 This study involves behavioral assessments, neurocognitive testing, blood sampling and magnetic resonance imaging MRI scanning. Goals of this study are to determine the impact of inflammation on glutamate concentrations in the basal ganglia and on the integrity of white matter tracts in the basal ganglia and other subcortical regions of middle-aged depressed versus non-depressed individuals and to associated the impact of glutamate and white matter changes on behavioral symptoms among the same group of patients. 