One specific hypothesis for the cause of tics in Tourette Syndrome attributes these symptoms to stereotyped motor habits hard-wired in the central nervous system. The basal ganglia and the modulation of their activity by dopamine are important neural substrates for such motor habits. The challenge in testing this hypothesis is to develop animal models that exhibit behavioral deficits and that also possess similar neurobiological mechanisms. I have generated a mutant mouse line with chronically increased dopaminergic activity. These mice exhibit stereotyped motor habits. For example, they display repetitive motor patterns, have difficulty inhibiting motor habits, and have impaired response habituation. The proposed study will further dissect these deficits in more behavioral studies. In addition, we will do biochemical analysis on the basal ganglia to understand the neurobiological mechanisms that account for these behavior deficits. Xiaoxi Zhuang, Ph.D. The University of Chicago, Chicago, IL Award: $71,995 Tourette Association of America Inc. – Research Grant Award 2001-2002