The medial globus pallidus is the term used for an output nuclei (a cluster of nerve cells, or neurons) from the basal ganglia. The basal ganglia are vast clusters of neurons that are responsible for involuntary movements.
The motor cortex transmits information directly to the basal ganglia, at the center of the brain, and the cerebellum, at the brain’s base. The ganglia also sends information back, through the thalamus, which is located nearby.
The basal ganglia produces inhibitory output (it stops things from happening), while the cerebellum's output is excitatory (makes things happen).
Alongside the pallidus, the other type of output nuclei is the substantia nigra pars reticulata, which is a section of the substantia nigra, a midbrain structure. Another common name for the pallidus is substantia innominata, which means “the great unknown.”
The medial globus pallidus consists of neurons that contain gamma-aminobutyric acid, which is also known as GABA. GABA is a neurotransmitter, a chemical that transmits signals from one neuron to another. These neurons send axons (threadlike sections of nerve cells) to various nuclei from the dorsal thalamus, and then over to the pedunculopontine (of the brain stem) and centromedian (of the thalamus) nuclei. The pallidus is close to the nucleus subthalamicus, the putamen, and the mesencephalon.