Researchers plan to use low frequency (1 Hz) transcranial magnetic stimulation (TMS) to decrease the excitability of the PPC opposite the side of the amputated limb. TMS involves the placement of a cooled electromagnet with a figure-eight coil on the patient's scalp and turning on the magnetic flux. This permits non-invasive, relatively localized stimulation of the surface of the brain (cerebral cortex). When an area of the brain is stimulated a period follows when that area cannot be stimulated again. In this case, researchers plan to use TMS to stimulate the PPC in order to decrease the level of excitability there.