The internal globus pallidus (GPi) or medial globus pallidus is only found in the primate brain and so is a younger portion of the globus pallidus. Like the GPe and the substantia nigra the GPi is a fast-spiking pacemaker but its activity does not show the long intervals of silence seen in the others. In addition to the striatal input there is also dopaminergic input from the SNpc. Unlike the GPe the GPi does have a thalamic output and a smaller output towards the habenula. It also gives output to other areas including the pedunculopontine nucleus and to the area behind the red nucleus. The evolutionary increase of the internal pallidus also brought an associated increase in the pallidothalamic tracts, and the appearance of the ventral lateral nucleus in the thalamus. The mediator is GABA.