Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that can be used to stimulate brain activity and gather information about brain function. It is very useful when studying the areas of the brain related to motor activity (motor cortex, corticospinal tract, and corpus callosum). Repetitive transcranial magnetic stimulation (rTMS) involves the placement of a cooled electromagnet with a figure-eight coil on the patient's scalp and rapidly turning on and off the magnetic flux. This permits non-invasive, relatively localized stimulation of the surface of the brain (cerebral cortex). The effect of magnetic stimulation varies, depending upon the location, intensity and frequency of the magnetic pulses.