 Hypothesis: The overarching hypothesis is that both diabetes and depression have the effect of lowering magnetization transfer ratios MTR in the anterior cingulate cortex, subcortical nuclei head of the caudate nucleus and putamen and the frontal white matter. These effects are cumulative and may not be additive in some regions. Our pilot data suggest that MTR will be lower in these regions in patients with type 2 diabetes both with and without depression when compared with healthy controls. In some regions eg. head of the caudate nucleus - see preliminary data the investigators anticipate that patients with diabetes and MDD will have the lowest and healthy controls will have the highest MT ratios. The group with unipolar depression without diabetes and the diabetic controls will have MT ratios that fall between these two groups. In other regions of interest, both groups with diabetes will have values significantly different from healthy controls, with patients diagnosed with unipolar depression falling between the healthy and diabetic groups. 