 i. 10 for 16 or more years of education ii. 6 for 8-15 years of education iii. 4 for 0-7 years of education Clinical Dementia Rating CDR 0.5, 1.0 or 2.0 Modified Hachinski Ischemic Scale HIS 4 Geriatric Depression Scale GDS 6 For subjects that decide to provide a CSF sample: Platelet count 100,000μL, Prothrombin Time PT 11 to 16 seconds, International Normalized Ratio 0.8 to 1.2 Study partner or caregiver to accompany subject to all scheduled visits Fluent in English Adequate visual acuity to allow neuropsychological testing Adequate auditory acuity to allow neuropsychological and ERP testing Good general health with no additional diseases expected to interfere with the study Willing to undergo neuroimaging and provide blood. The subject may optionally provide a CSF sample by lumbar puncture. 