Illustration of a amyloid plaques and aggregations of tau protein amongst neurons (nerve cells, grey) in the brain. Amyloid plaques are insoluble aggregates of beta-amyloid protein. They are believed to be linked to Alzheimer's disease by causing nerve cell death and affecting nerve cell signalling pathways. Tau protein is an abundant neural protein, aggregations of which are thought to play a role in Alzheimer's disease and other neural disorders.