Projections from the striatum to the midbrain are also arranged in an inverse dorsal-ventral topography. Thus, the dorsal aspects of the striatum terminate in the ventral regions of the midbrain, whereas the ventral areas terminate dorsally.22,119 Moreover, inputs from the ventromedial striatum, including the shell, terminate throughout an extensive dorsal region, including the VTA and the medial SNc, along with the medial SNr. Thus, the VS projects widely throughout the rostrocaudal extent of the SN, including a large mediolateral area of dopaminergic cells. Taken together, the VS innervates a large area of the midbrain, but receives a relatively limited afferent midbrain input. At central and caudal levels, this projection field extends laterally and includes much of the ventral tier cells. The central striatum projection terminates more ventrally, primarily in the ventral tier (and associated SNr). The dorsolateral striatum projections to the midbrain terminate in the ventrolateral midbrain in the pars reticulata, which includes some of the dopaminergic cell columns that extend into this region. Thus, in contrast to the VS, the dorsolateral striatum projects to a limited midbrain region, but receives a relatively extensive midbrain input.13
