Age-dependent differences in functional brain networks are atypical in Tourette syndrome

Tourette syndrome (TS) is a neurodevelopmental disorder characterized by motor and vocal tics. TS is complex, with symptoms that involve sensory, motor, and top-down control processes and that fluctuate over the course of development. While many have studied atypical brain structure and function associated with TS, the neural substrates supporting the complex range and time-course of symptoms is largely understudied. Here, we used functional connectivity MRI to examine functional networks across the whole-brain in children and adults with TS. To investigate the functional neuroanatomy of childhood and adulthood TS, we separately considered the sets of connections within each functional network and those between each pair of functional networks. We tested whether developmental stage (child, adult), diagnosis (TS, control), or an interaction between these factors was present among these connections. We found that developmental changes for most functional networks in TS were unaltered (i.e., developmental differences in TS were similar to those in typically developing children and adults). However, there were several within-network and cross-network connections that exhibited either "divergent" or "attenuated" development in TS. Connections involving the somatomotor, cingulo-opercular, auditory, dorsal attention, and default mode networks diverged from typical development in TS, demonstrating enhanced functional connectivity in adulthood TS. In contrast, connections involving the basal ganglia, thalamus, cerebellum, auditory, visual, reward, and ventral attention networks showed attenuated developmental differences in TS. These results suggest that adulthood TS is characterized by increased functional connectivity among functional networks that support cognitive control and attention, which may be implicated in suppressing, producing, and attending to tics. In contrast, subcortical systems that have been implicated in the initiation and production of tics may be immature in adulthood TS. Jointly, our results reveal how several cortical and subcortical functional networks interact and differ across development in TS.