In light of the close correlation between post-mortem NM-MRI and the quantity of NM-containing neurons (Kitao et al., 2013), our findings for AISN-volume and AISN-CNR may reflect the actual SN neuron loss, whereas the asymmetric striatal DAT density seen with AIPutamen, and the consequent asymmetry of clinical signs in PD patients, might be influenced by pre-synaptic compensatory mechanisms. The gene discussed is SLC6A3; the disease is Parkinson disease.