Basal ganglia and their functional connections. Basal ganglia (striate bodies)

The human body is made up of a large number of organs and structures, the main ones being the brain and the heart. The heart is the engine of life, and the brain is the coordinator of all processes. In addition to knowledge about the main parts of the brain, you need to know about the basal ganglia.

The basal ganglia are responsible for movement and coordination

The basal nuclei (ganglia) are accumulations of gray matter that form groups of nuclei. This part of the brain is responsible for movement and coordination.

Functions that the ganglia provide

Motor activity is manifested due to the constant control of the pyramidal (cortico-spiral) tract. But he does not provide it completely. Some of the functions are taken over by the basal ganglia. Parkinson's disease or Wilson's disease is caused precisely by pathological disorders of subcortical accumulations of gray matter. The functions of the basal ganglia are considered vital, and their disorders are difficult to treat.

According to scientists, the main task of the work of the nuclei is not motor activity itself, but its control over the functioning, as well as the connection of muscle groups and the nervous system. There is a function of control over human movements. Characterizes this interaction of two systems, which includes the accumulation of subcortical substance. The striopallidar and limbic systems have their own functional features. The first tends to control muscle contraction, which together forms coordination. The second is subject to the work and organization of vegetative functions. Their failure leads not only to discoordination of a person, but also to a violation of the mental activity of the brain.

Malfunctions in the functioning of the nuclei lead to impaired brain function

Structural features

The basal nuclei of the brain have a complex structure. According to the anatomical structure, they include:

striatum (striate body);
amygdaloidium (almond-shaped body);
fence.

The modern study of these accumulations has created a new, convenient division of the nuclei into an accumulation of black substance and a nucleus cover. But such a figurative structure does not give a complete picture of the anatomical connections and neurotransmitters, so it is the anatomical structure that should be considered. Thus, the concept of the striatum is characterized by the accumulation of white and gray matter. They are visible in a horizontal section of the cerebral hemispheres.

Basal ganglia is a complex term that includes concepts about the structure and functions of the striatum and amygdala. In addition, the striatum consists of the lenticular and caudate ganglion. Their location and connection has its own characteristics. The basal ganglia of the brain are separated by a neuronal capsule. The caudate ganglion is associated with the thalamus.

The caudate ganglion is associated with the thalamus

Features of the structure of the caudate ganglion

The second type of Golgi neurons is identical to the structure of the caudate nucleus. Neurons play an important role in the formation of accumulations of gray matter. This is noticeable by the similar features that unite them. The thinness of the axon and the shortening of the dendrites are identical. This core provides its main functions with its own connections with individual sections and departments of the brain:

thalamus;
pale ball;
cerebellum;
black substance;
vestibule nuclei.

The versatility of the nuclei makes them one of the most important parts of the brain. The basal ganglia and their connections provide not only coordination of movements, but also autonomic functions. We must not forget that the ganglia are also responsible for integrative and cognitive abilities.

The caudate nucleus, with its connections with individual parts of the brain, forms a single closed neural network. And a disruption in the work of any of its sections can cause serious problems with the neuro-motor activity of a person.

Neurons are essential to the gray matter of the brain

Features of the structure of the lenticular nucleus

The basal ganglia are interconnected by neuronal capsules. The lenticular nucleus is located outside the caudate and has an external connection with it. This ganglion has an angle shape with a capsule located in the middle. The inner surface of the nucleus is connected to the cerebral hemispheres, and the outer surface forms a connection with the head of the caudate ganglion.

White matter is a septum that separates the lenticular nucleus into two main systems that differ in color. Those that have a dark tint are the shell. And those that are lighter - refer to the structure of the pale ball. Modern scientists working in the field of neurosurgery consider the lentiform ganglion to be part of the striopallidar system. Its functions are associated with the autonomic action of thermoregulation, as well as metabolic processes. The role of the nucleus significantly exceeds the hypothalamus in these functions.

Fence and amygdala

A fence is a thin layer of gray matter. It has its own characteristics associated with the structure and relationships with the shell and the "island":

the fence is surrounded by a white substance;
the fence is connected to the body and the shell by internal and external neural connections;
the shell borders the amygdala.

Scientists believe that the amygdala performs several functions. In addition to the main ones related to the limbic system, it is a component of the department responsible for the sense of smell.

The connection is confirmed by the nerve fibers that connect the olfactory lobe with the perforated substance. Therefore, the amygdala and its work are an integral part of the organization and control of mental work. The psychological state of a person also suffers.

The amygdala performs primarily an olfactory function.

What problems does ganglion dysfunction lead to?

The resulting pathological failures and disorders in the basal ganglia quickly lead to a deterioration in the human condition. Not only his well-being suffers, but also the quality of mental activity. A person with disturbances in the functioning of this part of the brain can become disoriented, suffer from depression, etc. Two types of pathologies are to blame for this - neoplasms and functional insufficiency.

Any neoplasms in the subcortical part of the nuclei are dangerous. Their appearance and development leads to disability and even death. Therefore, at the slightest symptoms of pathology, you should consult a doctor for the purpose of diagnosis and treatment. The fault of the formation of cysts or other neoplasms are:

degeneration of nerve cells;
attack by infectious agents;
trauma;
hemorrhage.

Functional insufficiency is diagnosed less frequently. This is due to the nature of the occurrence of such a pathology. It manifests itself more often in infants during the period of maturation of the nervous system. In adults, failure is characterized by previous strokes or trauma.

Studies show that functional failure of the nuclei in more than 50% of cases is the main cause of the onset of signs of Parkinson's disease in old age. Treatment of such a disease depends on the severity of the pathology itself and the timeliness of contacting specialists.

Features of diagnosis and treatment

At the slightest sign of a violation of the activity of the basal ganglia, you should contact a neurologist. The reason for this may be the following symptoms:

violation of motor activity of muscles;
tremor;
frequent muscle spasms;
uncontrolled limb movements;
memory problems.

Diagnosis of diseases is carried out on the basis of a general examination. If necessary, the patient may be referred for a brain scan. This type of study can show dysfunctional zones not only in the basal ganglia, but also in other parts of the brain.

Treatment of dysfunctions of the basal ganglia is ineffective. Most often, therapy reduces symptoms. But in order for the result to be permanent, it should be treated for life. Any breaks can adversely affect the patient's well-being.

At the base of the cerebral hemispheres (the lower wall of the lateral ventricles) are the nuclei of gray matter - the basal ganglia. They make up about 3% of the volume of the hemispheres. All basal ganglia are functionally combined into two systems. The first group of nuclei is a striopallidar system (Fig. 41, 42, 43). These include: caudate nucleus (nucleus caudatus), shell (putamen) and pale ball (globus pallidus). The shell and caudate nucleus have a layered structure, and therefore their common name is the striatum (corpus striatum). The pale ball has no stratification and looks lighter than the striatum. The shell and pale ball are combined into a lentiform nucleus (nucleus lentiformis). The shell forms the outer layer of the lenticular nucleus, and the pale ball forms its inner parts. The pale ball, in turn, consists of the outer

and internal segments.
Anatomically, the caudate nucleus is closely related to the lateral ventricle. The anterior and medially expanded part of it - the head of the caudate nucleus forms the lateral wall of the anterior horn of the ventricle, the body of the nucleus - the lower wall of the central part of the ventricle, and the thin tail - the upper wall of the lower horn. Following the shape of the lateral ventricle, the caudate nucleus covers the lenticular nucleus with an arc (Fig. 42, 1; 43, 1 /). The caudate and lenticular nuclei are separated from each other by a layer of white matter - part of the internal capsule (capsula interna). Another part of the internal capsule separates the lenticular nucleus from the underlying thalamus (Fig. 43,
4).
80

(on the right - below the level of the bottom of the lateral ventricle; on the left - above the bottom of the lateral ventricle; the IV ventricle of the brain was opened from above):
1 - head of the caudate nucleus; 2 - shell; 3 - cortex of the cerebral islet; 4 - pale ball; 5 - fence; 6

Thus, the structure of the bottom of the lateral ventricle (which is a striopallidary system) can be schematically represented as follows: the wall of the ventricle itself forms a layered caudate nucleus, then a layer of white matter goes below -
81

Rice. 42. Topography of the basal nuclei of the telencephalon and stem structures (view
front left):
1 - caudate nucleus; 2 - shell; 3 - tonsil; 4 - black substance; 5 - frontal cortex; 6 - hypothalamus; 7 - thalamus

Rice. 43. Topography of the basal nuclei of the telencephalon and stem structures (view
rear left):
1 - caudate nucleus; 2 - shell; 3 - pale ball; 4 - internal capsule; 5 - subthalamic nucleus; 6

black substance; 7 - thalamus; 8 - subcortical nuclei of the cerebellum; 9 - cerebellum; 10 - spinal cord; eleven

1 2 3 4

the inner capsule, under it is a layered shell, even lower is a pale ball and again a layer of the inner capsule, lying on the nuclear structure of the diencephalon - the thalamus.
The striopallidar system receives afferent fibers from nonspecific medial thalamic nuclei, the frontal regions of the cerebral cortex, the cerebellar cortex, and the substantia nigra of the midbrain. The bulk of the efferent fibers of the striatum converge in radial bundles to the pale ball. Thus, the pale ball is the output structure of the striopallidary system. The efferent fibers of the globus pallidus go to the anterior nuclei of the thalamus, which are connected with the frontal and parietal cortex of the cerebral hemispheres. Some of the efferent fibers that do not switch in the nucleus of the globus pallidus go to the substantia nigra and the red nucleus of the midbrain. Striopallidum (Fig. 41; 42), together with its pathways, enters the extrapyramidal system, which has a tonic effect on motor activity. This system of control over movements is called extrapyramidal because it switches on the way to the spinal cord, bypassing the pyramids of the medulla oblongata. The striopallidar system is the highest center of involuntary and automated movements, reduces muscle tone, and inhibits the movements carried out by the motor cortex. Lateral to the striopallidal system of the basal ganglia is a thin plate of gray matter - a fence (claustrum). It is bounded on all sides by fibers of white matter.

outer capsule (capsula externa).

The rest of the basal ganglia are part of the limbic system of the brain (see Section 6.2.5.3). ahead of

the end of the lower horn of the lateral ventricle in the white matter of the temporal lobe of the cerebral hemispheres is a dense group of nuclei - the amygdala (amigdalae) (Fig. 42, 3). And finally, within the transparent septum lies the core of the septum (nucleus septipellucidi) (see Fig. 37, 21). In addition to the listed basal nuclei, the limbic system includes: the cortex of the cingulate gyrus of the limbic lobe of the cerebral hemispheres, the hippocampus, the mamillary nuclei of the hypothalamus, the anterior nuclei of the thalamus, and the structures of the olfactory brain.

Basal ganglia (basal nuclei) is a striopallidar system consisting of three pairs of large nuclei immersed in the white matter of the telencephalon at the base of the cerebral hemispheres, and connecting the sensory and associative cortex zones with the motor cortex.

Structure

The phylogenetically ancient part of the basal ganglia is the pale ball, the later formation is the striatum, and the youngest part is the fence.

The pale ball consists of external and internal segments; striatum - from the caudate nucleus and the shell. The fence is located between the shell and the insular (insular) cortex. Functionally, the basal ganglia also include the subthalamic nuclei and the substantia nigra.

Functional connections of the basal ganglia

Excitatory afferent impulses enter mainly the striatum (in the caudate nucleus) mainly from three sources:

1) from all areas of the cortex directly and indirectly through the thalamus;

2) from nonspecific nuclei of the thalamus;

3) from black substance.

Among the efferent connections of the basal ganglia, three main outputs can be noted:

from the striatum, inhibitory pathways go to the pale ball directly and with the participation of the subthalamic nucleus; from the pale ball begins the most important efferent path of the basal nuclei, going mainly to the motor ventral nuclei of the thalamus, from them the excitatory path goes to the motor cortex;
part of the efferent fibers from the globus pallidus and the striatum go to the centers of the brain stem (the reticular formation, the red nucleus and further to the spinal cord), and also through the inferior olive to the cerebellum;
from the striatum, inhibitory pathways go to the substantia nigra and, after switching, to the nuclei of the thalamus.

Therefore, the basal ganglia are intermediate. They connect the associative and, in part, the sensory cortex with the motor cortex. Therefore, in the structure of the basal nuclei, several parallel functional loops are distinguished, connecting them with the cerebral cortex.

Fig.1. Scheme of functional loops passing through the basal ganglia:

1 - skeletal motor loop; 2 - oculomotor loop; 3 - complex loop; DC, motor cortex; PMC, premotor cortex; SSC, somatosensory cortex; PFC, prefrontal association cortex; P8 - field of the eighth frontal cortex; P7 - field of the seventh parietal cortex; FAC, frontal association cortex; VLA, ventrolateral nucleus; MDN, mediodorsal nucleus; PVN, anterior ventral nucleus; BS - pale ball; CV is black matter.

The skeletal-motor loop connects the premotor, motor, and somatosensory areas of the cortex to the putamen. The impulse from it goes to the pale ball and the substantia nigra and then returns through the motor ventrolateral nucleus to the premotor cortex. It is believed that this loop serves to regulate such movement parameters as amplitude, strength, direction.

The oculomotor loop connects the areas of the cortex that control the direction of gaze to the caudate nucleus. From there, the impulse goes to the globus pallidus and the black substance, from which it is projected, respectively, to the associative mediodorsal and anterior relay ventral nuclei of the thalamus, and from them it returns to the frontal oculomotor field 8. This loop is involved in the regulation of spasmodic eye movements (sakkals).

The existence of complex loops is also assumed, along which impulses from the frontal associative zones of the cortex enter the caudate nucleus, the globus pallidus, and the substantia nigra. Then, through the mediodorsal and ventral anterior nuclei of the thalamus, it returns to the associative frontal cortex. It is believed that these loops are involved in the implementation of the higher psychophysiological functions of the brain: the control of motivations, prediction, and cognitive activity.

Functions

Functions of the striatum

Effect of the striatum on the globus pallidus. The influence is carried out mainly by the inhibitory mediator GABA. However, some of the globus pallidus neurons give mixed responses, and some only give EPSPs. That is, the striatum has a double effect on the pale ball: inhibitory and excitatory, with a predominance of inhibitory.

Influence of the striatum on the substantia nigra. There are bilateral connections between the substantia nigra and the striatum. The striatal neurons have an inhibitory effect on the neurons of the substantia nigra. In turn, substantia nigra neurons have a modulating effect on the background activity of striatal neurons. In addition to affecting the striatum, the substantia nigra has an inhibitory effect on the neurons of the thalamus.

Influence of the striatum on the thalamus. Irritation of the striatum causes the appearance of high-amplitude rhythms in the thalamus, characteristic of the non-REM sleep phase. The destruction of the striatum disrupts the sleep-wake cycle by reducing the duration of sleep.

Influence of the striatum on the motor cortex. The caudate nucleus of the striatum “brakes out” the degrees of freedom of movement that are unnecessary under given conditions, thus ensuring the formation of a clear motor-defensive reaction.

Stimulation of the striatum. Stimulation of the striatum in its various parts causes various reactions: turning the head and torso in the direction opposite to the irritation; delay in food production; suppression of pain.

The defeat of the striatum. The defeat of the caudate nucleus of the striatum leads to hyperkinesis (excessive movements) - chorea and athetosis.

Functions of the pale ball

From the striatum, the pale ball receives a predominantly inhibitory and partially excitatory influence. But it has a modulating effect on the motor cortex, cerebellum, red nucleus and reticular formation. The pale ball has an activating effect on the center of hunger and satiety. The destruction of the pale ball leads to weakness, drowsiness, emotional dullness.

The results of the activity of all basal ganglia:

development together with the cerebellum of complex motor acts;
control of motion parameters (strength, amplitude, speed and direction);
regulation of the sleep-wake cycle;
participation in the mechanism of formation of conditioned reflexes, complex forms of perception (for example, comprehension of the text);
participation in the act of inhibition of aggressive reactions.

The basal ganglia include the following anatomical formations:

the striatum (striatum), consisting of the caudate nucleus and the shell; pale ball (pallidum), subdivided into internal and external sections; substantia nigra and subthalamic nucleus of Lewis.

BG functions:

Centers of complex unconditioned reflexes and instincts
Participation in the formation of conditioned reflexes
Coordination of muscle tone and voluntary movements. Control of amplitude, strength, direction of movements
Coordination of combined motor acts
Eye movement control (saccades).
Programming complex purposeful movements
Centers of inhibition of aggressive reactions
Higher mental functions (motivation, forecasting, cognitive activity). Complex forms of perception of external information (for example, text comprehension)
Involved in the mechanisms of sleep

Afferent connections of the basal ganglia.

Most of the afferent signals coming to the basal ganglia enter the striatum. These signals come almost exclusively from three sources:

- from all areas of the cerebral cortex;

- from the intralamellar nuclei of the thalamus;

- from the substantia nigra (along the dopaminergic pathway).

Efferent fibers from the striatum go to the globus pallidus and substantia nigra. From the latter, not only the dopaminergic pathway to the striatum begins, but also the pathways leading to the thalamus.

The most important of all the efferent tracts of the basal ganglia originates from the inner part of the globus pallidus, ending in the thalamus, as well as in the roof of the midbrain. Through the stem formations, with which the basal ganglia are connected, centrifugal impulses follow to the segmental motor apparatus and muscles along the descending conductors.

- from red nuclei - along the rubrospinal tract;

- from the nucleus of Darkshevich - along the posterior longitudinal bundle to the nuclei of 3, 4,6 nerves and through it to the nucleus of the vestibular nerve;

- from the nucleus of the vestibular nerve - along the vestibulospinal tract;

- from the quadrigemina - along the tectospinal tract;

- from the reticular formation - along the reticulospinal tract.

Thus, the basal ganglia play mainly the role of an intermediate link in the chain connecting the motor areas of the cortex with all other areas of it.

Symptoms of damage to the basal ganglia.

Damage to the basal ganglia is accompanied by a wide variety of movement disorders. Of all these disorders, Parkinson's syndrome is the most well-known.

Gait - cautious, with small steps, slow, reminiscent of an old man's gait. The initiation of the movement is broken: it is not possible to move forward immediately. But in the future, the patient cannot immediately stop: he still continues to be pulled forward.

facial expressions- extremely poor, her face takes on a frozen mask-like expression. A smile, a grimace of crying with emotions belatedly arise and just as slowly disappear.

normal pose- the back is bent, the head is tilted to the chest, the arms are bent at the elbows, at the wrists, the legs are at the knee joints (pose of the petitioner).

Speech- quiet, monotonous, deaf, without sufficient modulation and sonority.

akinesia- (hypokinesia) - great difficulties in the manifestation and motor initiation: difficulty in starting and completing the movement.

Muscle stiffness- a constant increase in muscle tone, independent of the position of the joints and movements. The patient, having taken a certain position, keeps it for a long time, even if it is not comfortable. "Freezes" in the accepted position - plastic or wax rigidity. With passive movements, the muscles relax not gradually, but intermittently, as if in steps.

Resting tremor- trembling, which is observed at rest, is expressed in the distal extremities, sometimes in the lower jaw and is characterized by low amplitude, frequency and rhythm. The tremor disappears during purposeful movements and resumes after their completion (different from cerebellar tremor, which appears during movement and disappears at rest).

Parkinson's syndrome is associated with the destruction of the path (brake), going from the substantia nigra to the striatum. In the region of the striatum, the neurotransmitter dopamine is released from the fibers of this pathway. The manifestation of parkinsonism and, in particular, akinesia are successfully treated with the introduction of the precursor of dopamine - dopa. On the contrary, destruction of the globus pallidus and thalamus (ventrolateral nucleus), which interrupts the path to the motor cortex, leads to the suppression of involuntary movements, but does not relieve akinesia.

With damage to the caudate nucleus, athetosis develops - in the distal parts of the limbs, slow, worm-like, wriggling movements are observed at certain intervals, during which the limb assumes unnatural positions. Athetosis may be limited or widespread.

When the shell is damaged, chorea develops - it differs from athetosis in the speed of twitching and is observed in the proximal limbs and on the face. A rapid change in the localization of seizures is characteristic, then the facial muscles twitch, then the muscles of the leg, simultaneously the eye muscles and the arm, etc. In severe cases, the patient becomes like a clown. Often there is grimacing, smacking, speech is upset. Movements become sweeping, redundant, dancing gait.

The basal ganglia include the following anatomical formations: the striatum (striatum), consisting of the caudate nucleus and the shell; pale ball (pallidum), subdivided into internal and external sections; substantia nigra and subthalamic nucleus of Lewis.

BG functions:

Centers of complex unconditioned reflexes and instincts

Participation in the formation of conditioned reflexes

Coordination of muscle tone and voluntary movements. Control of amplitude, strength, direction of movements

Coordination of combined motor acts

Eye movement control (saccades).

Programming complex purposeful movements

Centers of inhibition of aggressive reactions

Higher mental functions (motivation, forecasting, cognitive activity). Complex forms of perception of external information (for example, text comprehension)

Involved in the mechanisms of sleep

Afferent connections of the basal ganglia. Most of the afferent signals coming to the basal ganglia enter the striatum. These signals come almost exclusively from three sources:

From all areas of the cerebral cortex;

From the intralamellar nuclei of the thalamus;

From substantia nigra (along the dopaminergic pathway).

From red nuclei - along the rubrospinal tract;

From the nucleus of Darkshevich - along the posterior longitudinal bundle to the nuclei of 3, 4,6 nerves and through it to the nucleus of the vestibular nerve;

From the nucleus of the vestibular nerve - along the vestibulospinal tract;

From the quadrigemina - along the tectospinal tract;

From the reticular formation - along the reticulospinal tract.

Thus, the basal ganglia play mainly the role of an intermediate link in the chain connecting the motor areas of the cortex with all other areas of it.

In the early phylogenesis, when the cerebral cortex was not yet developed, the striopallidar system was the main motor center that determined the behavior of the animal. Sensitive impulses flowing from the thalamus were processed here into motor impulses directed to the segmental apparatus and muscles. Due to the strio-pallidar apparatus, diffuse movements of the body of a rather complex nature were carried out: movement, swimming, etc.

At the same time, support was provided for general muscle tone, "readiness" of the segmental apparatus for action, redistribution of muscle tone during movements.

With the further evolution of the nervous system, the leading role in movements passes to the cerebral cortex with its motor analyzer and pyramidal system. Finally, a person has the most complex actions that are purposeful, arbitrary in nature with a fine differentiation of individual movements.

Nevertheless, the striopallidar system has not lost its significance in humans. It only passes into a subordinate, subordinated position, providing the “tuning” of the motor apparatuses, their “readiness for action” and the muscle tone necessary for the rapid implementation of the movement.

Formation of the function of the basal ganglia in ontogenesis. The basal ganglia develop more intensively than the visual tubercles. The pale nucleus is myelinated earlier than the striatum and cerebral cortex. It has been established that myelination in the globus pallidus almost completely ends by 8 months of fetal development. In the striatum, myelination begins in the fetus and ends only by 2 months of age. The caudate body during the first 2 years of life increases by 2 times, which is associated with the development of automatic motor acts in a child.

The motor activity of the newborn is largely associated with the pale nucleus, impulses from which cause uncoordinated movements of the head, trunk and limbs.

In a newborn, the pallidum already has connections with the thalamus, hypothalamus, and substantia nigra. The connection of the pallidum with the striatum develops later, some of the striopallidar fibers are myelinated in the first month of life, and the other part only by 6 months and later.

It is believed that acts such as crying are motorized by one pallidum. The development of the striatum is associated with the appearance of facial movements, and then the ability to sit and stand. Since the striatum has an inhibitory effect on the pallidum, a gradual separation of movements is created. In order to sit, the child must be able to hold his head and back upright. It appears at him to two months. Sitting begins at 6-8 months.

In the first months of life, the child has a negative support reaction: when you try to put him on his legs, he lifts them and pulls them to his stomach. Then this reaction becomes positive: when touching the support, the legs unbend. At 9 months, the child can stand with support, at 10 months, he stands freely.

From 4-5 months of age, voluntary movements develop rather quickly, but for a long time they are accompanied by various additional movements.

The appearance of voluntary (such as grasping) and expressive movements (smiling, laughing) is associated with the development of the striatal system and motor centers of the cerebral cortex. The child begins to laugh loudly from 8 months.

As all parts of the brain and cerebral cortex grow and develop, the movement of the child becomes less generalized and more coordinated. Only by the end of the preschool period is a certain balance of cortical and subcortical motor mechanisms established.

Symptoms of damage to the basal ganglia.