A functional neuroanatomy of ties in Tourette syndrome

Background: Ties are involuntary, brief, stereotyped motor and vocal behavi ors often associated with irresistible urges. They are a defining symptom o f the classic neuropsychiatric disorder, Tourette syndrome (TS), and consti tute an example of disordered human volition. The neural correlates of ties are not well understood and have not been imaged selectively. Methods: Event-related [O-15]H2O positron emission tomography techniques co mbined with time-synchronized audio and videotaping were used to determine the duration of, frequency of, and radiotracer input during ties in each of 72 scans from 6 patients with TS. This permitted a voxel-by-voxel correlat ional analysis within Statistical Parametric Mapping of patterns of neural activity associated with the ties. Results: Brain regions in which activity was significantly correlated with tic occurrence in the group included medial and lateral premotor cortices, anterior cingulate cortex, dorsolateral-rostral prefrontal cortex, inferior parietal cortex, putamen, and caudate, as well as primary motor cortex, th e Broca's area, superior temporal gyrus, insula, and claustrum. In an indiv idual patient with prominent coprolalia? such vocal ties were associated wi th activity in prerolandic and postrolandic language regions, insula, cauda te, thalamus, and cerebellum, while activity in sensorimotor cortex was not ed with motor ties. Conclusions: Aberrant activity in the interrelated sensorimotor, language, executive, and paralimbic circuits identified in this study may account for the initiation and execution of diverse motor and vocal behaviors that cha racterize ties in TS, as well as for the urges that often accompany them.