MAPT and Alzheimer disease: The HPC is one of the earliest affected brain regions in Alzheimer’s disease and loss of HPC volume is a good predictor of presence of Alzheimer’s disease.35 HPC dysfunction is also thought to contribute to memory impairment, a core feature of Alzheimer’s disease.34 Further, hallmarks of Alzheimer’s disease including neurofibrillary tangles, hyperphosphorylated tau proteins, amyloid plaques, and loss of neurons accumulate in the HPC.