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## Pathophysiology  ### Pathological studies 
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|Transcriptome analysis of the human striatum in Tourette syndrome \citep{25199956} | This 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. 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 the diagnostic criteria for pediatric autoimmune streptococcal-associated neuropsychiatric disorders or pediatric acute onset neuropsychiatric syndrome. There was a lack of overlap between the results obtained in the present study using brain tissue and previous studies using blood samples. The authors conclude that their results "strongly [implicate] disrupted interneuron signaling in the pathophysiology of severe TS and suggests that metabolic alterations may be linked to their death or dysfunction." |  ### Neuroimaging and electrophysiology studies  |  |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 . 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. The challenges using neuroimaging techniques to study pediatric and clinical subjects are described in detail along with various strategies that can be used to collect high-quality data (Greene ).  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.