SLC6A3 and Parkinson disease: Human imaging studies found several hypodopaminergic changes in the ventral striatum of PD patients with ICDs: a reduced dopamine transporter (DAT) density in 123I-FP-CIT-SPECT17–20, a reduced dopamine synthesis capacity in 18F-DOPA-PET at rest21, a reduced BOLD activation at rest22, and a reduced D2/D3 receptor availability at rest23–25 (Fig. 1).