PET Changes in Alzheimer's Disease (AD)

Previous studies indicate that the brain's glucose metabolism rate potentially may be an early indicator of damage to particular regions of the brain caused by AD, including loss of neurons, synapses, and other changes. Many of these changes are reported among patients with mild cognitive impairment (MCI), a group known to be at increased risk for AD. The overall goal of this study is to use FDG-PET (2-\[(18)F\]fluoro-2-deoxy-d-glucose/positron-emission tomography) to determine whether metabolic abnormalities in the hippocampus predict memory and brain deterioration in middle age, and to identify the brain glucose metabolism predictors of future MCI. Participants in the study will be grouped into 3 main groups of 35 each, including young individuals (20-40 years of age), 41-90 year-old normal, and MCI individuals with or without risk for memory decline. Participants will undergo baseline and 36-month follow-up exams to include comprehensive medical, neurologic, and psychiatric evalutions; lumbar puncture; a resting FDG-PET; an MRI scan; and a neuropsychological battery. A brief medical exam, full neuropsychological battery, and MRI scan will be administered at 18 months. Two subgroups (groups 4 and 5) of 15 each will be created from groups 1 and 2 at 18 months to participate in the evaluation of memory performance under acute hyperglycemia and saline challenges and effects on hippocampal formation and glucose metabolism.