ß-Amyloid peptides are the major constituents of senile plaques and neurofibrillary tangles that occur in the hippocampus, neocortex, and amygdala of patients with Alzheimer's disease. Aß (1-40) whether soluble or insoluble differentiates AD vs high pathology controls. The Arctic mutation E22G causes early onset of Alzheimer's compared to wild type and promotes protofibril formation and neurotoxicity.