Internal globus pallidus

Internal globus pallidus

The internal globus pallidus (GPi) is a subcomponent of the globus pallidus, which is part of the basal ganglia in the brain. The basal ganglia are a group of nuclei in the brain associated with a variety of functions including the regulation of voluntary motor movements, procedural learning, routine behaviors or "habits", eye movements, cognition, and emotion.

Anatomy

The internal globus pallidus is located within the telencephalon and is one of the two parts of the globus pallidus, the other being the external globus pallidus (GPe). The GPi is situated medial to the GPe and lateral to the thalamus. It is separated from the thalamus by the internal capsule, a white matter structure that contains many of the brain's ascending and descending axons.

Function

The GPi plays a crucial role in the regulation of voluntary movement. It is part of the indirect pathway and the direct pathway of the basal ganglia circuitry. In the direct pathway, the GPi receives inhibitory input from the striatum and sends inhibitory output to the thalamus, which in turn projects to the motor cortex. This pathway facilitates the initiation and execution of voluntary movements. In the indirect pathway, the GPi receives excitatory input from the subthalamic nucleus and sends inhibitory output to the thalamus, which helps to suppress unwanted movements.

Clinical Significance

Dysfunction of the GPi is associated with several movement disorders. For example, in Parkinson's disease, there is excessive inhibitory output from the GPi to the thalamus, leading to the characteristic motor symptoms of bradykinesia, rigidity, and tremor. Deep brain stimulation (DBS) of the GPi is a therapeutic option for patients with Parkinson's disease and other movement disorders such as dystonia.

Connections

The GPi has extensive connections with other parts of the basal ganglia, including the putamen, caudate nucleus, and the substantia nigra. It also has connections with the cerebral cortex and the brainstem, which are important for its role in motor control.

See Also

• Basal ganglia
• External globus pallidus
• Subthalamic nucleus
• Parkinson's disease
• Deep brain stimulation