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### Neuroimaging and electrophysiology studies  See also a review article on recent advances in TS neuroimaging \citep{26543796}. \citep{26543796}|  Issues that should be considered when designing MRI neuroimaging studies of children and clinical populations are identified (Greene: "Considerations for MRI study design and implementation in pediatric and clinical populations). This article describes a variety of ways to minimize head movement and to account for movement effects during data analysis. |  |Head movement effects \citep{25498430}|  An important (though frustrating) recent finding was that even very small head movements can cause artifactual findings in _structural_ MRI \citep{25498430}. .  Neroimaging scans were performed on 12 healthy adults while they were still or engaged in specific types of movments including nodding, headshaking and a movement that they invented and then repeated during the scan run. Even during scans when subjects remained still, there was an average of 3 mm/s RMSpm (RMS displacement per minute), but it was significantly higher during the motion conditions. In general there was a 1-3% local volume loss for each 1 mm/s RMSpm increase. The greatest thickness reductions were found in the pre- and post-central cortex, in the temporal lobes and pole, and enthorhinal and parahippocampal regions. Increased thickness associated with motion was seen in regions associated with deep sulci such as the medial orbital frontal and lateral frontal areas. Recommendations were made to reduce head motion during scans as much as possible and then control for motion in the statistical analysis, along with using correlational analyses to determine the associations between head motion and the predictors of interest. A more recent article \citep{26654788} described the development of a system for motion tracking and prospective motion correction, and mentions similar systems that are available for other scanner platforms. 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.   | **Title** | **Comment** |  |:----------|:------------|  | Striatal D1- and D2-type dopamine |Dopamine  receptors are linked to and  motor response inhibition in human subjects\citep{} |  "Stop-signal inhibition\citep{} |Stop-signal  reaction time was negatively correlated with D1- and D2-type BP_ND activation  inwhole striatum, with significant relationships involving  the dorsal striatum, but not the ventral striatum, and no striatum. No  significant correlations involving the continuous performance task." task were found suggesting that  Compare also \citep{25562824}. | |  | Motor execution and motor imagery \cite{26566185}|  An exploratory study found neural hyperactivation for both types of tasks when TS adults were compared to controls. Interestingly, the exception to this was that basal ganglia and thalamic activation was smaller in the TS subjects than the controls. Premotor activation during the motor imagery tasks was correlated with tic severity. |