MAPT and Alzheimer disease: This was distinct from the gray matter–dominant topology of tau depositions in the AD spectrum13, 14 and corresponded to previous [11C]PBB3 autoradiographical findings.19 Subject C‐IV‐1 had the shortest interval between onset and PET scans and exhibited a remarkable increase of [11C]PBB3 SUVRs in the midbrain, including the SN, hippocampus, and amygdala, suggesting that tau pathologies could arise from these regions (Fig. 1A).