This powerpoint presentation is a lecture note for Neuroanatomy students. It contains some clinical correlates.

1. NEUROANATOMY
The Basal Nuclei
RESEARCHED & PREPARED BY: STUDENT DR. ELVIS J. DAVIS
A. M. D COLLEGE OF MEDICINE
UNIVERSITY OF LIBERIA

2. Chapter Objective
 To describe the basal nuclei, their connections, and their functions and relate
them to diseases commonly affecting this area of the nervous system
9/25/2019Elvis J. Davis
2

3. Gross
 The basal ganglia are the large masses of gray matter situated within the white
core of each cerebral hemisphere and form essential constituents of the
extrapyramidal system.
 Anatomically, the term basal ganglia include:
•Corpus striatum,
•Claustrum, and
•Amygdaloid body
Functionally, the term basal ganglia also include substantia nigra, subthalamus and
the red nucleus.
9/25/2019Elvis J. Davis
3

4. Terminology
 Clinicians and neuroscientists use a variety of different terminologies to describe the basal nuclei. A
summary of the terminologies commonly used is shown below.
Neurologic Structure Basal Nucleus (Nuclei)
Caudate nucleus Caudate nucleus
Lentiform nucleus Globus pallidus plus putamen
Claustrum Claustrum
Corpus striatum Caudate nucleus plus lentiform
nucleus
Neostriatum (striatum) Caudate nucleus plus putamen
Amygdaloid body Amygdaloid nucleus
9/25/2019Elvis J. Davis
4

5. Corpus striatum
The corpus striatum is situated lateral to the thalamus. Topographically it is almost completely
divided into the caudate nucleus and the lentiform nucleus by a band of nerve fibres, the internal
capsule.
Phylogenetically corpus striatum forms two distinct functional units, the paleostriatum and the
neostriatum.
However, anteroinferior ends of these nuclei remain connected by a few bands of grey matter across
the anterior limb of internal capsule. These bands give it a striated appearance, hence the name
corpus striatum.
The basal nuclei are important in organizing and coordinating somatic motor activities. They are
also involved in automatic stereotyped postural and reflex motor activities such as normal individuals
swing their arms when they walk.
9/25/2019Elvis J. Davis
5

6. Corpus Striatium cont..
Caudate Nucleus
Caudate nucleus is a large comma-shaped mass of grey matter, which surrounds
the thalamus and is itself surrounded by the lateral ventricle. Its whole length of
convexity projects into the cavity of lateral ventricle.
The lateral surface of the nucleus is related to the internal capsule, which separates it
from the lentiform nucleus. For purposes of description, it can be divided into a head,
a body, and a tail.
The head of the caudate nucleus is large and rounded and forms the floor and
lateral wall of the anterior horn of the lateral ventricle.
9/25/2019Elvis J. Davis
6

7. Cont..
The head is continuous inferiorly with the putamen of the lentiform nucleus (the
caudate nucleus and the putamen are sometimes referred to as the neostriatum or
striatum).
The body of the caudate nucleus is long and narrow and is continuous with the
head in the region of the interventricular foramen. The body of the caudate nucleus
forms part of the floor of the body of the lateral ventricle.
The tail of the caudate nucleus is long and slender and is continuous with the body
in the region of the posterior end of the thalamus.
9/25/2019Elvis J. Davis
7

8. Cont..
It follows the contour of the lateral ventricle and continues forward in the roof of the
inferior horn of the lateral ventricle. It terminates anteriorly in the amygdaloid
nucleus.
Lentiform Nucleus
The lentiform nucleus is a wedge-shaped mass of gray matter whose broad convex
base is directed laterally and whose blade is directed medially. It is buried deep in the
white matter of the cerebral hemisphere and is related medially to the internal
capsule, which separates it from the caudate nucleus and the thalamus.
9/25/2019Elvis J. Davis
8

9. Cont.
The lentiform nucleus is related laterally to a thin sheet of white matter, the external
capsule, which separates it from a thin sheet of gray matter, called the claustrum.
The claustrum, in turn, separates the external capsule from the subcortical white
matter of the insula. The lentiform nucleus consists of two parts: a darker lateral part
putamen and a medial paler part globus pallidus.
The paleness of the globus pallidus is due to the presence of a high concentration of
myelinated nerve fibers.
9/25/2019Elvis J. Davis
9

10. LentiformNucleus
Lentiform nucleus is a large lens-shaped (biconvex) mass of grey matter beneath the
insula forming the lateral boundary of internal capsule. In horizontal section of
it appears wedge-shaped with broad convex base directed laterally.
It has three surfaces and divides into two parts:
Surfaces
The lateral surface is convex and related to thin sheet of white matter, the external
capsule. It is grooved by lateral striate arteries (the central branches of middle cerebral
artery).
Medial surface is more convex and related to internal capsule (limbs and genu). In
transverse sections, the medial surface is angulated at the genu.
9/25/2019Elvis J. Davis
10

11. Lentiform Nucleus cont.
Inferior surface is related to sublentiform part of internal capsule and lies close to the
anterior perforated substance.
Parts
A vertical plate of white matter (external medullary lamina) divides the lentiform nucleus
into two parts, the putamen and the globus pallidus. These are clearly seen on a cut
section. The putamen is larger lateral part and consists of densely packed small cells. It is
darker in colour, and structurally similar to the caudate nucleus.
The globus pallidus is smaller medial part. It is lighter in colour and consists of large
(motor) cells. It is also known as pallidum as it appears pale in section (pallid = pale).
The globus pallidus is further subdivided by an internal medullary lamina of white matter
into outer and inner segments
9/25/2019Elvis J. Davis
11

12. Connections of corpus striatum
 The striatum (caudate nucleus and putamen) is the receptive part while
globus pallidus is the efferent part (outflow centre) of the corpus striatum.
 Afferent connections
The striatum receives afferents chiefly from cerebral cortex, thalamus and substantia
nigra.
• Corticostriate fibres arise from a wide area of the ipsilateral cerebral cortex and
reach the striatum through both internal and external capsules.
9/25/2019Elvis J. Davis
12

13. Connections
Thalamostriate fibres arise from mediodorsal, intralaminar and midline nuclei of
the thalamus. The majority of these fibres end in the caudate nucleus, the remaining
pass through the internal capsule to reach the putamen.
Nigrostriate fibres arise from substantia nigra and ascend up to terminate in the
corpus striatum, mainly in putamen and caudate nucleus.
The nigrostriate fibres carry dopamine synthesized by nerve cells of substantia nigra
to striatum (melanin normally present in the substantia nigra is a byproduct of
dopamine metabolism). It is believed that these fibres have an inhibitory effect on
corpus striatum.
9/25/2019Elvis J. Davis
13

14. Efferent connections
Most of the output of striatum goes to the globus pallidus, however, some efferents
also go to substantia nigra.
The globus pallidus is the main efferent component of corpus striatum. The outflow
from globus pallidus goes mainly to the thalamus (ventrolateral and ventroanterior
nuclei).
This occurs by way of two fasciculi: (a) ansa lenticularis looping round the
posterior limb of internal capsule, and (b) fasciculus lenticularis traversing the internal
capsule.
9/25/2019Elvis J. Davis
14

15. connections
 Striatopallidal Fibers
Striatopallidal fibers pass from the caudate nucleus and putamen to the globus
pallidus. They have gamma-aminobutyric acid (GABA) as their neurotransmitter.
Striatonigral Fibers
Striatonigral fibers pass from the caudate nucleus and putamen to the substantia
nigra. Some of the fibers use GABA or acetylcholine as the neurotransmitter, while
others use substance P.
9/25/2019Elvis J. Davis
15

16. Connections
 Pallidofugal Fibers
Pallidofugal fibers are complicated and can be divided into groups: (1) the ansa
lenticularis, which pass to the thalamic nuclei; (2) the fasciculus lenticularis, which
pass to the subthalamus;(3) the pallidotegmental fibers, which terminate in the
caudal tegmentum of the midbrain; and (4) the pallidosubthalamic fibers, which pass
to the subthalamic nuclei.
9/25/2019Elvis J. Davis
16

17. connections
These fasciculi enter the region between the red nucleus and thalamus, where
they unite with the dentatorubro-thalamic tract to form the thalamic fasciculus,
which ends in the ventrolateral and ventroanterior nuclei of thalamus which in
turn project to the motor and premotor areas of cerebral cortex.
The subthalamic fasciculus passes through the internal capsule and forms direct
reciprocal connections between subthalamic nucleus and globus pallidus.
Some fibres from globus pallidus also pass to the substantia nigra (pallidonigral
fibres).
9/25/2019Elvis J. Davis
17

18. Functions of corpus striatum
In submammalian vertebrates, the corpus striatum is the sensory and motor
integrating and control center. In later evolution, the activity of corpus striatum has
become subordinate to those of cerebral cortex but remain essential for muscle tone,
quality of movement, posture and locomotion.
Corpus striatum controls the automatic associated movements like, swinging of arms
during walking.
It helps in smoothening the voluntary motor activity of the body.
9/25/2019Elvis J. Davis
18

19. Functions
 Claustrum
The claustrum is a thin sheet of gray matter that is separated from the lateral surface
of the lentiform nucleus by the external capsule. Lateral to the claustrum is the
subcortical white matter of the insula. The function of the claustrum is unknown.
Amygdaloid Body
Amygdaloid body is an almond-shaped mass of grey matter in the temporal lobe,
lying anterosuperior to the tip of inferior horn of lateral ventricle. It is situated deep
to uncus which serves as a surface landmark for its location.
9/25/2019Elvis J. Davis
19

20. Functions
Developmentally it is related to basal nuclei but functionally it is included in the
limbic system and therefore shares its functions.
Subthalamus (Subthalamic Nucleus)
This small nucleus in the ventral part of the diencephalon looks like a biconvex lens
in coronal section. It is located caudal to the lateral half of the thalamus and
inferomedial to the globus pallidus.
It is separated from thalamus by a smaller nucleus, called zona inserta. The
subthalamic nucleus and globus pallidus are interconnected by the subthalamic
fasciculus which traverses the internal capsule.
9/25/2019Elvis J. Davis
20

21. Functions of Basal Nuclei
 Concerned with planning and programming of voluntary movements.
•Determine how rapidly a movement is to be performed and how large the
movement must be.
•Decrease muscle tone and inhibit unwanted muscular activity.
•Regulate the muscle tone and thus helps in smoothening the voluntary motor
activities of the body.
•Control automatic associated movements, like swinging of arms during walking.
•Control group of movements for emotional expression.
•Control reflex muscular activity.
9/25/2019Elvis J. Davis
21

22. Clinical Correlation
 Disorders of the Basal Ganglia
Disorders of the basal nuclei are of two general types. Hyperkinetic disorders are
those in which there are excessive and abnormal movements, such as seen with
chorea, athetosis, and ballism.
Hypokinetic disorders include those in which there is a lack or slowness of
movement. Parkinson disease includes both types of motor disturbances.
9/25/2019Elvis J. Davis
22

23. Clinicals cont..
Chorea
In chorea, the patient exhibits involuntary, quick, jerky, irregular movements that are
nonrepetitive. Swift grimaces and sudden movements of the head or limbs are good
examples.
Athetosis
Athetosis consists of slow, sinuous, writhing movements that most commonly involve
the distal segments of the limbs. The athetosis results due to lesions in neo-striatum
and globus pallidus, breaking neuronal circuitry involving basal nuclei and cerebral
cortex.
9/25/2019Elvis J. Davis
23

24. Clinicals
Ballismus
It usually is characterized by violent burst of irregular movements in the trunk, girdles
and proximal extremities.
It usually involves the proximal musculature of opposite extremity, and limb suddenly
flies about in all directions out of control, i.e. contralateral flinging (ballistic)
movements of one or both extremities.
9/25/2019Elvis J. Davis
24

25. Clinicals
 The disease may be restricted to one limb (monoballismus), but usually involves
both upper and lower limbs on the contralateral side of the lesion
(hemiballismus).
 This is because the subthalamic nucleus of one side projects mainly to the
ipsilateral cortex through globus pallidus and thalamus.
9/25/2019Elvis J. Davis
25