Fig. 1. Functional subdivisions of the dopamine system across species.

Midbrain dopamine neurons are the source of dopamine projections to the striatum in primates (left) and rodents (right). Important neuroanatomical differences exist, especially when considering functional subdivisions of the striatum. In the primate, the limbic system (orange) originates in the dorsal tier of the substantia nigra (the ventral tegmental area equivalent). In the rodent, the limbic system originates in ventral tegmental area, which sits medially to the substantia nigra. The midbrain projections to the associative striatum (yellow) and sensorimotor striatum (blue) follow a dorsomedial-to-ventrolateral topology