SLC6A3 and REM sleep behavior disorder: Secondly, demographic, motor characteristics (tremor dominant versus rigid akinetic phenotype), as well as other non-motor symptoms (i.e., hyposmia, REM sleep behavior disorder, anxiety-depressive disorder, gastrointestinal, urinary, and cognitive impairment), can all be associated with altered DAT SPECT denervation patterns [15, 16, 38, 39].