Discussion
tic, vocal tic, tic suppression, voluntary tic suppression, tic suppressibility, tics, vocal tics
CORTEX, SUPPRESSION, BRAIN
In the current study, we wished to assess how functional connectivity associated with tic suppression was related to CBIT response. EEG was recorded during three 2-min tic suppression sessions at baseline and endpoint. Brain sources were then reconstructed. We assessed functional connectivity within a subnetwork involved in tic suppression (Morand-Beaulieu et al., Our analyses revealed that functional connectivity during tic suppression did not change from baseline to endpoint. In CBIT, tics are not directly suppressed but are replaced by competing responses (Piacentini et al., While functional connectivity during tic suppression is not altered by CBIT, it seems that it may predict its outcome. Indeed, baseline functional connectivity during tic suppression predicted reduction in vocal tic severity after CBIT. This suggests that strategies used in the voluntary suppression of vocal tics may be relevant during the course of the CBIT training. These results also suggest probable overlap between the mechanisms of voluntary tic suppression and those of behavior therapy for tics. However, in the present study, this effect was only present for vocal tics and not motor tics. In CBIT, competing responses for vocal tics generally consist of ‘controlled breathing’ (Woods et al., To the best of our knowledge, only one study directly assessed the link between tic suppression and CBIT. McGuire et al. (In our study, supplementary analyses revealed that the observed effect was mainly driven by the connection between the right superior frontal gyrus and the right inferior parietal cortex. In the Desikan-Killiany atlas, the anatomically-defined superior frontal gyrus encompasses the functionally-defined dorso-medial prefrontal cortex (dmPFC), and the inferior parietal cortex region includes both the inferior parietal gyrus and the angular gyrus (Desikan et al., Finding predictors of treatment response is important from at least two perspectives: identifying individuals for whom CBIT may work well and understanding by which processes reductions in tic severity occur during CBIT. So far, few baseline characteristics may predict who is more likely to strongly benefit from CBIT. Sukhodolsky et al. (The findings of this study must be interpreted in the context of some limitations. First, our sample size was small, and our results need to be replicated in larger samples. Second, while using EEG allows the assessment of the synchronization of brain oscillations in a fast frequency band (alpha; 8–13 Hz), using fMRI would allow a more precise localization of the brain regions involved in tic suppression and CBIT response, compared with source-reconstructed EEG. Third, our hypotheses were based on potential parallels between tic suppression and behavior therapy. Thus, we decided to focus on a single subnetwork which we know is involved in tic suppression. Future studies should assess other known brain networks to better understand the role of functional connectivity in CBIT. Fourth, this study did not include a tic frequency count to assess the degree of tic suppressibility. This is in contrast with studies using the Tic Suppression Task from Woods and Himle (