MAPT and frontotemporal dementia: Concentrations of sarkosyl-insoluble aggregates of tau protein were more varied in patients than in controls and represented 4–23% and 1–14% of total tau in the frontal cortex and cerebellum, respectively, of individual FTD cases, reaching significance only for frontal cortex of FTLD-MAPT-P301L cases (Fig. 2b).