Basal Nuclei: Types, main features and connections

This note briefly describes the gross features of basal nuclei and their main connections.

Basal nuclei represent a collection of masses of gray matter situated within each cerebral hemisphere.

They are

o   the caudate nucleus

o   the lentiform nucleus
consists of globus pallidus medially and putamen laterally

o   the amygdaloid nucleus, and

o   the claustrum

The caudate and lentiform nuclei are collectively referred as Corpus striatum. The caudate nucleus and putamen form one unit called striatum while the globus pallidus forms the other unit, called the pallidum.

The subthalamic nuclei, the substantia nigra, and the red nucleus are also functionally closely related to the basal nuclei.(These structures are beyond the scope of discussion here.)

The Caudate Nucleus:

It is a C shaped mass of grey matter and consists of a head, a body and a tail.

The Head 
  • large and rounded 
  • forms the lateral wall of the anterior horn of the lateral ventricle 
  • continuous inferiorly with the putamen of the lentiform nucleus

The Body 
  • long and narrow
  • continuous with the head in the region of the interventricular foramen 
  • forms part of the floor of the body of the lateral ventricle

The Tail 
  • long and slender
  • continuous with the body in the region of the posterior end of the thalamus
  • forms part of the roof of the inferior horn of the lateral ventricle
  • terminates anteriorly in the amygdaloid nucleus

The Lentiform Nucleus 
  • wedge-shaped with broad convex base directed laterally and blade directed medially
  • related medially to the internal capsule, which separates it from the caudate nucleus and the thalamus 
  • related laterally to external capsule separating it from the claustrum
  • divided into a larger, darker lateral portion, the putamen, and an inner lighter portion, the globus pallidus 
  • Inferiorly at its anterior end, the putamen is continuous with the head of the caudate nucleus

The Claustrum 
  • a thin sheet of gray matter
  • separated from the lateral surface of the lentiform nucleus by the external capsule
  • Laterally lies the subcortical white matter of the insula 
  • function unknown

Amygdaloid Nucleus
  • also known as amygdaloid body or amygdaloid complex or amygdale
  • situated in the temporal lobe close to the uncus 
  • related to the anterior end of the inferior horn of lateral ventricle
  • considered as the part of the limbic system

Connections of Basal Nuclei

The interconnections of the basal nuclei are complex. So, only the more important connections are described here. The basal nuclei play an important role in the control of posture and voluntary movement.

Connection of Corpus striatum (caudate nucleus and putamen)

Afferent Fibers

Corticostriate Fibers

  • Receives from all parts of the cerebral cortex (largely from sensory-motor cortex),
  • The fibers from cortex projects to a specific part of the caudate-putamen complex
  • Mostly ipsilateral (from the same side)

Thalamostriate Fibers

  • From intralaminar nuclei of the thalamus

Nigrostriate Fibers

  • From neurons in the substantia nigra
  • dopaminergic fibers
  • these fibers are inhibitory in function

Brainstem Striatal Fibers

  • These are the ascending fibers from the brainstem end
  • liberate serotonin at their terminals as the neurotransmitter
  • these fibers are inhibitory in function

Efferent Fibers

Striatopallidal Fibers

  • from the caudate nucleus and putamen to the globus pallidus 
  • neurotransmitter is  gamma-aminobutyric acid (GABA)

Striatonigral Fibers

  • 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

Connections of the Globus Pallidus

Afferent Fibers

Striatopallidal Fibers

  • from the caudate nucleus and putamen to the globus pallidus
  • these fibers have GABA as their neurotransmitter

Efferent Fibers

Pallidofugal Fibers

Pallidofugal fibers can be divided into following four 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
  4. the pallidosubthalamic fibers, which pass to the subthalamic nuclei


Gray’s Anatomy, 39th Edition
Snell’s Clinical Neuroanatomy 7th Edition