SLC6A3 and tauopathy: Second, some potential assessments were not performed: although PET with 18F-florzolotau can discriminate a wide range of tauopathies by the pattern of retention, a head-to-head comparison of 18F-florzolotau with another tau PET tracer that hardly binds to 4R tau, such as 18F-MK-6240 (43), or the dopamine transporter (DAT) imaging and/or 123I-metaiodobenzylguanidine (MIBG) scintigraphy (44, 45), might be helpful for a differential diagnosis; it might be desirable to perform a forward digit span, as this task can be sensitive to impairments of the “phonological loop” (6).