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### Neuroimaging studies  The challenges of  using neuroimaging techniques to study pediatric and clinical subjects are described in detail along with suggestions concerning  various strategies that can be used to collect higher quality data \citep{26754461}. One The profound effects on structural MRI findings  ofthese challenges was an important (though frustrating) recent finding that  even very small head movements can cause artifactual findings were identified  in structural MRI a well designed study  \citep{25498430}. Neuroimaging scans were performed on 12 healthy adults while they were still orwhile  engaged in specific types of movements movement  including nodding, head shaking or a movement each subject invented and then repeated during the scan run. Even during scans when subjects attempted to remain still, there was an average of 3 mm/s mm/min of accumulated motion measured using  RMSpm (root mean square displacement per minute), but it minute). Not surprisingly, displacement  was significantly higher during the motion conditions. In general there conditions and substantial impact  was a 1-3% local found on gray matter volume and thickness estimates. An average apparent  volume loss for each 1 mm/s RMSpm increase. of approximately 0.7% mm/min of subject motion was calculated.  The greatestthickness  reductions in gray matter  were found in the pre- and post-central cortex, in the temporal lobes and pole, and entorhinal and parahippocampal regions. Some motion-associated Motion-associated  increases in thickness  were seen when measured by thickness, but less so for gray matter volume measurements. Recommendations were made in some frontal regions and deep sulci such as the medial orbital frontal region. Significant effects due  to reduce motion were still present even after excluding scans that failed a rigorous quality control procedure. Recommendations included reducing  head motion during scans as much as possible and then control possible, controlling  for motion inthe  statistical analysis, along with analyses, and  using correlational analyses to determine the associations between head motion and the predictors of interest. A more recent article provides an approach \citep{26654788} described a method  to addressing this concern with limit the effects of movement artifacts by using  asystem for  motion tracking and system to provide  prospective motion correction \citep{26654788}. during scanning trials.  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 striatum 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.