Cortical Excitability in Obsessive-Compulsive and Related Disorders

This study will use transcranial magnetic stimulation (TMS) to study the function of the cerebral cortex (outer layer of the brain) in people with obsessive compulsive disorder (OCD) and related disorders. A non-invasive procedure, TMS activates areas of the brain with magnetic pulses that travel through the scalp and head and cause small electrical currents in the brain. People 18 years of age and older with OCD and disorders that may be related-tic disorders, such as Tourette's syndrome, focal dystonia (localized muscle cramps), body dysmorphic disorder (hypersensitivity to changes in appearance), eating disorders, such as anorexia nervosa, trichotillomania (compulsive hair-pulling)-may be eligible for this study. Healthy normal volunteers will also be enrolled. Candidates will be screened by telephone interview. Participants will undergo TMS. For this procedure, an insulated wire coil is placed on the subject's head. A brief electrical current passes through the coil, creating a magnetic pulse that travels through the scalp and skull and causes small electrical currents in the outer part of the brain. The stimulation may cause muscle, hand or arm twitching, or may affect movement or reflexes. During the stimulation, the subject may be asked to tense certain muscles slightly or perform other simple actions. The electrical activity of muscles during stimulation is recorded with a computer or other recording device, using electrodes attached to the skin with tape. Subjects will receive fewer than 500 magnetic pulses, and the study will take less than 3 hours. Participants may repeat the procedure on several occasions, if they agree.