MAPT and Alzheimer disease: When assessing the characteristics of the MCI tau‐negative group in the ADNI cohort, it was striking that they were younger than tau‐negative AD patients and similar in age to tau‐positive MCI patients (contrary to the difference between AD A+T− and AD A+T+), which indeed suggests that tau‐PET negativity in AD is different from tau‐PET negativity in MCI.