Amyloid Imaging With 11C-PiB in Healthy Aging and Mild Cognitive Impairment

The purpose of this study is to measure the amount of amyloid in the brain. Amyloid is a protein found in the brain of patients with Alzheimer's disease and can be detected using a Positron Emission Tomography (PET) scan. This study is interested in how amyloid levels in the brain relate to memory and thinking abilities.

The overarching goal of this study is to use 11C-PiB, a commonly used tracer that binds to amyloid plaques in the brain, as a biological marker of Alzheimer's disease (AD) related brain changes. Data from this PET-only study will be compared to and analyzed with data from the Investigators' longitudinal biomarker studies, COMIRB #15-1774 and COMIRB #18-2607. This enables investigators to examine how deposition of the amyloid protein relates to cognitive aging in both symptomatic and asymptomatic older adults. It will assist investigators in comparing rates of change in memory and thinking ability in healthy subjects who are amyloid positive versus amyloid negative, as well as in comparing rates of conversion to a higher level of impairment (e.g. such as Mild Cognitive Impairment converting to Alzheimer's Disease) based on the quantitative analysis of amyloid burden. Moreover, by capitalizing on data across the two studies, the investigators will be able to better understand the relationship between amyloid deposition (as assessed by PET; current proposal) and other biomarkers (as assessed in COMIRB #15-1774, COMIRB #18-2607), which ultimately may help the investigators better predict the onset and progression of clinical AD symptoms. Participants will be recruited solely from the longitudinal study (COMIRB # 15-1774) in order to provide data comparison on an individual and group basis. The goals of this study are as follows: 1. Evaluate the relationship between amyloid burden, as assessed by 11C-PiB, with both cross-sectional and longitudinal biomarkers (e.g. blood; nasal biopsy; CSF; MRI; DNA) obtained in the longitudinal study (COMIRB # 15-1774, COMIRB #18-2607). 2. Compare rates of change in memory and other cognitive abilities (obtained in COMIRB # 15-1774, COMIRB #18-2607) in healthy subjects who show elevated amyloid deposition with those who are "amyloid negative". 3. Evaluate the relationship between amyloid burden and health history, informant report of subjective cognitive and psychiatric difficulties, and participant-reported psychiatric symptoms. 4. Investigate predictive utility of amyloid burden in identifying individuals most at risk for conversion (e.g. healthy controls to MCI, and MCI to AD). 5. Identify why a subset of "amyloid positive" individuals do not show symptoms of clinical AD or delay conversion to MCI or AD.