Evolution of the doctrine of localization of functions in the cerebral cortex. Teaching I.P

The limbic system is a functional union of brain structures that provides complex forms of behavior.

The limbic system includes structures of the ancient cortex, old cortex, mesocortex and some subcortical formations. A feature of the limbic system is that the connections between its structures form many closed circles, and this creates conditions for long-term circulation of excitation in the system. The main circles with functional specificity are described. This is a large circle of Papes, which includes: hippocampus - fornix - mamillary bodies - mamillary-thalamic fasciculus Vic-d, Azira - anterior nuclei of the thalamus - cingulate cortex - parahippocampal gyrus - hippocampus.

A very important multifunctional structure in the large circle is the hippocampus. Its damage in humans disrupts memory for events that preceded the damage, memorization, processing of new information, discrimination of spatial signals are impaired, emotionality and initiative decrease, and the speed of basic nervous processes slows down.

The small circle of Nauta is formed by: amygdala - stria terminalis - hypothalamus - septum - amygdala.

An important structure of the small circle is the amygdala. Its functions are associated with ensuring defensive behavior, autonomic, motor, emotional reactions, and motivation of conditioned reflex behavior. Numerous autonomic effects of the amygdala are due to connections with the hypothalamus.

In general, the limbic system provides:

• 1. Organization of vegetative-somatic components of emotions.
• 2. Organization of short-term and long-term memory.
• 3. Participates in the formation of orientation-research activities (Klüver-Bucy syndrome).
• 4. Organizes the simplest motivational and informational communication (speech).
• 5. Participates in sleep mechanisms.
• 6. The center of the olfactory sensory system is located here.

According to Mac Lean (1970), from a functional point of view, the limbic is divided into: 1) the lower section - the amygdala and hippocampus, which are centers of emotions and behavior for survival and self-preservation; 2) the upper section - the cingulate gyrus and temporal cortex, they represent the centers of sociability and sexuality; 3) middle section - hypothalamus and cingulate gyrus - centers of biosocial instincts.

The hemispheres of the brain consist of white matter, which is covered on the outside by gray matter or cortex. The cortex is the youngest and most complex part of the brain, where sensory information is processed, motor commands are formed, and complex forms of behavior are integrated. In addition to neurons, there is a huge number of glial cells that perform ion-regulatory and trophic functions.

The cerebral cortex has morphofunctional features: 1) multi-layered arrangement of neurons; 2) modular principle of organization; 3) somatotopic localization of receptor systems; 4) screenability - distribution of external reception on the plane of the neuronal field of the cortical end of the analyzer; 5) dependence of the level of activity on the influence of subcortical structures and reticular formation; 6) presence of representation of all functions of the underlying structures of the central nervous system; 7) cytoarchitectonic distribution into fields; 8) the presence in specific projection sensory and motor systems of the cortex of secondary and tertiary fields with a predominance of associative functions; 9) the presence of specialized associative areas of the cortex; 10) dynamic localization of functions, which is expressed in the possibility of compensating for the functions of lost cortical structures; 11) overlap in the cortex of zones of neighboring peripheral receptive fields; 12) the possibility of long-term preservation of traces of irritation; 13) reciprocal functional relationship between excitatory and inhibitory states of the cortex; 14) ability to irradiate the state; 15) the presence of specific electrical activity.

The bark consists of 6 layers:

• 1. The outer molecular layer is represented by a plexus of nerve fibers that lie parallel to the surface of the cortical convolutions and are mainly dendrites of pyramidal cells. Afferent thalamocortical fibers from the nonspecific nuclei of the thalamus come here; they regulate the level of excitability of cortical neurons.
• 2. The outer granular layer is formed by small stellate cells, which determine the duration of circulation of excitation in the cortex and are related to memory.
• 3. The outer pyramidal layer is formed by medium-sized pyramidal cells.

Functionally, the 2nd and 3rd layers carry out cortico-cortical associative connections.

• 4. Afferent thalamocortical fibers from specific (projection) nuclei of the thalamus come to the internal granular layer.
• 5. The inner pyramidal layer is formed by giant pyramidal cells of Betz. The axons of these cells form the corticospinal and corticobulbar tracts, which are involved in the coordination of goal-directed movements and posture.
• 6. Polymorphic or spindle cell layer. This is where the corticothalamic pathways are formed.

All analyzers are characterized by the somatotopic principle of organizing the projection of peripheral receptor systems onto the cortex. For example, in the sensory cortex of the second central gyrus there are areas of representation of each point on the skin surface, in the motor cortex each muscle has its own topic, its own place, in the auditory cortex there is a topical localization of certain tones.

A feature of cortical fields is the screen principle of functioning, which lies in the fact that the receptor projects its signal not onto one cortical neuron, but onto their field, which is formed by collaterals and connections of neurons. In this case, the signal is focused not point to point, but on many neurons, which ensures its complete analysis and the possibility, if necessary, of transmission to other structures.

In the vertical direction, the input and output fibers together with the stellate cells form “columns”, which are the functional units of the cortex. And when the microelectrode is immersed perpendicularly into the cortex, along the entire path it encounters neurons that respond to one type of stimulation, while if the microelectrode goes horizontally along the cortex, then it encounters neurons that respond to different types of stimuli.

The presence of structurally different fields also implies their different functional purposes.

The most important motor area of ​​the cortex is located in the precentral gyrus. In 30 last century, Penfield established the presence of a correct spatial projection of somatic muscles of various parts of the body to the motor area of ​​the cortex. The most extensive and with the lowest threshold are the zones that control the movements of the hands and facial muscles. A secondary motor area was found on the medial surface next to the primary one. But these areas, in addition to the motor output from the cortex, have independent sensory inputs from skin and muscle receptors, so they were called the primary and secondary motosensory cortex.

The postcentral gyrus contains the first somatosensory area, which receives afferent signals from specific nuclei of the thalamus. They carry information from skin receptors and the motor system. And here the somatotopic organization is noted.

The second somatosensory area is located in the Sylvian fissure, and since. The first and second somatosensory zones, in addition to afferent inputs, also have motor outputs; it is more correct to call them primary and secondary sensorimotor zones.

The primary visual area is located in the occipital region.

In the temporal lobe is the auditory region.

In each lobe of the cerebral cortex, next to the projection zones, there are fields that are not associated with the performance of a specific function - this is the associative cortex, the neurons of which respond to stimulation of various modalities and are involved in the integration of sensory information, and also provide communication between the sensitive and motor areas of the cortex. This is the physiological basis of higher mental functions.

The frontal lobes have extensive bilateral connections with the limbic system of the brain and are involved in the control of innate behavioral acts with the help of accumulated experience, ensure the coordination of external and internal motivations for behavior, the development of behavioral strategies and action programs, and the mental characteristics of the individual.

There is no complete symmetry in the activity of the hemispheres. So, in 9 out of 10 people, the left hemisphere dominates for motor acts (right-handed) and speech. For most left-handers, the center of speech is also on the left. Those. There is no absolute dominance. Hemispheric asymmetry is especially noticeable when one hemisphere is separated from the other (commissurotomy). The left hemisphere contains the center of written language, stereognosis. In the left hemisphere, verbal, easily distinguishable, and familiar stimuli are better recognized. The left hemisphere is better at performing tasks involving temporal relationships, establishing similarities, and identifying stimuli by name. The left hemisphere carries out analytical and sequential perception, generalized recognition.

In the right hemisphere, stereognosis for the left hand, understanding of elementary speech, non-verbal thinking (i.e., thinking in images) is carried out; non-verbal, difficult-to-distinguish, and unfamiliar stimuli are better recognized. Tasks on spatial relationships, establishing differences, and identity of stimuli based on physical properties are performed better. In the right hemisphere, holistic, simultaneous perception and specific recognition take place.

The right hemisphere of 9 out of 10 people is slightly inhibited, the alpha rhythm dominates, which in turn somewhat slows down the left hemisphere and prevents it from becoming overexcited. When the right hemisphere is turned off, a person talks a lot and continuously (logorrhea), promises a lot, but does not keep his promises (chatterbox).

With the left hemisphere put to sleep, on the contrary, the person is silent and sad.

The right hemisphere is responsible for nonverbal (subconscious) thinking. The left hemisphere is responsible for understanding what the right hemisphere subconsciously sends to it.

The functional state of brain structures is studied by methods of recording electrical potentials. If the recording electrode is located in a subcortical structure, then the recorded activity is called a subcorticogram, if in the cerebral cortex - a corticogram, if the electrode is located on the surface of the scalp, then the total activity is recorded through it, in which there is a contribution from both the cortex and subcortical structures - this is a manifestation activity is called an electroencephalogram (EEG).

The EEG is a wave-like curve, the nature of which depends on the state of the cortex. So, at rest, a slow alpha rhythm (8-12 Hz, amplitude = 50 μV) predominates on the EEG in a person. During the transition to activity, the alpha rhythm changes to a fast beta rhythm (14 - 30 Hz, amplitude 25 μV). The process of falling asleep is accompanied by a slower theta rhythm (4 - 7 Hz) or delta rhythm (0.5 - 3.5 Hz, amplitude 100 - 300 μV). When, against the background of rest or another state of the human brain, an irritation is presented, for example, light, sound, electric current, then with the help of microelectrodes implanted into certain structures of the cortex, so-called evoked potentials are recorded, the latency period and amplitude of which depend on the intensity of irritation, and the components , the number and nature of oscillations depend on the adequacy of the stimulus.

This question is extremely important theoretically and especially practically. Hippocrates already knew that brain injuries lead to paralysis and convulsions on the opposite half of the body, and are sometimes accompanied by loss of speech.

In 1861, the French anatomist and surgeon Broca, in an autopsy of the corpses of several patients suffering from a speech disorder in the form of motor aphasia, discovered profound changes in the pars opercularis of the third frontal gyrus of the left hemisphere or in the white matter under this area of ​​the cortex. Based on his observations, Broca established a motor speech center in the cerebral cortex, which was later named after him.

The English neuropathologist Jackson (1864) also spoke in favor of the functional specialization of individual areas of the hemispheres on the basis of clinical data. Somewhat later (1870), German researchers Fritsch and Hitzig proved the existence of special areas in the dog’s cerebral cortex, irritation of which by a weak electric current is accompanied by a contraction of individual muscle groups. This discovery led to a large number of experiments, mainly confirming the existence of certain motor and sensory areas in the cerebral cortex of higher animals and humans.

On the issue of localization (representation) of function in the cerebral cortex, two diametrically opposed points of view competed with each other: localizationists and antilocalizationists (equipotentialists).

Localizationists were supporters of narrow localization of various functions, both simple and complex.

Anti-localizationists took a completely different view. They denied any localization of functions in the brain. All the bark was equal and homogeneous for them. All its structures, they believed, have the same capabilities for performing various functions (equipotential).

The problem of localization can receive a correct resolution only with a dialectical approach to it, taking into account both the integral activity of the entire brain and the different physiological significance of its individual parts. This is exactly how IP Pavlov approached the problem of localization. Numerous experiments by I.P. Pavlov and his colleagues with the extirpation of certain areas of the brain convincingly support the localization of functions in the cortex. Resection of a dog's occipital lobes of the cerebral hemispheres (vision centers) causes enormous damage to the conditioned reflexes it has developed to visual signals and leaves all conditioned reflexes to sound, tactile, olfactory and other stimuli intact. On the contrary, resection of the temporal lobes (hearing centers) leads to the disappearance of conditioned reflexes to sound signals and does not affect reflexes associated with optical signals, etc. The latest electroencephalography data also speaks against equipotentialism and in favor of the representation of the function in certain areas of the cerebral hemispheres . Irritation of a certain area of ​​the body leads to the appearance of reactive (evoked) potentials in the cortex in the “center” of this area.

I.P. Pavlov was a convinced supporter of localization of functions in the cerebral cortex, but only relative and dynamic localization. The relativity of localization is manifested in the fact that each part of the cerebral cortex, being the bearer of a certain special function, the “center” of this function, responsible for it, also participates in many other functions of the cortex, but no longer as the main link, not as the “center” ”, but on a par with many other areas.

The functional plasticity of the cortex, its ability to restore lost function by establishing new combinations speak not only of the relativity of the localization of functions, but also of its dynamism.

The basis of any more or less complex function is the coordinated activity of many areas of the cerebral cortex, but each of these areas participates in this function in its own way.

The basis of modern ideas about “systemic localization of functions” is the teaching of I. P. Pavlov about the dynamic stereotype. Thus, higher mental functions (speech, writing, reading, counting, gnosis, praxis) have a complex organization. They are never carried out by any isolated centers, but are always processes “located along a complex system of zones of the cerebral cortex” (A. R. Luria, 1969). These “functional systems” are mobile; in other words, the system of means by which this or that task can be solved changes, which, of course, does not reduce the importance for them of the well-studied “fixed” cortical areas of Broca, Wernicke, and others.

The centers of the human cerebral cortex are divided into symmetrical, present in both hemispheres, and asymmetrical, present in only one hemisphere. The latter include centers of speech and functions associated with the act of speech (writing, reading, etc.), existing only in one hemisphere: in the left - for right-handers, in the right - for left-handers.

Modern ideas about the structural and functional organization of the cerebral cortex come from the classical Pavlovian concept of analyzers, refined and supplemented by subsequent research. There are three types of cortical fields (G.I. Polyakov, 1969). Primary fields (analyzer nuclei) correspond to the architectural zones of the cortex, in which sensory pathways (projection zones) end. Secondary fields (peripheral sections of the analyzer nuclei) are located around the primary fields. These zones are indirectly connected to the receptors; more detailed processing of incoming signals occurs in them. Tertiary, or associative, fields are located in areas of mutual overlap of the cortical systems of the analyzers and occupy more than half of the total surface of the cortex in humans. In these zones, inter-analyzer connections are established, providing a generalized form of generalized action (V. M. Smirnov, 1972). Damage to these zones is accompanied by disturbances in gnosis, praxis, speech, and goal-directed behavior.

Lecture 12. LOCALIZATION OF FUNCTIONS IN THE LARGE HEMISPHERES CORTEX Cortical zones. Projection cortical zones: primary and secondary. Motor (motor) zones of the cerebral cortex. Tertiary cortical zones.

Loss of functions observed with damage to various parts of the cortex (inner surface). 1 - disorders of smell (not observed with unilateral lesions); 2 - visual disturbances (hemianopsia); 3 - sensitivity disorders; 4 - central paralysis or paresis. Data from experimental studies on the destruction or removal of certain areas of the cortex and clinical observations indicate that functions are confined to the activity of certain areas of the cortex. An area of ​​the cerebral cortex that has some specific function is called the cortical zone. There are projection, associative cortical zones and motor (motor) zones.

The projection cortical zone is the cortical representation of the analyzer. Neurons of projection zones receive signals of one modality (visual, auditory, etc.). There are: - primary projection zones; - secondary projection zones, providing the integrative function of perception. In the zone of a particular analyzer, tertiary fields, or associative zones, are also distinguished.

The primary projection fields of the cortex receive information mediated through the smallest number of switches in the subcortex (thalamus, diencephalon). The surface of peripheral receptors is, as it were, projected onto these fields. Nerve fibers enter the cerebral cortex mainly from the thalamus (these are afferent inputs).

The projection zones of the analyzing systems occupy the outer surface of the posterior cortex of the brain. This includes the visual (occipital), auditory (temporal) and sensory (parietal) areas of the cortex. The cortical department also includes representation of taste, olfactory, and visceral sensitivity

Primary sensory areas (Brodmann areas): visual - 17, auditory - 41 and somatosensory - 1, 2, 3 (collectively they are called sensory cortex), motor (4) and premotor (6) cortex

Primary sensory areas (Brodmann areas): visual - 17, auditory - 41 and somatosensory - 1, 2, 3 (collectively they are called sensory cortex), motor (4) and premotor (6) cortex Each field of the cerebral cortex is characterized by a special composition neurons, their location and connections between them. The fields of the sensory cortex, in which the primary processing of information from sensory organs occurs, differ sharply from the primary motor cortex, which is responsible for generating commands for voluntary muscle movements.

In the motor cortex, neurons shaped like pyramids predominate, and the sensory cortex is represented mainly by neurons whose body shape resembles grains or granules, which is why they are called granular. Structure of the cerebral cortex I. molecular II. external granular III. external pyramidal IV. internal granular V. ganglionic (giant pyramids) VI. polymorphic

Neurons of the primary projection zones of the cortex generally have the highest specificity. For example, neurons in the visual areas selectively respond to shades of color, direction of movement, character of lines, etc. However, in the primary zones of individual areas of the cortex there are also multimodal type neurons that respond to several types of stimuli and neurons whose reaction reflects the influence of nonspecific ( limbicoreticular) systems.

Projection afferent fibers end in the primary fields. Thus, fields 1 and 3, occupying the medial and lateral surfaces of the posterior central gyrus, are the primary projection fields of cutaneous sensitivity of the body surface.

The functional organization of projection zones in the cortex is based on the principle of topical localization. Perceptive elements located next to each other in the periphery (for example, areas of the skin) are projected onto the cortical surface also next to each other.

The lower limbs are represented in the medial part, and projections of the receptor fields of the skin surface of the head are located lowest on the lateral part of the gyrus. In this case, areas of the body surface richly equipped with receptors (fingers, lips, tongue) are projected onto a larger area of ​​the cortex than areas with fewer receptors (thigh, back, shoulder).

Fields 17-19, located in the occipital lobe, are the visual center of the cortex; field 17, occupying the occipital pole itself, is primary. The 18th and 19th fields adjacent to it perform the function of secondary fields and receive inputs from the 17th field.

The auditory projection fields are located in the temporal lobes (41, 42). Next to them, on the border of the temporal, occipital and parietal lobes, are located the 37th, 39th and 40th, characteristic only of the human cerebral cortex. For most people, these fields of the left hemisphere contain the speech center, which is responsible for the perception of oral and written speech.

Secondary projection fields, receiving information from the primary ones, are located next to them. The neurons of these fields are characterized by the perception of complex signs of stimuli, but at the same time the specificity corresponding to the neurons of the primary zones is preserved. The complication of the detector properties of neurons in the secondary zones can occur through the convergence of neurons in the primary zones on them. In the secondary zones (18th and 19th Brodmann fields) detectors of more complex contour elements appear: edges of limited line lengths, corners with different orientations, etc.

Motor (motor) zones of the cerebral cortex are areas of the motor cortex, the neurons of which cause a motor act. The motor areas of the cortex are located in the precentral gyrus of the frontal lobe (in front of the projection zones of cutaneous sensitivity). This part of the cortex is occupied by fields 4 and 6. From the V layer of these fields, the pyramidal tract originates, ending on the motor neurons of the spinal cord.

Premotor zone (field 6) The premotor zone of the cortex is located in front of the motor zone, it is responsible for muscle tone and coordinated movements of the head and torso. The main efferent outputs from the cortex are the axons of layer V pyramids. These are efferent, motor neurons involved in the regulation of motor functions.

Tertiary or interanalyzer zones (associative) Prefrontal zone (fields 9, 10, 45, 46, 47, 11), parietotemporal (fields 39, 40) Afferent and efferent projection zones of the cortex occupy a relatively small area. Most of the surface of the cortex is occupied by tertiary or interanalyzer zones, called associative zones. They receive multimodal inputs from the sensory areas of the cortex and thalamic associative nuclei and have outputs to the motor areas of the cortex. Associative zones provide integration of sensory inputs and play a significant role in mental activity (learning, thinking).

Functions of various areas of the neocortex: 5 3 7 6 4 1 2 Memory, needs Triggering behavior 1. Occipital lobe - visual cortex. 2. Temporal lobe – auditory cortex. 3. Anterior part of the parietal lobe – pain, skin and muscle sensitivity. 4. Inside the lateral sulcus (insula) – vestibular sensitivity and taste. 5. The posterior part of the frontal lobe is the motor cortex. 6. The posterior part of the parietal and temporal lobes is the associative parietal cortex: it combines signal flows from different sensory systems, speech centers, and thinking centers. 7. The anterior part of the frontal lobe - associative frontal cortex: taking into account sensory signals, signals from the centers of needs, memory and thinking, makes decisions about launching behavioral programs (“center of will and initiative”).

Individual large association areas are located next to the corresponding sensory areas. Some associative areas perform only a limited specialized function and are connected to other associative centers capable of subjecting information to further processing. For example, the auditory association area analyzes sounds, categorizing them, and then transmits signals to more specialized areas, such as the speech association area, where the meaning of words heard is perceived.

The association fields of the parietal lobe combine information coming from the somatosensory cortex (from the skin, muscles, tendons and joints regarding body position and movement) with visual and auditory information coming from the visual and auditory cortices of the occipital and temporal lobes. This combined information helps you have an accurate understanding of your own body while moving around in the environment.

Wernicke's area and Broca's area are two areas of the brain involved in the process of reproducing and understanding information related to speech. Both areas are located along the Sylvian fissure (the lateral fissure of the cerebral hemispheres). Aphasia is a complete or partial loss of speech caused by local lesions of the brain.

There are zones in the cerebral cortex - Brodmann areas

The 1st zone - motor - is represented by the central gyrus and the frontal zone in front of it - Brodmann's areas 4, 6, 8, 9. When it is irritated, various motor reactions occur; when it is destroyed, motor function disorders occur: adynamia, paresis, paralysis (respectively, weakening, sharp decline, disappearance).

In the 50s of the twentieth century, it was established that in the motor zone, different muscle groups are represented differently. The muscles of the lower limb are in the upper part of the 1st zone. The muscles of the upper limb and head are in the lower part of the 1st zone. The largest area is occupied by the projection of facial 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 areas). When this zone is irritated, sensations arise; when it is destroyed, loss of skin, proprio-, and interosensitivity occurs. Hypoesthesia - decreased sensitivity, anesthesia - loss of sensitivity, paresthesia - unusual sensations (goosebumps). The upper sections of the zone - the skin of the lower extremities and genital organs is represented. In the lower sections - the skin of the upper extremities, head, mouth.

The 1st and 2nd zones are closely related to each other functionally. In the motor zone there are many afferent neurons that receive impulses from proprioceptors - these are motosensory zones. In the sensitive zone there are many motor elements - these are sensorimotor zones - which are responsible for the occurrence of pain.

3rd zone - visual zone - occipital region of the cerebral cortex (17, 18, 19 Brodmann areas). When the 17th field is destroyed, there is loss of visual sensations (cortical blindness).

Different areas of the retina are projected differently into the 17th Brodmann field and have different locations; when a point destruction of the 17th field occurs, a vision of the environment appears, which is projected onto the corresponding areas of the retina. When the 18th Brodmann area is damaged, functions associated with visual image recognition are affected and the perception of writing is impaired. When the 19th Brodmann area is damaged, various visual hallucinations occur, visual memory and other visual functions suffer.

4th - auditory zone - temporal region of the cerebral cortex (22, 41, 42 Brodmann areas). If field 42 is damaged, the sound recognition function is impaired. When field 22 is destroyed, auditory hallucinations, impaired auditory orientation reactions, and musical deafness occur. If 41 fields are destroyed, cortical deafness occurs.

The 5th zone - olfactory - is located in the pyriform gyrus (Brodmann area 11).

6th zone - taste - 43 Brodmann area.

The 7th zone - the speech motor 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 speech motor center - located in the lower part of the frontal gyri - is the motor center of the tongue muscles. If this area is damaged, motor aphasia occurs.

Wernicke's sensory center - located in the temporal zone - is associated with the perception of oral speech. When damaged, sensory aphasia occurs - the person does not perceive oral speech, pronunciation suffers, and the perception of one’s own speech is impaired.

The center for the perception of written speech - located in the visual zone of the cerebral cortex - Brodmann's area 18. There are similar centers, but less developed, in the right hemisphere, the degree of their development depends on the blood supply. If a left-handed person has damage to the right hemisphere, 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.

Subsequently, the efforts of physiologists were aimed at searching for “critical” areas of the brain, the destruction of which led to disruption of the reflex activity of a particular organ. Gradually, an idea emerged about the rigid anatomical localization of “reflex arcs”, and accordingly the reflex itself began to be thought of as a mechanism of 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 developed. Ideas about the localization of elements of mental activity in the brain originated a long time ago. In almost every era, certain or

Other hypotheses for the representation in the brain of higher mental functions and consciousness in general.

Austrian physician and anatomist Franz Joseph Gall(1758-1828) compiled a detailed description of the anatomy and physiology of the human nervous system, equipped with an excellent atlas.

: A whole generation of researchers built on this data. Among Gall's anatomical discoveries are the following: identification of the main differences between the gray and white matter of the brain; determination of the origin of nerves in gray matter; definitive proof of the decussation of the pyramidal tracts and optic nerves; establishment of differences between “convergent” (in modern terminology “associative”) and “divergent” (“projection”) fibers (1808); first clear description of brain commissures; proof of the beginning of the cranial nerves in the medulla oblongata (1808), etc. Gall was one of the first to assign a decisive role to the cerebral cortex in the functional activity of the brain. Thus, he believed that the folding of the brain surface is an excellent solution by nature and evolution to an important problem: ensuring a maximum increase in 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 mainly 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 between function and structure, Gall back in 1790 made a request to introduce a new science into the arsenal of knowledge - phrenology(from the Greek phren - soul, mind, heart), which also received another name - psychomorphology, or narrow localizationism. As a doctor, Gall observed patients with various disorders of brain activity and noticed that the specifics of the disease largely depended on which part of the brain was damaged. This led him to the idea that each mental function corresponds to a special part of the brain. Seeing the endless variety of characters and individual mental qualities of people, Gall suggested that the strengthening (or greater predominance) in human behavior of any character trait or mental function entails the preferential development of a certain area of ​​the cerebral cortex where this function is represented. Thus, the thesis was put forward: function makes structure. As a result of the growth of this hypertrophied area of ​​the cortex (“brain cone”), pressure on the bones of the skull increases, which, in turn, causes the appearance of an external cranial tubercle over the corresponding area of ​​the brain. In case of underdevelopment of the function, vice versa.

A noticeable depression (“pit”) will appear on the surface of the skull. Using the method of “cranioscopy” created by Gall - studying the relief of the skull using palpation - and detailed “topographical” maps of the surface of the brain, which indicated the locations of all abilities (considered innate), Gall and his followers made a diagnosis, i.e. made a conclusion about the character and inclinations of a person, about his mental and moral qualities. Were 2 allocated? areas of the brain where certain abilities of an individual are localized (and 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 also those that indicated visual and auditory memory, orientation in space, a sense of time, and the instinct of procreation; such personal qualities. such as courage, ambition, piety, wit, secrecy, amorousness, caution, self-esteem, sophistication, hope, curiosity, amenability to education, self-love, independence, diligence, aggressiveness, fidelity, love of life, love of animals.

Gall's erroneous and pseudoscientific ideas (which were, however, extremely popular in his time) contained a rational grain: recognition of the close connection between the manifestations of mental functions and the activity of the cerebral cortex. The problem of finding differentiated “brain centers” and drawing attention to the functions of the brain was put on the agenda. Gall can truly be considered the founder of “cerebral localization.” Of course, for the further progress of psychophysiology, posing such a problem was more promising than the ancient search for the location of the “common sensory”.

The solution to the question of the localization of functions in the cerebral cortex was facilitated by 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 traumatic brain injuries the dependence of the impairment (or complete loss) of one or another function on damage to a certain area of ​​the brain. This allowed him to suggest that memory is localized in the cerebral cortex (it should be noted that back in the 17th century T. Willis came to a similar conclusion), imagination and judgment are localized in the white matter of the brain, apperception and will are located in the basal ganglia. According to Mayer, a kind of “integral organ” of behavior and psyche is the corpus callosum and the cerebellum.

Over time, clinical study of the consequences of brain damage was supplemented by laboratory artificial extirpation method(from the Latin ex(s)tirpatio - removal from the root), which makes it possible to partially or completely destroy (remove) areas of the brain of animals to determine their functional role in brain activity. At the beginning of the 19th century. They carried out mainly acute experiments on animals (frogs, birds); later, with the development of asepsis methods, they began to carry out chronic experiments, which made it possible to observe the behavior of animals for a more or less long time after surgery. 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 basis of complex behavioral reactions.

It turned out that depriving animals of the higher parts of the brain (birds - the forebrain, mammals - the cerebral cortex) in general did not cause disruption of the basic functions: respiration, digestion, excretion, blood circulation, metabolism and energy. The animals retained the ability to move and react to certain external influences. Consequently, the regulation of these physiological manifestations of vital activity occurs at lower (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 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 discovered that the brain is functionally heterogeneous and the destruction of one or another area leads to disruption of a certain physiological function. Thus, it turned out that the occipital areas of the cortex are associated with visual function, the temporal areas with auditory function, the area of ​​the sigmoid gyrus with motor function, as well as with skin and muscle sensitivity. Moreover, this differentiation of functions in individual areas of the higher parts of the brain improves with 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 extirpation method, scientists began to use the method of artificial stimulation of certain areas of the brain using electrical stimulation, which also made it possible to assess the functional role of the most important parts of the brain. The data obtained using these laboratory research methods, 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 body as a whole. So. in 1861, the French scientist, anthropologist and surgeon Paul Broca (1824-1880), on the basis of clinical facts, decisively spoke out against the physiological equivalence of the cerebral cortex. While autopsying the corpses of patients suffering from a speech disorder in the form of motor aphasia (the patients understood the speech of others, but could not speak themselves), he discovered changes in the posterior part of the inferior (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 speech center (today bearing his name) in the posterior third of the first temporal gyrus of the left hemisphere. Damage to this center leads to 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 (precentral gyrus, precentral region, anterior part of the pericentral lobule, posterior parts of the superior and middle frontal gyri), German researchers Gustav Fritsch and Eduard Hitzig established motor centers (motor cortical fields), irritation of which caused certain contractions of skeletal muscles, "and destruction led to deep disorders of motor behavior. In 4874, the Kyiv 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. The German researcher Hermann Munch (a student of J. Müller and E. Dubois-Reymond) discovered not only the motor cortical fields, but using the extirpation method he found the centers of sensory perceptions. He was able to show that the center of vision is located. in the posterior lobe of the brain, the hearing center is in the temporal lobe. Removal of the occipital lobe of the brain led to the loss of the animal's ability to see (with complete preservation of the visual apparatus). Already in

beginning of the 20th century outstanding Austrian neurologist Constantin Economo(1876-1931) the centers of swallowing and chewing were established in the so-called substantia nigra of the brain (1902), the centers that control sleep were found in the midbrain (1917). Looking ahead a little, let's 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, plotting 109 fields on it.

At the same time, it should be noted that in the 19th century. Serious arguments have been put forward against the position of narrow localizationists, according to whose views motor and sensory functions are confined to different areas of the cerebral cortex. Thus, the theory of the equivalence of areas of the cortex arose, affirming 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 ardent supporters of localizationism, were criticized by the French physiologist Marie Jean Pierre Flourens(1794-1867). Back in 1822, he pointed out the presence of a respiratory center in the medulla oblongata (which he called the “vital node”); connected coordination of movements with the activity of the cerebellum, vision - with the quadrigeminal region; The main function of the spinal cord was to conduct excitation along the nerves. However, despite such seemingly localizationist views, Flourens believed that the basic mental processes (including intellect and will) underlying purposeful human behavior are carried out as a result of the activity of the brain as an integral formation and therefore an integral behavioral function cannot be associated with any particular anatomical formation. Flourens conducted most of his experiments on pigeons and chickens, removing individual parts of their brains and observing changes in the behavior of the birds. Birds' behavior usually recovered some time after surgery, regardless of which areas of the brain were damaged, so Flourens concluded that the degree of impairment of various forms of behavior was determined primarily by how much brain tissue was removed during the operation. Having improved the technique of operations, he was the first to completely remove the forebrain hemispheres of animals and save their lives for further observations.

Based on experiments, Flourens 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, particularly severe behavioral disorders were observed in chickens after the destruction of the gray matter on the surface of the cerebral hemispheres - the so-called corticoid plate, an analogue of the mammalian cerebral cortex. Flourens proposed that this area of ​​the brain is the seat of the soul, or "governing spirit", and therefore acts as a single whole, having a homogeneous and equal mass (similar, for example, to the tissue structure of the liver). Despite the somewhat fantastic ideas of equipotentialists, it is worth noting the progressive element in their views. Firstly, complex psychophysiological functions were recognized as the result of the combined activity of brain formations. Secondly, the idea of ​​high dynamic plasticity of the brain, expressed in the interchangeability of its parts, was put forward.

• Gall managed to determine the “center of speech” quite accurately, but it was “officially” discovered by the French researcher Paul Broca (1861).
• In 1842, Mayer, working on determining the mechanical equivalent of heat, came to a generalizing law of conservation of energy.
• Unlike his predecessors, who endowed the nerve with the ability to sense (i.e., recognizing a certain mental quality behind it), Hall considered the nerve ending (in the sense organ) an “apsychic” formation.