The basal ganglia

Reading instructions
To get the most out of this learning tool, please read:
Bear, Mark F, Connors, Barry W., Paradiso, Michael A. Neuroscience : exploring the brain. - 2 ed.
Chapter 7 page 163-252

Illustrations and anmimation

The basal ganglia
The term basal ganglia relate to a set of nuclei that are located deep in the hemispheres. The basal ganglia is involved in the regulation of cortically initiated motor activity, which if disturbed leads to some form of movement disorder, “dyschinesia”. Basal ganglia also play a role in cognition and emotion.

The nuclei are cudate, putamen and globus pallidus (external and internal segment) and these nuclei are relevant to the influence of motor functions. Two additional structures, the substantia nigra in the base of the midbrain and the subthalamic nucleus in the ventral thalamus that are closely functionally associated with the motor functions of the nuclei of the basal ganglia.

Blood supply of the basal ganglia is provided via three arteries, anterior choroidal, middle cerebral and anterior cerebral.

The caudate nucleus/nucleus caudatus
The caudate nucleus with its extended gray mass is C-shaped with a head, that is continual with the putamen, a body and a tail. The body/ corpus lies adjacent to the inferior border of the anterior horn of the lateral ventricle. The slim tail/cauda leans backwards and constitutes the roof of the temporal horn of the lateral ventricle. The end terminates at the level of amygdala.

The caudate nucleus, together with putamen constitute the major site of input to the circuitry of the basal ganglia. The caudate nucleus and the putamen therefore seem to control large automatic movements of skeletal muscles such as swinging the arms while walking.

Putamen/ putamen and globus pallidus/globus pallidus
Putamen and globus pallidus lie alongside and form a lens-shaped mass termed the lenticular nucleus/ nucleus lentiformis.The lenticular nucleus is situated between the insula/insula and the internal capsule/capsula interna. The putamen is the larger convex grey mass positioned laterally and just underneath the insular cortex. Globus pallidus is subdivided into an internal and an external segment forming a triangular gray mass.The globus pallidus is the major outflow nucleus of the basal ganglia.

Internal capsule/capsula interna
The internal capsule is a large bundle of myelinated fibers that separates the lentiform nucleus from the caudate nucleus and thalamus. It consists of an anterior and a posterior limb and in horizontal sections of the brain it has a V-shape with a genu pointing medially. The internal capsule is not part of the basal ganglia but this fiber band runs through the basal ganglia. Fibers in the posterior limb/of the internal capsule, located between the thalamus and the lentiform nucleus contains major ascending and descending pathways such as the corticospinal tract/tractus corticospinalis and the corticobulbar tract/tractus corticobulbaris.