DRD2 and major depressive disorder: Acquisition: Simultaneous fMRI and 11C-raclopride PET targeting the dopamine D2 receptor. Analysis: BPND was estimated via the MRTM, using the cerebellum as the reference tissue. Functional connectivity analysis was performed using striatal regions exhibiting significant between-group BPND differences as seeds. Results: Increased BPND and decreased connectivity were observed in the striatum. The BPND was increased in both the left ventral striatum and right dorsal striatum in patients with MDD. Connectivity between these regions and cortical targets was also decreased in the MDD group.