PHF1 and Alzheimer disease: Future studies will elucidate the spatial and temporal sequence of multiple phosphorylated tau epitopes in vulnerable cortical circuits in AD, and whether these occur concurrently in the same cell types, especially comparing early‐stage, soluble phosphorylated tau epitopes to late‐stage, fibrillated markers (e.g., thioflavin S, paired helical filament‐1 [PHF‐1]).