Repetitive transcranial magnetic stimulation (rTMS) is used to try to stop the pre-tic sensations. For TMS, the subject sits in a chair. A wire coil is held on the subject s scalp, and a brief electrical current is passed through the coil, creating a magnetic pulse that stimulates a region of the brain. The goal of this stimulation is to reduce the sensory experience that precedes a tic in one region of the body. During stimulation, the subject hears a click and may feel a pulling sensation on the skin under the coil. There may be a twitch in the muscles of the face, arm or leg. This study uses a pattern of repeated pulses delivered in short bursts. Following each train of pulses, the effect of the stimulation on sensation will be tested by asking the subject to rate the strength of a pinprick and of a vibration. In addition, the nerves are stimulated with small shocks to evaluate the effect of the TMS on nerve activity. To determine the effect of TMS on the pre-tic sensation, subjects are asked to watch a clock and report when they are having a sensory experience. The effect on motor tics will be evaluated by using EMG to indicate the tics.