- Email: [email protected]
P076 A beagle model for understanding tDCS effects
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Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
Methods: A newly developed visuo-motor force tracking task is directed to the improvement of fine force control in the hand. During the task, a target force is presented on a computer screen and controlled by patients by pressing a power grip force manipulandum with the affected hand. In the present pilot study we investigated motor effects of fourweek training with the visuo-motor force tracking task combined with tDCS in 11 chronic stroke patients with different levels of paresis. Anodal (0.5 mA; 5 patients) or sham (6 patients) tDCS was applied on the primary motor cortex (M1) of the lesioned side for 20 min twice a day simultaneously with training.Upper Extremity Fugl-Meyer assessment (FMA; the primary outcome measure) was done before, after and on two months follow-up. Parameters of performance – ramp error, hold error, release duration and mean hold force – were calculated. Results: Total UE FMA score was significantly increased immediately after the treatment, but had declined at two months followup. The most prominent improvement occurred in the shoulderelbow sub-score of the FMA; in this segment (but not in the total UE FMA score) a significantly greater improvement in the Active compared to the Sham group was observed (Fig. 1). A clinically significant improvement (FMA > 5) was revealed in four patients out of five in the Active group and in two out of six – in the Sham group. Hold error decreased significantly in all patients; ramp error – in the Active group. Mean Hold Force during the first treatment session predicted the change in total UE FMA score after treatment (Fig. 2). Conclusions: The results show that this treatment protocol can result in clinically significant improvement of motor function in chronic stroke patients, including patients with severe paresis. Individual clinical characteristics of the patients could explain heterogeneity of results and lack of difference in the total UE FMA score. Performance during the initial session might inform about clinical outcomes and guide tDCS protocol optimization in future combined treatments. doi:10.1016/j.clinph.2016.10.199
Modelling and Biophysics P075 Time-varying coupling of EEG oscillations predicts excitability fluctuations in the primary motor cortex as reflected by motor evoked potentials amplitude: An EEG-TMS study—F. Vecchio a,*, F. Ferreri b, F. Miraglia a, D. Ponzo b, P.M. Rossini a,c (a IRCCS San Raffaele Pisana, Brain Connectivity Laboratory, Rome, Italy, b University Campus Biomedico, Department of Neurology, Rome, Italy, c Catholic University, Department of Neurology, Rome, Italy) ⇑
Corresponding author.
Introduction: Motor evoked potentials (MEPs) elicited by a train of consecutive, individual transcranial magnetic stimuli demonstrate fluctuations in amplitude with respect to time when recorded from a relaxed muscle. The influence of time-varying, instantaneous modifications of the electroencephalography (EEG) properties immediately preceding the transcranial magnetic stimulation (TMS) has rarely been explored. Objective: The aim of this study was to investigate the influence of the pre-TMS motor cortex and related areas EEG profile on time variants of the MEPs amplitude. Materials & methods: MRI-navigated TMS and multichannel TMScompatible EEG devices were used. For each experimental subject, posthoc analysis of the MEPs amplitude that was based on the 50th percentile of the MEPs amplitude distribution provided two
subgroups corresponding to ‘‘high” (large amplitude) and ‘‘low” (small amplitude). The pre-stimulus EEG characteristics (coherence and spectral profile) from the motor cortex and related areas were analyzed separately for the ‘‘high” and ‘‘low” MEPs and were then compared. Results: On the stimulated hemisphere, EEG coupling was observed more often in the high compared to the low MEP trials. Moreover, a paradigmatic pattern in which TMS was able to lead to significantly larger MEPs was found when the EEG of the stimulated motor cortex was coupled in the beta 2 band with the ipsilateral prefrontal cortex and in the delta band with the bilateral centroparietal-occipital cortices. Conclusions: This data provide evidence for a statistically significant influence of time-varying and spatially patterned synchronization of EEG rhythms in determining cortical excitability, namely motor cortex excitability in response to TMS. doi:10.1016/j.clinph.2016.10.200
P076 A beagle model for understanding tDCS effects—J. Been *, D. Kim, H. Seo, S.C. Jun (Gwangju Institute of Science and Technology (GIST), School of Electrical Engineering and Computer Science, Gwangju, South Korea) ⇑
Corresponding author.
Introduction: To characterize the efficacy of transcranial direct current stimulation (tDCS), various methods have been performed; particularly, the animal studies have conducted to investigate the behavioral or physiological effects of tDCS. A cost-effective computational study may demonstrate the detailed mechanism of tDCS by
Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
computing the stimulus-induced electric field (EF) distributions in the brain. Objective: For better understanding on animal tDCS study, we constructed 3D finite element model in beagle and estimated the effects of tDCS under the similar experimental condition. We computed distributions of EF/current density (CD) in beagle brain and investigated the other factors which may be hardly observed in the animal study. Materials & methods: In the animal study, a healthy male beagle (15–16 months old and 15.5 kg) received anodal tDCS (1 mA; 15 min) and then the electric potential was measured by electrocorticography electrodes attached directly on the left lateral gyrus (LG). Two pad-type electrodes (1 1 cm) were attached at the left prefrontal area (anode) and left occipital area (cathode). To mimic this animal study, we constructed the computational model using CT and MRI of the beagle used in the animal study. In tissue segmentation, we used a digital atlas of the beagle (Datta and Ritobrato, 2012) and Seg3D (www.seg3d.org). 3D tetrahedron meshes were generated using iso2mesh (Fig. 1). The CD distributions were computed by finite element method. Results: The left prefrontal and left parietal cortices were affected intensively by induced EF since anode and cathode electrodes were placed closely on those regions, as shown in (a). We observed that the left LG was also stimulated more than the right LG. In Fig. 2(b), we observed that considerable current flowed along the scalp due to the lowest electrical property of the skull. We understand that some fractional current penetrated the skull properly stimulated the frontal cortex and upper side of the brain. Conclusion: As a following animal study, we developed the computational model on beagle. We investigated the effects of tDCS in terms of distribution of CD. In the future, comparison between
Figure 1
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empirical and computational results will be conducted; we expect that this will be greatly helpful in understanding on mechanism of tDCS effects in the animal study.
Acknowledgements This work was supported by the GTI Project through a grant provided by GIST in 2016. Reference Datta, Ritobrato. PLoS One 2012; 7.12: e52140. doi:10.1016/j.clinph.2016.10.201
P077 In-vivo estimation of head conductivities frequency response with IES and SEEG-EEG —H. Altakroury *, L. Koessler, J. Hofmanis, V. Louis-Dorr (CRAN UMR CNRS 7039, ENSEM Université de Lorraine, Vandoeuvre, France) ⇑
Corresponding author.
Question: The objective of this research is to see whether the estimated conductivities using Intracerebral Electrical Stimulations (IES) in a FEM head model change with different stimulation frequencies.
Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
Methods: A newly developed visuo-motor force tracking task is directed to the improvement of fine force control in the hand. During the task, a target force is presented on a computer screen and controlled by patients by pressing a power grip force manipulandum with the affected hand. In the present pilot study we investigated motor effects of fourweek training with the visuo-motor force tracking task combined with tDCS in 11 chronic stroke patients with different levels of paresis. Anodal (0.5 mA; 5 patients) or sham (6 patients) tDCS was applied on the primary motor cortex (M1) of the lesioned side for 20 min twice a day simultaneously with training.Upper Extremity Fugl-Meyer assessment (FMA; the primary outcome measure) was done before, after and on two months follow-up. Parameters of performance – ramp error, hold error, release duration and mean hold force – were calculated. Results: Total UE FMA score was significantly increased immediately after the treatment, but had declined at two months followup. The most prominent improvement occurred in the shoulderelbow sub-score of the FMA; in this segment (but not in the total UE FMA score) a significantly greater improvement in the Active compared to the Sham group was observed (Fig. 1). A clinically significant improvement (FMA > 5) was revealed in four patients out of five in the Active group and in two out of six – in the Sham group. Hold error decreased significantly in all patients; ramp error – in the Active group. Mean Hold Force during the first treatment session predicted the change in total UE FMA score after treatment (Fig. 2). Conclusions: The results show that this treatment protocol can result in clinically significant improvement of motor function in chronic stroke patients, including patients with severe paresis. Individual clinical characteristics of the patients could explain heterogeneity of results and lack of difference in the total UE FMA score. Performance during the initial session might inform about clinical outcomes and guide tDCS protocol optimization in future combined treatments. doi:10.1016/j.clinph.2016.10.199
Modelling and Biophysics P075 Time-varying coupling of EEG oscillations predicts excitability fluctuations in the primary motor cortex as reflected by motor evoked potentials amplitude: An EEG-TMS study—F. Vecchio a,*, F. Ferreri b, F. Miraglia a, D. Ponzo b, P.M. Rossini a,c (a IRCCS San Raffaele Pisana, Brain Connectivity Laboratory, Rome, Italy, b University Campus Biomedico, Department of Neurology, Rome, Italy, c Catholic University, Department of Neurology, Rome, Italy) ⇑
Corresponding author.
Introduction: Motor evoked potentials (MEPs) elicited by a train of consecutive, individual transcranial magnetic stimuli demonstrate fluctuations in amplitude with respect to time when recorded from a relaxed muscle. The influence of time-varying, instantaneous modifications of the electroencephalography (EEG) properties immediately preceding the transcranial magnetic stimulation (TMS) has rarely been explored. Objective: The aim of this study was to investigate the influence of the pre-TMS motor cortex and related areas EEG profile on time variants of the MEPs amplitude. Materials & methods: MRI-navigated TMS and multichannel TMScompatible EEG devices were used. For each experimental subject, posthoc analysis of the MEPs amplitude that was based on the 50th percentile of the MEPs amplitude distribution provided two
subgroups corresponding to ‘‘high” (large amplitude) and ‘‘low” (small amplitude). The pre-stimulus EEG characteristics (coherence and spectral profile) from the motor cortex and related areas were analyzed separately for the ‘‘high” and ‘‘low” MEPs and were then compared. Results: On the stimulated hemisphere, EEG coupling was observed more often in the high compared to the low MEP trials. Moreover, a paradigmatic pattern in which TMS was able to lead to significantly larger MEPs was found when the EEG of the stimulated motor cortex was coupled in the beta 2 band with the ipsilateral prefrontal cortex and in the delta band with the bilateral centroparietal-occipital cortices. Conclusions: This data provide evidence for a statistically significant influence of time-varying and spatially patterned synchronization of EEG rhythms in determining cortical excitability, namely motor cortex excitability in response to TMS. doi:10.1016/j.clinph.2016.10.200
P076 A beagle model for understanding tDCS effects—J. Been *, D. Kim, H. Seo, S.C. Jun (Gwangju Institute of Science and Technology (GIST), School of Electrical Engineering and Computer Science, Gwangju, South Korea) ⇑
Corresponding author.
Introduction: To characterize the efficacy of transcranial direct current stimulation (tDCS), various methods have been performed; particularly, the animal studies have conducted to investigate the behavioral or physiological effects of tDCS. A cost-effective computational study may demonstrate the detailed mechanism of tDCS by
Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
computing the stimulus-induced electric field (EF) distributions in the brain. Objective: For better understanding on animal tDCS study, we constructed 3D finite element model in beagle and estimated the effects of tDCS under the similar experimental condition. We computed distributions of EF/current density (CD) in beagle brain and investigated the other factors which may be hardly observed in the animal study. Materials & methods: In the animal study, a healthy male beagle (15–16 months old and 15.5 kg) received anodal tDCS (1 mA; 15 min) and then the electric potential was measured by electrocorticography electrodes attached directly on the left lateral gyrus (LG). Two pad-type electrodes (1 1 cm) were attached at the left prefrontal area (anode) and left occipital area (cathode). To mimic this animal study, we constructed the computational model using CT and MRI of the beagle used in the animal study. In tissue segmentation, we used a digital atlas of the beagle (Datta and Ritobrato, 2012) and Seg3D (www.seg3d.org). 3D tetrahedron meshes were generated using iso2mesh (Fig. 1). The CD distributions were computed by finite element method. Results: The left prefrontal and left parietal cortices were affected intensively by induced EF since anode and cathode electrodes were placed closely on those regions, as shown in (a). We observed that the left LG was also stimulated more than the right LG. In Fig. 2(b), we observed that considerable current flowed along the scalp due to the lowest electrical property of the skull. We understand that some fractional current penetrated the skull properly stimulated the frontal cortex and upper side of the brain. Conclusion: As a following animal study, we developed the computational model on beagle. We investigated the effects of tDCS in terms of distribution of CD. In the future, comparison between
Figure 1
e43
empirical and computational results will be conducted; we expect that this will be greatly helpful in understanding on mechanism of tDCS effects in the animal study.
Acknowledgements This work was supported by the GTI Project through a grant provided by GIST in 2016. Reference Datta, Ritobrato. PLoS One 2012; 7.12: e52140. doi:10.1016/j.clinph.2016.10.201
P077 In-vivo estimation of head conductivities frequency response with IES and SEEG-EEG —H. Altakroury *, L. Koessler, J. Hofmanis, V. Louis-Dorr (CRAN UMR CNRS 7039, ENSEM Université de Lorraine, Vandoeuvre, France) ⇑
Corresponding author.
Question: The objective of this research is to see whether the estimated conductivities using Intracerebral Electrical Stimulations (IES) in a FEM head model change with different stimulation frequencies.