Basal ganglia of the brain

What are the basal ganglia?

The basal ganglia of the brain are functionally and anatomically related accumulations of gray matter in the deep parts of the brain. These structures are deepened into the white matter, which functions as an information transmitter. Even in the embryo, the basal ganglia develop from the ganglion tubercle, then forming into mature brain structures that perform strictly specific functions in the nervous system.

The basal ganglia are located at the base of the brain, lateral to the thalamus. Anatomically highly specific nuclei are part of the forebrain, which is located on the border of the frontal lobes and the brainstem. Often, by the term “ subcortex ”, experts mean precisely the set of basal ganglia of the brain.

Anatomists distinguish three concentrations of gray matter:

Striped body . This structure means a set of two not entirely differentiated parts: The caudate nucleus of the brain. It has a thickened head, forming in front one of the walls of the lateral ventricle of the brain. The thin tail of the nucleus is adjacent to the bottom of the lateral ventricle. The caudate nucleus also borders the thalamus.
Lenticular nucleus . This structure runs parallel to the previous accumulation of gray matter and, closer to the end, merges with it, forming the striatum. The lenticular nucleus consists of two white layers, each of which has its own name (globus pallidus, shell).

Corpus striatum received its name due to the alternating arrangement of white stripes on its gray matter. Recently, the lenticular nucleus has lost its functional meaning, and it is called exclusively in a topographical sense. The lenticular nucleus, as a functional compilation, is called the striopallidal system.

The fence or claustrum is a small thin gray plate located near the shell of the striatum.
Amygdala . This core is located under the shell. This structure also belongs to the limbic system of the brain. The amygdala usually means several separate functional formations, but they were combined due to their close location. This area of the brain has multiple connections with other brain structures, in particular with the hypothalamus, thalamus and cranial nerves.

The concentration of white matter is:

Internal capsule - white matter between the thalamus and the lentiform nucleus
Outer capsule - white substance between the lentil and the fence
The outermost capsule is the white substance between the enclosure and the insula.

The internal capsule is divided into 3 parts and contains the following pathways:

Front leg:

Frontothalamic tract - connection between the frontal cortex and the mediadersal nucleus of the thalamus
Frontopontine tract - connection between the frontal cortex and the pons

Knee:

Corticonuclear tract - connection between the nuclei of the motor cortex and the nuclei of the motor cranial nerves

Rear leg:

Corticospinal tract - conducts motor impulses from the cerebral cortex to the nuclei of the motor horns of the spinal cord
Thalamo-parietal fibers - Axons of thalamic neurons are connected to the postcentral gyrus
Temporo-parieto-occipital-pontine fasciculus - connects the pontine nuclei with the lobes of the brain
Auditory radiance
Visual radiance

Difference between the mantle and other structures of the telencephalon, 3 stages of development of the cortex

The cloak covers all other parts of the telencephalon. Consists of gray and white matter.

Gray matter - the cortex, is represented by clusters of neuron bodies lying on the surface (above the white matter).

White matter - pathways.

Three stages of cortex development:

The ancient cortex - the cells above the white matter - are not organized and are located chaotically. Located on the basal surface, closer to the amygdala.
Old cortex - the appearance of elements of ordered nerve cells by similarity and function. Layers are formed (no more than three). Located on the medial surface, next to the central part of the olfactory brain.
New cortex - cells are strictly ordered, differ in shape and function. Form layers (6 layers). Cells in different areas are different: Cytoarchitectonic fields (about 130),
Myelarchitectonic fields (100) - differences in the structure of processes,
Neuroarchitectonic fields (80) - along neuroglia,
Angioarchitectonic fields - according to the vascular pattern.

Functions of the basal ganglia

The basal ganglia provide the entire range of functions for maintaining the basic functioning of the body, be it metabolic processes or basic vital functions. Like any regulatory center in the brain, the set of functions is determined by the number of its connections with neighboring structures. The striopallidal system has many such connections with the cortical regions and areas of the brainstem. The system also has efferent and afferent pathways. The functions of the basal ganglia include:

control of the motor sphere: maintaining an innate or learned posture, ensuring stereotypical movements, response patterns, regulation of muscle tone in certain poses and situations, fine motor skills and integration of small motor movements (calligraphic writing);
speech, vocabulary;
the onset of sleep;
vascular reactions to changes in pressure, metabolism;
thermoregulation: heat transfer and heat generation.
In addition, the basal ganglia provide the activity of protective and orientation reflexes.

What 3 morphological substrates provide analytical and synthetic function?

Cloak functions:

1) Analytical - decomposition of objects and phenomena into individual characteristics.

For this purpose, there is a cortical center - a section of the cortex that contributes to the perception of one sign.

The bark itself consists of:

Cortical nucleus (contains cells specialized in one trait);
The scattered part (contains cells that perform the sensation of one sign, but can be rearranged to another sign).

2) Synthetic function - an idea of an object or phenomenon is made up of individual features. Synthetic functions perform:

Associative fields are the zone of intersection of the peripheral (scattered) parts of several cortical centers. Here are cells that are initially capable of performing two functions.
Association nerve fibers.

Symptoms of basal ganglia dysfunction

When the basal ganglia are damaged or dysfunctional, symptoms associated with impaired coordination and precision of movements occur. Such phenomena are called the collective concept of “ dyskinesia ,” which, in turn, is divided into two subtypes of pathologies: hyperkinetic and hypokinetic disorders. Symptoms of basal ganglia dysfunction include:

akinesia;
impoverishment of movements;
voluntary movements;
slow movements;
increase and decrease in muscle tone;
muscle tremor in a state of relative rest;
desynchronization of movements, lack of coordination between them;
poor facial expressions, scanned language;
erratic and arrhythmic movements of small muscles of the hand or fingers, the entire limb or part of the whole body;
pathological postures unusual for the patient.

Most manifestations of the pathological functioning of the basal ganglia are based on disturbances in the normal functioning of the neurotransmitter systems of the brain, in particular the dopaminergic modulating system of the brain. In addition, however, the causes of symptoms are previous infections, mechanical brain injuries or congenital pathologies.

Consequences of basal ganglia pathologies

Manifestations of pathology, even with successful treatment, will accompany the patient throughout his life and can cause disability. The development of the disease is most often corrected by taking medications, physiotherapeutic procedures, physical exercise, and strengthening the nervous system.

As you know, the adaptive forces of the body are great. But at the same time, the sick person and his relatives need to be patient and follow all the specialists’ instructions: the effectiveness of rehabilitation measures and future adaptation in society depend on this.

Pathological states of nuclei

The most common pathologies of the basal ganglia are:

Cortical palsy . This pathology is formed as a result of damage to the globus pallidus and the striopallidal system as a whole. Paralysis is accompanied by tonic spasms of the legs or arms, torso, and head. A patient with cortical paralysis makes chaotic slow movements with a small scope, stretches out his lips and moves his head. A grimace appears on his face, he twists his mouth.

Parkinson's disease . This pathology is manifested by muscle rigidity, impoverishment of motor activity, tremor and instability of body position. Modern medicine, unfortunately, has no alternatives other than symptomatic therapy. Drugs only relieve the symptoms of the disease without eliminating its cause.

Getington's disease is a genetically determined pathology of the basal ganglia. In addition to the physical manifestations of the disease (chaotic movements, involuntary muscle contractions, lack of coordination, spasmodic eye movements), patients also suffer from mental disorders. As the pathology progresses, patients undergo qualitative personality changes, their mental abilities are weakened, and the ability to think abstractly is lost. At the end of the pathology, as a rule, doctors are presented with a depressed, panicky, selfish and aggressive patient with weakened cognitive abilities.

Diagnosis and prognosis of pathology

Identification of pathologies of the basal ganglia begins in the office of a neurologist. If other deviations are present, then the help of functional diagnostic specialists may be needed.

The final diagnosis is made based on the following studies:

History;
General neurological and physical examination;
MRI or CT;
Examination of the blood supply to the brain;
Ultrasound;
Electroencephalography.

The prognosis of the pathology depends on many external factors: age, gender, general condition of the patient, the degree of the disease, the time of its detection and the effectiveness of the proposed treatment. However, according to statistics, in 50% of cases it is unfavorable.

After therapy and rehabilitation, the remaining patients still have a chance to adapt and lead a normal life in society.

Connections to the limbic system

Internal (short) connections - pass through two circles of Papets (large, small circle)

Impulses through the internal connections of the limbic system flow into the hippocampus and amygdala complex - this is the core of the limbic system.

External (long) connections:
Communication with all cortical centers;
With all associative fields of the cortex (integrative areas of the cortex);
Bilateral communication with the hypothalamus, reticular formation, brain stem.

In addition, the drug receives collaterals from all sensitive pathways.

Localization of centers of the second signaling system

The second signaling system is the provision of higher nervous activity in humans. All centers are reduced to human speech:

The center of speech articulation is in the posterior part of the inferior frontal gyrus;
The center of writing and written speech is in the posterior part of the middle frontal gyrus;
The center for the perception of oral speech is the upper section of the superior temporal gyrus;
The center of reading and perception of written speech is the angular gyrus.

The centers of the second signaling system are located next to those similar in function to the first signaling system.