Association part of the brain. Functional organization of the brain

Retikulo-stvOlnew level of integration

Reticular formation is a phylogenyheski old brain system, which does not representtha single anatomical whole and morphologically is a heterogeneous imagehovation. It is also difficult to determine the anatomical extent of the reticular formation, which occupies a central position along the entire length of the trunk (Fig. 68).

The neuronal basis of the integrating function of the reticular formation is long-growingYoue cells, the axons of which can spread influence both in the caudal and rostral directions. Reticular cells connect different parts within the reticular formation, and the latter with the spinal cord, cerebral hemispheres and cerebellum.

Each sensory system sends pathways into the reticular formation. The powerful influences of somatic and visceral nerves have been described, which makes it possible to consider retinal

cular formation vistsero-somaticYuintegration. Pathways to the reticular formation from the nuclei of the trigeminal nerve, vestibular nuclei, and superior olive are shown.

The cerebral cortex has regulatory influences on the activity of the reticular formation. Pathways from the reticular formation in the descending direction - to the spinal cord, cerebellum, nuclei of specific systems and in the ascending direction - to the structures of the cerebral hemispheres up to the cortex are also built according to topical principle, which indicates the functional specialization of the reticular nuclei.

The activity of reticular neurons is characterized by autogenic rhythm, which serves to carry out tonic influences on the spinal cord and cerebral hemispheres. The reticular neurons themselves are capable of responding to stimulation of almost all afferent pathways or central brain structures. This extensive convergence of influences varies significantly between different reticular units and depends on the functional state of the brain. If the reticular neuron differentiates input influences according to their modalities, then the polysynapse

tic chains of neurons with short axons along which activity spreads within the reticular formation itself deprive the initial signal of its modal specificity. Therefore, the thalamic nuclei receive activation, which is a product of multimodal integration on reticular neurons.

The differentiated nature of convergence, topical fractionation and heterogeneity in the organization of afferent and efferent connections allow us to conclude that the functions attributed to the reticular formation concern mainly integration And regulation different types of activities.

P.K. Anokhin (1968) drew attention to the heterochemical sensitivity of individual synapses and entire polyneuronal circuits activated by stimuli of various biological qualities (pain, hunger, etc.) -

Reticular influences through appropriate pathways can reach various relay nuclei of sensory systems and differentially modulate afferent flows. It has been shown, for example, that concentrating an animal’s attention on a visual object leads to blocking the transmission of sensory impulses in the auditory system (P. Ernandets-Peon, 1962). Phenomena called addiction are associated with the regulatory function of the reticular formation. Since habituation is considered the simplest type of learning, the reticular formation is credited with a certain role in the formation of conditioned reflexes (A. Gastaut, I. Ioshchi, etc.).

Integrated at the reticular level, unmodal afferent sendings, taking into account motivational factors, form impulse tonic influences on specific sensory systems, leading to modulation of the corresponding signaling through them. As a result, the prerequisites are created for the successful synthesis of various sensory signals at higher levels of the brain.

The other side of ascending reticular influences may be the creation at the thalamocortical level of such a functional state (or central brain tone) that will provide adequate conditions for the formation of multimodal afferent synthesis.

TAlamockortikaflaxsth level of integration.

Neurophysiology of associative systems of the brain. Along with specific and nonspecific systems, it is customary to distinguish as an independent category associative thalamocorticalbnse systems. In relation to higher mammals, this itsefigurative structures, not belonging to any one sensory system, but to genderhproviding information from multiple sensory systems. The associative nuclei of the thalamus belong to the “internal nuclei”, the afferent inputs to which come not from the sensory lemniscal pathways, but from their relay formations. In turn, these nuclei are projected onto limited cortical territories, which are called associateVny fields.

According to anatomical data, two higher associative systems of the brain are distinguished. The first includes the posterior group of associative nuclei projecting onto the parietal cortex and is called TalamoparyTnal system. The second at the thalamic level consists of the mediodorsal nucleus with its projection to the frontal region of the cortex and is called thalamofrontal system. Both associative systems are a product of progressive differentiation of the nonspecific thalamus and reach significant sizes in primates and humans.

Thalamoparietal system. The parietal cortex is the site of broad heterosensory convergence along fibers from the specific, associative and nonspecific nuclei of the thalamus, as well as along pathways from the sensory cortical areas and the symmetrical cortex of the opposite hemisphere.

Rice. 69. Types of interaction of multimodal signals on neurons of the parietal cortex of the brain of cats

on A and B : on the left - post-stimulus. histograms (on the x-axis the duration of the latent period, ms; on the y-axis - the number of action potentials); on the right - impulse activity of neurons; IN total (bottom) and impulse (top) activity, from top to bottom on A: response to sound, light and sound 4~ t -" Bt -" r - to £ and B - response to somatic irritation; light and light + somatic stimulation (two different experiences). Calibration: 250 µV, 100 ms. In the diagram: SSI - middle suprasylvian gyrus, dot - location of microelectrode tracks

Light influences have the strongest effect on the parietal cortex: they are described here along with multi-sensory and actual visual neurons, which respond to movements in a certain direction of complex geometric shapes. Sometimes these same cells respond to both sound stimuli and eye movements.

F Three types of intersensory interaction were discovered on neurons of the parietal cortex: I - summing neuron, which, with simultaneous heterosensory stimulation, responds with a stronger discharge with a shorter latent period than to monomodal stimuli; II inhibitory neuron, the latent period of the response increases when the stimulus turns from monosensory to heterosensory and III - complex detector, which responds with a pulse discharge only under complex heterosensory influence and does not respond to the isolated application of monomodal stimuli (Fig. 69). It was shown that in the parietal cortex there are polysensory cells that reflect the precortical, thalamic level of integration, along with such

neurons on the membrane of which the actual cortical mechanisms of intersensory synthesis are realized.

The parietal associative cortex sends powerful descending connections to many sensory, limbic, reticular and motor systems of the brain and even forms fibers as part of the corticospinal tract (O. S. Adrianov, 1976).

All of the above gives reason to consider the parietal areas of the cortex as the most important discriminatory- integrativesth apparatus of the cerebral hemispheres.

F After removal of the parietal fields of the cortex, deep disturbances occur in conditioned reflex activity, both in response to simple monomodal and especially multimodal complex signals. This is due to the special role of the parietal cortex in controlling the processes of selective attention, optimizing the mode of current activity, as well as the formation of orientation movements towards an identifiable signal.

In general, the thalamoparietal associative system of the brain is: 1) the central apparatus

primary simultaneous analysis and synthesis of situational afferentation and triggering of mechanisms of orientation movements, 2) one of the central apparatuses “body diagram” and sensory control of current motor activity and 3) the most important element of pre-launch integration, participating in the formation of holistic multimodal images.

Thalamofrontal system. The sensorimotor cortex has multiple projections from specific, associative and nonspecific parts of the thalamus, associative cortico-cortical and transcallosal inputs from the opposite hemisphere and is characterized by the presence of complex synaptic complexes for the convergence of multiple afferent influences on the same neuron. Not only interneurons, but also output elements of the sensorimotor cortex - neurons of the pyramidal tract - belong to the category of multisensory cells.

f Three types of responses of multisensory neurons of the sensorimotor cortex have been established: 1) addiction, which consists in reducing the probability of a response to each subsequent stimulus in the series; 2) sensitisfromation - strengthening of the response with repeated applications of the stimulus and 3) extrapolationI- formation of a proactive response of a neuron to each subsequent stimulus in a series.

Such plastic rearrangements of the response activity of neurons, depending on the nature of stimulation and functional state, intensity and modal composition of stimuli, indicate the presence of complex mechanisms of functional convergence, which are directly related to the formation of systemic reactions of the entire organism.

This cannot be said in relation to the frontal fields proper on the dorsolateral surface of the proreal gyrus of cats, which, according to neurophysiological and morphological data, do not yet have a direct connection with integrative

processes of the brain, but rather relate to structures of a nonspecific type. At the same time, the mesdiobasal sections of the frontal cortex form descending pathways to the thalamic nuclei of the limbic system. The consequences of removing the proreal gyrus in cats are a deficit in visual recognition (L, V. Cherenkova, 1975) or impairments in the accuracy of visually controlled motor acts (Yu. A. Yunatov, 1981). The latter is associated with the fact that the main space of the frontal cortex of cats is occupied by the oculomotor field 8. No disturbances in other sensory systems or the emotional-motivational sphere were noted.

0 Thus, the following basic mechanisms of the work of associative systems of the brain can be identified (A. S. Batuev, 1979, 1981, 1984).

1. Mechanism.mUltisenweed convergence. Its specificity is determined by the fact that afferent messages carrying information about the biological significance of a particular signal converge to the associative fields of the cortex. Such selected afferent influences enter into integration at the cortical level to form a program of targeted behavioral act.

2. Blade mechanismhesky rearrangements during heteromseparatelysx sensory influences. The dynamic nature of multisensory convergence can manifest itself either in selective habituation, or in sensitization, or, finally, in the formation of an extrapolation type of responses. The important role of dominant motivation in determining the spectrum of converging modalities and in organizing intracortical integration has been established. For the parietal cortex, the horizontal (laminar) type of interneuronal integration may be predominant, and for the sensorimotor associative cortex, the vertical (modular) type of interneuron integration may be predominant.

3. Mechanism for short-term storage of traces of integration, consisting

in long-term intracortical or thalamocortical reverberation of impulse flows (see Chapter 6). The latter explains defects in memory and learning in cats and dogs after destruction of the associative fields of the cortex or the corresponding nuclei of the thalamus.

Evolution of associative systems

In the parallel series in which modern mammals developed, although the general plan of the brain structure was preserved, its thalamo-cortical systems underwent the most significant morphofunctional rearrangements. The cortical mechanisms of the activity of sensory systems reach a high level of development with a clearly expressed tendency for the associative systems of the brain to increase with the properties of polysensory converting. In the dynamics of morphological transformations, there is a separation of zones of overlap of cortical projections, with which the implementation of the most complex forms of higher nervous activity is associated.

Within the class of mammals, three main levels of evolution of associative systems of the brain can be distinguished. It must be borne in mind that the degree of development of associative formations of the brain is considered as an indicator of the phylogenetic status of the species (G. I. Polyakov, 1964). Moreover, the brain of insectivores is considered as a predecessor with its further complication in parallel rows of rodents, carnivores and primates. Research has revealed unclear boundaries of differentiation within the neocortex and uncertainty in the functional identification of its fields. This is consistent with the absence of clear boundaries between sensory nuclei in the thalamus.

At the same time, a certain area of ​​the hedgehogs’ cortex (Fig. 70), according to morphological criteria, allows us to assume its inherent integrative properties even within such a primitively organized neocortex (G.P. Demyanenko, 1977). Primitives are projected to this area of ​​the hedgehogs’ cortex.

The main associative nuclei of the thalamus are mediodorsal and posterolateral. In this area, both multimodal monosensory and polysensory neurons were found (A. A. Pirogov, 1977). Such cortical elements are activated predominantly through a single channel, originating in the undifferentiated posterior group of thalamic nuclei. Thus, this thalamocortical system combines the properties of both nonspecific and associative systems of mammals (Fig. 70).

It was shown (I.V. Malyukova, 1974) that such a form of visual-auditory integration as a motor conditioned reflex to a simultaneous complex cannot be developed in hedgehogs and an attempt to form it leads to neurotic breakdowns. However, a complex chain motor conditioned reflex can be easily formed in response to a monomodal signal and is destroyed after removal of the associative area of ​​the neocortex. The most subtle components of sensorimotor integration, which complete the food-producing motor act, suffer more.

Consequently, although the primitive associative system of hedgehogs is not yet capable of organizing complex acts of intersensory integration, it is already beginning to participate in the implementation of processes of sensorimotor synthesis.

As already indicated, insectivores are the direct phylogenetic predecessors of rodents, carnivores and primates.

A study of the design of associative systems of the brain in rats, rabbits, cats, dogs and lower monkeys led to the following conclusion.

First level- rodents whose brains are close to those of insectivores. In rodents there is no clear differentiation of the thalamic cortex into specific and associative zones. The known diffuseness of the representation of sensory systems in the cerebral hemispheres of rodents correlates with the relatively low level of their analytical and synthetic activity.

Rice. 70. Scheme evolutionary maturenia integratiens brain apparatus in insectivores (a), carnivores (b) and primates (c):

only two specific sensory systems have been identified - visual and somatic (som and vis); thin lines are their projection paths; thick lines and shaded areas are associative systems, thick arrows are cortico-cortical connections; dotted zones of efferent cortical projections (mainly pyramidal); cog cerebral cortex; Thai - visual thalamus, th. front - thalamofrontal-nan; th.-pariet - thalamoparietal associative system of the cerebral hemispheres brain

tel. The weak expression of morphological differentiation and functional specialization of polysensory structures in rodents is a factor determining the imperfection of the integrative function of the brain.

In white rats, the formation of a conditioned reflex to the visual-auditory complex also turned out to be ineffective; repeated training in this difficult task led to neurotic breakdowns. At the same time, it was possible to develop a visual-tactile complex, although it was characterized by instability. An approximately similar picture emerged in rabbits, in which the differentiation of light and sound components from their simultaneous presentation in a complex did not reach a higher than 50-60% level. This reflects the low level of analytical and synthetic activity of insectivores and rodents.

Second level- carnivores, in which developed frontal and

parietal association fields and corresponding structures of the thalamus. Carnivores are characterized by significant structural and functional differences in associative thalamocortical systems from other brain structures. This is the presence of complex neuron-synantic components to which sensory streams carrying biologically significant information converge. Moreover, the thalamoparietal system reflects the complication of acts of spatial orientation and the formation of mechanisms that make up the current sensory background for performing purposeful behavioral acts. The thalamoparietal system is a consequence of the complication of the design and connections of the visual sensory system; it provides primary intersensory synthesis, forms a complex complex of environmental afferentation and the “body schema” system.

The thalamofrontal system is included in the cortical section of the somatic sensory system with a simultaneous projection of the limbic apparatus onto it.

tov brain. The thalamofrontal system is involved in organizing pre-launch integration and programming complex behavioral acts. The processes of motivational and emotional coloring of behavioral acts are reflected here to a greater extent due to the direct connections of this system with the entire limbic complex. Within the order of carnivores, the frontal sections of the neocortex become more complex, their size and functional role in the organization of complex forms of behavior that require the mobilization of short-term and long-term memory mechanisms increase.

In carnivores (cats, dogs), the development of a conditioned reflex to a multimodal complex is completed in 10-15 experiments. The level of differentiation of light and sound components from the complex reaches 70-90%; but this requires regular training. In other words, the signaling value of the complex is maintained under the condition of extinction of reactions to individual components. Consequently, predators have a higher level of analytical-synthetic activity, which consists in the ability to integrate multimodal signals into a holistic image.

Another important aspect of the integrative function of the brain is the degree of development of memory processes and the ability to predict upcoming behavior based on them. In the natural conditions of animal existence, any behavioral adaptation is relative and has a probabilistic nature. Therefore, in relation to the biological conditions of living of animals in a probabilistically variable external environment, probabilistic forecasting also takes place, which means that the adaptability of behavioral programs is determined by the degree of their redundancy and mobility.

Behavior in stationary random environments was studied. In response to a sound signal, the animal had to go to one of two feeders, most often to the one where it was most likely to receive reinforcement. The degree of probability of reinforcement from each

The milking trough changed (A. S. Batu-ev, I. V. Malkzhova, 1979; A. I. Kara-myan, I. L. Malkzhova, 1987). Cats are capable of forming behavior towards the feeder from which the probability of food reinforcement is highest. Moreover, their behavior changes in accordance with the change in the probability of reinforcement. Damage to the frontal parts of the neocortex: tex (mainly the sensorimotor cortex) preserves elementary conditioned reflexes, but destroys the ability to make probabilistic predictions.

The processes of intersensory integration are sufficiently developed in carnivores, although the cortical level of the associative systems of the brain overlaps with the output zones of the efferent cortical tracts. On the other hand, in carnivores the role of the pre-cortical level of intersensory integration is quite large and the cortex receives, along with modally specific afferent volleys, already processed nonspecific impulses from associative nuclei. Finally, each of the associative systems in carnivores is characterized by the dominance of one or another sensory input, which, naturally, does not contribute to the achievement of complete heterosensory integration.

Third level - primates in which the associative structures of the thalamus with their extensive and differentiated projection into the frontal and parietal areas of the cortex are included in the independent integral integrative system of the cerebral hemispheres. An essential feature of primates is the developed corticocortical connections, with the help of which associative fields can be combined into an integral hierarchically constructed system. Thanks to the compact system of myelinated associative fibers, the role of the cortical level of interaction of specific sensory zones with the associative neocortex increases. The associative fields of the neocortex are characterized by fine differentiation with the formation of integral structural and functional ensembles from neural elements.

The specificity of the associative neocortex is the convergence of multiple sensory messages about the biological significance of external signaling in it in accordance with the dominant motivation through afferent channels independent of each other. At the same time, the role of the actual cortical level of intersensory integration and provision of short-term memory processes increases. After the destruction of either the frontal or parietal associative fields of the cortex, not only the processes of intersensory synthesis, orientation-exploratory activity, and short-term memory are deeply affected, but also the formation of simpler forms of conditioned reflex activity.

The functional significance of individual associative systems is expanded and clarified in comparison with predatory systems. The predominance of any one sensory input is lost, and consequently, the possibilities for their integration expand. A topographic separation of associative fields from the afferent cortical formations themselves occurs, which reduces the specific importance of sensorimotor integration and expands the role of the cortex in the implementation of intersensory afferent synthesis. Their increasing interdependence arises to ensure the functioning of the integral integrative system of the hemispheres.

For primates (lower monkeys), the development of conditioned reflexes to a simultaneous complex is a relatively easy task, because in the process of applying a complex stimulus, the components spontaneously lose their signal value and the formed conditioned reflex connections are preserved for months without additional training. "In monkeys, a conditioned reflex can be developed even to three-membered complex of multimodal signals. This indicates a higher level of analytical and synthetic activity of the brain of monkeys in comparison with carnivores, which is reflected in greater structural differentiation and function.

national specialization of associative thalamocortical systems.

Monkeys easily cope with probabilistic forecasting tasks, but after destruction in the area of ​​the associative frontal cortex they lose this ability, their behavior acquires a monotonous perseverative character.

Obviously, the ability to use previous experience recorded in long-term memory to predict behavior in stationary random environments undergoes significant evolutionary transformations, which are determined by the degree of development of integrative brain systems, the levels of differentiation of which correlate with the degree of perfection of analytical-synthetic activity and the organization of complex forms of behavior.

Ontogenesis is associativesx brain systems

The study of the dynamics of the formation of associative systems of the brain showed heterochronnostb this process, which is apparently due to the inclusion of individual links of thalamocortical systems in the provision of various behavioral acts, the sequence of maturation of which is determined by their necessity for the implementation of the vital functions of a newborn animal (mature and immature born).

According to the concept of systemogenesis (P.K. Anokhin, 1968), the uneven maturation of neural elements and connections between them is explained by their involvement in the structure of various functional systems. The heterochronicity of their maturation is determined by their significance for the survival of the organism, especially during critical periods of life (see Chapter 2), when a newborn animal comes into direct contact with the environment. Anatomically and functionally, those sensory mechanisms (somatic, acoustic) that ensure survival at the initial stages of individual development are the first to mature.

In the associative nuclei of the thalamus, projections to the cerebral cortex of newborn kittens were found (V.P. Babmindra, L.A. Vasilyeva, 1987). At the same time, nonspecific thalamic nuclei form their projections to the cortex somewhat later; their main role is to control intrathalamic activity.

Despite the early formation of associative systems, their final maturation occurs over a fairly long period and ends in cats between the 2nd and 3rd months of life. It is by this time that kittens first form a full-fledged conditioned reflex to a simultaneous complex, approaching in its characteristics to a similar conditioned reflex of an adult animal (L. A. Vasilyeva, L. V. Cherenkova, 1986).

When the first critical stage of postnatal development is overcome, a period of rapid differentiation of brain structures begins and the emergence of bilateral connections of a diffuse nature between them. A structural-functional matrix is ​​being formed that will serve as the basis for the further deployment of coordination processes and the identification of local functional structures.

Thus, the principle of development - from diffuse nonspecific to local specific (A.I. Karamyan, 1976) - is a general biological pattern, which also governs the dynamics of the development of associative systems of the brain.

Finally, the third stage is associated with the moment of formation of inhibitory coordination mechanisms both in the cortex itself and in deep structures. The emergence of such mechanisms ensures a fine specialization of both sensory and associative systems of the brain, and therefore of various integral behavioral acts.

In our work on the nervous system simulator, we have so far only touched on well-studied aspects of its operation. But the difficulty of modeling the nervous system and the reason why artificial intelligence has not yet been created is the lack of a complete understanding of how a nerve cell works. Many processes occurring in a nerve cell and the nervous system as a whole are described in detail, but there is no clear algorithm for their operation that could be transferred to a model or computer program.

A simple idea for a neuron algorithm made it possible to solve this problem.

Table of contents
1. Nervous system simulator. Part 1. Simple adder
2. Nervous system simulator. Part 2. Modulated neuroelement
3. Nervous system simulator. Part 3. Associative neuroelement
4. Memory, memory consolidation and granny neurons
5. Simulation of emotions or electronic sense of novelty
6. The Amazing Cerebellum
7. Structure and starting settings of the brain

I like the analogy from Jeff Hawkins' book On Intelligence about developing a theory of how the brain works. When composing this puzzle, we are missing some elements, and some elements from another puzzle, but we have a large amount of data about the nervous system and the brain, which means we have an almost complete puzzle, so we can roughly imagine the whole picture, and, using our imagination to identify the missing elements.

My goal is to create a logical model of the functioning of the nervous system, one might say to create a sketch of what is depicted on an unfinished puzzle, and it must correspond and not contradict all the existing elements of the puzzle and at the same time be logically complete. To fill the gaps, some theoretical framework has been created, which may seem controversial to some. But for the model at this stage, the main thing is that it allows you to emulate both internal and external observable phenomena occurring in the nervous system. Within the framework of the resulting model, it is possible to explain many phenomena, such as memory and memory consolidation, emotions, neuron specialization and much more.

In the second part, we found out that there are three types of reflex activity established by academician I.P. Pavlov. If everything is extremely clear with the biological mechanisms of addiction and sensitization, then with the formation of conditioned reflexes not everything is as simple as it seems. The fact is that the external manifestations of this mechanism have been widely studied and described, but there is no explanation of how this happens at the cellular level.

For example, we know that when the activity of two nerve centers combines, a reflex arc is formed between them over time. Those. subsequently, when one nerve center is activated, excitation is transferred to another nerve center. If we figuratively divide such a reflex arc into segments, and consider such segments as separate elements. Then we can say that during the formation of a reflex arc of a conditioned reflex, a commutation of a directional nature occurs in each segment. Each segment selects a specific direction in which the transmission of nervous excitation occurs when it is activated. Of course, it is worth noting that this direction is not clearly defined for the segment, but can be correlated in certain values. You can even talk about strengthening transmission in a certain direction and weakening it in other directions.

When strengthening the reflex through repeated repetitions, we can talk about clarifying and strengthening the transmission in the direction for each segment. This concept leads to the conclusion that if we divide the entire cortex into similar segments, we will observe in each a certain directional orientation with varying accuracy and strength. Each segment will be part of some reflex arc of a conditioned or unconditioned reflex. Presumably, this orientation can be refined or changed during the learning process.

If we turn to the neural paradigm, it does not provide for directional orientation. We have a membrane and dendrites that receive signals and an axon, along which the signal is transmitted further to other cells after spatiotemporal summation, that is, the signal is transmitted in one direction along the axon to its endings. But at the same time, we still observe the formation of directional propagation of excitation in the brain, during the formation of conditioned reflexes.

Neuron paradigm

This idea of ​​the neuron was more likely formulated by cyberneticists than by neurophysiologists, but it is also common among physiologists. Everything is somewhat more complicated. Firstly, neurons can also be afferent, i.e. their axon brings a nerve impulse to the cell body and naturally it then spreads along the dendrites. Secondly, in addition to axo-dendritic synapses, there are also dendro-dendritic synapses. Thirdly, neurons exist without axons. Most likely, the neuron works in any direction; its membrane is a receiver, including the membrane on the dendrites. Dendrites, like roots, grow in different directions in search of other neurons, and at their tips there are transmitting synapses. If the neuron is activated, no matter in what part of the membrane, then activation of all synapses of the dendrites and axon will occur. But the amount of transmitter released will be different in different synapses and sometimes be absent altogether.

If we consider not a single cell as a functional unit of directional commutation, but a small area of ​​cells, then we can see that the cells and their processes are very tightly intertwined, and in different directions. This gives an element of directional communication with multiple inputs and outputs in different directions.

The shape of a neuron is determined by evolutionary changes. The shape of the cell was formed in nervous systems in which only the simplest functionality of nervous activity was carried out. When the development of life on Earth required the addition of the formation of catch reflexes to the set of functions of the nervous system, evolution took the path not of restructuring the cell, but of increasing their number and densely intertwining their processes.

Thus, the property of directional switching is distributed in groups of neurons, changing the strength of their synapses. An associative neuroelement is a functional unit in modeling and therefore its analogue in biology is a group of neurons for which the phenomenon of directed commutation will be expressed.

We found out that the direction of propagation of excitation is important for us, but how is this direction determined for each functional element. It is known that excitation tends to spread to another source of excitation, and a stronger and larger focus of excitation attracts weaker ones (conclusion of Pavlov I.P.). Those. if a functional element receives excitation, then somehow it must determine the direction that will subsequently be formed and stored in its structure.

In my modeling work, I started from the idea of ​​​​electromagnetic interaction of nerve cells, and this idea provided answers to many mysteries about the brain, provided a theory and model that explains many aspects of the nervous system.

The nerve impulse throughout the nervous system has the same shape, and by analogy with it, the associative neuroelement has the property of charge, which characterizes the change in the total charge on the surface of the membranes of the functional unit. Those. a certain law of change of some characteristic called charge is specified.

This is how the law is set in the program, the horizontal scale is time in hundredths of a second, the vertical scale is charge in relative units. It differs somewhat from the spike chart in that the peak portion is longer in duration. This is due to the fact that the spike values ​​are determined at one point in the nervous tissue during the passage of excitation, and the charge graph is a reflection of the charge over the entire surface of a cell or group of cells. Also, the state of rest of the nervous tissue is taken as zero on the charge scale. It should be noted that the law of charge change also reflects the trace potential, which was previously considered to be a consequence of some oscillation or equalization of charges separated by a membrane, but for the model this charge behavior turned out to be very important.

The figure above shows a diagram of an associative neuroelement. Signals from direct synapses (X1, X2, X3 ... Xn) enter the adder (a). And if the resulting amount exceeds a certain threshold (b), then the neuroelement will be activated. When a neuroelement is activated, its charge will begin to change in accordance with the established law (c). Information about these changes and the location of the element itself will be available to the entire system. Then, at a certain point in time, the mechanism for determining the vector of the preferred direction of excitation propagation (r) is launched. This occurs by obtaining a certain average charge position of all active neuroelements, i.e. center of mass of charges, characterized by a point in space. We will call this point a pattern point, because for each combination of active cells and the state of their charges at the calculated moment of time for each neuroelement, the position of this point will be different. Simply put, the charges of neuroelements influence the determination of the direction vector of the preferred propagation of excitation; a positive charge attracts excitation, a negative charge repels.

To determine the vector of preferred propagation of excitation, the following rule has been selected:

Where r is a vector whose beginning is in the center of the neuroelement for which the vector is determined, and the end is in the center of the nth neuroelement.

The rule and law of charge changes were selected empirically so as to simulate the formation of conditioned reflexes. .

After obtaining the vector of the preferred direction of propagation of excitation (T), the strength of synapses (Y1, Y2, Y3 ... Yn) is calculated. Each synapse is characterized by a synapse vector (S), the beginning of which lies in the center of the neuroelement and the end is connected to the center of the target neuroelement to which the signal is transmitted. The main parameter of a synapse is its strength F, the strength value is limited within certain limits, for example, an incentive synapse can have values ​​from 0 to 10.

Let's imagine that vector T forms a certain cone around itself, the apex of which is in the center of the neuroelement, and the base plane is perpendicular to vector T; if the synapse vector falls into the area limited by this cone, then the value of the synapse strength will be increased by a certain value. And accordingly, if the synapse vector is outside the cone area, then the synapse strength decreases, but the strength value does not go beyond the established maximum and minimum.

The area of ​​the cone around the vector T is characterized by the angle at the vertex of this cone, this angle is called the focus. The smaller the focus, the more accurately the direction of transmission of excitation in the neuroelement will be determined. As mentioned earlier, when the body repeats the same conditioned reflex, it is refined. Therefore, the following method of changing the focus was chosen for the model: when calculating the vector T, it is compared with its previous value, and if the vector changes slightly, then the focus decreases by a certain value, but if the vector has been changed greatly, then the focus returns to its maximum value. This results in a gradual decrease in focus as the same conditions are repeated over and over again.

A very important point here is how much the strength of the synapses will change with each activation. This is determined by the neuroplasticity parameter P.

The formula for the new value of synapse strength will look like:

Fnew = Fold + I × P × (Fmax - Fmin);
Fmin ≥ Fnew ≥ Fmax;
where P is neuroplasticity (0 ≥ P ≥ 1);
I – parameter that determines whether the synapse vector is within the region of increasing synapse strength (I = 1) or in the region of decreasing synapse strength (I = -1);
Fold – previous value of synapse strength;
Fmin – minimum value of synapse strength;
Fmax – maximum value of synapse strength.

Neuroplasticity in biology characterizes how susceptible a neuron is to changes in its structure under the influence of external conditions. Different areas of the brain have their own degree of plasticity, and it can also change depending on certain factors.

This example allows us to understand how conditioned reflexes are formed on the basis of associative neuroelements. White neuroelements form a reflex arc of an unconditioned reflex with a heading “R” and a response “1”. These neuroelements do not change the strengths of their synapses. Blue neuroelements do not initially participate in any reflex acts; they seem to fill the rest of the space of the nervous system, and they are randomly connected to each other through synapses. Therefore, if we activate one such neuroelement associated with the “Q” receptor, then a certain focus of excitation will arise, which will have a random distribution and, turning on itself after a while, it will go out without creating any response. If we combine the unconditioned reflex with the head “R” and the activation of the “Q” receptor in approximately the same time interval, then a reflex arc of the conditioned reflex will be formed. And the activation of just the “Q” receptor will lead to the answer “1”.

For clarity and optimization of the model, dynamic creation of neuroelements was used, which emulates the filled space of the nervous system with randomly interconnected elements. No growth of new neurons or new connections is modeled here; all changes occur only in the strength of synapses; it’s just that neuroelements not previously involved in any reflex act are not shown.

The following example shows how excitations behave when different centers are activated under equal conditions and with absolute plasticity (P = 1).

Change in the direction of excitation propagation under the influence of two excitation centers when plasticity is absolute (P = 1):

And at low plasticity (P = 0.1):

At this point we have finished looking at the basics of the nervous system model. In the next part we will look at applied things, how to use all this to simulate memory, emotions, and specialization of neurons.

Associative systems of the brain, their role in the sensory function of the brain and programming of behavior.

One of the main attributes of any complex purposeful movement is the formation of preliminary programs.
The role of the program in the structure of a motor act should be considered taking into account the biological motivation of the movement, its temporal parameters, motor differentiation, the degree of complexity of the coordination structure and the level of its automated strategy and tactics of movement. The biological motivation of a motor act is the main motivating (initial) factor for its implementation. It is motivations that form purposeful movements, and therefore determine their overall strategy. This means that if the movement strategy is based on biological (or social) motivation, then each specific motor act will be considered as a step towards satisfying this motivation, that is, it will solve some intermediate task or goal (Fig. 104). Biological motivations can lead either to the launch of “sealed”, that is, rigid, programs, establish their combinatorics, which we encounter in invertebrates and lower vertebrates and call instincts or complexes of fixed actions, or lead to the formation of new complex programs, simultaneously defining the degree of their lability. in cases where the action is completely an automatic consequence of the stimulus, it is impossible to talk about motivation. In this case, there are fixed relationships between the stimulus and the response. Motivation “breaks” these fixed connections between stimulus and response through the process of learning. For example, unlike many instinctive reactions, the reaction of pressing a pedal can be “separated” from the internal state of the animal. The operant situation, signal, reaction, reinforcement are completely arbitrary, not having fixed connections with each other.

Participation of associative systems of the brain in the organization of movement. The role of external factors, signals from the external environment and, accordingly, the role of sensory and associative systems of the brain in the formation of motivated movements is very significant. The specificity of the participation of the thalamoparietal associative system in the organization of movements is determined by two points.

On the one hand, it participates in the formation of an integrated circuit of the body, all parts of which are correlated not only with each other, but also with vestibular and visual signals.

On the other hand, it is involved in regulating attention to current environmental signals, taking into account the orientation of the whole body relative to these signals.

The thalamoparietal (like the inferotemporal) associative system is activated by current sensory signals, that is, it is mainly tied to the present moment in time, and is associated with the analysis of mainly spatial relationships of raziomodal features.

The frontal associative system has a reciprocal relationship with two functional systems of the brain:

1) parietal-temporal, which is associated with the processing and integration of multimodal sensory information;

2) telecephalic limbic system, including the limbic cortex and associated subcortical formations, especially the hypothalamus and areas of the midbrain and diencephalon.

Purposeful behavior is determined by the dominant motivation, which encourages the body to satisfy the prevailing need.

The adaptive nature of behavior is achieved with the help of many conditioned reflexes, which ensure the adaptation of the organism to a specific spatio-temporal situation. The nonspecific direction of search behavior is determined by the presence of a hypothalamic focus of stationary excitation, which has dominant properties (inertia, high excitability, ability to summation); search activity in a specific situation is determined by a system of cortical conditioned reflex connections as the basis of past life experience, which provides a directed search for an object to satisfy a need.

Higher integrative (associative) systems of the brain are the main apparatuses for controlling plastic forms of behavior, which are provided by the following mechanisms:

♦ selective convergence of biologically significant information;

♦ plastic changes under the influence of dominant motivation;

♦ short-term storage of integral images and programs for the upcoming behavioral act.

The degree of development of associative systems of the brain in the evolution of mammals correlates with the perfection of apaltic-sypthetic activity and the organization of complex forms of behavior.

The ability to form a sequence of movements and anticipate its implementation, as the most complex function of the brain, reaches its greatest development in a person who has the properties of verbal control of behavior.

BASICS OF NEUROPSYCHOLOGY

Topic 1. Functional organization of the brain and mental activity........1

Topic 2. Local brain systems................................................. ............................9

Topic 3. Mental processes and their brain organization………………......17

TOPIC 1 Functional organization of the brain and mental activity

1. What are the basic principles of the evolution and structure of the brain as an organ of the psyche? The basic principles of evolution and brain structure are:

1) At various stages of evolution, the relationship of the animal organism with the environment and its behavior were regulated by various apparatuses of the nervous system, and therefore The human brain (BM) is a product of long historical development .

At the elementary levels of development of the animal world (for example, in hydroid polyps), signals are received and movements are organized reticular nervous system; at this stage of evolution, there is no single center that processes information and regulates the behavior of the animal. The excitation flow is determined by those temporary dominant foci, which are created in one or another part of the animal’s nervous system. In the process of evolution, the network-like nervous system, preserved in the body of animals, gave way to new formations. Complex receptor devices were concentrated in the anterior sections of the animal's brain, and the signals received by them began to be sent to anterior ganglion, which processed the information received and switched excitation to the efferent pathways leading to the animal’s motor system.

Further, the evolution of the brain took two strategic directions. The first direction is the maximum preparedness of the organism for future conditions of existence (for example, insects). The anterior ganglion of insects becomes an ideal organ for the implementation of innate instinctive behavior, which can be triggered by elementary stimuli and, nevertheless, have a program of amazing complexity. The nervous apparatus of the anterior ganglion, well adapted for the implementation of innate behavioral programs, cannot, however, ensure adaptation to dramatically changing environmental conditions. The conservation of the species is made possible by the excess production of individuals, of which only a very few survive .

The second direction: in mammals, innate, instinctive forms of response are “overgrown” with individual reactions based on personal experience. The behavior of a mammal in various situations is much less certain than the behavior of insects; behavioral patterns are becoming fewer and fewer, and exploratory, indicative reactions take up more and more space. A flexible form of life requires much more brain matter. GM meets these tasks.

The insect brain is a multi-program executive machine, while the mammal brain is a self-learning machine, capable of probabilistic prediction. However, the main thing is not the quantity, but the quality of the structures of the brain matter. As part of the second direction of evolution, there is a steady increase in the size of the cerebral cortex. This department is the least specialized and most important for recording personal experience, which implies the possibility of continuous improvement.

2) The former nervous apparatus is preserved in the GM, giving way to new formations and acquiring a different role. They become devices that provide behavior background, taking an active part in the regulation states of the body, passing functions receiving, processing, storing information, creating new behavior programs And regulation and control of conscious activity senior staff of KGM.

Forms of behavior in humans of varying complexity can be carried out using different levels of the nervous system:

– the simplest elements of behavior (knee reflex) are carried out only by the mechanisms of the spinal cord;

– a complex innate form of behavior – the regulation of homeostasis, provided by respiration, digestion and thermoregulation, is carried out through mechanisms inherent in the GM trunk (medulla oblongata, hypothalamus);

– even more complex forms of behavior, involving the provision of tone, synergy and coordination, are closely related to the work of the diencephalon and subcortical motor nodes; their defeat, without causing disruption of complex cognitive processes, leads to a gross disruption of “background” behavior, for example. parkinsonism is a syndrome caused by damage to the extrapyramidal system;

– the most complex forms of activity cannot be achieved without the participation of the KGM, which is the organ of higher forms of animal behavior and conscious human behavior.

3) The principle of the vertical structure of the functional systems of the brain . All higher mental functions have not only horizontal (cortical), but also vertical (subcortical) brain organization. Separation of individual zones of the cortex through circular isolation may not entail significant changes in the behavior of animals, while pruning the cortex, isolating it from underlying formations, inevitably leads to significant disruptions in its regulatory functions. All this means that individual sections of the CGM are connected to each other not only using horizontal (transcortical) connections, but also through underlying formations through the system vertical connections. Ascending and descending connections turn the brain into a self-regulating system. Complex forms of behavior can be carried out at different levels of the nervous system, each of which makes its own contribution to the functional organization of behavior. The lower levels of the nervous apparatus are involved in organizing the work of the SGM, regulating and ensuring its tone. But the lower levels of the nervous apparatus do not work in complete isolation from the CGM and themselves experience its regulating influence.

2. What is the structural and functional organization of KGM? The brain and its cortex have a heterogeneous structure. There are gray matter, which makes up the cerebral cortex and subcortical gray formations, and white matter, consisting of conductive fibers that connect individual areas of the CGM with each other and with the periphery. The CGM consists of 6 layers of cells. Only layers IV and V directly connect the CGM with the periphery.

The fields of the cortex, distinguished by the developed IV layer of fine-grained nerve cells, are approached by sensory fibers that begin in the receptors; these zones are named primary sensory areas KGM. Generally sensitive (parietal), visual (occipital) and auditory (temporal) sensitive areas are distinguished.

Betz's giant pyramidal cells, which make up the V layer of the cortex, turned out to be sources of motor impulses, going from the cortex to the peripheral muscles, and the anterior central gyrus, in which they are concentrated, is called primary motor area KGM. Fibers starting in the anterior central gyrus and approaching a number of cranial nerve nuclei (CN) and the anterior horn of the spinal cord (SP) constitute motor (pyramidal) pathway.

Above each primary zone of the cortex with the predominant development of the IV - afferent or V - efferent cell layers, a system of secondary zones is built, in which the more complex layers II and III occupy a predominant place. These layers consist of cells with short axons, most of which do not have a direct connection with the periphery and receive their impulses from the subcortical formations lying deep in the brain, which carry out the primary processing of impulses coming from the periphery.

In the human CGM, areas can be distinguished that consist entirely of upper layers of cells and do not have a direct connection with the periphery. These areas are called tertiary zones of the cortex. In the KGM, two groups of tertiary regions can be distinguished. The first one is back – located at the junction of the occipital, parietal and temporal regions; it is designated as the posterior associative center or overlap area cortical sections of exteroceptive analyzers. This zone ensures the joint operation of the cortical links of individual analyzers. Second – front – located in the frontal lobe in front of the motor cortex and built above its motor sections. It is connected with all other parts of the cortex and, plays a significant role in building the most complex programs of human behavior.

The hierarchical structure of the KGM is a product of long historical development. In humans, the primary areas of the cortex occupy a very small place, being pushed aside by well-developed secondary areas, and the tertiary zones of the cortex become the most developed systems and occupy the vast majority of the CGM. This shows that the process of increasing the complexity of mental activity, which presupposes the conscious nature of programming activity, is associated with the development of the higher layers of the cortex.

Another functional characteristic of the structure of the animal's bone marrow is the relationship between the mass of cell bodies and the mass of cellular substance. In the implementation of complex nervous processes, a decisive role is played not only by the body of the nerve cell, but also by its numerous processes and the glial cells surrounding the neurons. An increase in the ratio of glial tissue to the mass of nerve cells (their bodies) at each new stage of evolution indicates increasing the controllability of the functions of individual brain zones.

An essential characteristic is degree of myelination corresponding nerve formations. The process of myelination - upon completion of which the nerve elements become ready for normal functioning - occurs unevenly in different zones of the cortex: myelination of elements of the primary zones ends quite early; the process of myelination in the secondary and tertiary zones of the cortex sometimes continues until 7-12 years of age. Apparatuses corresponding to the most complex, complex forms of mental activity mature at relatively late stages of development and, therefore, the formation of human mental activity proceeds from simpler to complex, mediated forms.

3. What is syndromic analysis and what is the systemic organization of mental processes? With local lesions of the brain (mainly the cortex), not just one mental function is disrupted, but a whole set of functions that make up a single neuropsychological syndrome, which is based on a violation of a certain factor. Syndromic analysis – the main way of neuropsychological research.

Syndromic analysis is based on three main principles. First– it involves a thorough qualitative qualification of mental function disorders, and not simply a statement that the function is impaired. Qualitative analysis means determining the form of mental dysfunction. Eg. When a mnestic defect is detected in a patient, it is necessary to find out whether these disorders are modally nonspecific in nature or are associated only with a certain modality, whether the link of immediate or delayed reproduction of material suffers primarily, etc.

Second position: disorders of higher mental functions consists in the analysis and comparison of primary disorders directly related to the disturbed factor and secondary disorders that arise according to the laws of the systemic organization of functions. Any human mental activity is a complex functional system, the implementation of which is ensured by a whole complex of jointly working areas of the brain. Each area of ​​the brain involved in ensuring a functional system, is responsible for its factor (its function), and its elimination leads to the fact that the normal implementation of the general function (which consists of many factors) becomes impossible, i.e. the functional system as a whole can be disrupted if a large number of zones are affected, and with lesions of different locations, it is disrupted in different ways.

Third position lies in the need to study the composition of not only impaired, but also preserved higher mental functions. Any limited cortical lesion disrupts the flow of some mental processes, leaving other processes intact - principle of double dissociation of functions.

Thus, qualitative qualification of disorders of mental processes, identification of the main defect (i.e. primary disorders) and secondary systemic disorders, analysis of the composition of not only impaired, but also preserved mental functions constitutes the essence of syndromic analysis aimed at topical diagnosis of local lesions of the brain.

A thorough neuropsychological analysis of the syndrome and double dissociation, which occurs with local brain lesions, allows us to get closer to the structural analysis (internal composition) of mental processes. To an unbiased observer, musical and speech hearing may appear to be two variants of the same psychological process. But the destruction of certain areas of the left temporal region leads to a pronounced impairment of speech hearing (making the discrimination of close speech sounds completely inaccessible), but keeps musical hearing intact. There is a description of one outstanding composer who, after a hemorrhage in the left temporal region, stopped distinguishing the sounds of speech and understanding speech addressed to him, but continued to create brilliant musical works. This means that such seemingly close mental processes as musical and speech hearing not only include different factors, but also rely on the work of different brain areas.

Such different psychological processes as orientation in space, counting and understanding of complex logical and grammatical structures, it would seem, do not have fundamentally common links that make it possible to combine them into one group. However, damage to the parieto-occipital (inferior parietal) parts of the left hemisphere inevitably leads to disruption of all these processes, and a patient with a similar localization of the lesion not only experiences noticeable difficulties in spatial orientation, but also exhibits gross defects in counting and in understanding complex logical-grammatical structures. This shows that all these seemingly different functions include common factor and the identification of these common factors contributes to a much deeper analysis of the structure of psychological processes.

4. What are the main functional blocks of the brain? Mental activity– this is an ideal, subjectively conscious activity of the body, carried out with the help of neurophysiological processes. Mental activity is carried out with the help of VND. Mental activity occurs only during the waking period and is conscious, and GNI occurs both during the sleep period as unconscious processing of information, and during the waking period as conscious and subconscious processing. Individual manifestations of human mental activity, conventionally identified as independent objects of study, are called mental processes(sensation, perception, idea, thinking, attention, emotions, will). The main significance of mental processes is the adaptation of the individual to the external environment.

Highlight 3 main functional blocks(3 main apparatuses of the brain), the participation of which is necessary for the implementation of any type of mental activity: 1) a block for regulating tone and wakefulness; 2) block for receiving, processing and storing information; 3) block of programming, regulation and control of complex forms of activity.

Each of these main blocks has hierarchical structure and consists of three types of cortical zones built on top of each other: primary(projection), where impulses come from the periphery or where impulses are sent to the periphery, secondary(projection-associative), where the received information is processed or the corresponding programs are prepared, and tertiary(overlap zones), which are the most late developing apparatuses of the cerebral hemispheres, and which in humans provide the most complex forms of mental activity, requiring the joint participation of many areas of the cerebral cortex.

Brain– the highest organ of the nervous system – as an anatomical and functional formation, it can be conditionally divided into several levels, each of which carries out its own functions.

I level– cortex– carries out higher control of sensory and motor functions, primary control of complex cognitive processes.

Level II–basal ganglia of the cerebral hemispheres– controls involuntary movements and regulates muscle tone.

Level III–hippocampus, pituitary gland, hypothalamus, cingulate cortex, amygdala nucleus– carries out primary control of emotional reactions and states, as well as endocrine regulation.

IV level(lowest) – reticular formation and other brainstem structures– controls vegetative processes.

Anatomically brain subdivided on the brainstem, cerebellum and cerebral hemispheres(right and left) . Each hemisphere has 4 lobes: frontal, parietal, occipital, temporal.

In humans, compared to animals, the cerebral cortex(cerebral cortex) is the most highly differentiated section of the nervous system. Topographically, there are convexital (related to the cranial vault), basal (related to the base of the skull), medial (between the hemispheres) cerebral cortex.

5. What is a block for regulating tone and wakefulness? In order to ensure the full flow of mental processes, a person must be in a state of wakefulness. Only under optimal waking conditions can a person receive and process information, recall the necessary selective systems of connections in memory, program his activities and monitor the course of his mental processes, correcting errors and maintaining the direction of his activities. In a state of sleep, clear regulation of mental processes is impossible, emerging memories and associations become disorganized, and directed selective (selective) performance of mental activity becomes impossible.

To carry out organized, purposeful activities, it is necessary to support optimal cortical tone. The devices that provide and regulate the tone of the cortex are not located in the cortex itself, but in the underlying stem and subcortical regions of the brain; these devices are located in a dual relationship with the bark, toning it and at the same time experiencing its regulating influence. In the trunk of the GM there is a special nerve formation, which, in its structure and in its functional properties, is adapted to carry out the role of mechanism regulating the state of the KGM, those. is able to change its tone and ensure its wakefulness. This reticular formation– education built according to the type nerve network, which contains the bodies of nerve cells, connected to each other by short processes. Through its network, excitation does not spread in separate, isolated impulses, not according to the “all or nothing” law, but gradually, gradually changing its level and, thus, modulating (activating and inhibiting) the state of the entire nervous system.

Some of the fibers of the reticular formation are directed upward, ending in the higher nerve formations - the thalamus, caudate body, and cortex. These formations were named ascending reticular system, which plays a crucial role in regulating cortical activity. Other fibers of the reticular formation have the opposite direction: they start from higher located nerve formations - the cortex, caudate body and thalamic nuclei - and are directed to the lower structures of the midbrain, hypothalamus and brain stem. These formations are called descending reticular system. They place underlying formations under the control of those programs that arise in the CGM and the implementation of which requires modification (change) and modulation of waking states.

Both sections of the reticular formation constitute a single self-regulating vertically located functional system, built on the principle of a reflex circle, which can provide changes in the tone of the cortex, but which at the same time is itself under the regulatory influence of those changes that occur in the CGM. This is a system of plastic adaptation to environmental conditions in the process of vigorous activity. Each department includes activation And brake paths (sections).

Stands out 3 main sources activation of the nervous apparatus. The first source of activation is metabolic processes of the body , underlying homeostasis and instinctive processes. Second source of activation associated with the entry into the body of irritations from the outside world and leads to the emergence of other forms of activation, manifested in the form orientation reflex. In the hippocampus, a significant place is occupied by neurons that perform a comparison (comparison) of old and new stimuli and provide a reaction to new signals or their properties with the extinction of the reaction (cessation of activity) to old, already familiar stimuli. These first 2 sources are associated with the ascending connections of the reticular formation.

The third source of activation is due to the fact that a significant part of human activity is due to intentions and plans, prospects and programs, which are formed in the process of his conscious life, are social in their order and are carried out with the closest participation of first the external, and then his internal speeches . Every idea formulated in a speech pursues some target and causes a whole program of actions aimed at achieving this goal. Reaching a goal stops the activity. But the emergence of intentions and the formulation of goals is not a purely intellectual act. Carrying out a plan or achieving a goal requires a certain amount of energy and can only be achieved with a certain level of activity.

This activation source is associated with descending connections of the cortex. It is these connections that make regulating influence of the cerebral cortex on underlying brainstem formations and are the mechanism by which The functional patterns of excitation that arise in the cortex involve the apparatus of the reticular formation of the ancient brain and receive an energy charge.

Thus along with specific sensory and motor functions, the CGM also has nonspecific modulating functions; irritation of certain areas of the cortex can have both activating and inhibitory effects on underlying nerve formations. Descending fibers come primarily from frontal prefrontal cortex and are that apparatus through which the higher parts of the cerebral cortex, directly involved in the formation of intentions and plans, control the work of the underlying apparatus of the reticular formation, thalamus and brainstem, thereby modulating their work and providing the most complex forms of conscious activity.

All this shows, firstly, that the devices of the first block not only tone the cortex, but also experience its differentiating influence, and secondly, that the first functional block of the brain works in close connection with the higher parts of the cortex.

CONCLUSION: The 1st block is built according to the type nonspecific a nervous network that carries out its function through gradual, gradual changes in states. The first block perceives and processes various information and regulates the state of the internal environment of the body using neurohumoral and biochemical mechanisms. The first block is involved in any mental activity and, especially in the processes of attention, memory, emotional states and consciousness in general.

6. What is a block for receiving, processing and storing information? This block is located in the convexital sections of the cortex and occupies its posterior sections, including the apparatus of the visual (occipital), auditory (temporal) and general sensory (parietal) areas. Neurons of block 2 work according to the “all or nothing” law, receiving individual impulses and transmitting them to other groups of neurons.

According to their functional characteristics, the devices of this block are adapted to receive exteroceptive stimuli coming to the brain from peripheral receptors, to analyze them into the smallest constituent details and to synthesize them into entire functional systems.

The basis of this block is primary projection zones of the cortex with high development of neurons of the IV afferent layer, which have the highest specificity. These cortical areas represent cortical apparatus of one or another modality-specific analyzer, are built according to a single principle of hierarchical organization.

Apparatuses are built above the primary zones of the cortex of the 2nd functional block of the brain secondary (gnostic) zones of the cortex, in which layer IV gives way to layers II and III, which do not have such pronounced modal specificity and include a significant number of associative neurons with short axons, which makes it possible to combine incoming excitations into the desired “functional patterns” and implement synthetic function.

But human cognitive activity never proceeds based on only one isolated modality (vision, hearing, touch); any objective perception, and especially representation, is the result of multimodal activity. Therefore, cognitive activity should be based on the joint work of the entire system of KGM zones. The function of ensuring such joint work of an entire group of analyzers is carried out by tertiary zones 2nd block ( overlap zones cortical sections of various analyzers). These zones are located on the border of the occipital, temporal and posterior central cortex (“posterior associative center”). Their function is almost entirely reduced to the integration of excitations coming from different analyzers. The overwhelming majority of neurons in these zones are multimodal in nature and respond to complex features of the environment (for example, signs of spatial location, number of elements), to which neurons of the primary and secondary zones do not respond.

The activity of the tertiary zones of the posterior cortex is necessary not only for the successful synthesis of visual information, but also to move from the level of direct visual synthesis to the level of symbolic processes, for operating with the meanings of words, complex grammatical and logical structures, number systems and abstract relationships. Those. the tertiary zones of the posterior parts of the cortex are apparatuses whose participation is necessary for the transformation of visual perception into abstract thinking, always mediated by internal schemes, and for storing organized experience in memory.

Laws of construction of the cortex, which is part of the 2nd and 3rd blocks of the brain. First Law – the law of the hierarchical structure of cortical zones. The hierarchy between the primary, secondary and tertiary zones of the cortex does not remain the same during ontogenesis: in a small child, for the successful formation of secondary zones, the preservation of the primary zones is necessary, and for the formation of tertiary zones, sufficient formation of the secondary zones of the cortex is necessary. Therefore, disruption of the lower cortical zones of the corresponding types at an early age inevitably leads to underdevelopment of the higher cortical zones; thus, as it was formulated by L.S. Vyg O tsky, The main line of interaction between cortical zones in childhood is directed “from bottom to top.”

On the contrary, in an adult with fully developed psychological functions, the leading place passes to the higher zones of the cortex. Perceiving the world around him, an adult organizes his impressions into logical systems: the highest, tertiary, zones of the cortex control the work of the secondary zones subordinate to them, and if the latter are damaged, they have a compensating effect on their work. This nature of the relationships between hierarchically constructed cortical zones in adulthood allowed L.S. Vyg O Tsky to conclude that at the late stage of ontogenesis, cortical zones interact “from top to bottom.”

Second law: law of decreasing specificity of hierarchically constructed cortical zones. The primary zones of the cortex of each of the parts that make up the 2nd block have maximum modal specificity. The secondary zones of the cortex, where layers II and III predominate, have modal specificity to a much lesser extent. Being closely connected with the cortical sections of the corresponding analyzers, these zones are characterized by modality-specific gnostic functions. Here, in some cases visual (secondary occipital zones) is integrated, in others – auditory (secondary temporal zones), in still others – tactile information (secondary parietal zones). To an even lesser extent, modal specificity characterizes the tertiary zones of the 2nd block: the function of the tertiary zones acquires supramodal character.

Secondary and tertiary cortical zones, in which multimodal and associative neurons predominate and which do not have a direct connection with the periphery, despite decreasing specificity, and perhaps precisely because of such decreasing specificity, acquire the ability to play organizing, integrating role in the work of more specific zones, become responsible for the organization of functional systems necessary for the implementation of complex cognitive processes. Afferent impulses arrive to the secondary fields not from the relay (switching) nuclei of the thalamus, but from the associative ones, i.e. secondary fields receive more complex processed information from the periphery than primary fields.

Third law: law of progressive lateralization of functions , i.e. connections of functions with a specific hemisphere of the brain as they move from the primary zones of the cortex to the secondary and then tertiary zones.

The primary zones of both hemispheres of the brain are equivalent. The situation is different when moving to the secondary and then tertiary zones. With the emergence right-handedness(its appearance is associated with labor and refers to the very early stages of human history), and then related speeches, a certain lateralization of functions arises, which is absent in animals, but which in humans becomes an important principle of the functional organization of the brain.

Left hemisphere in right-handed people becomes dominant; it begins to perform speech functions, while right the hemisphere not associated with the activity of the right hand and speech remains subdominant.

The dominant hemisphere plays a significant role not only in the brain organization of the speech processes themselves, but also in the brain organization of all higher forms of mental activity associated with speech - categorical perception, active speech memory, logical thinking, etc., while the subdominant hemisphere to a lesser extent participates in their course. In an adult, the functions of the secondary and tertiary zones of the dominant hemisphere begin to fundamentally differ from the functions of the secondary and tertiary zones of the subdominant hemisphere.

CONCLUSION: The 2nd block of the brain is located in the posterior sections of the hemispheres and includes the visual (occipital), auditory (temporal) and general sensitive (parietal) sections of the CGM and the corresponding subcortical structures. The devices of the 2nd block have a hierarchical structure, breaking up into primary (projection) zones, which receive information and split it into the smallest component parts, secondary (projection-associative) zones, which provide coding (synthesis) of these components and turn the somatotopic projection into functional organization, and tertiary zones (overlap zones), ensuring the joint work of various analyzers and the development of supramodal (symbolic) schemes that underlie complex forms of cognitive activity.

The indicated hierarchically constructed zones of the cortex of the 2nd block operate according to the laws of decreasing modal specificity and increasing functional lateralization. Both of these laws provide the possibility of the most complex forms of brain work that underlie the highest types of human cognitive activity, genetically associated with labor, and structurally with the participation of speech in the organization of mental processes.

7. What is the block of programming, regulation and control of complex forms of activity? Reception, processing and storage of external information constitute only one side of a person’s mental life. Its other side is the organization of active conscious mental activity. The third block of the brain is connected with this task - the block of programming, regulation and control of complex forms of activity.

A person does not passively react to incoming signals. He forms plans and programs of his actions, monitors their implementation and regulates his behavior, bringing it into conformity with these plans and programs; He controls his conscious activity, comparing the effect of his actions with his original intentions and correcting the mistakes he made. All these processes of active conscious activity require different brain apparatuses than the apparatuses of the 1st and 2nd blocks. These tasks are served by the devices of the 3rd functional block, which are located in anterior parts of the cerebral hemispheres, anterior to the anterior central gyrus. The “exit gate” of this block is motor cortex, the V layer of which contains Betz cells, the fibers from which go to the motor nuclei of the SC, and from there to the muscles, making up pyramid path. Anterior central gyrus(occupies the posterior part of the precentral area, Brodmann area 4) is the primary projection zone, the executive apparatus of the cerebral cortex. The primary motor cortex cannot operate in isolation; all human movements to one degree or another require tonic plastic background, which is provided by the basal ganglia and their fibers ( extrapyramidal pathway).

The motor composition of those impulses that the primary motor cortex sends to the periphery must be well prepared and included in certain programs. Without such preparation, impulses cannot provide appropriate movements. Of decisive importance in the preparation of motor impulses are the secondary and tertiary zones built above it, which obey the same principles of hierarchical structure and decreasing specificity. The main difference here is the fact that if in the second, afferent, block of the brain, processes proceed from primary to secondary and tertiary zones, then in the third, efferent, block, processes proceed in a descending direction, starting in the highest - tertiary and secondary zones, where motor plans and programs are formed, then moving on to the apparatus of the primary motor zone, which sends prepared motor impulses to the periphery.

Another difference between the 3rd block and the 2nd is that the 3rd block does not contain modality-specific zones, which are separate analyzers, but consists of efferent, motor-type devices that are under the constant influence of the devices of the afferent block.

The role of the main secondary zone of the 3rd block is played by premotor areas of the frontal region (occupy the vast majority of the precentral region, 6 and 8 Brodmann areas). Irritation of these parts of the cortex does not cause contractions of individual muscles, but entire complexes of movements that are systemically organized in nature (turns of the eyes, head and whole body and grasping movements of the hand), which indicates the integrative role of these cortical zones in the organization of movements.

The most essential part of the 3rd block of the brain is prefrontal regions of the brain(10 Brodmann field) , which, due to the absence of Betz cells in their composition and the presence of a large number of small cells (granules) in layers II and III, are sometimes called granular frontal cortex. These parts of the brain belong to the tertiary zones of the cortex, which perform associative functions and also play a decisive role in the formation of intentions and programs, in the regulation and control of the most complex forms of human behavior.

The prefrontal region of the brain has a rich system of connections with the underlying parts of the brain, the reticular formation and almost all parts of the cortex. Due to the bilateral nature of these connections, the prefrontal cortex is in a particularly advantageous position both for the secondary processing of complex afferentations coming from all parts of the brain, and for the organization of efferent impulses that make it possible to exert regulatory influences on all these structures.

The frontal lobes receive impulses from the systems of the 1st block, “charging” from it, at the same time they have an intense impact on the formations of the reticular formation, giving its activating impulses a differentiated character and bringing them into line with those dynamic patterns of behavior that are formed directly in frontal cortex.

Unlike the tertiary zones of the posterior parts of the brain the tertiary sections of the frontal lobes are actually built on top of all sections of the cerebral cortex(thanks to his extensive connections), thus fulfilling a much more universal function of general regulation of behavior than that which the posterior associative center has.

Destruction of the prefrontal cortex leads to a profound disruption of complex behavioral programs and to a pronounced disinhibition of immediate reactions to secondary stimuli (hyperreactivity), as a result of which the implementation of complex behavioral programs becomes impossible. The behavior of an animal after extirpation of the frontal lobes of the brain changes profoundly. In such an animal, no disturbances in the functioning of individual sense organs can be noted, but meaningful, purposeful behavior is deeply affected. This manifests itself not only in relation to current signals, but also in the formation of active behavior aimed at the future. Also, an animal without the frontal lobes is unable to detect and correct mistakes, as a result of which its behavior loses its organized, meaningful character.

CONCLUSION: The 3rd functional block includes the convexital frontal cortex with all its cortical and subcortical connections. The pyramidal tract originates in the anterior central gyrus. The anatomical structure of the 3rd block of the brain determines its leading role in programming and monitoring the course of mental functions, in the formation of plans and goals of mental activity, in the regulation and control of the results of individual actions, activities and behavior in general.

8. What is the interaction between the three main functional blocks of the brain? According to modern psychological concepts, each mental activity has a strictly defined structure: it begins with the phase of motives, intentions, plans, which then turn into a specific program of activity, including an “image of the result” and an idea of ​​​​how to implement the program, after which it continues in the form of the implementation phase programs using certain operations. Mental activity ends with the phase of comparing the results obtained with the original “image of the result.” If these data do not correspond, mental activity continues until the desired result is obtained. This pattern (or psychological structure) of mental activity can be related to the brain in the following way.

IN the primary stage of formation of motives (intentions) in any conscious mental activity (gnostic, mnestic, intellectual), predominantly the first block of the brain takes part. It also provides an optimal general level of brain activity and selective, selective forms of activity necessary for the implementation of specific types of mental activity. The first block of the brain is primarily responsible for the emotional “reinforcement” of mental activity (the experience of “success-failure”).

Stage of formation of goals and programs (programming mnestic activity) is associated primarily with the work of the 3rd block of the brain in the same way as stage of monitoring the implementation of the program.

Operational stage (stage of using various mnestic techniques) activity is carried out primarily with the help of the second block of the brain.

The defeat of any of the blocks affects any mental activity, as it leads to disruption of the corresponding stage (phase, stage) of its implementation.

Modern ideas about the structure of mental processes are based on the model of a reflex ring or a complex self-regulating system, each link of which includes both afferent and efferent components and which, in general, has the character of complex and active mental activity. Eg. object perception is not only multireceptor in nature, relying on the joint work of a whole group of analyzers, but always includes active motor components. The decisive role of eye movements in visual perception was noted by I.M. Sechenov. A fixed eye can hardly perceive an image consisting of many components; complex object perception presupposes active, exploratory eye movements that highlight the necessary signs, and only gradually, as it develops, takes on a collapsed character.

Conclusion: perception is carried out with the joint participation of all functional blocks of the brain, of which the first provides the necessary tone of the cortex, the second carries out the analysis and synthesis of incoming information, and the third provides directed search movements, thereby creating the active nature of perceptual activity. Such a complex structure of perception explains why its disturbances can occur when various brain apparatuses located far from each other are damaged.

Another example is about the construction of voluntary movement and action. The participation of efferent mechanisms in the construction of movement is obvious, but movement cannot be controlled by efferent impulses alone and that its organized flow requires constant afferent processes that signal the state of the joints and muscles, the position of the segments of the moving apparatus and the spatial coordinates in which the movement occurs. That. voluntary movement, and especially objective action, is based on the joint work of the most diverse parts of the brain, and if the devices of the 1st block provide the necessary muscle tone, without which no coordinated movement is possible, then the devices of the 2nd block make it possible to carry out those afferent syntheses, in the system of which movement occurs, and the devices of the 3rd block ensure the subordination of movement and action to the corresponding intentions, create programs for performing motor acts and provide that regulation and control of the flow of movements, thanks to which its organized, meaningful nature is preserved.

Based on numerous studies, the functional significance of various areas of the cerebral cortex has been established with certain accuracy.

Areas of the cerebral cortex that have characteristic cytoarchitectonics and nerve connections involved in performing certain functions are nerve centers. Damage to such areas of the cortex manifests itself in the loss of their inherent functions. The nerve centers of the cerebral cortex can be divided into projection and associative.

Projection centers are areas of the cerebral cortex, representing the cortical part of the analyzer, which have a direct morphofunctional connection through afferent or efferent pathways with neurons of the subcortical centers. They carry out the primary processing of incoming conscious afferent information and the implementation of conscious efferent information (voluntary motor acts).

Associative centers are areas of the cerebral cortex that do not have a direct connection with subcortical formations, but are connected by a temporary two-way connection with projection centers. Associative centers play a primary role in the implementation of higher nervous activity (deep processing of conscious afferent information, mental activity, memory, etc.).

At present, the dynamic localization of some functions of the cerebral cortex has been clarified quite accurately.

Areas of the cerebral cortex that are not projection or associative centers are involved in inter-analyzer integrative brain activity.

Projection nerve centers The cerebral cortex develops both in humans and in higher vertebrates. They begin to function immediately after birth. The formation of these centers is completed much earlier than associative ones. In practical terms, the following projection centers are important.

1. Projection center of general sensitivity (tactile, pain, temperature and conscious proprioceptive) is also called a skin analyzer of general sensitivity. It is localized in the cortex of the postcentral gyrus (fields 1, 2, 3). It ends with the fibers that run as part of the thalamo-cortical pathway. Each area of ​​the opposite half of the body has a distinct projection at the cortical end of the skin analyzer (somatotopic projection). In the upper part of the postcentral gyrus the lower limb and torso are projected, in the middle - the upper limb and in the lower - the head (Penfield's sensory homunculus). The size of the projection zones of the somatosensory cortex is directly proportional to the number of receptors located in the skin. This explains the presence of the largest somatosensory zones, corresponding to the face and hand (Fig. 3.25). Damage to the postcentral gyrus causes loss of tactile, pain, temperature sensitivity and muscle-articular sensation on the opposite half of the body.

Rice. 3.25.

• 1 – genitals; 2 – foot; 3 – thigh; 4 – torso; 5 – brush; 6 – index and thumb; 7 – face; 8 – teeth; 9 – tongue; 10 – pharynx and internal organs
• 2. Projection center of motor functions (kinesthetic center), or motor analyzer, is located in the motor area of ​​the cortex, including the precentral gyrus and the pericentral lobule (fields 4, 6). In the 3rd–4th layers of the cortex of the motor analyzer, the fibers running as part of the thalamo-cortical pathway end.

Here the analysis of proprioceptive (kinesthetic) stimuli is carried out. In the fifth layer of the cortex there is the nucleus of the motor analyzer, from the neurocytes of which the corticospinal and corticonuclear tracts originate. The precentral gyrus also has a clear somatotopic localization of motor functions. Muscles that perform complex and finely differentiated movements have a large projection area in the cortex of the precentral gyrus. The largest area is occupied by the projection of the muscles of the tongue, face and hand, the smallest area is occupied by the projection of the muscles of the trunk and lower extremities. The somatotopic projection to the precentral gyrus is called the “Penfield motor homunculus.” The human body is projected on the gyrus “upside down”, and the projection is carried out on the cortex of the opposite hemisphere (Fig. 3.26).

Afferent fibers ending in the sensitive layers of the cortex of the kinesthetic center initially pass as part of the Gaulle, Burdach and nuclear-thalamic tracts, conducting impulses of conscious proprioceptive sensitivity. Damage to the precentral gyrus leads to impaired perception of stimuli from skeletal muscles, ligaments, joints and periosteum. The corticospinal and corticonuclear tracts conduct impulses that provide conscious movements and have an inhibitory effect on the segmental apparatus of the brain stem and spinal cord. The cortical center of the motor analyzer, through a system of associative fibers, has numerous connections with various cortical sensory centers (the center of general sensitivity, the center of vision, hearing, vestibular functions, etc.). These connections are necessary to perform integrative functions when performing voluntary movements.

3. Projection center of the body diagram located in the region of the intraparietal sulcus (area 40s). It presents somatotopic projections of all parts of the body. The center of the body circuit receives impulses primarily from conscious proprioceptive sensitivity. The main functional purpose of this projection center is to determine the position of the body and its individual parts in space and assess muscle tone. When the superior parietal lobule is damaged, there is a violation of such functions as recognition of parts of one’s own body, sensation of extra limbs, and disturbances in determining the position of individual parts of the body in space.

Rice. 3.26.

• 1 – foot; 2 – shin; 3 – knee; 4 – thigh; 5 – torso; 6 – brush; 7 – thumb; 8 – neck; 9 – face; 10 – lips; 11 – tongue; 12 – larynx
• 4. projection hearing center, or the nucleus of the auditory analyzer, is located in the middle third of the superior temporal gyrus (field 22). In this center, the fibers of the auditory pathway end, originating from the neurons of the medial geniculate body (subcortical hearing center) of their own and, mainly, the opposite side. Ultimately, the fibers of the auditory tract pass through the auditory radiation.

When the projection center of hearing is damaged on one side, there is a decrease in hearing in both ears, and on the opposite side of the lesion, hearing decreases to a greater extent. Complete deafness is observed only with bilateral damage to the projection centers of hearing.

5. Projection center of vision, or the nucleus of the visual analyzer, is localized on the medial surface of the occipital lobe, along the edges of the calcarine groove (field 17). It ends with the fibers of the optic pathway on its own and opposite sides, originating from the neurons of the lateral geniculate body (subcortical center of vision). There is a certain somatotopic projection of various parts of the retina onto the calcarine sulcus.

Unilateral damage to the projection center of vision is accompanied by partial blindness in both eyes, but in different parts of the retina. Complete blindness occurs only with bilateral lesions.

• 6. Projection center of smell, or the nucleus of the olfactory analyzer, is located on the medial surface of the temporal lobe in the cortex of the parahippocampal gyrus and in the hook. Here the fibers of the olfactory pathway end on their own and opposite sides, originating from the neurons of the olfactory triangle. With unilateral damage to the projection center of smell, a decrease in the sense of smell and olfactory hallucinations are noted.
• 7. Projection center of taste, or the core of the taste analyzer, is located in the same place as the projection center of smell, i.e. in the limbic region of the brain (uncus and parahippocampal gyrus). In the projection center of taste, the fibers of the taste pathway of its own and the opposite side, originating from the neurons of the basal ganglia of the thalamus, end. When the limbic region is damaged, disorders of taste and smell are observed, and corresponding hallucinations often appear.
• 8. Projection center of sensitivity from internal organs, or visceroception analyzer, located in the lower third of the postcentral and precentral gyri (field 43). The cortical part of the visceroception analyzer receives afferent impulses from smooth muscles and mucous membranes of internal organs. In the cortex of this area, fibers of the interoceptive pathway end, originating from neurons of the ventrolateral nuclei of the thalamus, into which information enters along the nuclear-thalamic tract. In the projection center of visceroception, mainly pain sensations from internal organs and afferent impulses from smooth muscles are analyzed.
• 9. Projection center of vestibular functions, undoubtedly has its representation in the cerebral cortex, but information about its localization is ambiguous. It is generally accepted that the projection center of vestibular functions is located in the region of the middle and inferior temporal gyri (fields 20, 21). The adjacent sections of the parietal and frontal lobes also have a certain relationship to the vestibular analyzer. In the cortex of the projection center of the vestibular functions, fibers originating from the neurons of the median nuclei of the thalamus end. Lesions of these cortical centers are manifested by spontaneous dizziness, a feeling of instability, a feeling of falling through, a sensation of movement of surrounding objects and deformation of their contours.

Concluding the consideration of projection centers, it should be noted that the cortical analyzers of general sensitivity receive afferent information from the opposite side of the body, therefore, damage to the centers is accompanied by disorders of certain types of sensitivity only on the opposite side of the body. Cortical analyzers of special types of sensitivity (auditory, visual, olfactory, gustatory, vestibular) are connected to the receptors of the corresponding organs of their own and opposite sides, therefore, complete loss of the functions of these analyzers is observed only when the corresponding zones of the cerebral hemisphere cortex are damaged on both sides.

Associative nerve centers. These centers are formed later than the projection centers, and the timing of corticalization, i.e. maturation of the cerebral cortex is not the same in these centers. Associative centers are responsible for thought processes, memory and the implementation of verbal function.

• 1. Association center for "stereognosy" ", or the nucleus of the skin analyzer (the center for recognizing objects by touch). This center is located in the superior parietal lobule (field 7). It is bilateral: in the right hemisphere - for the left hand, in the left - for the right hand. The center of "stereognosia" is associated with the projection the center of general sensitivity (postcentral gyrus), from which nerve fibers conduct impulses of pain, temperature, tactile and proprioceptive sensitivity. Incoming impulses in the associative cortical center are analyzed and synthesized, resulting in the recognition of previously encountered objects. Throughout life, the center of “stereognosy” constantly develops and improves. When the superior parietal lobule is damaged, patients lose the ability to create a general holistic idea of ​​an object with their eyes closed, i.e. they cannot recognize this object by touch. Individual properties of objects, such as shape, volume, temperature, density, mass , are defined correctly.
• 2. Association center of "praxia", or an analyzer of purposeful habitual movements. This center is located in the inferior parietal lobule in the cortex of the supramarginal gyrus (area 40), in right-handers - in the left hemisphere of the cerebrum, in left-handers - in the right. In some people, the center of “praxia” is formed in both hemispheres; such people have equal control of the right and left hands and are called ambidextrous.

The center of “praxia” develops as a result of repeated repetition of complex purposeful actions. As a result of the consolidation of temporary connections, habitual skills are formed, for example, working on a typewriter, playing the piano, performing surgical procedures, etc. As life experience accumulates, the center of praxia is constantly improved. The cortex in the region of the supramarginal gyrus has connections with the posterior and anterior central gyri.

After synthetic and analytical activity is carried out, information from the “praxia” center enters the precentral gyrus to the pyramidal neurons, from where it reaches the motor nuclei of the anterior horns of the spinal cord along the corticospinal tract.

3. Association Vision Center, or visual memory analyzer, is located on the superolateral surface of the occipital lobe (fields 18–19), in the left hemisphere for right-handers, in the right hemisphere for left-handers. It provides memorization of objects by their shape, appearance, color. It is believed that neurons in field 18 provide visual memory, and neurons in field 19 provide orientation in an unfamiliar environment. Fields 18 and 19 have numerous associative connections with other cortical centers, due to which integrative visual perception occurs.

When the visual memory center is damaged, visual agnosia develops. Partial agnosia is more often observed (cannot recognize friends, your home, or yourself in the mirror). When field 19 is damaged, a distorted perception of objects is noted; the patient does not recognize familiar objects, but he sees them and avoids obstacles.

The human nervous system has specific centers. These are the centers of the second signaling system, providing the ability to communicate between people through articulate human speech. Human speech can be produced in the form of the production of articulate sounds ("articulation") and the representation of written characters ("graphics"). Accordingly, associative speech centers are formed in the cerebral cortex - the acoustic and optical speech centers, the articulation center and the graphic speech center. The named associative speech centers are formed near the corresponding projection centers. They develop in a certain sequence, starting from the first months after birth, and can improve until old age. Let's consider associative speech centers in the order of their formation in the brain.

4. Associated Hearing Center, or the acoustic speech center (Wernicke's center), located in the cortex of the posterior third of the superior temporal gyrus. Nerve fibers originating from the neurons of the projection center of hearing (the middle third of the superior temporal gyrus) end here. The associative hearing center begins to form in the second or third month after birth. As the center develops, the child begins to distinguish articulate speech among the surrounding sounds, first individual words, and then phrases and complex sentences.

When Wernicke's center is damaged, patients develop sensory aphasia. It manifests itself in the form of a loss of the ability to understand one’s own and others’ speech, although the patient hears well, reacts to sounds, and it seems to him that those around him are speaking in a language unfamiliar to him. The lack of auditory control over one’s own speech leads to a disruption in the construction of sentences; speech becomes incomprehensible, full of meaningless words and sounds. When Wernicke's center is damaged, since it is directly related to speech formation, not only the understanding of words suffers, but also their pronunciation.

5. Associative motor speech center (speech motor), or speech articulation center (Broca's center), is located in the cortex of the posterior third of the inferior frontal gyrus (area 44) in close proximity to the projection center of motor functions (precentral gyrus). The speech motor center begins to form in the third month after birth. It is one-sided - in right-handed people it develops in the left hemisphere, in left-handed people - in the right. Information from the speech motor center enters the precentral gyrus and further along the cortical-nuclear pathway - to the muscles of the tongue, larynx, pharynx, and muscles of the head and neck.

When the speech motor center is damaged, motor aphasia (loss of speech) occurs. With partial damage, speech can be slow, difficult, chanted, incoherent, and often characterized only by individual sounds. Patients understand the speech of those around them.

6. Associative optical speech center, or visual analyzer of written speech (lexia center, or Dejerine center), is located in the angular gyrus (field 39). The neurons of the optical speech center receive visual impulses from the neurons of the projection center of vision (field 17). In the center of "lexia" there is an analysis of visual information about letters, numbers, signs, the letter composition of words and understanding their meaning. The center is formed from the age of three, when the child begins to recognize letters, numbers and evaluate their sound meaning.

When the “lexia” center is damaged, alexia (reading disorder) occurs. The patient sees the letters, but does not understand their meaning and, therefore, cannot read the text.

7. Association Center for Written Signs, or motor analyzer of written signs (center of the carafe), located in the posterior part of the middle frontal gyrus (field 8) next to the precentral gyrus. The "carafe" center begins to form in the fifth or sixth year of life. This center receives information from the “praxia” center, intended to provide subtle, precise hand movements necessary for writing letters, numbers, and drawing. From the neurons of the carafe center, axons are sent to the middle part of the precentral gyrus. After the switch, information is sent along the corticospinal tract to the muscles of the upper limb. When the “decanter” center is damaged, the ability to write individual letters is lost, and “agraphia” occurs.

Thus, speech centers have a unilateral localization in the cerebral cortex. For right-handers they are located in the left hemisphere, for left-handers - in the right. It should be noted that associative speech centers develop throughout life.

8. Association center for combined head and eye rotation (cortical center of gaze) is located in the middle frontal gyrus (field 9) anterior to the motor analyzer of written signs (center of the carafe). It regulates the combined rotation of the head and eyes in the opposite direction due to impulses arriving at the projection center of motor functions (precentral gyrus) from the proprioceptors of the muscles of the eyeballs. In addition, this center receives impulses from the projection center of vision (cortex in the area of ​​the calcarine sulcus - field 17), originating from the neurons of the retina.