Focusing on neuroimaging studies of cognitive impairment in PD using the 2-back test, Ekman et al. reported decreased test performance in patients diagnosed with PD-MCI when compared with PD patients without MCI; this decrease was associated with reduced levels of dopamine transporter binding in the right caudate nucleus, as measured by single photon emission tomography [12]. The gene discussed is SLC6A3; the disease is Parkinson disease.