This study will compare tSERs in normal volunteers to those in TS patients. Patients with bilateral sensory tics will be contrasted with those who have unilateral sensory tics, comparing power of the response at latencies on affected versus unaffected sides. Subjects will be seated in the MEG and instructed to "feel the delivered sensation, and try not to tic for seventy seconds, without counting". The trigeminal nerve will be electrically stimulated at 0.25 Hz for 30 seconds, which will be followed by head localization and subsequent rest for tic release. To evaluate sensory gating, the design is similar except the trigeminal stimulation will occur in short trains. Patients will be surveyed to determine if the instructions intensified sensory tics.