Globus pallidus

Location and borders

The globus pallidus is located in the subcortical white matter of the telencephalon (telencephalon), although ontogenetically part of it originates from the diencephalon.

Topographical relationships:

• Lateral border: externally, the globus pallidus is covered by the putamen (putamen). They are separated by a thin band of white matter, the medial medullary lamina (lamina medullaris medialis).
• Medial border: from the diencephalon, the globus pallidus is separated by a massive layer of projection fibers—the internal capsule (capsula interna).
• Posterior border: posteriorly, the structure borders the rostral part of the substantia nigra (substantia nigra).

On a horizontal section of the brain, the globus pallidus is visualized as the inner part of the lentiform nucleus, lying medial to the putamen.

Structure and anatomical connections

The nucleus got its name due to its relatively pale color on anatomical preparations. Structurally, the globus pallidus consists of two segments: the internal and external (globus pallidus medialis et lateralis).

• Lentiform nucleus (nucleus lentiformis): includes the globus pallidus and putamen.
• Corpus striatum / striatum (corpus striatum): the globus pallidus and caudate nucleus are connected by numerous thin "bridges" of gray matter. The fibers of the internal capsule, growing through the initially homogeneous basal ganglia during embryogenesis, create the characteristic striated appearance.

Connections and pathways

The basal ganglia are interconnected with each other and with the motor areas of the cerebral cortex via feedback regulatory loops.

• Connections with the thalamus: the centromedian nucleus of the thalamus receives information from the internal segment of the globus pallidus. This nucleus is the largest within the intralaminar complex. The thalamus serves as a relay between the basal ganglia and the cortex; the basal ganglia exert an inhibitory or disinhibitory influence on the thalamus, thereby "permitting" or "prohibiting" the initiation of motor programs in the cortex.
• Connections with the subthalamus: the globus pallidus has reciprocal relationships with the subthalamic nucleus (nucleus subthalamicus).

Phylogeny and role in motor organization

In the course of evolution, the globus pallidus formed earlier than the caudate nucleus and putamen, which belong to the neostriatum; therefore, it is called the paleostriatum (paleostriatum).

In phylogenetically older species, the paleostriatum plays a major role in maintaining muscle tone and automated movement control. In humans, the new motor (pyramidal) system of the cerebral cortex has subordinated the older centers. The old neural centers are unable to compensate for the impairment of the new centers' function: when the motor cortex is damaged, a person loses the ability to walk.

Clinical significance and radiology

Lesions of the basal ganglia lead to an excess or deficit of motor impulses and pathological changes in muscle tone. In Parkinson's disease, a triad is described: rigidity, akinesia, and tremor.

• Associated movements (syncinesias): during the development of spastic paralysis, involuntary associated movements may occur in the paralyzed limbs. They are generated by phylogenetically older motor centers.
• MRI diagnostics: localized copper deposition in the internal part of the globus pallidus manifests as signal hypointensity—the tissue appears abnormally dark.

Class and exam questions

What else to study on this topic

• Putamen
• Caudate nucleus
• Internal capsule (Capsula interna)
• Substantia nigra
• Subthalamic nucleus (Nucleus subthalamicus)

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.