MAPT and Alzheimer disease: Additionally, behavioral and psychological impairments, such as hallucinations, delusions, anxiety, sleep disturbances, and restlessness, are also frequently noted. Fundamentally, AD is characterized by extracellular deposition of amyloid-beta (Aβ) plaques with abnormal buildup of intracellular neurofibrillary tangles (NFTs) or tau proteins as a result of protein misfolding.