The proposed study will investigate the role of cerebrovascular dysfunction during the earliest stages of
neurocognitive decline, prior to any obvious changes in cognition. Specifically, we will study whether
cognitively normal older adults at risk for Alzheimer's disease show increased cerebrovascular resistance. We
will also study how increased cerebrovascular resistance relates to brain dysfunction using functional brain
scans. Finally, we will investigate whether higher cerebrovascular resistance in cognitively normal older adults
predicts development of subtle cognitive decline over a two year follow-up interval.