Research has implicated dysfunction of cortico-striatal-thalamo circuits in the brain of people with Tourette’s disorder (TD). However, little is known about the dysregulation of brain chemicals that may contribute to TD. The use of proton Magnetic Resonance Spectroscopy (1H MRS) has the advantage of affording a non-invasive assessment of brain chemicals present in the brain. g-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system, has been hypothesized to play a critical role in several neuropsychiatric disorders, including TD. To date, no study has examined brain GABA in children with TD. Using 1H MRS, this study aims to examine whether TD is associated with alterations of GABA in the basal ganglia (BG) and the anterior cingulate cortex (ACC); brain regions that have been implicated in the disorder. Total Choline (tCho), total Creatine (tCr) and N-Acetylaspartate (NAA), all biomarkers for neurocellular health and metabolism in the brain, will also be quantified. For this study fifteen medically healthy adolescents between 12 and 17 years of age with TD and fifteen adolescents without TD will be enrolled. The striatum and anterior cingulate cortex of all the participants will be scanned with 1H MRS. We hypothesize that adolescents with TD will have significantly less GABA, tCho, tCr, and NAA in the basal ganglia and cortical regions of their brains compared to adolescents without TD. Vilma Gabbay, M.D., M.S., Barbara Coffey, M.D., M.S., Dikoma Shungu, Ph.D. New York University School of Medicine, New York, NY Award: 75,000 Commentary: It is generally accepted that TS is caused when something in the brain goes wrong and it is likely that many different factors can lead to the generation of tics. In their study, Drs. Gabbay, Coffey and Shungu will measure the levels of certain brain chemicals (neurotransmitters) in several areas of the brain thought to be involved in TS. They will compare the amounts of these chemicals in adolescents with and without TS. They expect to find that people with TS have less of these brain chemicals and they think that this could be one of the many factors that can lead to the generation of tics. Tourette Association of America Inc. – Research Grant Award 2009-2010