Source localization (response-locked).

<p>Top front view of the activation differences obtained via sLORETA analysis of the post-response ERPs. Crossed hands conditions were subtracted from parallel hands conditions. Only activation differences surpassing the significance threshold of p<.05 are depicted. As indicated by the blue color, the crossing of hands seems to have caused an increase in the activation in Brodman area 6/the middle frontal gyrus. Please note that the activation difference between parallel and crossed hands is bigger in the hemisphere which is not in charge of the motor response execution (red circles). This most probably depicts the post-response difference already observed in the RRPs shown in the right column of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062335#pone-0062335-g003" target="_blank">fig. 3a</a>. The used hand (RH and LH) is denoted at the left side of the figure while the hemisphere (R and L) is indicated next to the respective hemispheres. To further help orientation, black arrows indicate the central sulcus (CS) and the superior frontal sulcus (SFS).</p

Response-locked TF decompositions/wavelets.

<p>Electrodes FC1 and FC2 were used to form response-locked TF decompositions for the 16 different conditions as defined via hand position, spatial correspondence, motor execution and used hand. As a result, FC1 was considered “non-executive” and FC2 was considered “executive” in left hand responses. In right-hand responses, this categorization was reversed. Please note the difference between the parallel and crossed hands TF plots in the non-executive hemisphere (2^nd vs. 4^th row).</p

Visual illustration of experimental conditions/within-subject factors.

<p>The factor “motor execution” is depicted in the upper box. In the left section of that box, the executive hemisphere (the hemisphere responsible for the motor execution of the motor response) is marked red while in the right section of the box, non-executive hemisphere (the hemisphere not responsible for the motor execution of the motor response) is marked red. The factor “stimulus-response correspondence” is depicted in the lower box. Please note that there are parallel hands in the top rows of each of the four sub-boxes and crossed hands in the bottom rows. In a similar fashion, the left column of each of the four sub-boxes depicts left hand responses (the responding hand is indicated by light grey color), while the right column depicts right hand responses. In order to avoid explaining the obvious, we however refrained from explicitly depicting the conditions “used hand” (left anatomical hand vs. right anatomical hand) and “hand position” (parallel handy vs. crossed hands).</p

Response-locked ERPs and scalp topographies.

<p>Please note that all depicted results are based on CSD-transformed data. Hence, the units are given in µV/m². A) Response-locked ERPs at electrodes FC1 and FC2. Based on the observed differences, the 16 different conditions were subdivided into four data sets/graphs according to hand position and motor execution (whether the hemisphere underneath the respective electrode was in charge of the motor execution of the response). Each graph contains four individual curves for all possible combinations of used hand and spatial S-R correspondence. As a result, each of the four graphs contains two ERP curves from FC1 and two ERP curves from FC2. Please note the post-response difference between the parallel and crossed hands ERP curves in the non-executive hemisphere (right column). Time point zero denotes the time point of response execution. B) Response-locked scalp topographies visualizing activity at the time point of the negative post-response peak used for data analyses. This time point was individually determined on the basis of the semiautomatic peak picking procedure applied to the data depicted in figure section A. Note that electrodes FC1 and FC2 (black circles) account best for the observed frontal amplitude changes. C) Averaged response-locked scalp topographies each comprising a 200 ms time interval covering the time span from −200 ms till 400 ms. The maps were obtained by averaging the signal of all electrodes over an interval of 200 ms (from −200 ms to 0 ms, from 0 ms to 200 ms and from 200 ms to 400 ms, respectively). Due to amplitude differences, different scale settings were used for the three epochs. Black circles were used to highlight the localization of electrodes FC1 and FC2 which were used for several statistical analyses. In this context it is important to note that due to the process of temporal averaging, the electrodes showing the most pronounced peaks/greatest changes in amplitude are not necessarily those in the center of topographically depicted negativations/positivations (compare figure section B).</p

Results-based theoretical model.

<p>Given that the execution of the motor response and the spatial representation of the motor space are immutably locked to the two hemispheres of the brain <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062335#pone.0062335-Haggard1" target="_blank">[7]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062335#pone.0062335-Loayza1" target="_blank">[25]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062335#pone.0062335-Zhou1" target="_blank">[30]</a>, crossing hands (entering the "foreign” motor space) may impose a conflict. The consequences of an independent allocation of efferent and afferent information illustrated for left-hand responses. In crossed hands only, one hemisphere is executing the motor response while the response itself physically takes place in the motor space represented in the opposite hemisphere of the brain. For right hand responses, the allocation is mirror-inverted.</p

Neural correlates of altered sensorimotor gating in boys with Tourette Syndrome: A combined EMG/fMRI study

<p><i>Objectives</i>: It has been hypothesised that altered sensorimotor gating might be a core problem in Tourette Syndrome (TS). However, the underlying neurophysiological mechanisms are elusive. <i>Methods</i>: We applied functional magnetic resonance imaging (fMRI) to investigate the neural correlates of altered sensorimotor gating by means of prepulse inhibition (PPI) in 22 boys with TS and 22 healthy boys using tactile PPI. The electromyography of the startle response was recorded simultaneously to the acquisition of the fMRI images. <i>Results</i>: As expected, PPI of the startle response was reduced in boys with TS compared to the healthy boys. We found decreased PPI-related blood oxygen level-dependent (BOLD) activity in boys with TS in the middle frontal gyrus, postcentral gyrus, superior parietal cortex, cingulate gyrus and caudate body. In boys with TS PPI of the startle response was positively correlated to PPI-related BOLD activity in the superior parietal cortex. <i>Conclusions</i>: Our findings indicate that deficient sensorimotor gating in boys with TS is associated with reduced recruitment of brain regions responsible for the higher-order integration of somatosensory stimuli. Due to our strict sample selection we were able to reduce confounding by neural adaptation processes, long-term medication, gender or comorbidities.</p

Regression analyses on successful and erroneous trials.

<p>Brain regions showing significant positive and negative correlations across the total sample (N = 24) on successful and erroneous perceptual conflict trials (p<.005 uncorr., k>70 voxels).</p

Distribution of brain activation across successful and error trials during perceptual conflict.

<p>Random effects analyses of perceptual conflict trials (p<.005 uncorr., k>70 voxels) showed different activation patterns across the total sample and performance groups. (<b>A</b>) On successful trials across the total sample (upper panel) an activation pattern emerged encompassing PHG (BA's 35, 36) and caudate body. Good performers (lower left panel; shown in green) exhibited a more widely distributed activation pattern including fronto-limbic (BA's 11, 25), temporal (BA's 19, 39) and more posterior regions in the posterior cingulate (BA 30) and PHG (BA's 28, 35). Poor performers (lower right panel; shown in red) revealed no significant activation. (<b>B</b>) On error trials the total sample (upper panel) showed activation in fronto-parietal regions encompassing BA's 6, 9, 11, 32, 46 and 40. While for good performers (lower left panel; shown in green) no significant activation was seen poor performers (lower right panel; shown in red) revealed activation clusters in IFG and MFG (BA's 46, 47).</p

Event-related potentials of the Ne/ERN and CRN.

<div><p>The Ne/ERN (false responses) and CRN (correct responses) for HD and controls at electrode FCz (top) and at Fz (bottom).</p> <p>The x-axis denotes time in milliseconds (ms).</p> <p>The y-axis denotes voltage in µV.</p> <p>The bar plots denote significant differences in the peak-to-peak amplitude of the Ne/ERN between the groups for the electrodes FCz (left) and Fz (right).</p></div

Behavioral data.

<p>Response times and error rates across all trial types for both the total sample and performance groups.</p