Patients will have clinically documented Tourette's syndrome or chronic motor tic disorder as defined by DSM-IV-TR and evaluation of tic severity using the Yale Tic Scale. This criterion will be established by preliminary screening in the NINDS Movement Disorders Outpatient Clinic. Regarding co-morbid disorders such as ADHD and OCD, we will accept a mild degree of ADHD and mild to moderate degree of OCD. These disorders will be established by a psychiatrist using below listed scales and criteria. In order to participate in this study, patients will be asked to stop any medication that can influence the central nervous system for 2 weeks prior to exam. Patients taking fluoxetine will be asked to stop it 4 weeks prior to the exam. Stopping the medications for Tourette syndrome or tics, OCD and ADHD may lead to worsening of their symptoms.