Fig. 1.

Parcellation of the substantia nigra based on connectivity to the striatum.

A: Single subject example of seed region for tractography (SN/VTA) and the ventral striatum (blue) and dorsal striatum target regions (red).

B: The substantia nigra was parcellated into two overlapping subregions based on tractography-based connectivity to the striatum. The dorsomedial-SN (blue) connected to the ventral striatum, whereas a more ventrolateral-SN subregion (red) connected to the dorsal striatum. Images are of a group probability map thresholded at 50% overlap, overlayed on a group-average MT image in the axial, coronal and sagittal planes from left to right.