The basal nuclei are large masses of gray matter located in the core of each cerebral hemisphere. They include the corpus striatum (composed of the caudate nucleus and putamen), claustrum, amygdaloid body, substantia nigra, and subthalamus. The basal nuclei are involved in motor control, regulating muscle tone and planning voluntary movements. They receive input from the cortex and thalamus and send output mainly to the globus pallidus and substantia nigra. Dopamine release in the basal nuclei enhances motor activity by exciting the direct pathway and inhibiting the indirect pathway.

1. BASAL NUCLEI
PRESENTED BY
MUHAMMAD UZAIR KHAN
DPT IPM&R-KHYBER MEDICAL UNIVERSITY

2. The large masses of gray matter situated within the core of each cerebral hemisphere.
Anatomically the basal nuclei include:
(1) Corpus striatum
(2) Claustrum originate from telencephalon
(3) Amygdaloid body
Functionally they also include substantia nigra and subthalamus.
part of midbrain part of diencephalon
BASAL NUCLEI:

3. Basal nuclei

4. Basal nuclei

5. Basal nuclei

6. .

8. Basal nuclei:

9. Corpus striatum:

10. large C-shaped mass of gray matter
lies lateral to the thalamus .
The lateral surface of the nucleus is related to the internal capsule, which separates it from the lentiform
nucleus .
consists of a head, a body, and a tail.
The head of the caudate nucleus is large and rounded and forms the lateral wall of the anterior horn of the
lateral ventricle .
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).
Just superior to this point of union, strands of gray matter pass through the internal capsule, giving the
region a striated appearance, hence the term corpus striatum.
Caudate nucleus:

11. Caudate nucleus

12. 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 is continuous with the body in the
region of the posterior end of the thalamus.
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
Caudate nucleus:

13. The lentiform nucleus is a biconvex lens-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.
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.
Lentiform nucleus:

14. Lentiform nucleus

15. The claustrum, in turn, separates the external capsule from the subcortical white
matter of the insula.
A vertical plate of white matter external medullary lamina divides the nucleus
into a larger, darker lateral portion, the putamen, and an inner lighter portion,
the Globus pallidus .

16. The putamen lies in the brain
– medial to the insula
– bounded laterally by the external capsule
– medially by the Globus pallidus.
• As noted earlier, the putamen is continuous with the head of the caudate
nucleus.
• Although bridges of neurons between the caudate nucleus and the putamen
show the continuity of the nuclei, the two structures are separated by fibers of
the anterior limb of the internal capsule.
Putamen:

17. GP is smaller medial part.
Lighter pale in color hence called pallidum.
Further subdivided into outer(GPe) and
inner(GPi) segment by internal
medullary lamina.
Globus pallidus:

18. Caudate and putamen are receptive parts while GP is efferent part of corpus
striatum.
AFFERENT CONNECTIONS:
The striatum receives afferents from cerebral cortex, thalamus, substantia nigra,
via
Corticostriate fibers: from ipsilateral cerebral cortex to striatum.
Thalamostriate fibers: from mediodorsal, intralaminar and midline nuclei to
striatum.
Nigrostriate fibers: from SN to putamen and caudate.
Connections of corpus striatum:

19. EFFERNT CONNECTIONS:
Most of the output of the striatum goes to GP and it is the main efferent
component of basal nuclei.
The outflow from GP mainly goes to the thalamus (VL and VA nuclei).
This occur by way off two fasciculi:
1) Ansa lenticularis
2) Fasciculus lenticularis
Subthalamic fasciculus interconnect the subthalamic nuclei and GP
Connections of corpus striatum:

20. It is a saucer shaped mass of grey matter situated between the putamen and
insula.
Considered as the detached part of insula.
Its connections and functions are not known.
Claustrum:

21. The amygdaloid nucleus is situated in the temporal lobe close to the uncus .
The amygdaloid nucleus is considered to be part of the limbic system .
Through its connections, it can influence the body's response to environmental
changes.
In the sense of fear, for example, it can change the heart rate, blood pressure,
skin color, and rate of respiration.
Amygdaloid nucleus:

22. Concerned with planning and programing 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 activity.
Regulate 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 the reflex muscular activity.
FUNCTIONS OF THE BASAL NUCLEI

23. REMEMBER, THE DIRECT PATHWAY TURNS UP MOTOR ACTIVITY.

24. INDIRECT PATHWAY TURNS DOWN MOTOR ACTIVITY

25. As DOPAMINE is produced by cells in the pars compacta of the substantia nigra (SNc).
Nigrostriatal axon terminals release dopamine into the striatum.
Dopamine has an EXCITATORY effect upon cells in the striatum that are part of the
Direct Pathway. This is via D1 receptors.
Dopamine has an INHIBITORY effect upon striatal cells associated with the Indirect
Pathway. This is via D2 receptors.
In other words, the direct pathway (which turns up motor activity) is excited by
dopamine while the indirect pathway (which turns down motor activity) is inhibited.
Both of these effects lead to increased motor activity.
Substantia nigra

26. DOPAMINE EXCITES THE DIRECT AND
INHIBITS THE INDIRECT PATHWAY.
THE EFFECT OF THE DOPAMINERGIC NIGROSTRIATAL
PROJECTION IS TO INCREASE MOTOR ACTIVITY.

27. There is a population of cholinergic (ACh) neurons in the striatum whose axons
do not leave the striatum (called interneurons or local circuit neurons).
The cholinergic actions INHIBIT striatal cells of the Direct pathway and EXCITE
striatal cells of the Indirect pathway.
Thus the effects of ACh are OPPOSITE the effects of dopamine on the direct and
indirect pathways so the ACh effects on motor activity are opposite those of
dopamine.

28. ACh INHIBITS THE DIRECT AND
EXCITES THE INDIRECT PATHWAY
THE EFFECT OF THE CHOLINERGIC
STRIATAL INTERNEURONS IS
TO DECREASE MOTOR ACTIVITY.

29. .