 1 In TS, normal performance during a working memory WM task requires greater activation of specific brain regions parietal cortex, medial frontal cortex and thalamus than in control subjects, and this excess fMRI response is reduced improved by exogenous levodopa. 2 These fMRI results in TS relate specifically to WM, to TS, and to dopamine receptor activation, rather than to non-WM components of the cognitive task, comorbidity, placebo effects, or other confounds. 