SLC6A3 and Parkinson disease: Interestingly, it has been demonstrated that PD patients who were homozygous for the SLC6A3 10/10 repeat genotype displayed lower activity in the orbitofrontal cortex, which is related to reward outcome, in the Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI), compared to PD patients who were non-homozygous for the SLC6A3 10/10 genotype [62].