Usually the cognitive decline in AD is associated with the progressive development of extracellular senile plaques, which consist of fibrillar aggregates of amyloid-β (Aβ) deposits, and intracellular neurofibrillary tangles (NFT), composed of hyperphosphorylated tau protein located in the cortex and hippocampus of the affected brain; the disruption of synaptic function; and cerebral atrophy. The gene discussed is MAPT; the disease is Alzheimer disease.