basal nuclei, called ganglia by histologists of the last century, are nuclear-type structures that are located in the thickness of the white matter of the forebrain closer to its base. In mammals, the basal nuclei include a strongly elongated and curved caudate nucleus and embedded in the thickness of the white matter lenticular nucleus. With two white plates, it is divided into three parts: the largest, lying laterally shell, And pale ball, consisting of internal and external departments (Fig. 3.29).

These anatomical formations form the so-called striopallidary system(From Latin striatus - striped and pallidus - pale.) , which, according to phylogenetic and functional criteria, is divided into the ancient part of the paleostriatum and the new part - the neostriatum. paleostriatum represented by a pale ball, and neostriatum, appearing for the first time in reptiles, consists of a caudate nucleus and a shell, which are combined under the name striatum, or striatum. The caudate nucleus and putamen are anatomically related and are characterized by an alternation of white and gray matter, which justifies the origin of the term striped body.

The striopallidary system is also often referred to as subthalamic nucleus(Lewis solid) and black matter midbrain, which form a functional unity with the basal nuclei. The striatum consists mainly of small cells, the axons of which are directed to the globus pallidus and the substantia nigra of the midbrain.

The striatum is a kind of collector of afferent inputs going to the basal ganglia. The main sources of these inputs are the neocortex (primarily sensorimotor), nonspecific thalamic nuclei, and dopaminergic pathways from the substantia nigra.

As opposed to striatum pale ball consists of large neurons and is the concentration of the output, efferent pathways of the striopallidar system. The axons of neurons localized in the globus pallidum approach various nuclei of the diencephalon and midbrain, including the red nucleus, where the red nuclear-spinal path of the extrapyramidal system of motor regulation begins.

Another important efferent pathway runs from the inner globus pallidus to the anteroventral and ventrolateral nuclei of the thalamus, and from there continues to the motor cortex. The presence of this path causes a multi-link loop-like connection between the sensorimotor and motor areas of the cortex, which is carried out through the striatum and globus pallidus to the thalamus. It is noteworthy that, as part of this striopallidothalamocortical pathway, the basal nuclei act as an afferent link in relation to the motor areas of the cerebral cortex. Numerous connections of the striopallidary system with various parts of the brain testify to its participation in the processes of integration, however, so far, much remains unclear in the knowledge of the functions of the basal ganglia.

The basal ganglia play an important role in regulation of movements And sensorimotor coordination. It is known that with damage to the striatum, there is athetosis - slow worm-like movements of the hands and fingers.

Degeneration of the cells of this structure also causes another disease - chorea expressed in convulsive twitching of facial muscles and muscles of the limbs, which are observed at rest and during voluntary movements. However, attempts to elucidate the etiology of these phenomena in animal experiments have not yielded results. Destruction of the caudate nucleus in dogs and cats did not result in hyperkinesis, characteristic of the diseases described above.

Local electrical stimulation of some parts of the striatum in animals causes the so-called circulatory motor responses characterized by a turn of the head and torso in the direction opposite to irritation. Stimulation of other parts of the striatum, on the contrary, leads to inhibition of motor reactions caused by various sensory stimuli.

The presence of certain discrepancies between the experimental and clinical data, apparently, indicates the occurrence of systemic disorders in the mechanisms of movement regulation during pathological processes in the basal ganglia. Obviously, these disorders are associated with changes in the function of not only the striatum, but also other structures.

As an example, we can consider a possible pathophysiological mechanism for the occurrence of parkinsonism. This syndrome is associated with damage to the basal ganglia and is characterized by a complex of symptoms such as hypokinesia - low mobility and difficulty in the transition from rest to movement; waxy rigidity, or hypertonicity, independent of the position of the joints and the phase of movement; static tremor(trembling), most pronounced in the distal extremities.

All these symptoms are due to hyperactivity of the basal ganglia, which occurs when the dopaminergic (probably inhibitory) pathway that goes from the substantia nigra to the striatum is damaged. Thus, the etiology of parkinsonism is due to dysfunction of the striatum and structures of the midbrain, which are functionally combined into the striopallidar system.

To clarify the role of the basal ganglia in the implementation of movements, the data of microelectrode studies are successfully used. Experiments on monkeys have shown a correlation between striatal firing and slow, side-to-side, worm-like paw movements. As a rule, the discharge of a neuron precedes the onset of slow movement, and it is absent during fast "ballistic" movements. These facts allow us to conclude that striatal neurons are involved in the generation of slow movements that are corrected by sensory feedback. The basal ganglia represent one of the levels of the movement regulation system built according to the hierarchical principle.

Receiving information from the associative zones of the cortex, the basal ganglia participate in the creation of a program of purposeful movements, taking into account the dominant motivation. Further, the corresponding information from the basal nuclei enters the anterior thalamus, where it is integrated with information coming from the cerebellum. From the thalamic nuclei, the impulse reaches the motor cortex, which is responsible for the implementation of the targeted movement program through the underlying stem and spinal motor centers. So, in general terms, one can imagine the place of the basal nuclei in the integral system of the motor centers of the brain.

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Lenticular nucleus(nucl.

Basal nuclei and their functions

lentiformis) is located laterally and anteriorly from the thalamus. It is wedge-shaped with the apex facing the midline. Between the posterior face of the lenticular nucleus and the thalamus is located posterior limb of the internal capsule(crus posterius capsulae internae). The anterior face of the lenticular nucleus below and in front is fused with the head of the caudate nucleus.

Two strips of white matter divide the lenticular nucleus into three segments: lateral segment - shell(putamen), which has a dark color, is located on the outside, and the two ancient parts pale ball(globus pallidus) conical shape facing the middle.

Caudate nucleus

Caudate nucleus(nucl. caudatus) is club-shaped and curved back.

Its anterior part is expanded, called the head (caput) and is located above the lenticular nucleus, and its posterior part - the tail (cauda) runs above and lateral to the thalamus, separated from it by the brain strips (stria medullaris). The head of the caudate nucleus is involved in the formation of the lateral wall of the anterior horn of the lateral ventricle (cornu anterius ventriculi lateralis). The caudate nucleus consists of small and large pyramidal cells. Between the lenticular and caudate nuclei is the internal capsule (capsula interna).

Internal capsule(capsula interna) is located between the thalamus, lenticular and caudate nuclei and is a layer of white matter formed by projection fibers on the way to the cortex and from the cortex to the underlying parts of the central nervous system.

On a horizontal section of the cerebral hemisphere at the level of the middle of the thalamus, the inner capsule has a white color and resembles the shape of an angle open outwards. The internal capsule is divided into three sections: front leg(crus anterius capsulae internae), knee(genu capsulae internae) and back leg(crus posterius capsulae internae).

Above the inner capsule, the fibers form radiant crown(corona radiata). The short anterior leg of the capsule is formed by axons that originate from the cells of the cortex of the frontal lobe and go to the thalamus (tr.

frontothalamicus), into the red nucleus (tr. frontorubralis), to the cells of the nuclei of the bridge (tr. frontopontinus). In the knee of the internal capsule there is a cortical-nuclear pathway (tr. corticonuclearis), connecting the cells of the motor cortex with the nuclei of the motor cranial nerves (III, IV, V, VII, IX, X, XI, XII). The posterior leg of the internal capsule is somewhat longer than the anterior one, bordering on the thalamus and lenticular nucleus. In its anterior part there are fibers emanating from the cells of the posterior sections of the frontal (motor) cortex and heading to the nuclei of the anterior columns of the spinal cord.

Somewhat posterior to the cortico-spinal tract are fibers that run from the lateral nuclei of the thalamus to the posterior central gyrus, as well as from the cells of the cortex to the nuclei of the thalamus. In the posterior leg are fibers that pass from the cortex of the occipital and temporal lobes to the nuclei of the bridge. In the posterior section, auditory and optic fibers pass, starting from the internal and external geniculate bodies and ending in the temporal and occipital lobes.

Throughout the internal capsule are transverse fibers that connect the lenticular body with the caudate nucleus and thalamus. The fan-shaped diverging fibers of all pathways that form the inner capsule form a radiant crown in the space between it and the cerebral cortex. Minor damage to small areas of the internal capsule due to the compact arrangement of the fibers causes severe disorders of motor functions and loss of general sensitivity, hearing and vision on the side opposite to the injury.

striatum

striatum receives afferent impulses mainly from the thalamus, partly from the cortex; sends efferent impulses to the pale ball.

The striatum is considered as an effector nucleus that does not have independent motor functions, but controls the functions of a phylogenetically older motor center - pallidum a (pale ball).

The striatum regulates and partially inhibits the unconditioned reflex activity of the globus pallidus, i.e.

e. acts on it in the same way as a pale ball acts on a red nucleus. The striatum is considered the highest subcortical regulatory and coordination center of the motor apparatus.

In the striatum, according to experimental data, there are also higher vegetative coordination centers that regulate metabolism, heat generation and heat removal, and vascular reactions.

Apparently, in the striatum there are centers that integrate, combine unconditioned reflex motor and vegetative reactions into a single holistic act of behavior.

The striatum influences the organs innervated by the autonomic nervous system through its connections with the hypothalamus. With lesions of the striatum, a person has athetosis - stereotypical movements of the limbs, as well as chorea - strong irregular movements that occur without any order and sequence and capture almost all the muscles (“St. Witt's dance”).

Both athetosis and chorea are considered as the result of the loss of the inhibitory effect that the striatum has on the pale nucleus.

pale ball

pale ball(globus pallidus), pale nucleus, is a paired formation that is part of the lenticular nucleus, which is located in the cerebral hemispheres and is separated by an internal capsule. The pallidum is the motor nucleus. With its irritation, you can get a contraction of the cervical muscles, limbs and the entire body, mainly on the opposite side.

The pale nucleus receives impulses along afferent fibers coming from the thalamus and closing the thalamo-pallidar reflex arc. The pale nucleus, being effectorally connected with the centers of the middle and hindbrain, regulates and coordinates their work.

One of the functions of the pale nucleus is considered to be the inhibition of the underlying nuclei, mainly the red nucleus of the midbrain, and therefore, when the globus pallidus is damaged, there is a strong increase in the tone of the skeletal muscles - hypertonicity, i.e. hypertonicity.

to. the red core is released from the inhibitory influence of the pale ball. The thalamo-hypothalamic-pallidar system takes part in higher animals and humans in the implementation of complex unconditioned reflexes - defensive, orienting, food, sexual.

In humans, when the globus pallidum is stimulated, the phenomenon of increasing the volume of short-term memory by almost two times has been obtained.

Investigating the spatio-temporal relationships between the elements of speech (vowel phonemes) and the recorded impulse activity, a correlation was revealed, indicating the involvement of one or another structure in the process of auditory memory. In a number of cases, such ratios were obtained in the study of the pale ball, the dorsomedial thalamic nucleus.

Almond nucleus

Almond nucleus(corpus amygdaloideum), or the amygdaloid complex, is a group of nuclei and is localized inside the anterior pole of the temporal lobe, lateral to the septum of the perforated substance.

Amygdaloid complex is a structure that is part of the limbic system of the brain, which is characterized by a very low threshold of excitation, which can contribute to the development of epileptiform activity.

The complex contains both larger (pyramidal, pear-shaped) and medium-sized (multipolar, bipolar, candelabra-shaped) and small cells.

The amygdaloid complex is divided into a phylogenetically older corticomedial part and a newer basal-lateral part. The group of corticomesial nuclei is characterized by low activity of acetylcholinesterase (AChE) and is more associated with the olfactory function, forming projections into the paleocortex. The connection with sexual function is confirmed by the fact that stimulation of these nuclei facilitates the secretion of luliberin and folliberin.

The neurons of the basal-lateral nuclei are characterized by a higher activity of AChE, project to the neocortex and striatum, and also facilitate the secretion of ACTH and growth hormone. When the amygdaloid complex is stimulated, convulsions, emotionally colored reactions, fear, aggression, etc. occur.

Fence

Fence(claustrum) - a thin layer of gray matter, separated by an outer capsule of white matter from the lenticular nucleus. The fence at the bottom is in contact with the cores of the front perforated substance(substantia perforata anterior).

Assume participation in the implementation of oculomotor reactions of tracking the object.

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Functions of the basal nuclei

rice. 66) . nucleus caudatus), shell ( putamen) and pale ball ( globulus pallidusclaustrum). All four of these nuclei are called the striatum ( corpus striatum).

The striatum is also distinguished (s triatumNucleus lentioris

66. A - Location of the basal ganglia in the volume of the brain. The basal ganglia are shaded red, the thalamus is grey, and the rest of the brain is unshaded. 1 - Pallid globus, 2 - Thalamus, 3 - Putamen, 4 - Caudate nucleus, 5 - Amygdala (Astapova, 2004).

At the basal nuclei .

.

Excitatory pathways

Braking paths from the striatum go to substantia nigra and after switching - to the nuclei of the thalamus (Fig.

Rice. 68. Nerve pathways that secrete various types of neurotransmitters in the basal ganglia. Ah - acetylcholine; GABA - gamma-aminobutyric acid (Guyton, 2008)

In general, the basal nuclei, having bilateral connections with the cerebral cortex, thalamus, and brainstem nuclei, are involved in the creation of programs of purposeful movements, taking into account the dominant motivation. At the same time, the neurons of the striatum have an inhibitory effect (mediator - GABA) on the neurons of the substantia nigra. In turn, the neurons of the substantia nigra (mediator - dopamine) have a modulating effect (inhibitory and excitatory) on the background activity of striatal neurons.

Functions of the striatum.

Defeat

Functions of the pale ball.

The nuclei of the brain and their functions

Pale Orb Destruction adynamia hinders the implementation available conditioned reflexes and worsens development of new

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Functions of the basal nuclei

The basal nuclei are the massive subcortical nuclei of the telencephalon. They are located deep in the white matter of the hemispheres. These include

• caudate nucleus (consists of the head, body and tail),

Lenticular nucleus (consists of a shell and a pale ball - globus pallidus - a paired formation),

a fence,

amygdala.

These nuclei are separated from each other by layers of white matter, forming the inner, outer and outermost capsules.

The caudate and lenticular nuclei together make up the anatomical formation - the striatum (corpus striatum).

Caudate nucleus and putamen

The caudate nucleus and the putamen have a similar histological structure.

Their neurons belong to type II Golgi cells, that is, they have short dendrites, a thin axon; their size is up to 20 microns. There are 20 times more of these neurons than type I Golgi neurons, which have an extensive network of dendrites and are about 50 microns in size.

The functions of any formations of the brain are determined primarily by their connections, which are quite numerous in the basal ganglia.

Basal nuclei

These connections have a clear focus and functional outline.

The caudate nucleus and putamen receive descending connections mainly from the extrapyramidal cortex through the subcallosal bundle. Other fields of the cerebral cortex also send large numbers of axons to the caudate nucleus and putamen.

The main part of the axons of the caudate nucleus and the putamen goes to the pale ball, from here to the thalamus and only from it to the sensory fields.

Consequently, there is a vicious circle of connections between these formations. The caudate nucleus and the putamen also have functional connections with structures lying outside this circle: with the substantia nigra, the red nucleus, the Lewis body, the nuclei of the vestibule, the cerebellum, and the γ-cells of the spinal cord.

The abundance and nature of the connections between the caudate nucleus and the putamen testify to their participation in integrative processes, the organization and regulation of movements, and the regulation of the work of vegetative organs.

Irritation of field 8 of the cerebral cortex causes excitation of neurons of the caudate nucleus, and fields 6 - excitation of neurons of the caudate nucleus and putamen.

A single stimulation of the sensorimotor area of ​​the cerebral cortex can cause excitation or inhibition of the activity of neurons in the caudate nucleus. These reactions occur after 10-20 ms, which indicates direct and indirect connections of the cerebral cortex with the caudate nucleus.

The medial nuclei of the thalamus have direct connections with the caudate nucleus, as evidenced by the reaction of its neurons, which occurs 2–4 ms after stimulation of the thalamus.

The reaction of the neurons of the caudate nucleus is caused by skin irritations, light, sound stimuli.

Interactions between the caudate nucleus and the globus pallidus are dominated by inhibitory influences.

If the caudate nucleus is irritated, then most of the neurons of the pale ball are inhibited, and the smaller one is excited. In case of damage to the caudate nucleus, the animal develops motor hyperactivity.

The interaction of black matter and the caudate nucleus is based on direct and feedback connections between them. It has been established that stimulation of the caudate nucleus enhances the activity of neurons in the substantia nigra. Stimulation of the black substance leads to an increase, and destruction - to a decrease in the amount of dopamine in the caudate nucleus.

It has been established that dopamine is synthesized in the cells of the substantia nigra, and then transported to the synapses of neurons of the caudate nucleus at a rate of 0.8 mm/h. In the caudate nucleus in 1 g of nervous tissue, up to 10 μg of dopamine accumulates, which is 6 times more than in other parts of the forebrain, the globus pallidus, 19 times more than in the cerebellum. Thanks to dopamine, the disinhibitory mechanism of interaction between the caudate nucleus and the pale ball manifests itself.

The caudate nucleus and the globus pallidus take part in such integrative processes as conditioned reflex activity, motor activity.

This is revealed by stimulation of the caudate nucleus, shell and pale ball, destruction and by recording electrical activity.

Irritation of the caudate nucleus can completely prevent the perception of pain, visual, auditory and other types of stimulation. Irritation of the ventral region of the caudate nucleus reduces, and dorsal - increases salivation.

When the caudate nucleus is stimulated, the latent periods of reflexes are lengthened, and the alteration of conditioned reflexes is disturbed.

The development of conditioned reflexes against the background of stimulation of the caudate nucleus becomes impossible. Apparently, this is due to the fact that stimulation of the caudate nucleus causes inhibition of the activity of the cerebral cortex.

At the same time, with stimulation of the caudate nucleus, some types of isolated movements may appear.

Apparently, the caudate nucleus has, along with inhibitory and excitatory structures.

From the standpoint of functional anatomy, the caudate and lenticular nuclei are united by the concept striopallidar system. The striatal system includes the caudate nucleus and the shell, and the pallidar system includes the pale ball.

The striatum is considered as the main receptive field of the striopallidar system. This is where fibers from 4 main sources end

hemispheric cortex,

visual thalamus,

black substance

amygdala.

Cortical neurons have an excitatory effect on striatal neurons.

The neurons of the substantia nigra have an inhibitory effect on them.

The axons of the neurons of the striatal system end on the neurons of the pallidum, and have an inhibitory effect on them.

The pallidum is the output structure of the striopallidary system.

The main mass of efferent fibers converges to it.

The neurons of the globus pallidum have an excitatory effect on the motor neurons of the spinal cord.

The striopallidar system is the center of the extrapyramidal system. Its main function is the regulation of voluntary motor reactions. With her participation are created:

optimal posture for the intended action;

Optimal ratio of tone between muscles antagonists and synergists;

smoothness and proportionality of movements in time and space.

With the defeat of the striopallidary system, dyskinesia develops - a violation of motor acts.

Hypokinesia - pallor, inexpressiveness of movements. Strengthening the inhibitory effect of the striatal system on the pallidar system.

Hyperkinesia (chorea) - strong irregular movements, performed without any order and sequence, which capture the entire musculature - "St. Witt's dance". Reason: loss of the inhibitory effect of the striatal system on the pallidar system.

The fence and the amygdala are part of the limbic system.

The basal nuclei provide regulation of motor and autonomic functions, participate in the implementation of integrative processes of higher nervous activity.

Disturbances in the basal ganglia lead to motor dysfunctions, such as slowness of movement, changes in muscle tone, involuntary movements, and tremors.

These disorders are fixed in Parkinson's disease and Huntington's disease.

pale ball

The pale ball (globus pallidus s. pallidum) has predominantly large type I Golgi neurons. Connections of the globus pallidus with the thalamus, putamen, caudate nucleus, midbrain, hypothalamus, somatosensory system, etc. indicate its participation in the organization of simple and complex forms of behavior.

Irritation of the globus pallidus with implanted electrodes causes contraction of the muscles of the extremities, activation or inhibition of γ-motor neurons of the spinal cord.

In patients with hyperkinesis, irritation of different parts of the globus pallidus (depending on the location and frequency of irritation) increased or decreased hyperkinesis.

Stimulation of the globus pallidus, unlike stimulation of the caudate nucleus, does not cause inhibition, but provokes an orienting reaction, limb movements, eating behavior (sniffing, chewing, swallowing, etc.).

Damage to the globus pallidus causes hypomimia, masking of the face, tremor of the head and limbs in people (moreover, this tremor disappears at rest, in sleep and intensifies with movements), monotony of speech.

When the pale ball is damaged, myoclonus is observed - rapid twitching of the muscles of individual groups or individual muscles of the arms, back, face.

In the first hours after injury to the globus pallidus in an acute experiment on animals, motor activity sharply decreased, movements were characterized by discoordination, the presence of incomplete movements was noted, and a drooping posture was noted when sitting.

Having started the movement, the animal could not stop for a long time. In a person with globus pallidus dysfunction, it is difficult to start movements, auxiliary and reactive movements disappear when standing up, friendly hand movements when walking are disturbed, a symptom of propulsion appears: prolonged preparation for movement, then rapid movement and stop. Such cycles in patients are repeated many times.

Fence

The fence (claustrum) contains polymorphic neurons of different types.

It forms connections mainly with the cerebral cortex.

Deep localization and small size of the fence present certain difficulties for its physiological study. This nucleus has the form of a narrow strip of gray matter located under the cerebral cortex in the depths of the white matter.

Stimulation of the fence causes an orienting reaction, a turn of the head in the direction of irritation, chewing, swallowing, and sometimes vomiting movements.

Irritation of the fence inhibits the conditioned reflex to light and has little effect on the conditioned reflex to sound. Stimulation of the fence while eating slows down the process of eating food.

It is known that the thickness of the fence of the left hemisphere in humans is somewhat greater than that of the right; when the fence of the right hemisphere is damaged, speech disorders are observed.

Thus, the basal nuclei of the brain are integrative centers for the organization of motor skills, emotions, higher nervous activity, and each of these functions can be enhanced or inhibited by the activation of individual formations of the basal nuclei.

Functions of the basal nuclei

Basic structures of the basal ganglia ( rice. 66) . The basal ganglia are the caudate nucleus ( nucleus caudatus), shell ( putamen) and pale ball ( globulus pallidus); some authors attribute the fence to the basal nuclei ( claustrum).

All four of these nuclei are called the striatum ( corpus striatum). The striatum is also distinguished (s triatum) is the caudate nucleus and the shell. The pale ball and shell form a lenticular nucleus ( Nucleus lentioris). The striatum and globus pallidus form the striopallidar system.

66. A - Location of the basal ganglia in the volume of the brain. The basal ganglia are shaded red, the thalamus is grey, and the rest of the brain is unshaded.

1 - Pallid globus, 2 - Thalamus, 3 - Putamen, 4 - Caudate nucleus, 5 - Amygdala (Astapova, 2004).

Caudate nucleus Lenticular nucleus

B - Three-dimensional image of the location of the basal ganglia in the volume of the brain (Guyton, 2008)

Functional connections of the basal ganglia. At the basal nuclei no input from the spinal cord, but direct input from the cerebral cortex.

The basal nuclei are involved in the performance of motor functions, emotional and cognitive (cognitive) functions.

Excitatory pathways go mainly to the striatum: from all areas of the cerebral cortex (directly and through the thalamus), from the nonspecific nuclei of the thalamus, from the substantia nigra (midbrain)) (Fig.

Rice. 67. Connection of the contour of the basal ganglia with the corticospinal cerebellar system for the regulation of motor activity (Guyton, 2008)

The striatum itself has a mainly inhibitory and, partially, excitatory effect on the pale ball.

From the globus pallidus goes the most important path to the motor ventral nuclei of the thalamus, from them the excitatory path goes to the motor cortex of the brain. Part of the fibers from the striatum goes to the cerebellum and to the centers of the brain stem (RF, red nucleus and further to the spinal cord.

Braking paths from the striatum go to substantia nigra and after switching - to the nuclei of the thalamus (Fig. 68).

68. Nerve pathways that secrete various types of neurotransmitters in the basal ganglia. Ah - acetylcholine; GABA - gamma-aminobutyric acid (Guyton, 2008)

Motor functions of the basal ganglia. In general, the basal nuclei, having bilateral connections with the cerebral cortex, thalamus, and brainstem nuclei, are involved in the creation of programs of purposeful movements, taking into account the dominant motivation.

At the same time, the neurons of the striatum have an inhibitory effect (mediator - GABA) on the neurons of the substantia nigra. In turn, the neurons of the substantia nigra (mediator - dopamine) have a modulating effect (inhibitory and excitatory) on the background activity of striatal neurons.

In case of violation of dopaminergic influences on the basal nuclei, movement disorders such as parkinsonism are observed, in which the concentration of dopamine in both nuclei of the striatum drops sharply. The most important functions of the basal ganglia are performed by the striatum and the globus pallidus.

Functions of the striatum.

Participates in the implementation of the rotation of the head and trunk and walking in a circle, which are included in the structure of orienting behavior. Defeat of the caudate nucleus in diseases and destruction in the experiment leads to violent, excessive movements (hyperkinesis: chorea and athetosis).

Functions of the pale ball.

Has a modulating effect on the motor cortex, cerebellum, RF, red nucleus. During stimulation of the pale ball in animals, elementary motor reactions predominate in the form of contraction of the muscles of the limbs, neck and face, activation of eating behavior.

Pale Orb Destruction accompanied by a decrease in motor activity - there is adynamia(pallor of motor reactions), as well as it (destruction) is accompanied by the development of drowsiness, "emotional dullness", which hinders the implementation available conditioned reflexes and worsens development of new(impairs short-term memory).

Basal, or subcortical, nuclei are structures of the forebrain, which include: the caudate nucleus, the putamen, the pale ball and the subthalamic nucleus. They are located below.

The development and cellular structure of the caudate nucleus and the shell are the same, therefore they are considered as a single formation - the striatum. The basal nuclei have multiple afferent and efferent connections with the cortex, diencephalon, midbrain, limbic system, and cerebellum. In this regard, they take part in the regulation of motor activity and, in particular, slow or worm-like movements. An example of such motor acts is slow walking, stepping over obstacles, etc.

Experiments with the destruction of the striatum proved its important role in the organization of animal behavior.

The pale ball is the center of complex motor reactions and is involved in ensuring the correct distribution of muscle tone.

The pale ball performs its functions indirectly through formations - the red core and the black substance.

The pale ball also has a connection with the reticular formation. It provides complex motor reactions of the body and some autonomic reactions. Stimulation of the globus pallidus causes the activation of the center of hunger and eating behavior. The destruction of the pale ball contributes to the development of drowsiness and the difficulty in developing new conditioned reflexes.

With the defeat of the basal ganglia in animals and humans, a variety of uncontrolled motor reactions can occur.

In general, the basal nuclei are involved in the regulation of not only the motor activity of the body, but also a number of autonomic functions.

Basal nuclei and their structure

Subcortical (basal) nuclei refer to subcortical formations that have a common origin with the cerebral hemispheres and are located inside their white matter, between the frontal lobes and the diencephalon. These include caudate nucleus And shell, united by the common name "striated body" because the accumulation of nerve cells that form the gray matter alternates with layers of white matter. Together with pale ball they form striopallidar system of subcortical nuclei. The striopallidary system also includes the claustrum, the subthalamic (subtubercular) nucleus, and the substantia nigra (Fig. 1).

Rice. 1. Basal nuclei of the brain and their connections with other systems: A - anatomy of the basal nuclei; B - connections of the basal nuclei with the corticospinal and cerebellar systems that control movement

The striopallidar system is the link between the cortex and the brain stem. Afferent and efferent pathways are suitable for this system.

Functionally, the basal nuclei are a superstructure over the red nuclei of the midbrain and provide plastic tone, i.e. the ability to hold an innate or learned posture for a long time, for example, the posture of a cat that guards a mouse, or a long-term retention of a posture by a ballerina performing some kind of step. When the cerebral cortex is removed, "wax rigidity" is observed, which is an expression of plastic tone without the regulatory influence of the cerebral cortex. An animal deprived of the cerebral cortex freezes for a long time in one position.

The subcortical nuclei ensure the implementation of slow, stereotyped, calculated movements, and the centers of the basal ganglia - the regulation of congenital and acquired movement programs, as well as the regulation of muscle tone.

Violation of various structures of the subcortical nuclei is accompanied by numerous motor and tonic shifts. So, in newborns, incomplete maturation of the basal ganglia leads to sharp convulsive flexion movements. As these structures develop, smoothness and calculated movements appear.

One of the main tasks of the basal ganglia in the implementation of motor control is the control of complex stereotypes of motor activity (for example, writing the letters of the alphabet). When there is severe damage to the basal ganglia, the cerebral cortex cannot properly maintain this complex stereotype. Instead, reproducing what has already been written becomes difficult, as if one had to learn to write for the first time. Examples of other stereotypes that are provided by the basal ganglia are cutting paper with scissors, hammering a nail, digging with a shovel in the ground, controlling eye and voice movements, and other well-practiced movements.

Caudate nucleus plays an important role in the conscious (cognitive) control of motor activity. Most of our motor acts arise as a result of their reflection and comparison with the information available in memory.

Violation of the functions of the caudate nucleus is accompanied by the development of hyperkinesis such as involuntary facial reactions, tremor, athetosis, chorea (twitching of the limbs, torso, as in an uncoordinated dance), motor hyperactivity in the form of aimless movement from place to place.

The caudate nucleus takes part in speech, motor acts. So, with a disorder of the anterior part of the caudate nucleus, speech is disturbed, difficulties arise in turning the head and eyes in the direction of sound, and damage to the posterior part of the caudate nucleus is accompanied by a loss of vocabulary, a decrease in short-term memory, the cessation of voluntary breathing, speech delay.

Irritation striatum leads to sleep in the animal. This effect is explained by the fact that the striatum causes inhibition of the activating influences of the nonspecific nuclei of the thalamus on the cortex. The striatum regulates a number of vegetative functions: vascular reactions, metabolism, heat generation and heat release.

pale ball regulates complex motor acts. When it is irritated, a contraction of the muscles of the limbs is observed. Damage to the pale ball causes masking of the face, tremor of the head, limbs, monotony of speech, combined movements of the arms and legs when walking are disturbed.

With the participation of the pale ball, the regulation of orientation and defensive reflexes is carried out. When the pale ball is disturbed, food reactions change, for example, the rat refuses food. This is due to the loss of connection between the globus pallidus and the hypothalamus. In cats and rats, there is a complete disappearance of food-procuring reflexes after bilateral destruction of the globus pallidus.

Functions of the basal nuclei

Basic structures of the basal ganglia ( rice. 66) . The basal ganglia are the caudate nucleus ( nucleus caudatus), shell ( putamen) and pale ball ( globulus pallidus); some authors attribute the fence to the basal nuclei ( claustrum). All four of these nuclei are called the striatum ( corpus striatum). The striatum is also distinguished (s triatum) is the caudate nucleus and the shell. The pale ball and shell form a lenticular nucleus ( Nucleus lentioris). The striatum and globus pallidus form the striopallidar system.

Rice. 66. A - Location of the basal ganglia in the volume of the brain. The basal ganglia are shaded red, the thalamus is grey, and the rest of the brain is unshaded. 1 - Pallid globus, 2 - Thalamus, 3 - Putamen, 4 - Caudate nucleus, 5 - Amygdala (Astapova, 2004). B - Three-dimensional image of the location of the basal ganglia in the volume of the brain (Guyton, 2008)

Functional connections of the basal ganglia. At the basal nuclei no input from the spinal cord, but direct input from the cerebral cortex.

The basal nuclei are involved in the performance of motor functions, emotional and cognitive (cognitive) functions.

Excitatory pathways go mainly to the striatum: from all areas of the cerebral cortex (directly and through the thalamus), from the nonspecific nuclei of the thalamus, from the substantia nigra (midbrain)) (Fig. 67).

Rice. 67. Connection of the contour of the basal ganglia with the corticospinal cerebellar system for the regulation of motor activity (Guyton, 2008)

The striatum itself has a mainly inhibitory and, partially, excitatory effect on the pale ball. From the globus pallidus goes the most important path to the motor ventral nuclei of the thalamus, from them the excitatory path goes to the motor cortex of the brain. Part of the fibers from the striatum goes to the cerebellum and to the centers of the brain stem (RF, red nucleus and further to the spinal cord.

Braking paths from the striatum go to substantia nigra and after switching - to the nuclei of the thalamus (Fig. 68).

Rice. 68. Nerve pathways that secrete various types of neurotransmitters in the basal ganglia. Ah - acetylcholine; GABA - gamma-aminobutyric acid (Guyton, 2008)

Motor functions of the basal ganglia. In general, the basal nuclei, having bilateral connections with the cerebral cortex, thalamus, and brainstem nuclei, are involved in the creation of programs of purposeful movements, taking into account the dominant motivation. At the same time, the neurons of the striatum have an inhibitory effect (mediator - GABA) on the neurons of the substantia nigra. In turn, the neurons of the substantia nigra (mediator - dopamine) have a modulating effect (inhibitory and excitatory) on the background activity of striatal neurons. In case of violation of dopaminergic influences on the basal nuclei, movement disorders such as parkinsonism are observed, in which the concentration of dopamine in both nuclei of the striatum drops sharply. The most important functions of the basal ganglia are performed by the striatum and the globus pallidus.

Functions of the striatum. Participates in the implementation of the rotation of the head and trunk and walking in a circle, which are included in the structure of orienting behavior. Defeat of the caudate nucleus in diseases and destruction in the experiment leads to violent, excessive movements (hyperkinesis: chorea and athetosis).

Functions of the pale ball. Has a modulating effect on the motor cortex, cerebellum, RF, red nucleus. During stimulation of the pale ball in animals, elementary motor reactions predominate in the form of contraction of the muscles of the limbs, neck and face, activation of eating behavior. Pale Orb Destruction accompanied by a decrease in motor activity - there is adynamia(pallor of motor reactions), as well as it (destruction) is accompanied by the development of drowsiness, "emotional dullness", which hinders the implementation available conditioned reflexes and worsens development of new(impairs short-term memory).

The basal nuclei include the caudate nucleus, the lenticular nucleus, the claustrum, the amygdala, and the nucleus accumbens.

The largest of these nuclei is caudate nucleus (n. caudatus). It is elongated in the rostro-caudal direction (from front to back) and has a C-shape (Fig. 9.1).

Rice. 9.1.

dotted lines indicate cerebral ventricles

The thickened anterior part forms the head of the caudate nucleus, it passes into the body and ends with a tail. On a horizontal cut (Fig. 9.2, 7-8 ) only the head and tail of this nucleus are visible. On the medial side, the caudate nucleus adjoins the thalamus, separated from it by a terminal strip (see Fig. 8.1).

Somewhat lateral and below the caudate nucleus is located lentiform nucleus (n. lentiformis) (see Fig. 9.1). It is divided into three parts by thin layers of white matter (Fig. 9.2, 9-11). The lateral part is the nucleus, called shell (putamen). The two medial parts are the outer and inner segments pale ball (globus pallidus). The pale ball is lighter than the shell, as it is penetrated by numerous myelinated fibers.

The lenticular nucleus is separated from the caudate nucleus and thalamus by a layer of white matter - internal capsule (capsula interna)(Fig. 9.2, 12). All the projection fibers of the hemispheres pass through it, which connect the cerebral cortex with the underlying structures of the central nervous system. From above, the ascending fibers form a radiant crown in the white matter of the hemispheres ( corona radiata), and downwards, the fibers of the descending pathways in the form of compact bundles are sent to the legs of the midbrain.

Even more lateral to the shell, between it and the insular cortex (see below) lies a strip of gray matter - fence (claustrum).

The caudate nucleus, the globus pallidus, and the shell appear as alternating bands of gray and white matter on section. Because of this, they were united under the common name " striped body" (corpus striatum). When studying the cellular composition and nature of the connections of the basal ganglia, it turned out that the globus pallidus is a phylogenetically older formation and differs significantly from the caudate nucleus and putamen. In this regard, the pale ball (globus paUidus) isolated from the striatum as a separate unit - pallidum. Phylogenetically younger caudate nucleus and putamen are called neostriatum, or simply striatum. Together they form striopallidary system with very wide connections.

Rice. 9.2.

vault commissures:

• 1 - longitudinal median fissure; 2 - frontal pole; 3 - occipital pole;
• 4 - knee of the corpus callosum; 5 - the cavity of the transparent septum; 6 - transparent partition plate; 7-8 - head (7) and tail (8) caudate nucleus;
• 9 - shell; 10 - fence; 11 - outer and inner segments of the pale ball;
• 12 - inner capsule; 13-14 - front (13) and rear (14) horns of the lateral ventricle; 15 - III ventricle; 16 - insular lobe; 17 - mamillo-thalamic bundle; 18 - commissure of the arch; 19 - roller of the corpus callosum; 20 - hippocampus;
• 21 - fringe of the hippocampus; 22 - thalamus

The striatum receives the main afferents of the striopallidar system. These are fibers from the cerebral cortex, mainly from the zone of musculoskeletal sensitivity and the motor zone (fields 1-4; see Fig. 9.9) and the frontal lobe as a whole. Also here come dopaminergic fibers from the compact part of the substantia nigra, fibers from the cerebellum and from nonspecific thalamic nuclei. Most of the efferents of the striatum go to the pale ball. Part of the fibers goes to the reticular part of the substantia nigra. There are also less significant connections with various motor structures.

The globus pallidus receives its main afferents from the striatum and, in addition, from the subthalamus. Pallidum efferents go to the thalamic nuclei VA, VL (motor projection nuclei), and they also go to the subthalamus and the leash nuclei in the epithalamus.

The main functions of the striopallidar system are related to the control of movements. Along with the cerebellum, it is the largest subcortical motor center. Moreover, if the cerebellum is associated with the regulation of specific parameters of the movements performed (the amplitude of muscle contractions, their consistency during simultaneous implementation, etc.), then the striopallidary system is considered as an area that controls the start of movements and contains information about motor programs - sequential complexes of movements. Indeed, when movements are initiated, activation of nerve cells is observed first in the associative frontal cortex, then in the striatum and globus pallidus, premotor cortex, and only then in the motor cortex of the cerebral hemispheres and cerebellum. Like the cerebellum, the structures of the striopallidar system are involved in motor learning and the transformation of initially voluntary (i.e., performed by mind control) movements into automated ones. If, for example, the striatum is damaged, pathological movements are triggered - high-amplitude twitching of the hands (chorea), twisting of the torso (athetosis). Manifestations of parkinsonism (tremor, etc.) are also mainly associated with a violation of the influence of the substantia nigra on the caudate nucleus.

amygdala (corpus amygdaloideum) - a spherical formation located under the shell near the inside of the anterior temporal cortex (see Fig. 9.1, 4). The amygdala (tonsil) is in contact with the tail of the caudate nucleus, which, twisting, enters the temporal lobes. It has numerous connections with the cerebral cortex, hypothalamus, and olfactory brain structures. The amygdala is part of the LS of the brain and plays an important role in the activity of the system of needs and emotions (in particular, in the regulation of manifestations of aggressiveness, fear, etc.). Damage to the amygdala often leads to profound changes in the psyche, depressive and manic states.

The nucleus accumbens (n. accumbens) is located in the ventrorostral region of the basal ganglia, in front of the pale ball under the head of the caudate nucleus (see Fig. 9.1, 6). This nucleus is the most important center of positive reinforcement and a key area of ​​the mesolimbic pathway (see section 6.6). The accumbens receives its main afferents from the frontal association cortex, the amygdala, and the ventral tegmental area. Efferents from this nucleus go to the globus pallidus, from there to the MD nucleus of the thalamus, which gives projections to the frontal association cortex. Most of the mental processes associated with receiving pleasure (and learning that occurs against the background of this pleasure) are based on the activation of accumbens.

Subcortical or basal nuclei called accumulations of gray matter in the thickness of the lower and lateral walls of the cerebral hemispheres. These include striatum, globus pallidum, and palisade.

striatum comprises caudate nucleus and putamen. Afferent nerve fibers go to it from the motor and associative zones of the cortex, thalamus, substantia nigra of the midbrain. Communication with the substantia nigra is carried out with the help of dopaminergic synapses. The dopamine released in them inhibits the neurons of the striatum. In addition, signals from the striatum come from the cerebellum, red and vestibular nuclei. From it, the axons of neurons go to the pale ball. In turn, efferent pathways go from the globus pallidus to the thalamus and motor nuclei of the midbrain, i.e. red nucleus and black substance. The striatum has a predominantly inhibitory effect on the neurons of the pale ball. The main function of the subcortical nuclei is the regulation of movement. The cortex, through the subcortical nuclei, organizes and regulates additional, auxiliary movements necessary for the correct execution of the main motor act or facilitating it. This, for example, is a certain position of the torso and legs when doing work with the hands. When the function of the subcortical nuclei is impaired, auxiliary movements become either excessive or completely absent. In particular, when parkinson's disease or shaking paralysis, facial expressions completely disappear, and the face becomes mask-like, walking is carried out in small steps. Patients with ore start and end movements, tremor of the limbs is pronounced. Muscle tone is increased. The occurrence of Parkinson's disease is due to a violation of the conduction of nerve impulses from the substantia nigra to the striatum through the dopaminergic synapses that provide this transmission (L-DCFA).

Striatal lesions and hyperactivity of the globus pallidus are associated with diseases with excessive movements, i.e. hyperkinesis. These are twitching of the muscles of the face, neck, torso, limbs. As well as motor hyperactivity in the form of aimless movement. For example, it is observed when chorea.

In addition, the striatum takes part in the organization of conditioned reflexes, memory processes, and the regulation of eating behavior.

The general principle of the organization of movement.

Thus, due to the centers of the spinal, medulla oblongata, midbrain, cerebellum, subcortical nuclei, unconscious movements are organized. Conscious are carried out in three ways:

With the help of pyramidal cells of the cortex and descending pyramidal tracts. The value of this mechanism is small.

Through the cerebellum.

Through the basal nuclei.

For the organization of movements, afferent impulses of the spinal motor system are of particular importance. The perception of muscle tension is carried out by muscle spindles and tendon receptors. All muscles have short, spindle-shaped cells. Several of these spindles are enclosed in a connective tissue capsule. Therefore they are called intrafusal . There are two types of intrafusal fibers: nuclear chain fibers and nuclear bag fibers. The latter are thicker and longer than the former. These fibers perform various functions. A thick afferent nerve fiber belonging to group 1A passes through the capsule to the muscle spindles. After entering the capsule, it branches, and each branch forms a spiral around the center of the nuclear bag of intrafusal fibers. Therefore, this ending is called annulospiral . On the periphery of the spindle, i.e. its distal parts are secondary afferent endings. In addition, efferent fibers from the motor neurons of the spinal cord approach the spindles. When they are excited, the spindles shorten. This is necessary to regulate the sensitivity of the spindles to stretch. Secondary afferent endings are also stretch receptors, but their sensitivity is less than annulospiral ones. Basically, their function is to control the degree of muscle tension with a constant tone of extrafusal muscle cells.

In the tendons are golgi tendon organs. They are formed by tendon filaments extending from several extrafusal, i.e. working muscle cells. Branchings of the myelinated afferent nerves of group 1B are located on these threads.

There are relatively more muscle spindles in the muscles responsible for fine movements. There are fewer golgi receptors than spindles.

Muscle spindles perceive mainly changes in muscle length. Tendon receptors - its tension. Impulses from these receptors travel via afferent nerves to the motor centers of the spinal cord, and via ascending pathways to the cerebellum and cortex. As a result of the analysis of propreoreceptor signals in the cerebellum, involuntary coordination of contractions of individual muscles and muscle groups occurs. It is carried out through the centers of the middle and medulla oblongata. Processing of signals by the cortex leads to the emergence of muscle sensation and the organization of voluntary movements through the pyramidal tracts, cerebellum and subcortical nuclei.

limbic system.

The limbic system includes such formations of the ancient and old cortex as olfactory bulbs, hippocampus, cingulate gyrus, dentate fascia, parahippocampal gyrus, as well as subcortical amygdala nucleus and anterior thalamic nucleus. This system of brain structures is called limbic because they form a ring (limb) at the border of the brain stem and neocortex. The structures of the limbic system have numerous bilateral connections between themselves, as well as with the frontal, temporal lobes of the cortex and the hypothalamus.

Through these connections, it regulates and performs the following functions:

Regulation of autonomic functions and maintenance of homeostasis. The limbic system is called visceral brain , as it carries out a fine regulation of the functions of the organs of blood circulation, respiration, digestion, metabolism, etc. The special significance of the limbic system is that it responds to small deviations in the parameters of homeostasis. It affects these functions through the autonomic centers of the hypothalamus and the pituitary gland.

Formation of emotions. During operations on the brain, it was found that irritation of the amygdala causes the appearance of causeless emotions of fear, anger, and rage in patients. When the amygdala is removed in animals, aggressive behavior completely disappears (psychosurgery). Irritation of some zones of the cingulate gyrus leads to the emergence of unmotivated joy or sadness. And since the limbic system is also involved in the regulation of the functions of visceral systems, all autonomic reactions that occur with emotions (changes in heart function, blood pressure, sweating) are also carried out by it.

Formation of motivations. The limbic system is involved in the emergence and organization of the orientation of motivations. The amygdala regulates food motivation. Some of its areas inhibit the activity of the saturation center and stimulate the hunger center of the hypothalamus. Others act in the opposite way. Due to these centers of food motivation of the amygdala, behavior is formed for tasty and unpalatable food. It also has departments that regulate sexual motivation. When they are irritated, hypersexuality and pronounced sexual motivation occur.

Participation in the mechanisms of memory. In the mechanisms of memorization, a special role belongs to the hippocampus. First, it classifies and encodes all the information that needs to be stored in long-term memory. Secondly, it ensures the extraction and reproduction of the necessary information at a particular moment. It is assumed that the ability to learn is determined by the innate activity of the corresponding hippocampal neurons.

Due to the fact that the limbic system plays an important role in the formation of motivations and emotions, when its functions are disturbed, changes in the psycho-emotional sphere occur. In particular, the state of anxiety and motor excitation. In this case, assign tranquilizers that inhibit the formation and release of serotonin in the interneuronal synapses of the limbic system. Used for depression antidepressants that enhance the formation and accumulation of norepinephrine. It is assumed that schizophrenia, manifested by pathology of thinking, delusions, hallucinations, is due to changes in the normal connections between the cortex and the limbic system. This is due to increased dophin production in the presynaptic endings of dopaminergic neurons. Aminazin and others antipsychotics block the synthesis of dopamine and cause remission. amphetamines(phenamine) increase the formation of dopamine and can cause psychosis.