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Resting state functional connectivity in Tourette Syndrome

By D.I. Larabi


Tourette Syndrome (TS) is a disorder characterized by involuntary, stereotyped, repetitive movements (motor tics) or sounds (vocal tics). There is strong evidence that implicates basal ganglia and cortico-striatal-thalamo-cortical (CSTC) abnormalities as central to the pathogenesis of TS. Repetitive over-activity of a specific set of striatal neurons would result in repeated, stereotyped, unwanted movements. In this way TS can be seen as a loss of the normal ability to suppress or 'gate' irrelevant sensory information. Resting state fMRI (rs-fMRI) can be used to discover patterns of coherence, these tell us about areas (circuits) of the brain that work together. By comparing blood flow scans of TS-patients to controls, we hope to learn more about the specific differences that correspond to having TS. With resting state functional connectivity (rs-fcMRI) research six separate networks are defined. One of these networks is the Default Mode Network (DMN). The default mode network is based in the ventromedial prefrontal cortex, the rostral anterior cingulate cortex (rACC), the posterior cingulate cortex (PCC), the inferior parietal cortex en precuneus. This network is active when an individual is awake and alert, but not actively involved in an attention demanding or goal-directed task. The functional significance of the default mode network is not yet clear. We hypothesize that different regions of the DMN are activated less during the resting state and that different regions that are active during tics are deactivated less during resting state in patients with TS. The SCA approach is used in this study. With SCA the cross-correlation coefficients of the time series in a particular anatomical seed region of interest (ROI) with all other voxels in the brain are calculated. This reveals the functional connectivity strength compared to this seed region. Fifteen individuals and 15 healthy subjects of the same gender, handedness and of similar age were recruited. The data was pre-processed, coregistrated to the corresponding anatomical scan and analyzed. A single study ROI general linear model (GLM) and a multi study GLM was done. In the controls group this showed the same resting state functional connectivity as showed in earlier studies in healthy subjects. In the patients group the thalamus and midbrain/pons were also activated in resting state, which can be explained by the fact that these regions are active during movement and tics. According to these results the DMN seems to function normally in adults with TS.

Year: 2010
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