Plaques are deposits of a protein fragment called beta-amyloid that build up in the spaces between
nerve cells. Tangles are twisted fibers of another protein called tau that build up inside cells. Though
autopsy studies show that most people develop some plaques and tangles as they age, those with
Alzheimer's tend to develop far more. Plaques and tangles tend to develop in predictable patterns,
beginning in the areas of the brain most important for memory before spreading to other regions.
Scien- tists do not know exactly what role plaques and tangles play in Alzheimer's,
though most believe that they are somehow critical in blocking communication among nerve cells
and disrupting processes the cells need to survive. It's the destruction and death of nerve cells
that causethe memory failure, personality changes, problems in carrying out daily activities
and other symptoms of Alzheimer's disease.