Inclusion Criteria:

• All enrolled subjects will be over the age of 21.
• Will have an informant who will be able to provide independent evaluation of functioning.
• Subjects will only be included if English is their primary language or if they are bilingual.
• In order to be included in the study all subjects must have insidious onset, report progression of their symptoms, and meet current clinical diagnostic criteria for typical amnestic Alzheimer's Disease (AD) or an atypical AD syndrome.
• All atypical AD syndromes must present with early and dominant impairments in a cognitive domain that is not memory, including language (verbal and/or written), visuospatial/perceptual function, executive function, working memory, behavioral control, calculation or praxis.
• All atypical AD subjects must have relative preservation of episodic memory compared to impairment in the non-episodic memory domain. As discussed above, subjects will only be included in the study if they have Aβ deposition on PET imaging, to ensure that all subjects have underlying AD.

Exclusion Criteria:

• Subjects will be excluded if they do not meet our inclusion criteria or if they have a stroke or tumor that could explain their symptoms.
• Subjects who present with mild cognitive impairment without evidence of dementia will not be recruited into the study.
• Subjects who meet specific criteria for another neurodegenerative disorder, including semantic dementia, primary progressive apraxia of speech, or progressive supranuclear palsy, will be excluded.
• Subjects will not be excluded if they have depression, features of Lewy body disease or behavioral features.
• Subjects will be excluded if they have poor vision (20/400).
• Women who are pregnant or post-partum and breast-feeding will be excluded. All women who can become pregnant must have a pregnancy test no more than 48 hours before the PET scan.
• Subjects will also be excluded if MRI is contraindicated, if there is severe claustrophobia, if there are conditions that may confound brain imaging studies (e.g., structural abnormalities), or if they are medically unstable or are on medications that might affect brain structure or metabolism (e.g., chemotherapy).
• Subjects will also be excluded if they do not have an informant, or do not consent to research.

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