The basal ganglia are a group of nuclei located within the cerebral hemispheres that include the caudate nucleus, lentiform nucleus, amygdaloid nucleus, and claustrum. The caudate nucleus has a C-shape and is located medial to the internal capsule, while the lentiform nucleus has a biconvex lens shape and is located lateral to the internal capsule. The basal ganglia facilitate purposeful movements and inhibit unwanted movements through connections between the cortex, substantia nigra, globus pallidus, thalamus, and other regions. Diseases that impact the basal ganglia like Parkinson's disease, Huntington's disease, and Sydenham's chorea can lead to movement disorders.

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Basal Ganglia
(Short note/long question)
Introduction:
 It is a number of nuclear (grey matter) masses which lie within the cerebral hemisphere.
They consists of :
 Caudate nucleus
 Lentiform nucleus : Putamen and Globus pallidus
 Amygdaloid nucleus
 Claustrum.
Corpus striatum: Caudate nucleus and putamen part of lentiform nucleus form corpus striatum
(Neostriatum) (They are known as corpus striatum due to appearance of alternating band of
grey and white matter at fused part of head of caudate nucleus and putamen with fibers of
internal capsule).
Globus pallidus in part of paleostriatum.
(No need to draw this diagram- only for understanding)

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Caudate nucleus: (*****Important - Viva)
 It is “C” shape nucleus located medial to internal capsule projecting in the cavity of
lateral ventricle.
Parts of Caudate nucleus:
1. Head: located in the floor of anterior horn of lateral ventricle and partly fused
with putamen of lentiform nucleus.
2. Body: located in the floor of central part of lateral ventricle.
3. Tail: Tapering part located in the roof of inferior horn of lateral ventricle and
connected to amygdaloid nucleus
(Draw this Diagram for the short note)
Lentiform nucleus: (*****Important - Viva)
 It is biconvex lens shape nucleus located lateral to internal capsule.
 Parts of lentiform nucleus:
1. Putamen: lateral and dark coloured nucleus and partly fused with head of
caudate nucleus.
2. Globus pallidus: medial and pale coloured nuclus.

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Amygdaloid nucleus:
 It is small nucleus located in the roof of inferior of lateral ventricle.
Claustrum:
 It is strip of grey matter lateral to lentiform nucleus.
Connections of Basal Ganglia:
Connections and neurotransmitters of Corpus striatum:
 Afferent fibers:
1. Corticostriate fibers: from cortex of cerebrum to corpus striatum (Caudate
nucleus and putamen). Glutamate is neurotransmitter and excitatory to corpus
striatum
2. Nigrostriatal fibers: from substantia nigra (Midbrain) to corpus striatum
(Caudate nucleus and putamen). These are dopaminergic neurons and inhibitory
to corpus striatum and degeneration of these neurons leads to Parkinson’s
disease.
 Efferent fibers:
1. Striatonigral fibers: from corpus striatum (Caudate nucleus and putamen) to
substantia nigra (Midbrain).
2. Striatopallidal fibers: from corpus striatum (Caudate nucleus and putamen) to
globus pallidus. GABA is neurotransmitter and inhibitory to globus pallidus.
Connections of Globus pallidus:
 Afferent fibers:
1. Striatopallidal fibers: from corpus striatum (Caudate nucleus and putamen) to
globus pallidus.
 Efferent fibers:
1. Pallidothalamic fibers: From Globus pallidus to thalamus via ansa lenticularis or
lenticularis fasciculus and from thalamus they go to cortex of cerebrum via
thalamocortical radiation.
2. Pallidosubthalamic fibers: From Globus pallidus to subthalamus and from
subthalamus.

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(Draw this Diagram for the short note)

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(No need to draw this diagram- only for understanding)
 Function of Basal ganglia:
1. Their function is to facilitate purposeful behaviour and movements and to
inhibit unwanted or inappropriate (not suitable ) movements.
2. They are also responsible for synchronized movements of limbs e.g. swinging
of arms while walking.
3. Amygdaloid nucleus is concerned with aggressive behavior.

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 Applied Anatomy of Basal ganglia:
1. Huntington’s Disease
It is an degenerative autosomal dominant inherited disease with the onset
occurring in adult life. Within the striatum, there is progressive degeneration of
the globus pallidus ( indirect segment ).
Choreiform movements first appear as involuntary movements of the
extremities and twitching of the face (facial grimacing).
Progressive dementia occurs with loss of memory and intellectual capacity There
is degeneration of the GABA; P-secreting and acetylcholine-secreting.
2. Parkinson’s disease
It is a neurodegenerative disease of elderly, of unknown cause. It is characterized
by akinesia, flexed posture, rigidity and a resting tremor and mask like face.
It is due to loss of striatal dopamine levels. It is treated by levodopa which
restores normal striatal function
3. Sydenham’s Chorea ( St Vitus’ dance )
The patient exhibits involuntary, quick, jerky, spasmodic, irregular movements
that are nonrepetitive. Sudden movements of the head; trunk or limbs. It is a
common manifestation of rheumatic fever.
4. Hemiballism
Sudden choreiform movements of the limbs on one side of the body. It caused
by a lesion of contralateral subthalamic nucleus.
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