Basal ganglia


A set of subcortical structures that direct intentional movements.

The basal ganglia are located near the thalamus and hypothalamus.

The basal ganglia is a group of nuclei in the brain that are interconnected with the cerebral cortex, thalamus, and brainstem. 

Just underneath the cerebral cortex are interconnected subcortical masses of grey matter, the basal ganglia (or nuclei). 

The basal ganglia receive input from the substantia nigra of the midbrain and motor areas of the cerebral cortex, and send signals back to both of these locations. 

The basal ganglia are involved in motor control, and are found lateral to the thalamus. 

The main components of the basal ganglia are the caudate nucleus, the putamen, the globus pallidus, the substantia nigra, the nucleus accumbens, and the subthalamic nucleus. 

The putamen and globus pallidus are also collectively known as the lentiform nucleus, because together they form a lens-shaped body. 

The putamen and caudate nucleus are also collectively called the corpus striatum after their striped appearance.

They receive input from the cerebral cortex, which sends outputs to the motor centers in the brain stem.

A part of the basal ganglia called the striatum controls posture and movement.

If there is an inadequate supply of dopamine, the striatum is affected, which can lead to visible behavioral symptoms of Parkinson’s disease.

Refers to a group of subcortical nuclei, of varied origin, which are situated at the base of the forebrain.

They are strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas.

Associated with a variety of functions including: control of voluntary motor movements, procedural learning, habit learning, eye movements, cognition, and emotion.

Main components are the striatum; both dorsal striatum (caudate nucleus and putamen) and ventral striatum (nucleus accumbens and olfactory tubercle), globus pallidus, ventral pallidum, substantia nigra, and subthalamic nucleus.


The components of the striatum have complex internal anatomical and neurochemical organization.

The basal ganglia form a fundamental component of the cerebrum.

In contrast to the cortical layer that lines the surface of the forebrain, the basal ganglia are masses of gray matter lying deep in the brain not far from the junction of the thalamus.

The basal ganglia lie to the side of and surround the thalamus, and consist of left and right sides that are virtual mirror images of each other.

Divided into four distinct structures: striatum. pallidum, substantia nigra and the subthalamic nucleus,

The striatum and the pallidum, are relatively large.

The substantia nigra and the subthalamic nucleus, are smaller.

The subthalamic nucleus and substantia nigra lie farther back in the brain than the striatum and pallidum.

The striatum is a subcortical structure generally divided into the dorsal striatum and ventral striatum, or a medial lateral classification

The striatum is composed mostly of medium spiny GABAergic neurons, which project to the external (lateral) globus pallidus and internal (medial) globus pallidus as well as the substantia nigra pars reticulata.

The projections of the striatum into the globus pallidus and substantia nigra are primarily dopaminergic, enkephalin, dynorphin and substance P are also expressed.

The striatum also contains interneurons that use nitric oxide as a neurotransmitter, have cholinergic interneurons, and have parvalbumin and calretinin-expressing neurons.

The dorsal striatum is involved in sensorimotor activities.

The ventral striatum is believed to play a role in reward and other limbic functions.

The dorsal striatum is divided into the caudate and putamen by the internal capsule while the ventral striatum is composed of the nucleus accumbens and olfactory tubercle.

The head of the caudate demonstrating connectivity to the prefrontal cortex, cingulate cortex and amygdala.

The body and tail of the caudate project to the sensorimotor and limbic regions of the striatum respectively.

Striatopallidal fibers connect the striatum to the pallidus.

The pallidum consists of the globus pallidus together with a smaller ventral extension called the ventral pallidum.

The globus pallidus appears anatomically as a single neural


The globus pallidus can be divided into two functionally distinct parts, called the internal (or medial) and external (lateral) segments.

Both segments of the the globus pallidus contain primarily GABAergic neurons, which therefore have inhibitory effects on their targets.

Pallidal neurons operate by a disinhibition principle, firing at steady high rates in the absence of input, and signals from the striatum cause them to pause or reduce their rate of firing.

The net effect of striatal input to the pallidum is a reduction of the tonic inhibition exerted by pallidal cells on their targets with an increased rate of firing in the targets.

The substantia nigra is a midbrain gray matter portion of the basal ganglia.

The substantia nigra has two parts -the pars compacta and the pars reticulata.

The pars substantia nigra often works in unison with the globus pallidus, and the pars reticulata complex inhibits the thalamus.

Substantia nigra pars compacta however, produces the neurotransmitter dopamine, which is significant in maintaining balance in the striatal pathway.

The subthalamic nucleus is a diencephalic gray matter of the basal ganglia

The subthalamic nucleus the only portion of the ganglia that produces the excitatory neurotransmitter, glutamate.

The subthalamic nucleus’ role is to stimulate the substantia nigra reticulata -Globus pallidus complex.

The subthalamic nucleus receives inhibitory input from the external part of the globus pallidus and sends excitatory input to the globus pallidus internal.

The basal ganglia circuitry is divided into a limbic, two associative prefrontal, an oculomotor and one motor pathway.

Its direct pathway has been proposed to facilitate motor actions, timing of motor actions, gating of working memory, and motor responses to specific stimuli.

The indirect pathway originates in the dorsal striatum and inhibits the globes pallidus externa , resulting in disinhibition of the globes pallidus interna, which is then free to inhibit the thalamus.

A combination of these indirect pathways resulting in a hyperdirect pathway that results in inhibition of basal ganglia inputs besides one specific focus has been proposed as part of the center surround theory.

The basal ganglia contains many afferent glutamatergic inputs, with predominantly GABAergic efferent fibers.

The basal ganglia contains modulatory cholinergic pathways, significant dopamine in the pathways originating in the ventral tegmental area and substantia nigra, as well as various neuropeptides.

Basal ganglia neuropeptides include substance P, neurokinin A, cholecystokinin, neurotensin, neurokinin B, neuropeptide Y, somatostatin, dynorphin, enkephaline.

Neuromodulators found in the basal ganglia include nitric oxide, carbon monoxide, and phenylethylamine.

The basal ganglia has a role in controlling eye movements that is influenced by a network of brain regions that converges on a midbrain area called the superior colliculus.

The superior colliculus form two-dimensional retinotopic maps of visual space, and neural activity drives an eye movement directed toward the corresponding point in space.

The superior colliculus is strongly inhibited by the basal ganglia, originating in the substantia nigra pars reticulata.

Neurons in the substantia nigra pars reticulata. usually fire continuously at high rates, but at the onset of an eye movement they pause, thereby releasing the superior colliculus from inhibition.

Basal ganglia disease is a group of movement disorders that result from either excessive output from the basal ganglia to the thalamus, called hypokinetic disorders, or from insufficient output, named hyperkinetic disorders.

Hypokinetic disorders arise from an excessive output from the basal ganglia, which inhibits the output from the thalamus to the cortex, and thus limits voluntary movement.

Hyperkinetic disorders result from a low output from the basal ganglia to the thalamus.

Hyperkinetic disorders does not have enough inhibition to the thalamic projections to the cortex and thus gives uncontrolled/involuntary movements.

Disorders that have been linked to the basal ganglia:



Athymhormic syndrome

Attention-deficit hyperactivity disorder (ADHD)



Cerebral palsy: basal ganglia damage during second and third trimester of pregnancy



Fahr’s disease

Foreign accent syndrome (FAS)

Huntington’s disease


Lesch-Nyhan syndrome

Major Depressive Disorder

Obsessive-compulsive disorder

Other anxiety disorders


Parkinson’s disease

Spasmodic dysphonia


Sydenham’s chorea

Tardive dyskinesia

Tourette’s disorder

Wilson’s disease


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