APA Dictionary of Psychology

n. a family of peptides produced when amyloid precursor protein (APP) is cleaved by certain enzymes. It is produced continuously in healthy brains and normally cleared efficiently, but in Alzheimer’s disease and sometimes in Lewy body dementia, it tends to misfold, aggregate, and form extracellular amyloid plaques, oligomers, and fibrils, contributing to neuronal impairment, neuroinflammation, and eventual neuronal loss. Amyloid-β levels are central biomarkers in the medical diagnosis of Alzheimer’s disease. Also called beta-amyloid (β-amyloid).