Furthermore, since there is strong evidence that DAT binding is reduced in the prodromal stage of PD (Nandhagopal et al., 2008, Sossi et al., 2010), these techniques can be applied to images from subjects at increased risk of PD (e.g. mutation carriers or subjects with rapid-eye-movement sleep behavior disorder) in an attempt to discern dopaminergic patterns that might be involved in pathogenesis and to assess the impact of novel disease modifying therapies. This evidence concerns the gene SLC6A3 and Parkinson disease.