A total of 22 subjects were recruited in this study including 8 young controls (4 men and 4 women, age range: 24–40 years, mean 31) and 14 older adults (6 men and 8 women, age range: 50–73 years, mean 61). In order to match the prevalence of AD in the older population, 1 AD and 2 MCI patients were included as positive controls whose diagnoses were based on consensus conference case reviews. The rest of the older individuals were selected from a carefully characterized cohort known as The Wisconsin Registry for AD Prevention (WRAP), many of whom have a parent with AD and are considered at high risk to develop AD (20 (link)). The study was approved by the Institutional Review Board at the University of Wisconsin. All participants provided informed consent prior to participation. The consent process included an initial screening for MRI and PET compatibility and discussion of major safety exclusion criteria. Study exclusion criteria included contraindications to MRI and PET; less than 10 years of education; pregnancy; major head trauma, psychiatric disease such as schizophrenia and substance dependence, or abnormal structural MRI and neuropsychological testing as part of study participation. Excluded medications include psychoactive medications, neuroleptics, short or long acting nitrates, and warfarin or other drugs that may affect CBF (such as caffeine within 3 hours and nicotine within 1 hour of the imaging exam).