A developmental fMRI study of self-regulatory control in Tourette's syndrome.

OBJECTIVE: Disturbances in the maturation of neural systems that mediate self-regulatory processes may contribute to the development of Tourette's syndrome by releasing motor and vocal tics from regulatory control. The purpose of this study was to examine the age correlates of functional activity in neural circuits that subserve self-regulatory control in children and adults with Tourette's syndrome.
METHOD: The participants were 136 children and adults, which included 66 Tourette's syndrome patients and 70 healthy comparison subjects. During performance of the Stroop interference task, the authors compared the functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent response in patients with Tourette's syndrome with that of healthy comparison subjects. General linear modeling of Stroop-related activations was used to compare the differential effects of age and behavioral performance on changes in self-regulatory control between the two diagnostic groups.
RESULTS: Although the correlations of age with behavioral performance on the Stroop task were similar between patients with Tourette's syndrome and healthy comparison subjects, the two groups differed significantly in their correlations of age with the magnitude of regional brain activation during the task. Interactions of age with diagnosis were detected in the ventral prefrontal (Brodmann's areas 10 and 24) and posterior cingulate cortices (Brodmann's area 31), and post hoc analyses indicated that subjects with Tourette's syndrome deactivated these regions less with advancing age. Greater activation of bilateral frontostriatal regions (Brodmann's areas 9/46, 45/46; lenticular nucleus; and thalamus) accompanied poorer performance in the patient group, which-in the presence of normal behavioral performance on the Stroop task-suggests that greater activation of the frontostriatal systems helps to maintain task performance in individuals with Tourette's syndrome.
CONCLUSIONS: Normative developmental correlates of activity in frontostriatal circuits that subserve self-regulatory control are disturbed in persons with Tourette's syndrome. These aberrant developmental correlates are likely a consequence of greater anatomical and functional disturbances in these circuits in adults with Tourette's syndrome, which leads to impaired regulation of tic behaviors. Reduced default-mode processing in ventral prefrontal and posterior cingulate cortices in adults with Tourette's syndrome suggests the presence of greater difficulty in engaging mental processes that become active when freed from the demands of more challenging cognitive tasks. However, individuals with Tourette's syndrome appear to co-opt normal developmental processes in circuits that subserve age-related improvement in self-regulatory control while presumably struggling to maintain adequate task performance.