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Basal ganglia circuitry

Schematic diagram of the pyramidal (right side) and extrapyramidal (left side) components of the human motor system. Projections that are excitatory are depicted in gray, whereas inhibitory projections are black. Nuclei giving rise to inhibitory GABAergic projection are shaded. Abbreviations: D1, D2 - striatal projection neurons bearing predominantly D1 or D2-type dopamine receptors; DCN - deep cerebellar nuclei; GPe - globus pallidus external segment; GPi - globus pallidus internal segment; SNc - substantia nigra pars compacta; SNr - substantia nigra pars reticulata; STN - subthalamic nucleus; VIM - ventralis intermedius thalamus; VL/VA - ventrolateral and ventral anterior thalamus. (Contributed by Dr. Nicolaas Bohnen.)

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