Major depressive disorder deep brain stimulation illustration (front view). Illustration of the Libra® Deep Brain Stimulation System, an investigational device being tested in clinical research studies for major depressive disorder. The Libra system sends mild electrical pulses to a specific target in the brain from a device implanted in the chest. This device was developed by St. Jude Medical Inc. Caution: Investigational device, limited by United States law to investigational use. (Graphic: St. Jude Medical Inc.)