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Background Inhibitory oscillatory mechanisms subserving tic compensation have been put forward in Tourette syndrome. Modulation of the beta rhythm (15–25 Hz) as the well-established oscillatory movement execution-inhibition indicator was tested during a cognitive-motor task in patients with Tourette syndrome. Methods Performing a Go/NoGo task, 12 patients with Tourette syndrome and 12 matched controls were recorded using whole-head magnetoencephalography. Results Compared to healthy participants, patients showed less beta suppression in the sensorimotor area and enhanced beta power in parieto-occipital brain regions contralaterally to the response hand. Average beta power and power gain correlated negatively with tic severity. Conclusions Increased motor inhibitory as well as visuomotor attentional processes are likely to subserve tic compensation. Correlational results suggest that stronger inhibitory compensation accompanies less tic severity. © 2015 International Parkinson and Movement Disorder Society

Tourette syndrome (TS) is a neuro-psychiatric disorder being characterized by motor and phonic tics typically preceded by sensory urges. Given the latter the role of the sensory system and sensorimotor interaction in TS has recently gained increased attention. 12 TS patients and 12 matched control subjects performed two tasks, requiring simple finger movements: a Go/NoGo task and a self paced movement task. Neurophysiological data was recorded using magnetoencephalography (MEG). Event related responses around movement onset, i.e. motor field (MF) occurring directly prior to the movement and movement evoked field (MEF) immediately after movement onset were analyzed using dipole modeling. MF peak amplitudes did not differ between groups in either task. In contrast, in both tasks MEF peak amplitudes were increased in TS patients. Moreover, larger MEF amplitudes during self paced movements were inversely correlated with motor tic frequency and severity. Enlarged MEF amplitudes as a marker of early sensory feedback of one's own movements probably represent enlarged sensory input from the periphery resulting from altered subcortical gating. We conclude that TS patients exhibit altered sensory–motor processing involved in voluntary movement control, which might also be successful in tic control.

Background In Gilles de la Tourette syndrome (GTS) increased activation of the primary motor cortex (M1) before and during movement execution followed by increased inhibition after movement termination was reported. The present study aimed at investigating, whether this activation pattern is due to altered functional interaction between motor cortical areas. Methodology/Principal Findings 10 GTS-patients and 10 control subjects performed a self-paced finger movement task while neuromagnetic brain activity was recorded using Magnetoencephalography (MEG). Cerebro-cerebral coherence as a measure of functional interaction was calculated. During movement preparation and execution coherence between contralateral M1 and supplementary motor area (SMA) was significantly increased at beta-frequency in GTS-patients. After movement termination no significant differences between groups were evident. Conclusions/Significance The present data suggest that increased M1 activation in GTS-patients might be due to increased functional interaction between SMA and M1 most likely reflecting a pathophysiological marker of GTS. The data extend previous findings of motor-cortical alterations in GTS by showing that local activation changes are associated with alterations of functional networks between premotor and primary motor areas. Interestingly enough, alterations were evident during preparation and execution of voluntary movements, which implies a general theme of increased motor-cortical interaction in GTS.

Background Long-term potentiation (LTP) and long-term depression (LTD) play important roles in mediating activity-dependent changes in synaptic transmission and are believed to be crucial mechanisms underlying learning and cortical plasticity. In human subjects, however, the lack of adequate input stimuli for the induction of LTP and LTD makes it difficult to study directly the impact of such protocols on behavior. Results Using tactile high- and low-frequency stimulation protocols in humans, we explored the potential of such protocols for the induction of perceptual changes. We delivered tactile high-frequency and low-frequency stimuli (t-HFS, t-LFS) to skin sites of approximately 50 mm2 on the tip of the index finger. As assessed by 2-point discrimination, we demonstrate that 20 minutes of t-HFS improved tactile discrimination, while t-LFS impaired performance. T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster. While t-HFS changes were spatially very specific with no changes on the neighboring fingers, impaired tactile performance after t-LFS was also observed on the right middle-finger. A central finding was that for both t-LFS and t-HFS perceptual changes were dependent on the size of the stimulated skin area. No changes were observed when the stimulated area was very small (< 1 mm2) indicating special requirements for spatial summation. Conclusion Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.

Fragestellung: Aus tierexperimentellen Befunden ist bekannt, dass Langzeitpotenzierung (LTP) und Langzeitdepression (LTD) grundlegende Elemente fur die Induktion plastischer Reorganisationsmechanismen im zentralen Nervensystem darstellen. Neuere Studien beim Menschen belegen, dass es mithilfe der repetitive transkranielle Magnetstimulation (rTMS) moglich ist, LTP- und LTD-artige Veranderungen in der Erregbarkeit des Gehirns zu induzieren. Unter der Verwendung eines kurzen hochfrequenten (50Hz) TMS Stimulationsmuster konnte kurzlich gezeigt werden, dass es nach Applikation einer sog. Theta Burst Stimulation (TBS) zu langanhaltenden Veranderungen der Erregbarkeit im stimulierten Kortexareal kommen kann. Allerdings fehlen bislang Studien daruber, ob die TBS Applikation bei Menschen auch eine Verhaltensrelevanz besitzt. Ziel dieser Studie war es, die Effektivitat der TBS Applikation uber den Bereich des linken primaren somatosensorischen Kortex (SI) im Hinblick auf mogliche TBS-induzierte Veranderungen in der taktile Perzeption bei Menschen zu untersuchen. Methodik und Ergebnisse: Die taktile Diskriminationsfahigkeit des rechten Zeigefingers wurde mithilfe der taktile Zwei-Punkt Diskrimination vor und unmittelbar nach TBS Applikation uber SI getestet. Dabei zeigte sich, dass durch TBS die Diskriminationsleistung des rechten Zeigefingers relativ zur sham-TBS signifikant verbessert werden konnte. Daruber hinaus konnte mithilfe von paired-pulse SEP Ableitungen eine Verringerung der intrakortikalen Inhibition innerhalb des stimulierten Kortexareals beobachtet werden. Zur Uberprufung der lokalen Spezifitat von TBS-induzierten Veranderungen wurde die TBS in einer zusatzlichen Gruppe von Probanden uber dem Bereich der linken tibialis anterior Muskelrepresentation des motorischen Kortex appliziert und die Diskriminationsfahigkeit des rechten Zeigefingers vor und nach TBS getestet. Die Ergebnisse belegen, dass eine TBS Applikation auserhalb von SI zu keinen signifikanten Veranderungen der taktilen Diskriminationsleistung fuhrt. Schlussfolgerung: Zusammenfassend konnte in dieser Studie erstmals die Effektivitat der TBS zur Induktion von perzeptuellen Verhaltensveranderungen bei Menschen gezeigt werden. Basierend auf diesen Befunden konnte die TBS Applikation eine vielversprechende unterstutzende Technik in der Neurorehabilitation sein, um die Wahrscheinlichkeit einer erfolgreichen Rehabilitation bei unterschiedlichen Patientenpopulationen zu steigern.

Adopting the patterns of theta burst stimulation (TBS) used in brain-slice preparations, a novel and rapid method of conditioning the human brain has recently been introduced. Using short bursts of high-frequency (50 Hz) repetitive transcranial magnetic stimulation (rTMS) has been shown to induce lasting changes in brain physiology of the motor cortex. In the present study, we tested whether a few minutes of intermittent theta burst stimulation (iTBS) over left primary somatosensory cortex (SI) evokes excitability changes within the stimulated brain area and whether such changes are accompanied by changes in tactile discrimination behavior. As a measure of altered perception we assessed tactile discrimination thresholds on the right and left index fingers (d2) before and after iTBS. We found an improved discrimination performance on the right d2 that was present for at least 30 min after termination of iTBS. Similar improvements were found for the ring finger, while left d2 remained unaffected in all cases. As a control, iTBS over the tibialis anterior muscle representation within primary motor cortex had no effects on tactile discrimination. Recording somatosensory evoked potentials over left SI after median nerve stimulation revealed a reduction in paired-pulse inhibition after iTBS that was associated but not correlated with improved discrimination performance. No excitability changes could be found for SI contralateral to iTBS. Testing the performance of simple motor tasks revealed no alterations after iTBS was applied over left SI. Our results demonstrate that iTBS protocols resembling those used in slice preparations for the induction of long-term potentiation are also effective in driving lasting improvements of the perception of touch in human subjects together with an enhancement of cortical excitability.