A 75-year-old woman is taken to the physician because of worsening forgetfulness. She has trouble playing cards with her friends because she cannot remember what game is being played. She recently got lost during a walk in the neighborhood she has lived in for 35 years. Which substance is most likely to be increased in the brain of this woman?

This woman has Alzheimer's disease. Increased amounts of beta-amyloid peptide is found in the brains of patients with Alzheimer's disease. The peptide accumulates in amyloid plaques with diameters up to several hundred millimeters in widespread areas of the brain, including the cerebral coex, hippocampus, basal ganglia, thalamus, and cerebellum. Due to beta-amyloid deposition, there is decreases cholinergic discharge to various pas of brain