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Many researchers have used a variety of experimental paradigms to study motor response inhibition since tic expression seems related to motor inhibition. In healthy adults performance on a stop-signal task and a continuous performance task was examined using positron emission tomography to measure striatal D1- and D2-type receptor availability \citep{25878272}. Stop-signal reaction time was negatively correlated with both D1- and D2-type receptor activation in both the associative striaum and the sensory motor striatum. Neither D1- nor D2-type receptor activation was associated with Go reaction time or Stop signal reaction time on the continuous performance task suggesting that these two tasks are associated with different neurochemical mechanisms related to motor response inhibition.   A review examined task-based fMRI studies on TS in areas such as premonitory urges, tic suppression, and voluntary motor execution \citep{26402403}. A summary of free-ticcing conditions from four studies identified the regions that were most commonly activated as the left cerebellum, right cingulum, middle frontal gyrus, the rolandic operculum, right pallidum, right SMA and thalamus. Two studies examined the neural regions associated with tic generation. Only the left middle frontal gyrus was activated during both tic generation and tic suppression. On NoGo trials TS subjects exhibited greater activation in the bilateral prefrontal cortex, thalamus and caudate while voluntary motor execution was associated with greater activation in the left prefrontal cortex, right cingulum, and the anterior portion of the SMA. The right dorsal premotor and the SMA were identified as the regions with activity correlated with tic severity ratings across studies. The premotor cortices of the medial wall (SMA/anterior cingulate cortex) were found to be involved across the various types of studies. The thalamus was involved in all types of studies except for self-produced movements. A The authors also provided a  brief summary of the issues that still need to be addressed in neuroimaging studies is provided. studies.  A whole brain analysis of cortical gray matter found reduced gray matter thickness in the insula and sensorimotor cortex for TS children and young adults compared to a matched control group \citep{26538289}. In addition, Premonitory Urge for Tics Scale scores were negatively correlated with grey matter thickness in these areas. These results demonstrate the value of examining neural substrates associated with premonitory urges separately from the ones associated with tic generation.  Resting-state functional magnetic resonance imaging identified greater functional connectivity between the right dorsal anterior insula and the bilateral supplementary motor area in TS adults compared to controls \citep{25855089}. Post-hoc analyses found significant correlations between PUTS scores and both right dAI-right SMA2 and right dAI-left SMA1 connectivity suggesting that these regions might be involved in the increased awareness of body sensations that tend to be associated with premonitory urges. The authors paid attention to head movement and removed high-movement frames, but recent analyses suggest that the motion threshold of 0.4mm and the lack of global signal regression in this analysis may have introduced some artifactual correlations between brain regions due to residual small head movements during the scan \citep{25462692}.