Practice Effects and Amyloid Imaging Using 18F-PIB or Flutemetamol PET and FDG-PET

Alzheimer's disease (AD) is the most common cause of progressive cognitive decline in the United States. AD is characterized by severe impairments in learning, memory and other cognitive abilities that significantly interfere with daily functioning. The neuropathologic hallmarks of AD consist of neuritic plaques, neurofibrillary tangles, and selective neuronal cell loss. Amyloid plaques, which contain Abeta protein, are believed to play an integral role in the development of AD. Elevated levels of Abeta in the brain are also correlated with cognitive decline. Alzheimer's (AD) develops insidiously, making it difficult to identify early, yet treatment is most effective when begun during the early stages of the disease. Thus, it has become important for researchers to identify markers of early AD. This project will examine the relationship between four potential markers that may indicate the early development of AD: 1. Mild cognitive impairment (MCI)or normal cognition 2. Practice effects 3. Amyloid plaque binding on 18F-PIB PET 4. Glucose hypometabolism on FDG PET This project will recruit 25 subjects from an ongoing community-based study of memory and practice effects in cognitively normal, community-dwelling individuals who are age 65 and over (NIA #5K23AG028417-05). Each subject will undergo positron emission tomography (PET) with both 18F-Flutemetamol and FDG. The overall objective of this companion project is to study the biodistribution and binding of 18F-Flutemetamol in these subjects using PET imaging, which will provide biological evidence to support the overall hypothesis that failure to benefit from practice on a learning paradigm is an early marker of AD.