Transcranial magnetic stimulation (TMS) is a procedure that uses magnetic fields to stimulate nerve cells in the brain to improve symptoms of depression. Transcranial magnetic stimulation may be tried when other depression treatments haven't worked.With TMS, a large electromagnetic coil is placed against your scalp near your forehead. The electromagnet used in TMS creates electric currents that stimulate nerve cells in the region of your brain involved in mood control and depression.