Alternatively, it could be that the in vivo binding demonstrated here mirrors the postmortem binding of [18F]AV-1451 to TDP-43 type C,14 34 despite the low level or absent binding to most TDP-43 pathology.14 34 Overall, we retain an open mind as to the identity of the non-Tau proteins and cell types to which [18F]AV-1451 is binding in semantic dementia. This evidence concerns the gene MAPT and semantic dementia.