Some physiological aspects of the basal ganglia. Excitation of the neurons of the globus pallidus by the brain stem structures.

The caudate efferent fibers to the globus pallidus are inhibitory in nature. The pallidothalamic fibers are also inhibitory, exerting monosynaptic IPSPs on the thalamic cells located anteroventrally to the ventrolateral nucleus. Therefore, these two inhibitory neuronal circuits make a double inhibitory chain. To operate the inhibitory circuit, excitatory input to the pallidum is necessary. Stimulation of the ipsilateral brain stem including lemniscus medialis, mesencephalic reticular formation and some other structures, produces short latency excitation of the pallidal cells.