Alterations of sensorimotor predictive processes and their electrophysiological signatures in Tourette syndrome

People with Tourette syndrome exhibit excessive motor actions known as tics. An aversive sensation called the premonitory urge often precedes these tics, leading to the conceptualization of Tourette syndrome as a sensorimotor disorder. In typical individuals, motor actions adapt flexibly to changes in the predictability of sensory cues. However, it remains unclear whether such sensorimotor predictions are altered in Tourette syndrome and, if so, which neural processes might underlie these changes. This study examined 30 individuals with Tourette syndrome and 30 control participants while recording EEG. Participants performed a motor cueing version of the Posner task, requiring behavioural adjustments to varying levels of cue predictability. Notably, while control participants exhibited the expected interaction between validity and cue predictability on motor responses, this effect was absent in individuals with Tourette syndrome. Neural signatures of flexible predictability-dependent processing were characterized by applying a Bayesian observer model to estimate trial-wise subjective beliefs about cue predictability from response speed and using these model-derived cue predictability estimates in single-trial regression analyses with EEG data. Our findings revealed that model-derived cue predictability modulated P3a amplitude, P3b onset and P3b amplitude differentially. Importantly, P3b amplitude modulations reflected beliefs about cue predictability, which were diminished in participants with Tourette syndrome. Overall, our results indicate that individuals with Tourette syndrome exhibit abnormal behavioural adaptation to the changing predictability of motor cues, suggesting an impaired processing of sensorimotor predictions. At the neural level, this is reflected by impaired activity associated with updating stimulus-response associations.