Several lines of evidence suggest that the neuropathological and clinical decline leading to Alzheimer disease (AD) begins years before patients develop the full AD clinical syndrome (NINCDS-ADRDA diagnostic criteria; McKhann et al, 1984). Mild memory complaints build gradually years before patients develop dementia. The neuropathological hallmarks of AD, "preclinical" neuritic plaques (Braak & Braak, 1991) and neurofibrillary tangles (Price & Morris, 1999), are also present years prior to clinical diagnosis. These abnormal protein deposits correlate strongly with cognitive decline.