Amyloid-related Imaging Abnormalities (Microbleeds) in Atypical AD

Inclusion Criteria: * over the age of 21 * will have an informant/study partner who will be able to provide independent evaluation of functioning * must fulfill clinical diagnostic criteria for atypical AD, and hence should either have a chief complaint of difficulty with language and fulfill criteria for logopenic variant of primary progressive aphasia, or present with visuospatial/perceptual deficits and fulfill criteria for posterior cortical atrophy * speaks English as their primary language (including bilingual patients whose primary language is English) * agrees to and is eligible to undergo MRI and PET scanning * if woman of child bearing age, must agree to pregnancy test no more than 48 hours before the PET scans Exclusion Criteria: * subjects with concurrent illnesses that could account for the presenting syndrome, such as traumatic brain injury, strokes or developmental syndromes * subjects meeting criteria for another neurodegenerative disease, particularly typical Alzheimer's dementia * women that are pregnant or post-partum and breast-feeding * subjects will also be excluded if MRI is contraindicated (metal in head, cardiac pace maker, e.t.c.), if there is severe claustrophobia, and if there are conditions that may confound brain imaging studies (e.g. structural abnormalities, including subdural hematoma or intracranial neoplasm) * subjects will also be excluded if they do not have an informant, do not consent to research or do not complete all components of t…