 The design of this study includes recruitment of two cohorts, including Mild Cognitive Impairment MCI andor early Alzheimer Disease subjects from memory clinics and subjects with strokesTIA from stroke prevention clinics. Inclusion criteria include the presence of moderateextensive white matter disease, eg. Fazekas score of 2 with confluent peri-ventricular hyperintensities or Fazekas score of 3, as determined by previous MR or CT, 60 years of age, Mini-Mental Status Exam MMSE scores 20. Subjects will undergo 3T structural MRI including T1, PDT2, FLAIR, GRE, DTI, ASL, and resting state fMRI, glucose PET, amyloid PET using AV-45 florbetapir and neuropsychological testing, as well as blood sampling. Repeat MR and PETCT imaging and neuropsychological testing will be conducted at 24 months. The imaging portion is designed to closely parallel the Alzheimers Disease Neuroimaging Initiative ADNI in order to benefit from the availability of both cognitively normal controls NC, MCI and Alzheimers disease subjects with minimal WMD. 