Figure 6A.
Basal Ganglia - Direct and Indirect Pathways. This diagram depicts the basic circuitry of the basal ganglia and the related CSTC circuits emphasizing the roles of the "direct" and "indirect" pathways in modulating the activity of thalamo-cortical projections (adapted from ref. 61). The role of nigrostriatal dopamine projections in mediating the output of the basal ganglia appears to depend on the balance of D1 vs. D2 dopamine receptor stimulation in the striatum. Indeed the stimulation of D1 and D2 receptors produce opposing effects in both rodents (32) and primates (28, 29).

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published 2000