Researchers would like to use repetitive transcranial stimulation (rTMS) to better understand the roles of individual brain regions on the processes of learning and reasoning. 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.