All Participants

• Age 55-90, with a minimum age of 65 for the normal control group and the significant memory concern group
• Study partner who has frequent contact with the participant (an average of 10 hours per week or more) and can accompany the participant to all clinic visits
• Seeing and hearing ability adequate for neuropsychological testing
• Good general health
• Participant is not pregnant, lactating, or of childbearing potential (women must be 2 years postmenopausal or surgically sterile)
• Six grades of education or a good work history (sufficient to exclude mental retardation)
• Must speak English or Spanish fluently
• No medical contraindications to MRI
• Stability of permitted medications for 4 weeks; in particular, participants may take antidepressants lacking significant anticholinergic side effects, estrogen replacement therapy, gingko biloba (permissible but discouraged); washout from psychoactive medication for at least 4 weeks prior to screening
• Hachinski score of less than or equal to 4; Geriatric Depression Scale less than 6

Cognitively Normal Participants

• Free of memory complaints
• Normal memory function score on Wechsler Memory Scale; Mini-Mental State Exam (MMSE) score of 24-30; Clinical Dementia Rating (CDR) = 0; Memory Box score = 0
• Cognitively normal, based on an absence of significant impairment in cognitive functions or activities of daily living

Signicant Memory Concern Participants

• Significant subjective memory concern as reported by subject, study partner, or clinician and confirmed by Cognitive Change Index of ≥16
• Normal memory function score on Wechsler Memory Scale (adjusted for education); Mini-Mental State Exam (MMSE) score of 24-30; Clinical Dementia Rating (CDR) = 0; Memory Box score = 0
• Cognitively normal, based on an absence of significant impairment in cognitive functions or activities of daily living
• Medications permitted if stable for 4 weeks, including: antidepressants lacking significant anticholinergic side effects, estrogen replacement therapy, gingko biloba (permissible but discouraged); washout from psychoactive medication (such as excluded antidepressants, neuroleptics, chronic anxiolytics or sedative hypnotics) for at least 4 weeks prior to screening

EMCI and LMCI Participants

• Subjective memory concern as reported by participant, study partner, or clinician
• Abnormal memory function score on Wechsler Memory Scale; Mini-Mental State Exam (MMSE) score of 24-30; Clinical Dementia Rating (CDR) = 0.5; Memory Box score = 0.5 or higher
• General cognition and functional performance such that a diagnosis of AD cannot be made by the site physician
• Cholinesterase inhibitors and memantine are allowable if stable for 12 weeks prior to screening

Alzheimer's Disease Participants

• Subjective memory concern as reported by subject, study partner, or clinician
• Abnormal memory function score on Wechsler Memory Scale; Mini-Mental State Exam (MMSE) score of 20-26; Clinical Dementia Rating (CDR) = 0.5 or 1.0
• Meets criteria for probable Alzheimer's disease
• Cholinesterase inhibitors and memantine are allowable if stable for 12 weeks prior to screening

Follow-up Participants from ADNI1 and ADNI-GO

• Must have been enrolled and followed in ADNI1 for at least one year or enrolled in ADNI-GO with original diagnosis of cognitively normal, MCI, or EMCI regardless of whether a diagnostic conversion has occurred since initial enrollment in ADNI
• Willing and able to continue to participate; a reduced battery of tests is allowable if the subject is not able/willing to complete the full battery
• Study partner is available who has frequent contact with the participant (e.g. an average of 10 hours per week or more), and can accompany the participant to all clinic visits for the duration of the protocol