The part of the brain located below the cortex is mainly represented, as I have already mentioned, by the white matter of which myelin-coated nerve fibers are composed. For example, directly above the ventricles - the cavities of the brain - is the corpus callosum, which connects the right and left hemispheres of the brain. Nerve fibers that cross the corpus callosum combine the brain into a single functional whole, but potentially the hemispheres can work independently of each other.
For clarification, you can give an example of the eyes. We have two eyes, which usually act together as one. Nevertheless, if we close one eye, we can see quite well with one eye. In no case can a one-eyed person be considered blind. Similarly, the removal of one hemisphere in an experimental animal does not make it brainless. The remaining hemisphere, in one way or another, takes on the functions of the remote. Usually each hemisphere is responsible, first of all, for “its” half of the body. If, leaving both hemispheres in place, you cross the corpus callosum, then the coordination of the halves of the brain is lost, and both halves of the body come under more or less independent control of the unconnected hemispheres of the brain. In a literal sense, two brains are formed in an animal. Such experiments were performed on monkeys. (After cutting the corpus callosum, some more fibers of the optic nerves were dissected so that each eye was connected with only one hemisphere of the brain.) After such an operation, it was possible to train each eye individually to perform various tasks. For example, a monkey can be taught to orient itself on a cross in a circle, as on a marker of a food container. If only the left eye is left open during training, only it will be trained to solve the problem. If after that you close the left eye of the monkey and open the right, then it will not cope with the task and will seek food by trial and error. If each eye is trained to solve opposite problems, and then both eyes are opened, then the monkey will solve them one at a time, changing activity. It seems that the hemispheres of the brain each time politely pass each other the baton.
Naturally, in such an ambiguous situation, when two independent brains control the functions of the body, there is always a danger of confusion and internal conflicts. To avoid this situation, one of the hemispheres (in a person is almost always left) becomes dominant, that is, dominant. Broca's speech-driving zone, which I mentioned, is located in the left hemisphere, and not in the right. The left hemisphere controls the right half of the body, and this explains the fact that the vast majority of people on Earth are right-handed. Moreover, even in left-handed people, the left hemisphere is still the dominant hemisphere. Ambidextras, which do not have a pronounced dominance of any one hemisphere, sometimes experience difficulties with the formation of speech in early childhood. The subcortical parts of the brain are not only composed of white matter. Under the bark are also compact areas of gray matter. They are called basal ganglia.
1 The word "ganglion" is of Greek origin and means "knot". Hippocrates and his followers called this word nodular-like subcutaneous tumors. Galen, a Roman physician who worked around 200 AD, began using the term to refer to clusters of nerve cells protruding along nerve trunks. In this sense, this word is used at the present time.
Above other basal ganglia in the under crust is a caudate nucleus. The gray matter of the caudate nucleus bends downward, forming the amygdala. On the side of the amygdala nucleus there is a lenticular nucleus, and between them is a layer of white matter called the inner capsule. The nuclei are not completely homogeneous formations, they also contain white matter of the pathways along which myelinated nerve fibers pass, which gives the basal ganglia a striped striation. Because of this, both nuclei received the unifying name of the striatum.
Inside the dome, formed by a complex of the striatum, caudate nucleus and lenticular nucleus, there is another large area of \u200b\u200bgray matter called the thalamus or optic tubercle.
The basal ganglia are difficult to study, since they are hidden deep beneath the cortex of the cerebral hemispheres. However, there are indications that the subcortical basal ganglia play a large role in brain functions - both active and passive. The white matter of the striatum can be considered in some sense a narrow bottleneck. It should be passed by all motor nerve fibers coming from the cortex, and all sensitive nerve fibers ascending to the cortex. Therefore, any damage in this area will lead to extensive damage to bodily functions. Such a lesion may, for example, deprive sensitivity and the ability to move the entire half of the body, the opposite of the hemisphere in which damage to the subcortical ganglia occurred. Such a one-sided lesion is called heminlegia (“a stroke of half the body”, Greek). (Loss of mobility is called the Greek term “paralysis", which means "relaxation." The muscles, so to speak, relax. The disease that leads to the sudden development of paralysis is often called a stroke or stroke, because a person affected by this ailment suddenly falls from his feet, as if from a blow by an invisible blunt object on the head.)
It has been suggested that one of the functions of the basal ganglia is to control the activity of the motor region of the cerebral cortex. (This function is inherent in the extrapyramidal system, of which the basal ganglia are part.) The subcortical nodes keep the cortex from being too reckless and quick to act. In case of violations in the basal ganglia, the corresponding sections of the cortex begin to discharge uncontrollably, which leads to convulsive involuntary contractions of the muscles. Typically, such disorders affect the muscles of the neck, head, hands and fingers. As a result, the head and hands are constantly trembling finely. This trembling is especially noticeable at rest. It decreases or disappears when any purposeful movement begins. In other words, trembling disappears when the cortex begins real actions, and does not produce individual rhythmic discharges.
The muscles of other groups become abnormally motionless in such cases, although there is no real paralysis. Mimicry loses its vitality, the face becomes masky, the gait is constrained, hands hang motionless along the body, without making the movements characteristic of walking. This combination of reduced mobility of the shoulders, forearms and face with increased pathological mobility of the head and hands was given the controversial name of tremor paralysis. Shivering paralysis was first described in detail by the English physician James Parkinson in 1817 and has since been called Parkinson's disease.
Some relief comes from the intentional damage to certain basal ganglia, which appear to be the cause of the “dog tremor”. One way is to use a thin probe to touch the affected area, which stops tremor (trembling) and stiffness (immobility). Then this area is destroyed by liquid nitrogen having a temperature of -50 ° C. With a relapse of symptoms, the procedure can be repeated. Obviously, a down node is better than a down node.
In some cases, damage to the basal ganglia leads to the appearance of more extensive disorders, manifested in the form of spastic contractions of large muscle masses. It seems that the patient performs a clumsy convulsive dance. These movements are called chorea ("chorea" - "dance", Greek.). Chorea can affect children after rheumatism, when the infectious process affects the subcortical formations of the brain. The first to describe this form of the disease in 1686 was the English physician Thomas Sydenham, which is why it is called the Sydenham chorea.
In the Middle Ages, even epidemic outbreaks of "dance mania" were observed, which at times covered regions and provinces. Probably, these were not epidemics of true chorea, the roots of this phenomenon must be sought in mental disorders. It must be thought that psychic mania was the result of observing cases of true chorea. Someone fell into the same state because of hysterical mimicry, while others followed him.
Measure, which led to outbreaks. A belief was born that it is possible to recover from this mania by making a pilgrimage to the tomb of St. Witt. For this reason, Sydenham’s chorea is also called “St. Witt’s Dance”.
There is also a hereditary chorea, often referred to as Huntington’s chorea, by the name of the American physician George Summer Huntington, who first described it in 1872. This is a more serious disease than the dance of St. Witt, which ultimately heals spontaneously. Gentiigton's chorea appears for the first time in adulthood (between 30 and 50 years old). At the same time, mental disorders develop. The condition of patients gradually worsens, and in the end death occurs. This is a hereditary disease, as one of its names says. Two brothers who had Huntington's chorea once migrated from England to the United States. It is believed that all patients in the United States are descendants of these brothers.
The thalamus is the center of somatosensory sensitivity - the center of perception of touch, pain, heat, cold and muscle feeling. This is a very important part of the reticular activating formation, which receives and sifts incoming sensory data. The strongest stimuli, such as pain, extremely high or low temperature, are filtered out in the thalamus, and milder stimuli in the form of touch, heat or coolness pass further to the cerebral cortex. It seems that only minor incentives can be entrusted to the cortex, which allow for a leisurely examination and a leisurely reaction. Gross stimuli, which require an immediate response and are urgent, are quickly processed in the thalamus, followed by a more or less automatic reaction.
Because of this, there is a tendency to distinguish between the cortex - the center of cold thoughts - and the thalamus - the center of hot emotions. Indeed, it is the thalamus that controls the activity of facial muscles under conditions of emotional stress, so that even if the cortical control of the same muscles is affected and the face remains masked in a calm state, it can suddenly be distorted by a cramp in response to a strong emotion. In addition, animals with bark removed are very easily enraged. Despite these facts, the idea of \u200b\u200bsuch a separation of functions between the cortex and the thalamus is an unacceptable simplification. Emotions cannot arise from any one, very small part of the brain - this must be clearly recognized. The emergence of emotions is a complex integrative process, which includes the activity of the cortex of the frontal and temporal lobes. Removal of the temporal lobes in experimental animals weakens the emotional response, although the thalamus remains intact.
In recent years, researchers have paid close attention to the most ancient in evolutionary terms sections of the subcortical structures of the old olfactory brain. These structures are associated with emotions and stimulants that provoke strong emotions - sexual and nutritional. This site appears to coordinate sensory data with bodily needs, in other words, with visceral needs. Parts of the visceral brain were called Broca's limbic lobe (“limb” in Latin means “border”), since this area surrounds and delimits the corpus callosum from the rest of the brain. For this reason, the visceral brain is sometimes called the limbic system.
Basal ganglia - This is a combination of three paired formations located in the final brain at the base of the cerebral hemispheres: phylogenetically its older part - the pale globe, later formation - the striatum and the youngest in evolutionary terms - the fence.
A pale ball consists of the outer and inner segments. The striatum is from the caudate nucleus and shell. A fence is a formation that lies between the shell and islet bark.
Functional relationships of the basal ganglia. The exciting afferent impulse enters the striatum mainly from three sources:
from all areas of the cerebral cortex directly through the thalamus;
from non-specific intralaminar nuclei of the thalamus;
from black matter.
Among the efferent connections of the basal ganglia, three main outputs can be distinguished:
from the striatum, the inhibitory paths 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 ganglia, going mainly to the thalamus (namely, its motor ventral nuclei), and from them the exciting path goes to the motor cortex;
part of the efferent fibers from the pale ball and striatum goes to the centers of the brain stem (reticular formation, red nucleus and further to the spinal cord), as well as through the lower olive to the cerebellum;
from the striatum, the inhibitory paths go to the black matter, and after switching to the thalamus nuclei.
Assessing the connections of the basal ganglia as a whole, scientists note that this structure is a specific intermediate link (switching station) connecting the associative and, partially, sensory cortex with the motor cortex.
Several parallel acting functional loops connecting the basal ganglia and the cerebral cortex are distinguished in the structure of the connections of the basal ganglia.
Skeletal motor loop. It connects the premotor, motor and somatosensory regions of the cortex with the shell of the basal ganglia, the impulse from which goes into the pale ball and black matter and then returns through the motor ventral nucleus to the premotor region of the cortex. Scientists believe that this loop serves to regulate motion parameters such as amplitude, strength, and direction.
Oculomotor loop. It connects the areas of the cortex that control the direction of view (field 8 of the frontal cortex and field 7 of the parietal cortex) with the caudate nucleus of the basal ganglia. From there, the impulse enters the pale ball and black substance, from which it is projected into the associative mediorsal and anterior relay ventral nuclei of the thalamus, respectively, and from them it returns to the frontal oculomotor field 8. This loop takes part in the regulation of, for example, spasmodic eye movements.
Scientists also suggest the existence of complex loops, through which the impulse from the frontal associative zones of the cortex enters the structures of the basal ganglia (caudate nucleus, pale ball, black substance) and returns through the mediorsal and ventral anterior nuclei of the thalamus to the associative frontal cortex. It is believed that these loops are involved in the implementation of higher psychophysiological functions of the brain: control of motivation, predicting the results of actions, cognitive (cognitive) activity.
Along with the identification of the direct functional connections of the basal ganglia as a whole, scientists also identify the functions of individual formations of the basal ganglia. One of these formations, as noted above, is the striatum.
Striatum functions. The main objects of the functional influence of the striatum are a pale ball, black substance, thalamus and motor cortex.
The effect of the striatum on a pale ball. It is carried out mainly through thin brake fibers. In this regard, the striatum exerts a inhibitory effect on the pale ball.
The effect of the striatum on the black substance. Between the black matter and the striatum there are two-way bonds. Striatal neurons have an inhibitory effect on neurons of the black substance. In turn, neurons of black matter through a dopamine mediator have a modulating effect on the background activity of striatal neurons. The nature of this influence (inhibitory, stimulating, or both) has not yet been established by scientists. In addition to influencing the striatum, black matter inhibits the thalamus neurons and receives exciting afferent inputs from the subthalamic nucleus.
The effect of the striatum on the thalamus. In the middle of the twentieth century, scientists found that irritation of the thalamus causes the appearance of manifestations typical of the slow sleep phase. Subsequently, it was proved that these manifestations can be achieved not only by irritation of the thalamus, but also of the striatum. The destruction of the striatum disrupts the cyclic pattern of sleep - wakefulness (reduces sleep time in this cycle).
The effect of the striatum on the motor cortex. Clinical studies conducted in 1980 O.S. Andrianov proved the inhibitory effect of the tail of the striatum on the motor cortex.
Direct stimulation of the striatum by implanting the electrodes, according to clinicians, causes relatively simple motor reactions: turning the head and body to the opposite side of irritation, bending the limb on the opposite side, etc. etc.), as well as suppressing the sensation of pain.
The defeat of the striatum (in particular its caudate nucleus) causes excessive movement. The patient, as it were, could not cope with his muscles. Experimental studies conducted on mammals showed that hyperactivity disorder develops steadily in animals with damage to the striatum. The number of aimless movements in space increases by 5 - 7 times.
Another formation of the basal ganglia is a pale ball, which also performs its functions.
Functions of a pale ball. Obtaining mainly inhibitory influences from the striatum, the pale ball has a modulating effect on the motor cortex, reticular formation, cerebellum and red nucleus. When stimulating a pale ball in animals, elementary motor reactions in the form of contraction of the muscles of the limbs, neck, etc. are predominant. In addition, the influence of the pale ball on some areas of the hypothalamus (the center of hunger and the posterior hypothalamus) was revealed, as evidenced by the activation of eating behavior noted by scientists. The destruction of the pale ball is accompanied by a decrease in motor activity. There is an aversion to any movements (adynamia), drowsiness, emotional dullness, it is difficult to implement existing and develop new conditioned reflexes.
Thus, the participation of the basal ganglia in the regulation of movements is the main, but not their only function. The most important motor function is the development (along with the cerebellum) of complex motor programs that are implemented through the motor cortex and provide the motor component of behavior. At the same time, the basal ganglia control such motion parameters as force, amplitude, speed and direction. In addition, the basal ganglia are included in the regulation of the sleep - wake cycle, in the mechanisms of formation of conditioned reflexes, in complex forms of perception (for example, comprehension of the text).
Questions for self-control:
What are the basal ganglia represented by?
General characteristics of the functional connections of the basal ganglia.
Characterization of the functional loops of the basal ganglia.
Functions of the striatum.
Functions of a pale ball.
The basal ganglia.
The accumulation of gray matter in the thickness of the cerebral hemispheres.
Function:
1) correction of a complex motor act program;
2) the formation of emotional-affective reactions;
3) assessment.
Basal nuclei have the structure of nuclear centers.
Synonyms:
Subcortical ganglia;
Basal ganglia;
Strio-pollidar system.
Anatomically to the basal nucleirelate:
Caudate nucleus;
Lenticular nucleus;
amygdala.
The head of the caudate nucleus and the anterior shell of the lenticular nucleus form a striatum.
The medially located part of the lenticular nucleus is called a pale ball. It represents an independent unit ( pallidum).
The connections of the basal nucleus.
Afferent:
1) from the thalamus;
2) from the hypothalamus;
3) from the tire of the midbrain;
4) from the substantia nigra, afferent pathways end on the cells of the striatum.
5) from the striatum to the pale ball.
The pale ball receives an afferent signal:
1) directly from the bark;
2) from the cortex through the thalamus;
3) from the striatum;
4 from the central gray matter of the diencephalon;
5) from the roof and tire of the midbrain;
6) from black substance.
Efferent fibers:
1) from a pale ball to the thalamus;
2) the caudate nucleus and shell send signals to the thalamus through a pale ball;
3) the hypothalamus;
4) black substance;
5) red core;
6) to the core of the lower olive;
7) the quadruple.
There is no exact information about the links between the fence and the amygdala.
Physiology of basal nuclei.
The wide connections of the BY cause the complexity of the functional significance of the BY in various neurophysiological and psychophysiological processes.
The participation of the BB was established:
1) in complex motor acts;
2) autonomic functions;
3) unconditioned reflexes (sexual, food, defensive);
4) sensory processes;
5) conditioned reflexes;
6) emotions.
The role of BB in complex motor acts is that they cause myotatic reflexes, optimal redistribution of muscle tone due to modulating effects on the underlying CNS structures involved in the regulation of movements.
Research Methods
1) irritation- electro and chemostimulation;
2) destruction;
3) electrophysiological method
4) dynamics analysis
5)
6) with implanted electrodes.
Destructionstriatum → disinhibition of the pale ball and midbrain structures (black substance, RF of the trunk), which is accompanied by a change in muscle tone and the appearance of hyperkinesis.
With the destruction of the pale ball or its pathology, muscle hypertonicity, rigidity, hyperkinesis are observed. However, hyperkinesis is associated not with the loss of function of a separate BB, but with a conjugated violation of the functions of the thalamus and midbrain, which regulate muscle tone.
EffectsBYA.
At stimulationshown:
1) ease of perception of motor and bioelectric manifestations of epileptiform reactions of the tonic type;
2) the inhibitory effect of the caudate nucleus and shell on a pale ball;
3) stimulation of the caudate nucleus and shell → disorientation, chaotic motor activity. It is connected with the transfer function of the BB of pulses from the Russian Federation to the crust.
Vegetative functions.Vegetative components of behavioral reactions.
Emotional reactions:
Mimic reactions;
Increased motor activity;
The inhibitory effect of caudate nucleus irritation on the intellect.
Studies of the influence of the caudate nucleus on conditioned reflex activity and purposeful movements indicate both inhibition and the facilitating nature of these influences.
Forebrain, basal ganglia and cortex.
Physiology of the basal ganglia.
These are paired nuclei located between the frontal lobes and the diencephalon.
Structures:
1. striatum (tail and shell);
2. a pale ball;
3. black substance;
4. the subthalamic nucleus.
Communication BG. Afferent.
Most of the afferent fibers enter the striatum from:
1. all areas of the crust of BP;
2. from the nuclei of the thalamus;
3. from the cerebellum;
4. from the substantia nigra through dopaminergic pathways.
Efferent bonds.
1. from the striatum to the pale ball;
2. to black substance;
3. from the inner part of the pale ball → the thalamus (and to a lesser extent to the roof of the midbrain) → the motor region of the cortex;
4. to the hypothalamus from a pale ball;
5. to the red nucleus and the Russian Federation → rubrospinal path, reticulospinal path.
BG function.
1. Organization of motor programs. This role is due to the connection with the cortex and other parts of the central nervous system.
2. Correction of individual motor reactions. This is due to the fact that the subcortical ganglia are part of an extrapyramidal system that provides correction of motor activity due to connections of the BG with motor nuclei. And the motor nuclei, in turn, are associated with the nuclei of FMN and the spinal cord.
3. Provide conditioned reflexes.
Research Methods
1) irritation- electro and chemostimulation;
2) destruction;
3) electrophysiological method(registration of EEG and evoked potentials);
4) dynamics analysisconditioned reflex activity against the background of stimulation or shutdown of BY;
5) analysis of clinical and neurological syndromes;
6) psychophysiological studieswith implanted electrodes.
Effects of irritation.
Striatum.
1. Motor reactions: there are slow (worm-like) movements of the head, limbs.
2. Behavioral reactions:
a) inhibition of orienting reflexes;
b) inhibition of volitional movements;
c) inhibition of the motor activity of emotions during food production.
Pale ball.
1. Motor reactions:
contraction of facial, masticatory muscles, contraction of limb muscles, in a change in the frequency of tremor (if any).
2. Behavioral reactions:
motor components of food-producing behavior are enhanced.
They are a modulator of the hypothalamus.
The effects of the destruction of nuclei and bonds between the structures of BG.
Between substantia nigra and striatum - Parkinson's syndrome - trembling paralysis.
Symptoms
1. hand trembling with a frequency of 4 to 7 Hz (tremor);
2. mask-like face - waxy rigidity;
3. the absence or sharp decrease in gestures;
4. careful walk in small steps;
In neurological studies - akinesia, that is, patients experience great difficulties before starting or ending movements. Parkinsonism is treated with the drug L– dopa, but should be taken for life, because parkinsonism is associated with impaired release of dopamine mediator by substantia nigra.
Effects of nuclear damage.
Striatum.
1. Athetosis - continuous rhythmic movements of the limbs.
2. Chorea - Strong, irregular movements, exciting almost all of the muscles.
These conditions are associated with the loss of the inhibitory effect of the striatum on a pale ball.
3. Hypotonus and hyperkinesis .
Pale ball.1.Hypertonicity and hyperkinesis. (stiffness of movements, depletion of facial expressions, plastic tone).
Basal ganglia
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Basal ganglia of the brain (striatal bodies)include three paired formations:
- Neostriatum (caudate nucleus and shell),
- Paleostriatum (pale ball),
- Fence.
Neostriatum Functions
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The neostriatum is an evolutionarily later formation than the paleostriatum and functionally inhibits it.
The functions of any formations of the brain are determined, first of all, by their connections with neostriatum.Neostriatum connections have a clear topographic orientation and functional outline.
The caudate nucleus and shell receive downward links mainly from the extrapyramidal cortex, but other fields of the cortex send a large number of axons to them. The main part of the axons of the caudal nucleus and shell goes to the pale ball, from here to the thalamus and only from it to the sensory fields.
Therefore, between these formations there is a vicious circle:
- neostriatum - paleostriatum - thalamus - bark - neostriatum.
The neostriatum also has functional connections with structures lying outside this circle: with the substantia nigra, red nucleus, Lewis body, vestibular nuclei, cerebellum, gamma cells of the spinal cord.
The abundance and nature of neostriatum connections attest to its participation in integrative processesin organization and regulation movementswork regulation autonomic organs.
In the interactions of the neostriatum and paleostriatum, inhibitory influences prevail among themselves. If the caudate nucleus is irritated, then most of the neurons of the pale ball are inhibited, part is first excited - then it is inhibited, a smaller part of the neurons is excited. In case of damage to the caudate nucleus, the animal develops motor hyperactivity.
The interaction of the substantia nigra with the neostriatum is based on direct and inverse relationships between them. Stimulation of the caudate nucleus enhances the activity of neurons of the black substance. Stimulation of the black substance leads to an increase, and its destruction reduces the amount of dopamine in the caudate nucleus. Dopamine is synthesized in the cells of the substantia nigra, and then transported at a speed of 0.8 mm per hour to the synapses of the neurons of the caudate nucleus. In a neostriatum, up to 10 μg of dopamine is accumulated per 1 g of nerve tissue, which is 6 times more than in other parts of the forebrain, for example, in a pale ball and 19 times more than in the cerebellum. Dopamine suppresses the background activity of most neurons of the caudate nucleus, and this allows you to remove the inhibitory effect of this nucleus on the activity of the pale ball. Thanks to dopamine, the disinhibition mechanism of interaction between the neo- and paleo-striatum appears. With a lack of dopamine in the neostriatum, which is observed with dysfunction of the black substance, the neurons of the pale ball disinhibition, activate the back-stem systems, this leads to motor disorders in the form of muscle stiffness.
Corticostrial connections are topically localized. So, the front areas of the brain are connected with the head of the caudate nucleus. Pathology arising in one of the interconnected areas: neostriatum bark, is functionally compensated by the preserved structure.
The neostriatum and paleostriatum take part in such integrative processes as conditioned reflex activityactive activity.This is revealed during their stimulation, destruction, and during the recording of electrical activity.
Direct irritation of some areas of the neostriatum causes the head to turn in the direction opposite to the irritated hemisphere, the animal begins to move in a circle, i.e. a so-called circulatory reaction occurs.
Irritation of other areas of the neostriatum causes the cessation of all types of activity of a person or animal:
- indicative
- emotional
- motor,
- food.
At the same time, slow-wave electrical activity is observed in the cerebral cortex.
In a person during a neurosurgical operation, stimulation of the caudate nucleus disrupts verbal contact with the patient: if the patient says something, he stops talking, and after the cessation of irritation does not remember that he was addressed. In cases of skull injuries with symptoms of neostriatum irritation in patients, retro-, antero- or retro-anterograde amnesia is noted. Irritation of the caudate nucleus at different stages of the development of the reflex leads to inhibition of the implementation of this reflex.
Irritation of the caudate nucleus can completely prevent the perception of painful, visual, auditory and other types of stimulation.
Irritation of the ventral region of the caudate nucleus reduces, and the dorsal region increases salivation.
A number of subcortical structures also receive inhibitory effects from the caudate nucleus. So, the stimulation of the caudate nuclei caused spindle-shaped activity in the optic tubercle, pale ball, subthalamic body, black matter, etc.
Thus, the inhibition of the activity of the caudate nucleus is inhibition of the activity of the cortex, subcortex, inhibition of unconditioned and conditioned-reflex behavior.
The caudate nucleus, along with inhibitory structures, is also exciting. Since the stimulation of the neostriatum inhibits the movements caused from other points of the brain, it can also inhibit the movements caused by the irritation of the neostriatum itself. At the same time, if its excitatory systems are stimulated in isolation, they cause this or that movement. If we assume that the function of the caudate nucleus is to ensure the transition of one type of motion to another, i.e. the cessation of one movement and the provision of a new one by creating postures, conditions for isolated movements, the existence becomes clear twofunctions of the caudate nucleus - brakeand exciting.
The effects of turning off the neostriatum showed that the function of its nuclei is associated with the regulation of muscle tone. So, when these nuclei were damaged, hyperkinesis of the type was observed: involuntary mimic reactions, tremors, athetosis, torsion spasm, chorea (twitching of limbs, trunk, as in an uncoordinated dance), motor hyperactivity in the form of aimless movement from place to place.
In case of damage to the neostriatum, there are disorders of higher nervous activity, difficulty in orientation in space, impaired memory, and a slowdown in body growth. After bilateral damage to the caudate nucleus, conditioned reflexes disappear for a long time, the development of new reflexes is difficult, differentiation, if formed, differs in fragility, delayed reactions cannot be developed.
When the caudate nucleus is damaged, the general behavior is characterized by stagnation, inertness, and the difficulty of switching from one form of behavior to another.
When exposed to the caudate nucleus, movement disorders occur:
- bilateral damage to the striatum leads to an unbridled desire to move forward,
- unilateral damage - leads to manege movements.
Despite the great functional similarities between the caudate nucleus and the shell, there are still a number of functions specific to the latter. For shellcharacteristic participation in the organization of eating behavior; a number of trophic disorders of the skin, internal organs (for example, hepatolecticular degeneration) occurs with a deficiency of shell function. Irritations of the shell lead to changes in breathing, salivation.
From the facts that stimulation of the neostriatum leads to inhibition of the conditioned reflex, one would expect that the destruction of the caudate nucleus will cause a relief in conditioned reflex activity. But it turned out that the destruction of the caudate nucleus also leads to inhibition of conditioned activity. Apparently, the function of the caudate nucleus is not just inhibitory, but consists in the correlation and integration of RAM processes. This is also evidenced by the fact that information on various sensory systems converges on the neurons of the caudate nucleus, since most of these neurons are polysensory. Thus, the neostriatum is a subcortical integrative and associative center.
The functions of the paleostriatum (pale ball)
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Unlike the neostriatum, stimulation of the paleostriatum does not cause inhibition, but provokes indicative reaction, limb movements, eating behavior(chewing, swallowing, etc.).
The destruction of the pale ball leads to hypomimia, physical inactivity, emotional dullness. Damage to the pale ball causes people to mask their faces, tremor of the head, limbs, and this tremor disappears at rest, in a dream and intensifies with movements, speech becomes monotonous. If the pale ball is damaged, myoclonus takes place - quick twitching of individual muscle groups or individual muscles of the hands, back, face. In a person with a pale ball dysfunction, the onset of movements becomes difficult, auxiliary and reactive movements when standing up disappear, friendly hand movements when walking are disrupted.
Fence Functions
The localization and small size of the fence present certain difficulties in its physiological study. This core has the form of a narrow strip of gray matter. Medially, it borders the outer capsule, laterally - with the extremum capsule.
The fence is closely connected with the islet cortex by both direct and feedback. In addition, links from the fence to the frontal, occipital, temporal cortex are traced, and feedback from the cortex to the fence is shown. The fence is connected with the olfactory bulb, with the olfactory cortex of its and contralateral side, as well as with the fence of the other hemisphere. Of the subcortical formations, the fence is associated with the shell, caudate nucleus, black matter, almond-shaped complex, optic tubercle, and a pale ball.
The responses of the fence neurons are widely presented to somatic, auditory, visual stimuli, and these reactions are mainly of an excitatory nature.
In the event of a complete degeneration of the fence, patients cannot speak, although they are fully conscious. Stimulation of the fence causes an indicative reaction, head rotation, chewing, swallowing, and sometimes vomiting. The effects of fence irritation on the conditioned reflex, the presentation of stimulation in different phases of the conditioned reflex slows down the conditioned reflex to the count, has little effect on the sound reflex. If irritation was carried out simultaneously with the supply of a conditioned signal, then the conditioned reflex was inhibited. Stimulating the fence while eating inhibits eating food. If the fence of the left hemisphere is damaged in a person, speech disorders are observed.
Thus, the basal ganglia of the brain are integrative centersthe organization motor skills, emotions, higher nervous activity.
Moreover, each of these functions can be enhanced or inhibited by the activation of individual formations of basal nuclei.
In the article we will talk about the basal ganglia. What is it and what role does this structure play in human health? All questions will be discussed in detail in the article, after which you will understand the importance of absolutely every “detail” in your body and head.
What is this about?
We all know very well that the human brain is a very complex unique structure in which absolutely all elements are inextricably and firmly connected with the help of millions of neural connections. There is gray in the brain and the first is the usual accumulation of many nerve cells, and the second is responsible for the speed of transmission of impulses between neurons. In addition to the bark, naturally, there are other structures. They are nuclei or basal ganglia, consisting of gray matter and located in white. In many ways, they are responsible for the normal functioning of the nervous system.
Basal Ganglia: Physiology
These nuclei are located near the cerebral hemispheres. They have a lot of processes of large length, which are called axons. Thanks to them, information, that is, nerve impulses, is transmitted to different brain structures.
Structure
The structure of the basal ganglia is diverse. Basically, according to this classification, they are divided into those that belong to the extrapyramidal and limbic system. Both of these systems have a huge impact on the functioning of the brain, are in close interaction with it. They affect the thalamus, parietal and frontal lobes. Extrapyramidal network consists of basal ganglia. The subcortical parts of the brain are completely penetrated by it, and it has the most important influence on the work of all the functions of the human body. These modest formations very often remain underestimated, and yet their work has not yet been fully studied.
Functions
The functions of the basal ganglia are not many, but they are significant. As we already know, they are strongly connected with all other brain structures. Actually, from the understanding of this statement the main ones follow:
- Monitoring the implementation of integration processes in higher nervous activity.
- Influence on the work of the autonomic nervous system.
- Regulation of human motor processes.
What are they involved in?
There are a number of processes in which kernels are directly involved. The basal ganglia, the structure, development and functions of which we are considering, participate in such actions:
- affect a person’s dexterity when using scissors;
- precision nailing;
- reaction speed, dribbling, accuracy of getting into the basket and knocking-off dexterity of the ball when playing basketball, football, volleyball;
- voice possession while singing;
- coordination of actions while digging the earth.
Also, these nuclei affect complex motor processes, for example, fine motor skills. This is expressed in the way the hand moves while writing or drawing. If the work of these brain structures is impaired, then the handwriting will be illegible, rude, "uncertain." In other words, it will seem that a person only recently picked up a pen.
New studies have proven that basal ganglia can also affect the type of movement:
- controllable or sudden;
- repeated many times or new, completely unknown;
- simple monosyllables or sequential and even simultaneous.
Many researchers reasonably believe that the functions of the basal ganglia are that a person can act automatically. This suggests that many of the actions that a person performs on the go, without paying special attention to them, are possible precisely thanks to the cores. The physiology of the basal ganglia is such that they control and regulate the automatic activity of a person, without taking resources from the central nervous system. That is, we must understand that it is these structures that largely control how a person acts under stress or in an incomprehensible dangerous situation.
In ordinary life, the basal nuclei simply transmit impulses that come from the frontal lobes to other brain structures. The goal is the targeted implementation of known actions without stress on the central nervous system. However, in dangerous situations, the ganglia "switch" and allow a person to automatically make the most optimal decision.
Pathology
Lesions of the basal ganglia can be very different. Let's consider some of them. These are degenerative lesions of the human brain (for example, Parkinson's disease or Huntington's chorea). These can be hereditary genetic diseases that are associated with metabolic disorders. Pathologies characterized by malfunctions of the enzyme systems. Diseases of the thyroid gland can also occur due to abnormalities in the functioning of the nuclei. Possible pathologies resulting from manganese poisoning. Brain tumors can affect the operation of the basal nuclei, and this is perhaps the most unpleasant situation.
Pathology Forms
Researchers conditionally distinguish two main forms of pathology that can occur in humans:
- Functional problems. This is often found in children. The reason in most cases is genetics. May occur in adults after a stroke, severe injury, or hemorrhage. By the way, in old age it is a violation of the extrapyramidal system of a person that causes Parkinson's disease.
- Tumors and cysts. Such a pathology is very dangerous, it requires immediate medical attention. A characteristic symptom is the presence of serious and protracted neurological diseases.
It is also worth noting that the basal ganglia of the brain can affect the flexibility of human behavior. This means that a person begins to get lost in various situations, cannot quickly react, adapt to difficulties, or simply act according to his usual algorithm. It is also difficult to understand how, according to the logic of things, one must act in a situation that is simple for a normal person.
The defeat of the basal ganglia is dangerous because a person becomes practically uneducable. This is logical, because learning is like an automated task, and these kernels are responsible for such tasks, as we know. However, it is treatable, albeit very slow. In this case, the results will be insignificant. Against this background, a person ceases to control his coordination of movements. From the side it seems that he moves sharply and impetuously, as if twitching. In this case, tremor of the extremities or some involuntary actions can really occur, over which the patient is not in control.
Correction
The treatment for the disorder depends entirely on what caused it. The treatment is carried out by a neuropathologist. Very often, a problem can only be solved with the help of a constant intake of drugs. These systems are not able to recover independently, and alternative methods are extremely rare. The main thing that is required of a person is a timely visit to a doctor, as only this will improve the situation and even avoid very unpleasant symptoms. The doctor makes a diagnosis, observing the patient. Also, modern diagnostic methods are used, such as MRI and CT of the brain.
Summing up the article, I want to say that for the normal functioning of the human body, and in particular the brain, the correct functioning of all its structures, and even those that at first glance may seem completely insignificant, is very important.