It is characterized by general disorientation of the brain's ability to think, understand, remember and to speak. The person having Alzheimer's disease develops dementia, depression, paranoia and changes in the emotional behavior. Alzheimer's disease differs in age at onset, symptomatology, extent of disease and presence of risk factors. Pathological Changes in Brain Related to Alzheimer's Disease There are many theories behind the pathogenesis of Alzheimer's disease. One theory suggests that Alzheimer's disease brain pathologically accumulates neurofibrillary tangles.The neurofibrillary tangles contain phosphorylated tau, which is harmful ...