This study will recruit patients who are being seen with a memory complaint or the first time. It will be prospective in nature. Subjects will initially be evaluated by clinicians and then clinicians will fill out a rating questionnaire as to their level of certainty of various possible dementia diagnoses. Then, during the testing portion of the study, subjects will return to have an EEG test completed measuring event related potentials during an acoustic oddball paradigm task. The EEG will be completed by a technician who has no knowledge of the subject's clinical diagnosis. After the EEG is performed, the data will be evaluated by the study clinician in a blinded fashion. The clinician will log the EEG results as being either consistent with Alzheimer's disease or not. Finally, there will be analysis of the initial clinical rating by clinicians in comparison to a given subject's EEG results and interpretation. This will allow determination as to whether or not the clinical diagnosis was in agreement or disagreement with the EEG data and interpretation. At this time point a second clinician rating questionnaire will be completed to assess the current level of confidence and diagnostic certainty in light of the now revealed EEG data in addition to clinical data. There will also be quantitative analysis of MRI structural data regarding regional atrophy patterns as well as Amyloid PET data for some of the participants which will act as a diagnostic gold standard.