 Approximately half of those who develop depression in late life never had depression before. The classic view is that changes taking place in our brains as we age contribute to the development of late-onset depression. This view is supported by the relative absence of family history for those with late onset depression. This research study will recruit 70 older adults with late life depression and 70 older adults without depression. All participants will receive a sub-clinical, non-contrast magnetic resonance imaging MRI scan at the beginning of the study and then again 12 weeks later at the completion of the study. The depressed older participants will also receive a Food and Drug Administration FDA-approved antidepressant, escitalopram Lexapro, as treatment for their depressive symptoms over 12 weeks. This MRI study may help the researchers identify how abnormalities in brain systems that control our ability to ignore distractions, control our emotions, and anticipate reward may contribute to the development of depression in older adults. The investigators hope that the findings promote the development of tests that may improve the detection of older adults at risk for poor treatment outcomes and eventually guide the development of novel treatments for depression. 