RecruitingDevice studyPCS in Severe Treatment Resistant DepressionThis research study is designed to test if electrical stimulation of the surface of the brain in the frontal region will help treat depressive symptoms. Participants receive intermittent electrical stimulation to the brain, which involves surgically placing electric leads in between the tough fibrous membrane covering the surface of the brain and the surface of the brain itself. This type of stimulation is referred to as bilateral subdural prefrontal cortical stimulation (PCS) because it will specifically target the outer layer of the brain at the midline, right behind the forehead. It uses a pacemaker-like device, the Proclaim Elite SCS System (non-rechargeable) or the Eterna SCS System (rechargeable), both by Abbott Laboratories for stimulation. Although the U.S. Food and Drug Administration (FDA) has approved the Proclaim Elite SCS system for brain stimulation for patients with chronic pain and muscular diseases, such as Parkinson's, its use is still investigational, and the surgery is still experimental for patients who have depression.