Low glucose metabolism during brain stimulation in older Down's syndrome subjects at risk for Alzheimer's disease prior to dementia

OBJECTIVE: Down's syndrome is characterized by the genetically programmed accumulation of substantial Alzheimer's disease neuropathology after age 40 and the development of early dementia years later, providing a unique human model to investigate the preclinical phases of Alzheimer's disease. Older nondemented adults with Down's syndrome show normal rates of regional cerebral glucose metabolism at rest before the onset of dementia, indicating that their neurons maintain function at rest. The authors hypothesized that an audiovisual stimulation paradigm, acting as a stress test, would reveal abnormalities in cerebral glucose metabolism before dementia in the neocortical parietal and temporal areas most vulnerable to Alzheimer's disease. METHOD: Regional cerebral glucose metabolism was assessed by means of positron emission tomography (PET) with [18F]fluorodeoxyglucose in eight younger (mean age = 35 years, SD = 2) and eight older (mean age = 50, SD = 7) healthy, nondemented adults wi..