The aim of the proposed study is to determine if the NMDA receptor antagonist memantine has a neuroprotective effect on magnetic resonance spectroscopic imaging (MRS) measures of brain NAA and magnetic resonance imaging (MRI) volumetric measures of hippocampal volume. In secondary analyses, we will determine if measures of clinical stabilization produced by memantine in the treatment of Alzheimer's disease (AD) parallels stabilization of MRS measures of brain NAA and MRI volumetric measures of hippocampal volume.