Paul Holtzheimer, M.D., Dartmouth-Hitchcock Medical Center, will try to distinguish between two kinds of treatment-resistant depression to better tailor treatments to symptoms. He will look at a population whose depression has not improved in response to typical treatments. Dr. Holtzheimer predicts refractory depression is rooted in one of two distinct brain areas, requiring two distinct kinds of treatment. His team will test this idea by applying transcranial magnetic stimulation (TMS), an alternative treatment, to the two different brain areas in people with depression and then measuring how it affects their symptoms and behavior.