Patients suffering from severe depression who have not responded to other treatments may be helped by deep brain stimulation, researchers said on Monday. The treatment, which is like a pacemaker for the brain, uses electrodes implanted in the brain to switch off or interrupt electrical circuits linked to depression. In four out of six patients who failed on all other treatments, deep brain stimulation relieved their depression. "Patients would experience an immediate shutdown of a negative state," Dr Helen Mayberg, a neurologist at Emory University School of Medicine in Atlanta, Georgia told a news conference. The technique was developed for Parkinson's disease patients but Mayberg and her colleagues have adapted it for patients with severe depression. Using brain-imaging techniques, the scientists implanted electrodes deep into an area of the brain that they had linked to depression while the patients were under a local anaesthetic. As their brains were stimulated, the patients, who were awake, were told to explain what they were feeling. They described a sense of calmness or easiness. There were no side effects, according to the researcher.