged, blindness occurs. Above field 17 is field 18, in case of damage to which vision is preserved and only visual memory is lost. Even higher is field 19, with the defeat of which one loses orientation in an unusual environment.
3. The nucleus of the olfactory analyzer is located in the phylogenetically most ancient part of the cerebral cortex, within the base of the olfactory brain - uncus, partly Ammon's horn (field 11).
4. According to some data, the core of the taste analyzer 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 relationship between olfactory and taste sensations. It has been established that taste disorder occurs when field 43 is affected.
The analyzers of smell, taste and hearing of each hemisphere are connected with the receptors of the corresponding organs of both sides of the body.
5. The core of the skin analyzer (tactile, pain and temperature sensitivity) is located in the posterior central gyrus (fields 1, 2, 3) and in the cortex of the upper 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 of general sensitivity are especially developed at the head end of the body, in the region of the mouth, which plays a huge role in capturing food, a strong development of the mouth receptors has also been preserved in humans. In this regard, the region of the latter occupies an unreasonably large zone in the cortex of the posterior central gyrus. At the same time, in connection with the development of the hand as a labor organ, the tactile receptors in the skin of the hand increased sharply, which also became the organ of touch. Correspondingly, the areas of the cortex related to the receptors of the upper limb sharply outnumber the region of the lower limb. Therefore, if you draw a figure of a person head down (to the base of the skull) and feet up (to the upper edge of the hemisphere) into the posterior central gyrus, 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 superior to the rest, small body and small legs. 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 a part in the medulla oblongata.
A particular type of skin sensitivity - recognition of objects by touch, stereognosia (stereos - spatial, gnosis - knowledge) - is associated with a section of the cortex of the upper parietal lobule (field 7) crosswise: the left hemisphere corresponds right hand, right - left hand. When the surface 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 is thus "a grandiose mosaic, a grandiose signaling board." Thanks to the analyzers, signals from the external and internal environment of the body fall onto this “board”. These signals, according to I. P. Pavlov, constitute the first signal system of reality, manifested in the form of concrete visual thinking (sensations and complexes of sensations - perceptions). The first signaling system is also found in animals. But “in the developing animal world, in the human phase, an extraordinary addition to the mechanisms nervous activity. For an animal, reality is signaled almost exclusively only by stimuli and traces of them in the cerebral hemispheres, which directly reach special cells of the visual, auditory, and other receptors of the organism. This is what we also have in ourselves as impressions, sensations and ideas from the external environment, both general natural and from our social, excluding the word, audible and visible. This is the first signaling system we have in common with animals. But the word constituted the second, specially our signal system of reality, being the signal of the first signals... it was the word that made us human.”
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 found in animals), and then the second - it is only in humans and is a verbal system. The second signal system is human thinking, which is always verbal, because language is the material shell of thinking. Language is "... the immediate reality of thought."
Through a very long repetition, temporary connections were formed between certain signals (audible sounds and visible signs) and movements of the lips, tongue, muscles of the larynx, on the one hand, and with real stimuli or ideas about them, on the other. Thus, on the basis of the first signal system, the second one arose.
Reflecting this process of phylogenesis, in ontogeny, the first signal system is first laid down in a person, and then the second. In order for the second signaling system to start functioning, the child's communication with other people and the acquisition of oral and written language skills are required, which takes a number of years. If a child is born deaf or loses his hearing before he begins to speak, then his inherent ability to speak 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 testifies to the decisive influence of the environment for 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 the implementation of speech. These areas of the cortex are the nuclei of speech analyzers.
Therefore, in order to understand the anatomical substrate of the second signaling system, in addition to knowing the structure of the cerebral cortex as a whole, it is also necessary to take into account the cortical ends of speech analyzers (Fig. 300).
1. Since speech was a means of communication between people in the process of their joint labor activity, then motor speech analyzers developed in close proximity to the core of the general motor analyzer.
The motor speech articulation analyzer (motor speech analyzer) is located in the posterior part of the inferior frontal gyrus (gyrus Vgoca, field 44), in close proximity to the lower motor zone. It analyzes the stimuli 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. With the defeat of field 44, the ability to produce the simplest movements of the speech muscles, to scream and even sing, remains, but the ability to pronounce words is lost - motor aphasia (phasis - speech). In front of field 44 is field 45 related to speech and singing. When it is defeated, vocal amusia arises - the inability to sing, compose musical phrases, as well as agrammatism - the inability to compose sentences from words.
2. Since the development of oral speech is associated with the organ of hearing, an auditory analyzer of oral speech has developed in close proximity to the sound analyzer. Its nucleus is located in the posterior part of the superior temporal gyrus, deep in the lateral sulcus (field 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 the help of it, a person controls his 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 - verbal deafness, or sensory aphasia. When field 22 (the middle third of the superior temporal gyrus) is affected, musical deafness occurs: the patient does not know the motives, and musical sounds are perceived by him as chaotic noise.
3. At a higher stage of development, mankind has learned not only to speak, but also to write. Written speech requires certain hand movements when writing letters or other signs, which is associated with a motor analyzer (general). Therefore, the motor analyzer of written speech is placed 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 the learned hand movements necessary for writing (field 40 in the lower parietal lobule). If field 40 is damaged, all types of movement are preserved, but the ability of subtle movements necessary to draw 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 analyzer of written speech has developed in close proximity to the visual analyzer, which, naturally, is connected to the sulcus calcarinus, where the general visual analyzer is located. The visual analyzer of written speech is located in the lower parietal lobule, with gyrus angularis (field 39). If field 39 is damaged, vision is preserved, but the ability to read (alexia) is lost, that is, to analyze written letters and compose words and phrases from them.
All speech analyzers are laid down in both hemispheres, but develop only on one side (in right-handers - on the left, in left-handers - on the right) and functionally turn out to be asymmetric. This connection between the motor analyzer of the hand (organ of labor) and speech analyzers is explained by the close connection between labor and speech, which had a decisive influence on the development of the brain.
"... Labor, and then articulate speech along with it ..." led to the development of the brain. This connection is also used in medicinal purposes. When the speech-motor analyzer is damaged, the elementary motor ability of the speech muscles is preserved, but the possibility of oral speech is lost (motor aphasia). In these cases, it is sometimes possible to restore speech by a long exercise of the left hand (in right-handed people), the work of which favors the development of the rudimentary right-hand nucleus of the motor speech 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 signaling system is not only these analyzers. Since the function of speech 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 are made up of a large number nerve cells (100 billion) with short processes, thanks to which the possibility of an unlimited closing function, wide associations is created, which is the essence of the activity of the second signaling system. At the same time, the second signaling system does not function separately from the first, but in close connection with it, more precisely on the basis of it, since the second signals can arise only if the first ones are present. “The basic laws established in the operation of the first signaling system must also govern the second, because this is the work of the same nervous tissue.”
IP Pavlov's doctrine of two signal systems provides a materialistic explanation of human mental activity and constitutes the natural scientific basis for VI 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.
Feeling is a subjective image of the objective world.
In the receptor, an external stimulus, 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, in healthy people will cause a sensation of green color in the cerebral cortex (subjective image), and in a patient with color blindness (due to a different structure of the retina) - a sensation of red color.
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).
Hence, from the point of view of Lenin's theory of reflection, the brain can be characterized as an organ of reflection of reality.
After all that has been said about the structure of the central nervous system, one can note the human signs of the structure of the brain, that is, the specific features of its structure that distinguish man from animals (Fig. 301, 302).
1. The predominance of the brain over the spinal cord. So, in carnivores (for example, in a cat), the brain is 4 times heavier than the spinal cord, in primates (for example, in a macaque) - 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 in mammals is 22-48% of the weight of the brain, in the gorilla - 5-6%, in humans - only 2%.
2. The weight of the brain. In terms of the absolute weight of the brain, a person does not take first place, since in large animals the brain is heavier than that of a person (1500 g): in a dolphin - 1800 g, in an elephant - 5200 g, in a whale - 7000 g. To reveal the true ratios of brain weight to body weight, recently they began to define the "square index of the brain", that is, the product of the absolute weight of the brain by the relative one. This pointer made it possible to distinguish a person from the entire animal world.
So, in rodents it is 0.19, in carnivores - 1.14, in cetaceans (dolphins) - 6.27, in anthropoids - 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 (paleencephalon).
4. The highest development of the frontal lobe of the brain. According to Brodman, 8-12% of the entire surface of the hemispheres falls on the frontal lobes in lower monkeys, 16% in anthropoid monkeys, and 30% in humans.
5. The predominance of the new cerebral cortex over the old (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. Furrows and convolutions increase the area of the gray matter cortex, therefore, the more developed the cortex of the cerebral hemispheres, the greater the folding of the brain. The increase in folding is achieved by the large development of small furrows of the third category, the depth of the furrows and their asymmetric arrangement. Not a single animal has at the same time such a large number of furrows and convolutions, while being as 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.
Summing up 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 - over the deep ones.
Ideas about the localization of functions in the cerebral cortex are of great practical importance for solving problems of the topic of lesions in the cerebral hemispheres. However, to this day, much in this section remains controversial and not fully resolved. The doctrine of the localization of functions in the cortex has a rather long history - from the denial of the localization of functions in it to the distribution in the cortex in strictly limited territories of all the functions of human activity, up to the highest qualities of the latter (memory, will, etc.), and, finally , until returning to the "equipotentiality" of the cortex, that is, again, in essence, to the denial of the localization of functions (recently abroad).
Ideas about the equivalence (equipotentiality) of various cortical fields come into conflict with the huge factual material accumulated by morphologists, physiologists and clinicians. Everyday clinical experience shows that there are certain unshakable natural dependences of functional disorders on the location of the pathological focus. Based on these basic provisions, the clinician solves the problems of topical diagnosis. However, this is the case as long as we operate with disorders related to relatively simple functions: movements, sensitivity, etc. In other words, localization in the so-called "projection" zones - cortical fields directly connected by their paths with the underlying parts of the nervous system and the periphery. The functions of the cortex are more complex, phylogenetically younger, and cannot be narrowly localized; very extensive areas of the cortex, and even the entire cortex as a whole, are involved in the implementation of complex functions. That is why the solution of problems of the topic of lesions based on speech disorders, apraxia, agnosia, and, moreover, mental disorders, as clinical experience shows, is more difficult and sometimes inaccurate.
At the same time, within the cerebral cortex there are areas whose damage causes one or another character, one or another degree, for example, speech disorders, disorders of gnosia and praxia, the topodiagnostic value of which is also significant. From this, however, it does not follow that there are special, narrowly localized centers that "manage" these most complex forms of human activity. It is necessary to clearly distinguish between the localization of functions and the localization of symptoms.
The foundations of a new and progressive theory of the localization of functions in the brain were created by I.P. Pavlov.
Instead of the concept of the cerebral cortex as, to a certain extent, an isolated superstructure over other floors of the nervous system with narrowly localized areas connected along the surface (associative) and with the periphery (projection) areas, I.P. Pavlov created the doctrine of the functional unity of neurons belonging to various parts of the nervous system - from receptors on the periphery to the cerebral cortex - the doctrine of analyzers. What we call the center is the highest, cortical, section of the analyzer. Each analyzer is associated with certain areas of the cerebral cortex (Fig. 64).
I.P. Pavlov makes significant adjustments to the previous ideas about the limited territories of the cortical centers, to the doctrine of the narrow localization of functions. Here is what he says about the projection of receptors into the cerebral cortex.
“Each peripheral receptor apparatus has a central, special, isolated territory in the cortex, as its terminal station, which represents its exact projection. Here, thanks to a special design, there can be a denser placement of cells, more numerous cell connections and the absence of cells of other functions, the most complex irritations occur, form (higher synthesis) and their exact differentiation (higher analysis) takes place. But these receptor elements extend further for a very long time. long distance, maybe all over the bark. This conclusion, based on extensive experimental and physiological studies, is in full agreement with the latest morphological data on the impossibility of precise differentiation of cortical cyto-architectonic fields.
Consequently, the functions of the analyzers (or, in other words, the operation of the first signaling system) cannot be associated only with the cortical projection zones (the nuclei of the analyzers). Moreover, it is impossible to narrowly localize the most complex, purely human functions - the functions of the second signaling system.
I.P. Pavlov defines the functions of human signaling systems as follows. “I imagine the totality of higher nervous activity in this way. In higher animals, up to and including humans, the first instance for complex relationships of an organism with the environment is the subcortex closest to the hemispheres with its most complex unconditioned reflexes (our terminology), instincts, drives, affects, emotions (diverse, common terminology). These reflexes are caused by relatively few unconditional external agents. Hence - a limited orientation in the environment and at the same time a weak adaptation.
The second instance is the large hemispheres ... Here it arises with the help of a conditional connection (association) new principle activity: the signaling of a few, unconditional external agents by an innumerable mass of other agents, at the same time constantly analyzed and synthesized, enabling a very large orientation in the same environment and, by the same token, a much greater adaptation. This constitutes the only signaling system in the animal body and the first in man.
In a person, another signaling system is added, signaling the first system with speech, its basis or basal component - kinesthetic stimuli of the speech organs. This introduces a new principle of nervous activity - the abstraction and at the same time the generalization of countless signals of the previous system, in turn, again with the analysis and synthesis of these first generalized signals - the principle that determines an unlimited orientation in the surrounding world and creates the highest adaptation of a person - science, as in the form of a universal empiricism, as well as in its specialized form.
The work of the second signal system is inextricably linked with the functions of all analyzers, therefore it is impossible to imagine the localization of the complex functions of the second signal system in any limited cortical fields.
The significance of the legacy left to us by the great physiologist for the correct development of the doctrine of the localization of functions in the cerebral cortex is exceptionally great. I.P. Pavlov laid the foundations for a new theory of dynamic localization of functions in the cortex. The concept of dynamic localization implies the possibility of using the same cortical structures in various combinations to serve various complex cortical functions.
Keeping a number of definitions and interpretations that have become established in the clinic, we will try to make some adjustments to our presentation in the light of the teachings of I.P. Pavlov about the nervous system and its pathology.
So, first of all, we need to consider the question of the so-called projection and association centers. The usual idea of motor, sensory and other projection centers (anterior and posterior central gyrus, visual, auditory centers, etc.) is associated with the concept of a rather limited localization of a particular function in a given area of the cortex, and this center is directly connected with the underlying nerve devices , and subsequently with the periphery, with its conductors (hence the definition - "projective"). An example of such a center and its conductor is, for example, the anterior central gyrus and the pyramidal path; fissura calcarina and radiatio optica, etc. Projection centers are connected by associative paths with other centers, with the surface of the cortex. These wide and powerful associative pathways determine the possibility of the combined activity of various cortical areas, the establishment of new connections, and the formation, therefore, of conditioned reflexes.
"Association centers", in contrast to projection centers, do not have a direct connection with the underlying parts of the nervous system and the periphery; they are connected only with other areas of the cortex, including the "projection centers". An example of an "association center" is the so-called "center of stereognosy" in the parietal lobe, located posterior to the posterior central gyrus (Fig. 65). Individual stimuli that occur when an object is felt by hand enter the posterior central gyrus through the thalamo-cortical pathways: tactile, shapes and sizes (joint-muscular feeling), weight, temperature, etc. All these sensations are transmitted through association fibers from the posterior central gyrus to the "stereognostic center", where they are combined and create a common sensory image of the object. The connections of the “stereognostic center” with other areas of the cortex make it possible to identify, compare this image with the idea already in memory of this object, its properties, purpose, etc. (i.e., analysis and synthesis of perception is carried out). This "center", therefore, has no direct connection with the underlying parts of the nervous system and is connected by association fibers with a number of other fields of the cerebral cortex.
The division of centers into projection and association seems to us incorrect. The large hemispheres are a set of analyzers for analyzing, on the one hand, the external world and, on the other, internal processes. The receptive centers of the cortex appear to be very complicated and territorially extremely widespread. The upper layers of the cerebral cortex, in fact, are entirely occupied by the perceiving centers or, in the terminology of I.P. Pavlov, "brain ends of analyzers".
From all the lobes, from the lower layers of the cortex, there are already efferent conductors connecting the cortical ends of the analyzers with the executive organs through the subcortical, stem and spinal apparatuses. An example of such an efferent conductor is the pyramidal pathway - this intercalary neuron between the kinesthetic (motor) analyzer and the peripheral motor neuron.
How, then, from this point of view, to reconcile the position about the presence of motor projection centers (in the anterior central gyrus, the center of eye rotation, etc.), when they are turned off, a person experiences paralysis, and when irritated, convulsions with a completely clear somatotopic distribution and correspondence? Here we are talking only about the defeat of the motor projection area for the pyramidal pathways, and not the "projection motor centers".
There is no doubt that "voluntary" movements are conditioned motor reflexes, i.e., movements that have developed, "trodden" in the process of individual life experience: but in the development, organization and already established activity of skeletal muscles, everything depends on the afferent device - skin and motor analyzer (clinically - skin and joint-muscular sensitivity, more broadly - kinesthetic sense), without which fine and precise coordination of a motor act is impossible.
Rice. 64. Cortical departments of analyzers (scheme).
a - outer surface; b - inner surface. Red - skin analyzer; yellow - auditory analyzer: blue - visual analyzer; green - olfactory analyzer; dotted line - motor analyzer.
The motor analyzer (whose task is the analysis and synthesis of “voluntary” movements) does not at all correspond to the ideas of cortical motor “projection” centers with certain boundaries of the latter and a clear somatotopic distribution. The motor analyzer, like all analyzers, is associated with very wide areas of the cortex, and the motor function (in relation to "voluntary" movements) is extremely complex (if we take into account not only the determinism of movements and behavior in general, not only the complexity of action complexes, but also afferent kinesthetic systems , and orientation in relation to the environment and parts of one's own body in space, etc.).
What is the idea of "projection centers"? It was argued that the latter represent a kind of input or output "starting gate" for impulses coming into or out of the cortex. And if we accept that “motor projection cortical centers” are only such “gates” (for the broad concept of a motor analyzer is necessarily associated with the function of analysis and synthesis), then it should be considered that within the anterior central gyrus (and in territories similar to it), and then only in certain of its layers, there is a motor projection area or zone.
How then to imagine the rest of the "projection" centers (skin sensitivity, vision, hearing, taste, smell) associated with other (non-kinesthetic) afferent systems? We think that there is no fundamental difference here: in fact, both in the region of the posterior central gyrus, and within the fissurae calcarinae, etc., impulses flow to the cells of a certain layer of the cortex from the periphery, which is “projected” here, and analysis and synthesis occurs within many layers and wide areas.
Consequently, in each analyzer (its cortical section), including the motor one, there is an area or zone that “projects” onto the periphery (motor area) or into which the periphery is “projected” (sensitive areas, including kinesthetic receptors for the motor analyzer ).
It is possible that the "projective core of the analyzer" can be identified with the concept of a motor or sensitive projection zone. Maximum violations, wrote I.I. Pavlov, analysis and synthesis occurs when just such a “projective nucleus” is damaged; If. If we take for the real maximum "breakage" of the analyzer the maximum violation of the function, which is objectively absolutely correct, then the greatest manifestation of damage to the motor analyzer is central paralysis, and the most sensitive - anesthesia. From this point of view, it would be correct to identify the concept of “analyzer core” with the concept of “analyzer projection area”.
Rice. 65. Loss of functions observed in the defeat of various parts of the cerebral cortex (outer surface).
2 - visual disturbances (hemianopsia); 3 - sensitivity disorders; 4 - central paralysis or paresis; 5 - agraphia; 6 - cortical paralysis of gaze and turning of the head in the opposite direction; 7 - motor aphasia; 8 - hearing disorders (with unilateral lesions are not observed); 9 - amnestic aphasia; 10 - alexia; 11 - visual agnosia (with bilateral lesions); 12 - astereognosia; 13 - apraxia; 14 - sensory aphasia.
Based on the foregoing, we consider it correct to replace the concept of a projection center with the concept of a projection area in the analyzer zone. Then the division of cortical "centers" into projection and association ones is unreasonable: there are analyzers (their cortical departments) and within their limits - projection areas.
In the future, the efforts of physiologists turned out to be aimed at finding "critical" areas of the brain, the destruction of which led to a violation of the reflex activity of one or another organ. Gradually, the idea of a rigid anatomical localization of “reflex arcs” developed, and, accordingly, the reflex itself began to be thought of as a mechanism for the operation of only the lower parts of the brain (spinal centers).
At the same time, the question of the localization of functions in the higher parts of the brain was being developed. Ideas about the localization of elements of mental activity in the brain arose long ago. In almost every era, one or more
Other hypotheses of representation in the brain of higher mental functions and consciousness in general.
Austrian physician and anatomist Franz Joseph Gall(1758- 1828) made up detailed description anatomy and physiology of the human nervous system, provided with an excellent atlas.
: A whole generation of researchers have been based on these data. Gall's anatomical discoveries include the following: identification of the main differences between the gray and white matter of the brain; determination of the origin of nerves in the gray matter; definitive proof of decussation of the pyramidal tracts and optic nerves; establishment of differences between "convergent" (according to modern terminology "associative") and "divergent" ("projective") fibers (1808); the first clear description of the commissures of the brain; proof of the beginning of the cranial nerves in the medulla oblongata (1808), etc. Gall was one of the first to give a decisive role to the cerebral cortex in the functional activity of the brain. Thus, he believed that the folding of the cerebral surface was an excellent solution by nature and evolution to an important task: to maximize the surface area of the brain while maintaining its volume more or less constant. Gall introduced the term "arc", familiar to every physiologist, and described its clear division into three parts.
However, Gall's name is mostly known in connection with his rather dubious (and sometimes scandalous!) doctrine of the localization of higher mental functions in the brain. Attaching great importance to the correspondence of function and structure, Gall as early as 1790 made an application for the introduction of a new science into the arsenal of knowledge - phrenology(from the Greek phren - soul, mind, heart), which also received a different name - psychomorphology, or narrow localizationism. As a doctor, Gall observed patients with various disorders of brain activity and noticed that the specificity of the disease largely depends on which part of the brain substance is damaged. This led him to the idea that each mental function corresponds to a specific part of the brain. Seeing the endless variety of characters and individual mental qualities of people, Gall suggested that the strengthening (or greater predominance) of any character trait or mental function in a person’s behavior also entails the predominant development of a certain area of the cerebral cortex where this function is represented. Thus, the thesis was put forward: the function makes the structure. As a result of the growth of this hypertrophied area of the cortex ("brain cones"), pressure on the bones of the skull increases, which, in turn, causes the appearance of an external cranial tubercle above the corresponding area of \u200b\u200bthe brain. In case of underdevelopment of the function, vice versa.
On the surface of the skull there will be a noticeable depression ("fossa"). Using the method of "cranioscopy" created by Gall - the study of the relief of the skull with the help of palpation - and detailed "topographic" maps of the surface of the brain, which indicated the places of localization of all abilities (considered innate), Gall and his followers made a diagnosis, i.e. made a conclusion about character and inclinations of a person, about his mental and moral qualities. Were 2 allocated? areas of the brain where certain abilities of the individual are localized (moreover, 19 of them were recognized as common to humans and animals, and 8 as purely human). In addition to the "bumps" responsible for the implementation of physiological functions, there were those that testified to visual and auditory memory, orientation in space, a sense of time, the instinct of procreation; such personality traits. as courage, ambition, piety, wit, secrecy, amorousness, caution, self-esteem, refinement, hope, curiosity, malleability of education, pride, independence, diligence, aggressiveness, fidelity, love of life, love of animals.
Gall's erroneous and pseudoscientific ideas (which, however, were extremely popular in their time) contained a rational grain: the recognition of the closest connection between the manifestations of mental functions and the activity of the cerebral cortex. The problem of finding differentiated "think tanks" and drawing attention to the functions of the brain was put on the agenda. Gall can truly be considered the founder of "brain localization". Undoubtedly, for the further progress of psychophysiology, the formulation of such a problem was more promising than vintage search location of the "common sensory area".
The solution of the problem of the localization of functions in the cerebral cortex was facilitated by the data accumulating in clinical practice and in animal experiments. German physician, anatomist and physicist Julius Robert Mayer(1814-1878), who practiced for a long time in Parisian clinics, and also served as a ship's doctor, observed in patients with craniocerebral injuries the dependence of a violation (or complete loss) of a particular function on damage to a certain part of the brain. This allowed him to suggest that memory is localized in the cerebral cortex (it should be noted that T. Willis came to a similar conclusion back in the 17th century), imagination and judgments in the white matter of the brain, apperception and will in the basal ganglia. A kind of "integral organ" of behavior and the psyche is, according to Mayer, the corpus callosum and the cerebellum.
Over time, the clinical study of the consequences of brain damage was supplemented by laboratory studies. artificial extirpation method(from Latin ex (s) tirpatio - removal with a root), which allows you to partially or completely destroy (remove) parts of the brain of animals to determine their functional role in brain activity. IN early XIX V. mainly acute experiments were carried out on animals (frogs, birds), later, with the development of asepsis methods, chronic experiments began to be carried out, which made it possible to observe the behavior of animals for a more or less long time after the operation. Removal of various parts of the brain (including the cerebral cortex) in mammals (cats, dogs, monkeys) made it possible to elucidate the structural and functional foundations of complex behavioral reactions.
It turned out that the deprivation of animals of the higher parts of the brain (birds - the forebrain, mammals - the cerebral cortex) in general did not cause a violation of the main functions: respiration, digestion, excretion, blood circulation, metabolism and energy. Animals retained the ability to move, to respond to certain external influences. Consequently, the regulation of these physiological manifestations of vital activity occurs at the underlying (compared to the cerebral cortex) levels of the brain. However, when the higher parts of the brain were removed, profound changes in the behavior of animals occurred: they became practically blind and deaf, “stupid”; they lost previously acquired skills and could not develop new ones, could not adequately navigate in the environment, did not distinguish and could not differentiate objects in the surrounding space. In a word, animals became "living automata" with monotonous and rather primitive ways of responding.
In experiments with partial removal of areas of the cerebral cortex, it was found that the brain is functionally heterogeneous and the destruction of one area or another leads to a violation of a certain physiological function. So, it turned out that the occipital areas of the cortex are associated with visual function, the temporal - with auditory, the region of the sigmoid gyrus - with motor function, as well as with skin and muscle sensitivity. Moreover, this differentiation of functions in individual regions of the higher parts of the brain is being improved in the course of the evolutionary development of animals.
The strategy of scientific research in the study of brain functions led to the fact that, in addition to the method of extirpation, scientists began to use the method of artificial stimulation of certain areas of the brain using electrical stimulation, which also made it possible to evaluate the functional role of the most important parts of the brain. The data obtained using these methods of laboratory research, as well as the results of clinical observations, outlined one of the main directions of psychophysiology in the 19th century. - determination of the localization of nerve centers responsible for higher mental functions and behavior of the organism as a whole. So. in 1861, the French scientist, anthropologist and surgeon Paul Broca (1824-1880), on the basis of clinical facts, strongly opposed the physiological equivalence of the cerebral cortex. During the autopsy of the corpses of patients suffering from a speech disorder in the form of motor aphasia (the patients understood someone else's speech, but could not speak themselves), he found changes in the posterior part of the lower (third) frontal gyrus of the left hemisphere or in the white matter under this area of the cortex. Thus, as a result of these observations, Broca established the position of the motor (motor) center of speech, later named after him. In 1874, the German psychiatrist and neurologist K? Wernicke (1848-1905) described the sensory center of speech (today bearing his name) in the posterior third of the first temporal gyrus of the left hemisphere. The defeat of this center leads to the loss of the ability to understand human speech (sensory aphasia). Even earlier, in 1863, using the method of electrical stimulation of certain areas of the cortex (the precentral gyrus, the precentral region, the anterior part of the pericentral lobule, the posterior parts of the superior and middle frontal gyri), the German researchers Gustav Fritsch and Eduard Gitzig established motor centers (motor cortical fields), the irritation of which caused certain contractions of the skeletal muscles, "and the destruction led to profound disorders of motor behavior. In 4874, the Kiev anatomist and physician Vladimir Alekseevich Betz (1834-1894) discovered efferent nerve cells of motor centers - giant pyramidal cells of layer V cortex, named after him Betz cells German researcher Hermann Munch (student of I. Müller and E. Dubois-Reymond) discovered not only the motor cortical fields, using the method of extirpation, he found the centers of sensory perceptions He managed to show that the center of vision is located in the posterior lobe of the brain, the center of hearing - in the temporal lobe. Removal of the occipital lobe of the brain led to the loss of the animals' ability to see (with complete preservation of the visual apparatus). Already in
early 20th century eminent Austrian neurologist Konstantin Economo(1876-1931) the centers of swallowing and chewing were established in the so-called black matter of the brain (1902), the centers that control sleep - in the midbrain (1917). Looking ahead a little, we say that Economo gave an excellent description of the structure of the cerebral cortex an adult and in 1925 refined the cytoarchitectonic map of the cortical fields of the brain, putting 109 fields on it.
However, it should be noted that in the XIX century. against the position of narrow localizationists, according to whose views motor and sensory functions are confined to various areas cerebral cortex, serious arguments were put forward. Thus, a theory of the equivalence of sections of the cortex arose, asserting the idea of the equal importance of cortical formations for the implementation of any activity of the body, - equipotentialism. In this regard, the phrenological views of Gall, one of the most vehement supporters of localizationism, were criticized by the French physiologist Marie Jean Pierre Flourance(1794-1867). Back in 1822, he pointed out the presence of a respiratory center in the medulla oblongata (which he called the "vital knot"); linked coordination of movements with the activity of the cerebellum, vision - with the quadrigemina; I saw the main function of the spinal cord in conducting excitation along the nerves. However, despite such seemingly localizationist views, Flurence believed that the basic mental processes (including intellect and will) underlying the purposeful behavior of a person are carried out as a result of the activity of the brain as a holistic formation and, therefore, a holistic behavioral function. cannot be confined to any particular anatomical entity. Flourance spent most of his experiments on pigeons and chickens, removing parts of their brains and observing changes in the behavior of birds. Usually, after some time after the operation, the behavior of birds was restored regardless of which areas of the brain were damaged, so Flurance concluded that the degree of violation of various forms of behavior is determined primarily by how much brain tissue was removed during the operation. Having improved the technique of operations, he was the first to be able to completely remove the hemispheres of the forebrain from animals and save their life for further observations.
Based on the experiments, Flurance came to the conclusion that the forebrain hemispheres play a decisive role in the implementation of a behavioral act. Their complete removal leads to the loss of all "intelligent" functions. Moreover, especially severe behavioral disorders were observed in chickens after the destruction of the gray matter of the surface of the cerebral hemispheres - the so-called corticoid plate, an analogue of the cerebral cortex of mammals. Flourance suggested that this region of the brain is the seat of the soul, or "ruling spirit", and therefore acts as a whole, having a homogeneous and equivalent mass (similar, for example, to the tissue structure of the liver). Despite the somewhat fantastic ideas of the equipotentialists, one should note the progressive element in their views. First, complex psychophysiological functions were recognized as the result of the combined activity of brain formations. Secondly, the idea of a high dynamic plasticity of the brain, expressed in the interchangeability of its parts, was put forward.
- Gall managed to quite accurately determine the "center of speech", but "officially" it was discovered by the French researcher Paul Broca (1861).
- In 1842 Mayer, working on the definition of the mechanical equivalent of heat, came to a generalized law of conservation of energy.
- Unlike his predecessors, who endowed the nerve with the ability to feel (that is, they recognized a certain mental quality behind it), Hall considered the nerve ending (in the sense organ) to be an "apsychic" formation.
In the cerebral cortex, zones are distinguished - Brodmann fields
The 1st zone - motor - is represented by the central gyrus and the frontal zone in front of it - 4, 6, 8, 9 Brodmann's fields. When it is irritated - various motor reactions; when it is destroyed - violations of motor functions: adynamia, paresis, paralysis (respectively - weakening, sharp decrease, disappearance).
In the 1950s, it was established that different muscle groups are represented differently in the motor zone. The muscles of the lower limb - in the upper section of the 1st zone. Muscles of the upper limb and head - in the lower part of the 1st zone. The largest area is occupied by the projection of mimic muscles, muscles of the tongue and small muscles of the hand.
2nd zone - sensitive - areas of the cerebral cortex posterior to the central sulcus (1, 2, 3, 4, 5, 7 Brodmann fields). When this zone is irritated, sensations arise, when it is destroyed, loss of skin, proprio-, interosensitivity occurs. Hypothesia - decreased sensitivity, anesthesia - loss of sensitivity, paresthesia - unusual sensations (goosebumps). Upper divisions zones - the skin of the lower extremities, genital organs is represented. In the lower sections - the skin of the upper limbs, head, mouth.
The 1st and 2nd zones are closely related to each other functionally. There are many afferent neurons in the motor zone that receive impulses from proprioreceptors - these are motosensory zones. In the sensitive area, there are many motor elements - these are sensorimotor zones - are responsible for the occurrence of pain.
3rd zone - visual zone - occipital region of the cerebral cortex (17, 18, 19 Brodmann fields). With the destruction of the 17th field - loss of visual sensations (cortical blindness).
Different parts of the retina are not equally projected into the 17th Brodmann field and have a different location; with a point destruction of the 17th field, the vision of the environment falls out, which is projected onto the corresponding parts of the retina. With the defeat of the 18th field of Brodmann, the functions associated with the recognition of a visual image suffer and the perception of writing is disturbed. With the defeat of the 19th field of Brodmann, various visual hallucinations occur, visual memory and other visual functions suffer.
4th - auditory zone - temporal region of the cerebral cortex (22, 41, 42 Brodmann fields). If 42 fields are damaged, the function of sound recognition is impaired. When the 22nd field is destroyed, auditory hallucinations, impaired auditory orienting reactions, and musical deafness occur. With the destruction of 41 fields - cortical deafness.
The 5th zone - olfactory - is located in the piriform gyrus (11 Brodmann's field).
6th zone - taste - 43 Brodman's field.
The 7th zone - the motor speech zone (according to Jackson - the center of speech) - in most people (right-handed) is located in the left hemisphere.
This zone consists of 3 departments.
Broca's motor speech center - located in the lower part of the frontal gyri - is the motor center of the muscles of the tongue. With the defeat of this area - motor aphasia.
The sensory center of Wernicke - located in the temporal zone - is associated with the perception of oral speech. With a lesion, sensory aphasia occurs - a person does not perceive oral speech, pronunciation suffers, as the perception of one's own speech is disturbed.
The center for the perception of written speech - located in the visual zone of the cerebral cortex - 18 Brodmann's field, similar centers, but less developed, are also in the right hemisphere, the degree of their development depends on the blood supply. If the right hemisphere is damaged in a left-handed person, the speech function suffers to a lesser extent. If the left hemisphere is damaged in children, then the right hemisphere takes over its function. In adults, the ability of the right hemisphere to reproduce speech functions is lost.
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