These include neuromelanin,33 35 iron, calcium and Biondi ring tangles.34 None of these potential targets is anatomically compatible with the pattern of cortical binding seen here, which is in a distribution expected for pathology in semantic dementia.25 31 One plausible explanation for the elevated signal observed here could be spill out from increased binding in white matter, for example, to the expression of monoamine oxidase B by reactive astrocytes. The gene discussed is MAOB; the disease is semantic dementia.