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P 33. “Sub-threshold” TMS consistently excites corticospinal motor neurons
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Society Proceedings / Clinical Neurophysiology 124 (2013) e39–e187
Fig. 1. (A) The electric field distribution on the cortical surface for stimulation over left hemispheric M1, (B) right lateral cerebellum and (C) supplementary motor area 30 mm anterior to Cz. The field strength is displayed on a scale from 0 to 150 V/m
the optimal stimulation intensity per individual for locations outside M1 can only be determined with TMS simulations. doi:10.1016/j.clinph.2013.04.110
P 33. “Sub-threshold” TMS consistently excites corticospinal motor neurons—M. Bedulli, M.A. Kaoumi-Stephan, D. Benninger (Centre Hospitalier Universitaire Vaudois (CHUV), Départment des Neurosciences Cliniques, Lausanne, Switzerland) Background/objective: The Triple Stimulation Technique (TST) has proven the potential of TMS to achieve depolarization of all cortical and spinal motor neurons of a target muscle and its utility in a more precise quantification of the corticospinal conduction. Here we investigated with the TST whether conventional “sub-threshold” TMS excites the corticospinal motor neurons. Methods: In 10 right-handed young healthy participants resting and active motor thresholds (rMT and aMT) were assessed by the adaptive method (Groppa S 2012) with TMS alone and by using the TST. We investigated motor potentials evoked by TMS alone and with the TST of the right first dorsal interosseus (FDI) muscle at sub-threshold intensity (80% rMT as determined with TMS). The order of assessments was randomized. Results: Both active and resting MTs were significantly lower when assessed with the TST than with TMS alone, and active MT was significantly lower than the rMT, in both methods. TST consistently demonstrated MEPs at sub-threshold stimulation intensity, which could not be shown with TMS alone. Conclusion: The TST provides evidence for lower motor cortex threshold levels than determined by conventional methods, also as motor potentials proving depolarization of corticospinal motor neurons are evoked at conventionally considered “sub-threshold” TMS intensities. This needs to be taken into account in conditioning paradigms. doi:10.1016/j.clinph.2013.04.111
P 34. Inter-individual variation during transcranial direct current stimulation and normalization of dose using MRI-derived computational models—D. Truong, B. Guleyupoglu, A. Datta, P. Minhas, L. Parra, M. Bikson (The City College of New York, Biomedical Engineering, New York, United States) Transcranial Direct Current Stimulation (tDCS) is a non-invasive, versatile, and safe neuromodulation technology under investigation for the treatment of neuropsychiatric disorders, adjunct to rehabilitation, and cognitive enhancement in healthy adults. Despite promising results, there is variability in responsiveness. One potential source of variability is the intensity of current delivered to the brain
which is a function of both the operator controlled tDCS dose (electrode montage and total applied current) and subject specific anatomy. We are interested in both the scale of this variability across anatomical typical adults and methods to normalize inter-individual variation by customizing tDCS dose. Computational FEM simulations are a standard technique to predict brain current flow during tDCS and can be based on subject specific anatomical MRI. To investigate this variability, we modeled multiple tDCS and HD-tDCS montages across eight adults. The current flow profile across all subjects and montages was influenced by gross anatomy as well as details in cortical gyri/sulci. This data suggests that subject specific modeling can facilitate consistent and more efficacious tDCS. doi:10.1016/j.clinph.2013.04.112
Poster Session I Cognitive Neuroscience I P 35. Investigating a causal role of the supramarginal gyrus for pitch memory using transcranial direct current stimulation—N.K. Schaal a, V.J. Williamson b, M.J. Banissy b (a Heinrich-Heine-Universität, Experimentelle Psychologie, Abteilung Allgemeine Psychologie, Düsseldorf, Germany, b Goldsmiths, University of London, London, United Kingdom) Functional neuroimaging studies have shown an activation of the supramarginal gyrus during recognition pitch memory tasks and also showing a positive correlation of stronger activation of the left supramarginal gyrus and better task performance on the pitch memory task (Gaab et al., 2003, 2006). A previous transcranial direct current stimulation study using cathodal stimulation over the left supramarginal gyrus reported a detrimental effect on short-term pitch memory performance; indicating an important role of the left supramarginal gyrus for pitch memory (Vines et al., 2006). The current study investigated a causal involvement of the left supramarginal gyrus for the pitch memory process in non-musicians by using anodal and sham transcranial direct current stimulation to see whether this has a significant effect on the performance across different pitch memory paradigms (a recognition and a recall pitch memory task were used). A face memory task, used as a visual control task, was included to determine whether effects are specific to pitch memory. A between subject design was used. The two groups, which were matched by age, gender and pitch memory performance (evaluated in a preliminary test), either received anodal or sham stimulation over the left supramarginal gyrus and completed the three tasks in randomised order (between-subject design). The results show that the anodal group performed significantly better on both pitch memory tasks (see Figs. 1 and 2) but performance did not differ on the face memory task. These findings provide strong support for the causal involvement of the supramarginal gyrus
Society Proceedings / Clinical Neurophysiology 124 (2013) e39–e187
Fig. 1. (A) The electric field distribution on the cortical surface for stimulation over left hemispheric M1, (B) right lateral cerebellum and (C) supplementary motor area 30 mm anterior to Cz. The field strength is displayed on a scale from 0 to 150 V/m
the optimal stimulation intensity per individual for locations outside M1 can only be determined with TMS simulations. doi:10.1016/j.clinph.2013.04.110
P 33. “Sub-threshold” TMS consistently excites corticospinal motor neurons—M. Bedulli, M.A. Kaoumi-Stephan, D. Benninger (Centre Hospitalier Universitaire Vaudois (CHUV), Départment des Neurosciences Cliniques, Lausanne, Switzerland) Background/objective: The Triple Stimulation Technique (TST) has proven the potential of TMS to achieve depolarization of all cortical and spinal motor neurons of a target muscle and its utility in a more precise quantification of the corticospinal conduction. Here we investigated with the TST whether conventional “sub-threshold” TMS excites the corticospinal motor neurons. Methods: In 10 right-handed young healthy participants resting and active motor thresholds (rMT and aMT) were assessed by the adaptive method (Groppa S 2012) with TMS alone and by using the TST. We investigated motor potentials evoked by TMS alone and with the TST of the right first dorsal interosseus (FDI) muscle at sub-threshold intensity (80% rMT as determined with TMS). The order of assessments was randomized. Results: Both active and resting MTs were significantly lower when assessed with the TST than with TMS alone, and active MT was significantly lower than the rMT, in both methods. TST consistently demonstrated MEPs at sub-threshold stimulation intensity, which could not be shown with TMS alone. Conclusion: The TST provides evidence for lower motor cortex threshold levels than determined by conventional methods, also as motor potentials proving depolarization of corticospinal motor neurons are evoked at conventionally considered “sub-threshold” TMS intensities. This needs to be taken into account in conditioning paradigms. doi:10.1016/j.clinph.2013.04.111
P 34. Inter-individual variation during transcranial direct current stimulation and normalization of dose using MRI-derived computational models—D. Truong, B. Guleyupoglu, A. Datta, P. Minhas, L. Parra, M. Bikson (The City College of New York, Biomedical Engineering, New York, United States) Transcranial Direct Current Stimulation (tDCS) is a non-invasive, versatile, and safe neuromodulation technology under investigation for the treatment of neuropsychiatric disorders, adjunct to rehabilitation, and cognitive enhancement in healthy adults. Despite promising results, there is variability in responsiveness. One potential source of variability is the intensity of current delivered to the brain
which is a function of both the operator controlled tDCS dose (electrode montage and total applied current) and subject specific anatomy. We are interested in both the scale of this variability across anatomical typical adults and methods to normalize inter-individual variation by customizing tDCS dose. Computational FEM simulations are a standard technique to predict brain current flow during tDCS and can be based on subject specific anatomical MRI. To investigate this variability, we modeled multiple tDCS and HD-tDCS montages across eight adults. The current flow profile across all subjects and montages was influenced by gross anatomy as well as details in cortical gyri/sulci. This data suggests that subject specific modeling can facilitate consistent and more efficacious tDCS. doi:10.1016/j.clinph.2013.04.112
Poster Session I Cognitive Neuroscience I P 35. Investigating a causal role of the supramarginal gyrus for pitch memory using transcranial direct current stimulation—N.K. Schaal a, V.J. Williamson b, M.J. Banissy b (a Heinrich-Heine-Universität, Experimentelle Psychologie, Abteilung Allgemeine Psychologie, Düsseldorf, Germany, b Goldsmiths, University of London, London, United Kingdom) Functional neuroimaging studies have shown an activation of the supramarginal gyrus during recognition pitch memory tasks and also showing a positive correlation of stronger activation of the left supramarginal gyrus and better task performance on the pitch memory task (Gaab et al., 2003, 2006). A previous transcranial direct current stimulation study using cathodal stimulation over the left supramarginal gyrus reported a detrimental effect on short-term pitch memory performance; indicating an important role of the left supramarginal gyrus for pitch memory (Vines et al., 2006). The current study investigated a causal involvement of the left supramarginal gyrus for the pitch memory process in non-musicians by using anodal and sham transcranial direct current stimulation to see whether this has a significant effect on the performance across different pitch memory paradigms (a recognition and a recall pitch memory task were used). A face memory task, used as a visual control task, was included to determine whether effects are specific to pitch memory. A between subject design was used. The two groups, which were matched by age, gender and pitch memory performance (evaluated in a preliminary test), either received anodal or sham stimulation over the left supramarginal gyrus and completed the three tasks in randomised order (between-subject design). The results show that the anodal group performed significantly better on both pitch memory tasks (see Figs. 1 and 2) but performance did not differ on the face memory task. These findings provide strong support for the causal involvement of the supramarginal gyrus