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P148 Dose–effect of transcranial static magnetic field stimulation on excitatory and inhibitory intracortical circuits
Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
P146 Sulcus-based linear mapping of sensorimotor integration in the hand motor area—R. Dubbioso a,*, E. Raffin b, A. Karabanov a, S. Nielsen a, A. Thielscher a,c, H. Siebner a (a Hvidovre Hospital, University of Copenhagen, Centre for Functional and Diagnostic Imaging and Research Danish Research Centre for Magnetic Resonance (DRCMR), Hvidovre, Denmark , b Grenoble Institute of Neuroscience, Research Centre U836 Inserm-UJF, Team 11 Brain Function & Neuromodulation, Grenoble, France, c Technical University of Denmark, Biomedical Engineering Section, Kongens Lyngby, Denmark) ⇑
Corresponding author.
Introduction: We have recently introduced neuronavigated linear transcranial magnetic stimulation (TMS) mapping as a method to capture motor somatotopy in the hand motor area (M1HAND). In contrast to other mapping methods, linear TMS mapping adjusts the TMS coil position and orientation to the individual shape of the central sulcus (CS). Here we used this technique to map the spatial representation of short-latency afferent inhibition (SAI) in M1HAND. SAI refers to a suppression of the motor evoked potential (MEP) amplitude by preceding peripheral electrical nerve stimulation of the contralateral hand. SAI is somatotopically specific: it’s stronger when electrical stimulation is applied close to the TMS-target muscle (homotopic stimulation) and weaker when not (heterotopic stimulation). Aim: We hypothesized a somatotopic expression of SAI in M1HAND for homotopic as opposed to heterotopic stimulation. Methods: Electrical stimulation of the left index finger or little finger was applied 23 ms before TMS of right M1HAND. MEPs were recorded from left first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles. SAI was applied randomly at seven M1 target sites following the individual shape of the right CS. Results: We found a clear somatotopic representation of SAI. Homotopic SAI of the ADM muscle was expressed more medially than homotopic SAI of the FDI muscle along the M1HAND. We also found somatotopy for heterotopic stimulation. Here SAI was replaced by a ‘‘surrounding” facilitation of the heterotopic muscle. Conclusions: Linear sulcal TMS mapping revealed a somatotopically defined centre-surround organization of sensorimotor integration in the human M1HAND. doi:10.1016/j.clinph.2016.10.267
P147 Effects of cTBS on the integration of haptic light fingertip contact and body sway—D. Kaulmann *, L. Johannsen (Technische Universität München, Munich, Germany) ⇑
Corresponding author.
Question: In the present study we aimed to investigate the effects of continuous theta burst stimulation (cTBS) over the posterior parietal cortex (PPC) and how it effects body sway and the integration of light touch. Methods: In right-handed young adults, cTBS with an intensity of 80% of the passive motor threshold was applied for 60 s over the left and right Posterior Partial Cortex. Additionally, a sham condition was applied. Target locations were identified using real-time neuronavigation. Participants were tested blindfolded in quiet upright Tandem-Romberg stance before and after each stimulation interval. During these tests they were instructed to actively initiate and cease
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finger contact with an earth-fixed referent in response to an acoustic signal. Testing was carried out on two non-consecutive sessions. Body sway was recorded in terms of Centre of Pressure (CoP) and trunk kinematics in addition to forces and torques at the contact point. Results: The results of 13 healthy right handed participants reveal that cTBS over the right PPC affected postural control. The overall level of body sway was decreased after inhibition, while the effect of Light Touch was still present. Inhibition of the left PPC or sham stimulation did not decrease the overall level of body sway. Conclusion: The cause of this effect might be strategies of the motor control system that lead to a co-contraction and thus reducing body sway. However, this does not mean that participants were more stable. Another possible explanation might be that inhibition of the right PPC disrupts processes for state estimation of body sway in spatial reference frames or mechanisms of stability selfexploration (i.e. Zatsiorsky and Duarte, Motor Control, 1999; Ehrenfried et al., Brain Res Cogn Brain Res, 2003; Kiemel et al., J Neurophysiol, 2006). doi:10.1016/j.clinph.2016.10.268
P148 Dose–effect of transcranial static magnetic field stimulation on excitatory and inhibitory intracortical circuits—M. Dileone a,b,*, L. Mordillo Mateos b,*, A. Oliviero b, G. Foffani a,b (a HM Puerta del Sur, Centro Integral de Neurociencias, Mostoles (Madrid), Spain, b Hospital Nacional de Parapléjicos, Toledo, Spain) ⇑
Corresponding authors.
Question: Transcranial static magnetic field stimulation (tSMS) is a new low-cost, non-invasive brain stimulation (NIBS) technique. When tSMS is applied for 10–15 min over the motor cortex, it leads to a short-lasting decrease of cortical excitability in healthy subjects, as measured by a decreased amplitude of motor-evoked potentials (MEPs), associated with an increase of short-latency intracortical inhibition (SICI). Here we aimed to test the effects of a longer application of tSMS (30 min) on excitatory and inhibitory intracortical circuits. Methods: We performed 3 randomized double-blind shamcontrolled experiments in a total of 31 right-handed healthy subjects. In experiment 1 we assessed MEP amplitudes before and after tSMS (or sham) applied for 30 min to the non-dominant motor cortex. In experiment 2 we tested the effects of 30 min of tSMS on SICI and I wave interaction. In experiment 3 we evaluated the effects of 10 min of tSMS on SICI and on the first peak of I wave interaction (short-latency intracortical facilitation, SICF). Results: Prolonged application of tSMS (30 min) significantly decreased MEP amplitudes compared to sham till 30 min after the end of tSMS and, surprisingly, reduced SICI while increasing SICF. By applying tSMS for only 10 min, we found a significant and short-lasting increase of SICI with reduction of SICF. Conclusions: We found that a prolonged application of tSMS leads to a long-lasting reduction in motor cortex excitability, similar to those typically induced by continuous theta-burst stimulation (cTBS) and cathodal transcranial direct current stimulation (tDCS). Moreover, SICI and SICF could be modulated in a bidirectional way by tSMS, depending on the application time, revealing a dose–effect of tSMS on excitatory and inhibitory intracortical circuits. doi:10.1016/j.clinph.2016.10.269
P146 Sulcus-based linear mapping of sensorimotor integration in the hand motor area—R. Dubbioso a,*, E. Raffin b, A. Karabanov a, S. Nielsen a, A. Thielscher a,c, H. Siebner a (a Hvidovre Hospital, University of Copenhagen, Centre for Functional and Diagnostic Imaging and Research Danish Research Centre for Magnetic Resonance (DRCMR), Hvidovre, Denmark , b Grenoble Institute of Neuroscience, Research Centre U836 Inserm-UJF, Team 11 Brain Function & Neuromodulation, Grenoble, France, c Technical University of Denmark, Biomedical Engineering Section, Kongens Lyngby, Denmark) ⇑
Corresponding author.
Introduction: We have recently introduced neuronavigated linear transcranial magnetic stimulation (TMS) mapping as a method to capture motor somatotopy in the hand motor area (M1HAND). In contrast to other mapping methods, linear TMS mapping adjusts the TMS coil position and orientation to the individual shape of the central sulcus (CS). Here we used this technique to map the spatial representation of short-latency afferent inhibition (SAI) in M1HAND. SAI refers to a suppression of the motor evoked potential (MEP) amplitude by preceding peripheral electrical nerve stimulation of the contralateral hand. SAI is somatotopically specific: it’s stronger when electrical stimulation is applied close to the TMS-target muscle (homotopic stimulation) and weaker when not (heterotopic stimulation). Aim: We hypothesized a somatotopic expression of SAI in M1HAND for homotopic as opposed to heterotopic stimulation. Methods: Electrical stimulation of the left index finger or little finger was applied 23 ms before TMS of right M1HAND. MEPs were recorded from left first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles. SAI was applied randomly at seven M1 target sites following the individual shape of the right CS. Results: We found a clear somatotopic representation of SAI. Homotopic SAI of the ADM muscle was expressed more medially than homotopic SAI of the FDI muscle along the M1HAND. We also found somatotopy for heterotopic stimulation. Here SAI was replaced by a ‘‘surrounding” facilitation of the heterotopic muscle. Conclusions: Linear sulcal TMS mapping revealed a somatotopically defined centre-surround organization of sensorimotor integration in the human M1HAND. doi:10.1016/j.clinph.2016.10.267
P147 Effects of cTBS on the integration of haptic light fingertip contact and body sway—D. Kaulmann *, L. Johannsen (Technische Universität München, Munich, Germany) ⇑
Corresponding author.
Question: In the present study we aimed to investigate the effects of continuous theta burst stimulation (cTBS) over the posterior parietal cortex (PPC) and how it effects body sway and the integration of light touch. Methods: In right-handed young adults, cTBS with an intensity of 80% of the passive motor threshold was applied for 60 s over the left and right Posterior Partial Cortex. Additionally, a sham condition was applied. Target locations were identified using real-time neuronavigation. Participants were tested blindfolded in quiet upright Tandem-Romberg stance before and after each stimulation interval. During these tests they were instructed to actively initiate and cease
e87
finger contact with an earth-fixed referent in response to an acoustic signal. Testing was carried out on two non-consecutive sessions. Body sway was recorded in terms of Centre of Pressure (CoP) and trunk kinematics in addition to forces and torques at the contact point. Results: The results of 13 healthy right handed participants reveal that cTBS over the right PPC affected postural control. The overall level of body sway was decreased after inhibition, while the effect of Light Touch was still present. Inhibition of the left PPC or sham stimulation did not decrease the overall level of body sway. Conclusion: The cause of this effect might be strategies of the motor control system that lead to a co-contraction and thus reducing body sway. However, this does not mean that participants were more stable. Another possible explanation might be that inhibition of the right PPC disrupts processes for state estimation of body sway in spatial reference frames or mechanisms of stability selfexploration (i.e. Zatsiorsky and Duarte, Motor Control, 1999; Ehrenfried et al., Brain Res Cogn Brain Res, 2003; Kiemel et al., J Neurophysiol, 2006). doi:10.1016/j.clinph.2016.10.268
P148 Dose–effect of transcranial static magnetic field stimulation on excitatory and inhibitory intracortical circuits—M. Dileone a,b,*, L. Mordillo Mateos b,*, A. Oliviero b, G. Foffani a,b (a HM Puerta del Sur, Centro Integral de Neurociencias, Mostoles (Madrid), Spain, b Hospital Nacional de Parapléjicos, Toledo, Spain) ⇑
Corresponding authors.
Question: Transcranial static magnetic field stimulation (tSMS) is a new low-cost, non-invasive brain stimulation (NIBS) technique. When tSMS is applied for 10–15 min over the motor cortex, it leads to a short-lasting decrease of cortical excitability in healthy subjects, as measured by a decreased amplitude of motor-evoked potentials (MEPs), associated with an increase of short-latency intracortical inhibition (SICI). Here we aimed to test the effects of a longer application of tSMS (30 min) on excitatory and inhibitory intracortical circuits. Methods: We performed 3 randomized double-blind shamcontrolled experiments in a total of 31 right-handed healthy subjects. In experiment 1 we assessed MEP amplitudes before and after tSMS (or sham) applied for 30 min to the non-dominant motor cortex. In experiment 2 we tested the effects of 30 min of tSMS on SICI and I wave interaction. In experiment 3 we evaluated the effects of 10 min of tSMS on SICI and on the first peak of I wave interaction (short-latency intracortical facilitation, SICF). Results: Prolonged application of tSMS (30 min) significantly decreased MEP amplitudes compared to sham till 30 min after the end of tSMS and, surprisingly, reduced SICI while increasing SICF. By applying tSMS for only 10 min, we found a significant and short-lasting increase of SICI with reduction of SICF. Conclusions: We found that a prolonged application of tSMS leads to a long-lasting reduction in motor cortex excitability, similar to those typically induced by continuous theta-burst stimulation (cTBS) and cathodal transcranial direct current stimulation (tDCS). Moreover, SICI and SICF could be modulated in a bidirectional way by tSMS, depending on the application time, revealing a dose–effect of tSMS on excitatory and inhibitory intracortical circuits. doi:10.1016/j.clinph.2016.10.269