The use of healthy young participants eliminates a number of confounds that exist in PD such as dopamine receptor sensitization secondary to chronic exposure (Voon et al., 2009) as well as altered synaptic regulation of dopamine in the form of decreased dopamine transporter (DAT), which also occurs in PD (Harrington et al., 1996; Kordower et al., 2013). The gene discussed is SLC6A3; the disease is Parkinson disease.