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### Pathological studies  An important study follows up on the autopsy results from the Vaccarino lab by comparing RNA transcripts from the basal ganglia of 9 TS and 9 matched control subjects \citet{25199956}. \citep{25199956}.  The most strongly associated set of downregulated transcripts involved striatal interneurons, consistent with the autopsy studies. The leading set of upregulated transcripts involved immune-related genes even though none of the TS subjects met proposed diagnostic criteria for PANDAS or PANS. The results obtained in the present study using brain tissue did not overlap with those of previous studies using blood samples. The authors interpret their results as implicating disrupted basal ganglia interneuron signaling in the pathophysiology of severe TS. ### Animal models 
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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}. The profound effects of even very small head movements on structural MRI analyses were identified in a well-designed study \citep{25498430}. T1-weighted MRI of brain was acquired in 12 healthy adults while they were still or engaged in specific types of 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/min of accumulated motion measured using RMSpm (root mean square displacement per minute). During the motion conditions, substantial impact was found on gray matter volume and thickness estimates. Apparent volume loss averaged approximately 0.7% mm/min of subject motion. The greatest reductions in gray matter occurred in pre- and post-central cortex and in the temporal lobes. Motion-associated increases in thickness were seen in some frontal regions and deep sulci such as the medial orbital frontal region. Significant effects due to 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, controlling for motion in statistical analyses, and using correlational analyses to determine the associations between head motion and the predictors of interest. Tisdall and colleagues described a method to limit the effects of movement artifacts by using a motion tracking system to provide prospective motion correction during scanning \citet{26654788}. \citep{26654788}.  A whole-brain analysis of cortical gray matter found reduced gray matter (GM) thickness in the insula and sensorimotor cortex for TS children and young adults compared to a matched control group \citep{26538289}. GM thickness in these areas correlated negatively with Premonitory Urge for Tics Scale scores.