Additional Study Information: THE PURPOSE OF THIS STUDY is to find out whether a type of brain imaging (called "Magnetic Resonance Spectroscopy Imaging" of "MRS") might be useful to help assess the presence of Alzheimer's disease (AD) and assess progression of the disease. MRS uses magnetic resonance imaging (MRI) methods to image the chemicals in the brain. You may be eligible to participate in this study as a control, or if you have mild cognitive impairment or mild Alzheimer disease.