Where Is Balance Located In The Brain

Where Is Balance Located In The Brain – This article is about the vertebrate basal ganglia. For detailed information on primate-specific circuits, see Primate basal ganglia.

The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei found in the brains of vertebrates. In humans and some primates there are differences, mainly in the division of the globus pallidus into external and internal regions and in the division of the striatum. They are located at the base of the forebrain and at the top of the midbrain and have strong connections with the cerebral cortex, thalamus, brainstem and other areas of the brain. The basal ganglia are associated with a number of functions, including the regulation of voluntary motor movements, procedural learning, habit formation, conditioned learning,

Where Is Balance Located In The Brain

Where Is Balance Located In The Brain

The main functional components of the basal ganglia include the striatum, which consists of both the dorsal striatum (nucleus caudate and putam) and the ventral striatum (nucleus accumbs and olfactorius tuberculum), the globus pallidus, ventral pallidum, substantia nigra, and the subthalamic nucleus.

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Each of these components has complex internal anatomical and neurochemical structures. The largest component, the striatum (dorsal and ventral), receives input from various brain regions, but only sds output to other parts of the basal ganglia. The globus pallidus receives input from the striatum and inhibitory output from the sds to a number of motor areas. The substantia nigra is the source of striatal input for the neurotransmitter dopamine, which plays an important role in basal ganglia function. The subthalamic nucleus receives input mainly from the striatum and cerebral cortex and projects to the globus pallidus.

The basal ganglia are thought to play a key role in action selection and assist in choosing which behavior to perform. More specifically, they regulate motor and premotor cortical areas, facilitating smooth voluntary movements.

Experimental studies show that the basal ganglia have an inhibitory effect on a number of motor systems and that the release of this inhibition allows activation of the motor system. The “behavioral switching” that occurs in the basal ganglia is influenced by signals from many parts of the brain, including the prefrontal cortex, which plays a key role in executive functions.

It is also believed that the basal ganglia are not only responsible for the selection of motor actions, but also for the selection of more cognitive actions.

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The basal ganglia are of great importance for normal brain function and behavior. Their dysfunction results in a wide range of neurological conditions including disorders of behavioral and movement control, as well as cognitive deficits that are similar to those resulting from damage to the prefrontal cortex.

Behaviors include Tourette’s syndrome, obsessive-compulsive disorder, and addiction. Movement disorders include, in particular, Parkinson’s disease, which involves the degeneration of dopamine-producing cells in the substantia nigra; Huntington’s disease, which primarily involves damage to the striatum;

Dystonia; and more rarely hemiballismus. The basal ganglia have a limbic sector, the components of which are assigned different names: nucleus accumbs, vtral pallidum, and vtral tegmal area (VTA). There is considerable evidence that this limbic region plays a key role in reward learning, as well as in cognitive function and frontal lobe functioning, via the mesolimbic pathway from the VTA to the nucleus accumbens, which uses the neurotransmitter dopamine, and the mesocortical pathway. A number of highly addictive drugs, including cocaine, amphetamine, and nicotine, are thought to work by increasing the effectiveness of this dopamine signal. There is also evidence of overactivity of the VTA dopaminergic projection in schizophrenia.

Where Is Balance Located In The Brain

In terms of development, the human central nervous system is often classified based on the original three primitive vesicles from which it develops: These primary vesicles form in the normal development of the neural tube of the embryo and initially include the proscephalon, mescephalon, and rhombcephalon. , in rostral to caudal (head to tail) orientation. Later in the development of the nervous system, each part itself turns into smaller components. During development, the cells that migrate tangentially to form the basal ganglia are guided by the lateral and medial ganglion eminences.

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The following chart shows this developmental classification and traces it back to the anatomical structures found in the basal ganglia.

Coronal sections of the human brain showing the basal ganglia. White matter is shown in dark gray, gray matter is shown in light gray.

The basal ganglia form the basic component of the cerebrum. Unlike the cortical layer that lines the surface of the forebrain, the basal ganglia are a collection of distinct masses of gray matter lying deep in the brain not far from the thalamic junction. They lie on the side and surround the thalamus.

Like most parts of the brain, the basal ganglia consist of left and right sides that are virtual mirror images of each other.

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In terms of anatomy, the basal ganglia are divided into four distinct structures depending on how superior or rostral they are (in other words, depending on how close they are to the top of the head): Two of them, the striatum and the pallidum. , are relatively large; the other two, the substantia nigra and the subthalamic nucleus, are smaller. In the image on the right, two coronal sections of the human brain show the location of the components of the basal ganglia. It should be noted that this section does not show that the subthalamic nucleus and substantia nigra lie further back (posterior) in the brain than the striatum and pallidum.

The striatum is a subcortical structure generally divided into dorsal striatum and ventral striatum, although the medial lateral classification is believed to be more behaviorally relevant.

The striatum consists mainly of medium spiny neurons. These GABAergic neurons project to the external (lateral) globus pallidus and internal (medial) globus pallidus, as well as to the substantia nigra pars reticulata. Projections to the globus pallidus and substantia nigra are primarily dopaminergic, although kephalin, dynorphin, and substance P are expressed. The striatum also contains interneurons that divide into nitrergic neurons (due to the use of nitric oxide as a neurotransmitter), tonically active (i.e., constantly releasing neurotransmitter unless inhibited) cholinergic interneurons, parvalbumin-expressing neurons, and calretinin-expressing neurons.

Where Is Balance Located In The Brain

The dorsal striatum receives significant glutamatergic inputs from the cortex, as well as dopaminergic inputs from the substantia nigra pars compacta. The dorsal striatum is generally considered to be involved in ssorimotor activities. The ventral striatum receives glutamatergic inputs from limbic regions as well as dopaminergic inputs from the VTA via the mesolimbic pathway. The ventral striatum is thought to play a role in reward and other limbic functions.

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The dorsal striatum is divided by the internal capsule into the caudatum and putam, while the ventral striatum consists of the nucleus accumbs and the olfactorius tuberculum.

The caudate has three primary areas of connectivity, with the head of the caudate demonstrating connectivity to the prefrontal cortex, cingulate cortex, and amygdala. The body and tail show differences between the dorsolateral border and the ventral caudate, projecting into the ssorimotor and limbic regions of the striatum.

The pallidum consists of a large structure called the globus pallidus (“pale ball”) along with a smaller vtral excta called the vtral pallidum. The globus pallidus appears as a single nerve mass, but it can be divided into two functionally distinct parts, called the inner (or medial) and outer (lateral) segments, abbreviated GPi and GPe.

Both segments contain primarily GABAergic neurons, which therefore have inhibitory effects on their targets. These two segments participate in distinct neural circuits. The GPe receives input mainly from the striatum and projects to the subthalamic nucleus. The GPi receives signals from the striatum via “direct” and “indirect” pathways. Pallidal neurons work on the principle of disinhibition. These neurons fire at a steady high rate in the input abscissa, and signals from the striatum cause them to stop or decrease their firing rate. Because pallidal neurons themselves have inhibitory effects on their targets, the net effect of striatal input to the pallidum is to reduce the tonic inhibition exerted by pallidal cells on their targets (disinhibition) with increased firing rates to targets.

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Substantia nigra is part of the gray matter of the midbrain of the basal ganglia, which has two parts – pars compacta (SNc) and pars reticulata (SNr). The SNr often works together with the GPi, and the SNr-GPi complex inhibits the thalamus. However, the substantia nigra pars compacta (SNc) produces the neurotransmitter dopamine, which is very important for maintaining balance in the striatal pathway. The circuit section below explains the role and circuit connections of each of the components of the basal ganglia.

The subthalamic nucleus is a dicephalic part of the gray matter of the basal ganglia and the only part of the ganglia that produces the excitatory neurotransmitter, glutamate. The role of the subthalamic nucleus is to stimulate the SNr-GPi complex and is part of the indirect pathway. The subthalamic nucleus receives inhibitory input from the external part of the globus pallidus and sds excitatory input to the GPi.

Connectivity diagram showing excitatory glutamatergic pathways as red, inhibitory GABAergic pathways as blue, and modulatory dopaminergic pathways as magta. (Abbreviations: GPe: globus pallidus external; GPi: globus pallidus internal; STN: subthalamic nucleus; SNc: substantia nigra pars compacta; SNr: substantia nigra pars reticulata)

Where Is Balance Located In The Brain

Basal ganglia connectivity as revealed

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