<qa>  What must MCI and mild AD patients have?2. Meet criteria for either a amnestic mild cognitive impairment single or mixed domain or mild Alzheimers disease, or b have no cognitive impairment based on history, exam, neuropsychological testing, and consensus diagnosis. MCI and mild AD patients must have Clinical Dementia Rating scale score of 0.5 or 1. Unimpaired subjects must have Clinical Dementia Rating scale score of 0. 