MAPT and Alzheimer disease: Based on PET scan patterns of high Aβ and low tau, the amyloid hypothesis states that Aβ aggregation triggers a chain of events that ultimately results in AD pathology, while based on patterns of low Aβ and high tau, the tau hypothesis postulates that tau tangle pathology precedes the Aβ plaques formation and that tau phosphorylation and aggregation are the main cause of AD.