 Exploratory Aim 1: In an exploratory manner the investigators will estimate cerebral blood volume, a measure of the cerebral microvasculature, in critical brain regions involved in frontal-subcortical circuitry anterior cingulate, dorsolateral white, head of the caudate nucleus and the putamen in subjects in our depressed diabetic group and the three comparison groups using dynamic susceptibility contrast MR imaging perfusion-weighted MR imaging. 