BASAL
GANGLIA
DR. BERYL S. OMINDE
LEARNING OUTCOMES
By the end of this lecture, you should be able to describe the
following regarding the basal ganglia;
1. The anatomical and functional components
2. Phylogenetic classification
3. Functions
4. Connections; Direct and indirect pathway
5. Lesions of the basal ganglia
Introduction
Corpus striatum- caudate, putamen, globus pallidus
Striatum- caudate, putamen
Lentiform nucleus- putamen, globus pallidus
Corpus striatum
• Location: Lateral to thalamus
• Divisions: Caudate and Lentiform nuclei
• Internal capsule: A white mater band of nerve fibers
• Separates the nuclei, except at their anteroinferior ends, where grey matter bridges give a striated
appearance, hence the name corpus striatum.
Lentiform Nucleus: Putamen (darker lateral)
Globus pallidus (paler medial)
Functional & Evolutionary Aspects
• Paleostriatum (Pallidum): Ancient structure (Globus pallidus)
• Neostriatum (Striatum): Recent development (Caudate nucleus + Putamen)
Phylogenetically
• Archistriatum- amygdala
• Paleostriatum-globus pallidus
• Neostriatum- caudate, putamen
Function- Coordinate movement
Caudate nucleus
•A large, comma-shaped mass of grey matter enclosed by lateral ventricle
•Surrounds the thalamus
•Its convex surface projects into the lateral ventricle
Parts of the Caudate Nucleus
•Head: Rounded anterior portion, in front of interventricular foramen
•Body: Extends posteriorly, gradually tapering
•Tail: Continues caudally and merges with amygdaloid body
Caudate in relation to fourth ventricle
Parts of Caudate and connection to amygdala
Lentiform
•Lens-shaped (biconvex) grey matter mass beneath the insula
•Forms the lateral boundary of internal capsule
nucleus •Divided into two parts by external medullary lamina (white matter)
Lentiform nucleus
Basal ganglia
Connections of basal ganglia
Neurotransmitters involved:
• Dopamine
• Acetylcholine
• Glutamate
• GABA (γ-aminobutyric acid)
Input to Basal Ganglia (striatum)
• Cerebral cortex- corticostriate → Glutamate
• Thalamus - thalamostriate→ Glutamate
• Substantia nigra (Pars Compacta) – nigrostriate→ Dopamine
• Raphe nucleus → Serotonin
Neurotransmitters
❖ GABAgic-inhibitory
❖ Cholinergic- excitatory
❖ Dopaminergic (Parkinson’s)
Output from basal ganglia (globus pallidus)
• To
• substantia nigra (Pars reticulate)
• Red nucleus
• Subthalamic nucleus
❖GABA -inhibitory
Claustrum
•A thin, saucer-shaped mass of grey matter
•Located btw putamen and insula.
•Function: unknown.
Intrinsic Basal Ganglia Connections
1) Direct pathway from striatum to GP internal segment and substantia nigra
pars reticulata.
2) Indirect pathway from striatum to
GP external segment to subthalamus
GP internal segment to VA/VL thalamus.
• Direct path→ excitation of thalamus = facilitation of movement
• Indirect path→inhibition of thalamus = inhibition of movement
Cerebral Cortex
Glutamate Striatum Glutamate
Indirect D2 D1
GABA-enk GABA-dyn
Pathway
Globus
Pallidus Direct Thalamus
externa DA Pathway
Subthalamic
Nucleus SNc
Glutamate GABA
Brainstem and
Globus pallidus interna/Substantia Nigra reticulata
Spinal Cord
3/10/2025 23
Amygdaloid
Body/ Amygdala
•Almond-shaped mass of grey matter in the temporal lobe
• Located anterosuperior to tip of inferior horn of lateral ventricle.
•Lies deep to uncus
•Function & Classification:
•Developmentally related to basal nuclei.
•Functionally part of limbic system → emotion and behavior.
Connections of the
amygdala
• Sends fibres via stria terminalis, which
follows inner curve of caudate nucleus.
• Stria terminalis terminates in:
1. septal area,
2. anterior perforated substance, and
3. anterior hypothalamic nuclei.
Substantia Nigra
• Located in the midbrain
Parts
Red nucleus
• Located in the midbrain
• Ovoid
• With iron pigments
❖Regulate movement- force, velocity, direction
❖Execute learnt automated movement
• Afferent: Dentatorubral tract
• Efferent: Rubrospinal
• Some authors don’t consider red nucleus as part of basal ganglia
Subthalamus (Subthalamic Nucleus):
• Location:
• Small nucleus in the ventral part of diencephalon.
• Positioned caudal to lateral half of the thalamus.
• Inferomedial to globus pallidus
• Structure:
• Appears biconvex lens-shaped in coronal section.
• Separated from thalamus by a smaller nucleus called zona inserta.
Functions of Basal ganglia
Lesions of Basal ganglia
•Result in involuntary movements and muscle tone disturbances.
•Disorders Associated:
1.Parkinsonism – Most common disorder, characterized by tremors, rigidity, and bradykinesia.
2.Chorea – Rapid, irregular, involuntary movements (degenerating striatum)
3.Athetosis – Slow, writhing movements, usually in hands and fingers.
4.Ballismus – Sudden, violent flinging movements of the limbs (subthalamic nucleus
• Parkison’s TRAP ( dopaminergic neurons/ substantia nigra/nigrostriate tract)
- Tremors at rest
- Rigidity
- Akinesia/ dyskinesia
- Postural defects
Tx. L-Dopa
Parkinsonism (Parkinson’s Dx / Paralysis Agitans)
• Cause:
• Deficiency of dopamine in the corpus striatum.
• Results from lesions in the substantia nigra or its nigrostriatal fibers.
• Typically occurs after 50 years of age.
• Characteristic Features:
• Resting tremors – Involuntary shaking, especially in hands.
• Muscular rigidity – Lead-pipe or cogwheel rigidity.
• Pill-rolling movements – Repetitive finger-thumb motion.
• Mask-like face – Loss of facial expression.
• Stiff, shuffling gait – Difficulty in initiating walking.
• Stooped posture – Forward bending of the body.
• Slowing of movements (Bradykinesia) – Absence of associated movements like arm
swinging during walking.
Differences between Parkinson’s disease and Parkinsonism
Subthalamic infarction- Hemiballismus
THANK YOU!
