This study is being done to learn about inflammation and amyloid in Alzheimer's disease. A
type of brain scan called a PET scan is used measure 1) inflammation and 2) abnormal
accumulation of a the amount of a certain protein fragment called beta-amyloid (plaques) in
the brain. These are thought to be involved in Alzheimer's disease. The investigators will
also perform brain MRI and do tests to measure the participants' memory and thinking.