Somatosensory Gating of Pneumatic Stimuli in Adults with Chronic Tic Disorder

Individuals with chronic tic disorder (CTD) frequently report sensory over-responsivity, defined as heightened awareness of and/or behavioral reactivity to stimuli that are non-aversive to most neurotypical individuals. Within CTD populations, sensory over-responsivity is associated with severity of tics and co-occurring psychiatric symptoms. Despite its prevalence and association with core facets of the phenotype, the neurobiological basis of sensory over-responsivity in CTD remains unclear. Sensory gating, the physiological process of filtering out repetitive stimuli in early perceptual stages to facilitate attention to more salient stimuli, is one potential mechanism underpinning sensory over-responsivity in CTD. The current study sought to quantify somatosensory gating of pneumatic stimuli in adults with CTD using dense-array EEG and to determine the relationship between somatosensory gating and self-reported tactile responsivity. Neurotypical adults (n = 34) and adults with CTD (n = 28) completed a self-report and rater-administered neuropsychiatric evaluation, followed by an event-related potential somatosensory gating paradigm. Contrary to our hypotheses, somatosensory gating, as quantified by gating differences and regression analysis marginal effects, did not differ between groups for P50, N140, or P300 components, and gating indices were not associated with tactile responsivity. However, relative to neurotypical adults, adults with CTD had significantly smaller P50 amplitudes following S1, the first of the paired pneumatic stimuli. Moreover, adults with CTD with smaller S1 P50 amplitudes reported greater tactile responsivity. No other component amplitudes differed between groups. Findings suggest that adults with CTD have altered pre-conscious processing of non-noxious tactile stimuli and that this is linked with tactile over-responsivity.