Light micrograph (TEM) of a section through the brain of a patient with Alzheimer's disease showing amyloid plaques and neurofibrillary tangles of tau protein. Amyloid plaques are insoluble aggregates of beta-amyloid protein. They are thought to cause cell death and disrupt cell function, leading to the symptoms of Alzheimer's disease, which include memory loss, personality changes and confusion. Tau protein is an abundant neural protein, aggregations of which are thought to play a role in Alzheimer's disease and other neural disorders. Magnification: x3,800 when printed at 10 centimetres wide.