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EP 134. Effect of transcranial random noise stimulation depends on sensitivity to sham stimulation
Abstracts / Clinical Neurophysiology 127 (2016) e210–e303
Background and aims: The anatomical borders of eloquent speech areas, e.g. Broca’s area, have been vaguely defined and exhibit high inter-subject variability (Amunts and Zilles, 2012), mainly due to inconsistent morphology of the inferior frontal gyrus (IFG) (Ebeling et al., 1989) and small-scale incongruity of functional segregation with respect to anatomical landmarks (Garrett et al., 2012; Quiñones-Hinojosa et al., 2003). However, knowing the exact boundaries of the eloquent cortex became clinically important in preventing postoperative deficits after brain surgery (Garrett et al., 2012; Hollon et al., 2015). The awake electrical stimulation mapping (ESM) has become the preferred method to delineate the speech cortex, as the current non-invasive alternatives lack specificity and spatial resolution (Garrett et al., 2012; Hollon et al., 2015). Since the structural connectivity-based parcellation using diffusion tensor imaging (DTI) has been shown to closely relate to the cytoarchitectonics in the IFG (Klein et al., 2007), we tested whether the location of eloquent cortex could be better predicted by preoperative DTI rather than by its relation to gyrification. Methods: Seventeen patients (8 males, median age 33, range 18– 63) suffering from primary brain tumor underwent pre-operative 3T MRI scanning using a high resolution T1 MPRAGE and a single shell diffusion weighted imaging (DWI) sequence (60 directions, b = 1000 s/mm2, resolution 2 2 2 mm), and intraoperative direct cortical electrical stimulation with a bipolar Ojemann electrode during awake language mapping. After standard preprocessing, probabilistic fiber tracking (PROBTRACKX in FSL (Behrens et al., 2007)) was carried out using 5 mm spheres as cortico-subcortical seeds placed at the intraoperatively defined positive stimulation sites. The resulting cortical projections were then overlaid onto the individual cortex surface (Freesurfer) and compared visually and using binary logical operations. Results: A variety of stimulation-positive functional sites was detected, producing anomia, counting, speech and motor arrest. Anomia sites were found both in the pars triangularis and pars opercularis of the inferior frontal gyrus (also in individual patients). Even opercular anomia sites followed the connectivity pattern of triangular anomia sites and had stronger connections to the rostral parts of the mesial prefrontal cortex and pre-supplementary motor area (pre-SMA) than to the precentral gyrus and SMA proper, as opposed to opercular speech or counting arrest sites which also connected more strongly to more posterior parts of the brain, mostly posterior temporal cortex. Thus, even adjacent sites on the same gyrus that differed in function showed dissociable structural connectivity. Conclusions: Our results suggest that structure–function relationships are more evident between function and structural connectivity than between function and gyrification. Acknowledgement: This study was supported by the German Research Foundation, the European Union, and the German Academic Exchange Service (DAAD). References Amunts, Zilles. Trends Cogn Sci 2012;16(8):418–26. Ebeling et al. AJNR Am J Neuroradiol 1989;10(5):937–42. Garrett et al. Neurosurg Clin N Am 2012;23(3):497–506. Quiñones-Hinojosa et al. J Neurosurg 2003;99(2):311–8. Hollon et al. Semin Radiat Oncol 2015;25(3):181–8. Klein et al. NeuroImage 2007;34(1):204–11. Behrens et al. NeuroImage 2007;34(1):144–55. doi:10.1016/j.clinph.2016.05.173
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EP 134. Effect of transcranial random noise stimulation depends on sensitivity to sham stimulation—V. Kortüm *, M. Brede, K. Parkosadze, M. Siniatchkin, V. Moliadze (Schleswig-Holstein University Hospital (UK-SH), Christian-Albrechts-University, Kiel, Department of Medical Psychology and Medical Sociology, Kiel, Germany) ⇑
Corresponding author.
Introduction: Tranccranial random noise stimulation (tRNS) induces a consistent excitability increase lasting at least 60 min after 10 min of stimulation, as demonstrated by both physiological measures and behavioural Tasks (Terney et al., 2008). The present study tests whether the tRNS-induced changes in corticospinal excitability varies as a function of individual differences in sensitivity to sham stimulation. Methods: The study was approved by the Ethic Committee of the Faculty of Medicine Christian-Albrechts University Kiel. 24 participants, aged between 18 and 30 years, participated in the study. All subjects were right-handed according to the Edinburgh handedness inventory (Oldfield, 1971). Stimulation techniques: tRNS (1 mA, 10 min) was applied through a pair of saline-soaked surface sponge electrodes (5 7 cm). The minimum period between sessions for a single subject was 7 days, and sessions were applied in randomized order. Monitoring of motor cortical excitability: To examine changes in corticospinal excitability, motor evoked potentials (MEPs) of the right first dorsal interosseous muscle (FDI) were recording following stimulation of its motor-cortical representation field by single-pulse TMS. For further analysis we divided three subgroups according to excitatory (‘Excitatory group’, n = 9), inhibitory (‘Inhibitory group’, n = 7) or no respond (‘Non responder group’, n = 8) to sham- stimulation (Wilcoxon signed-rank test for dependent sampling). For this, we compared the MEP-amplitude in mean of the three time points after stimulation with the MEP-amplitude in mean before. Results: In all subjects the tRNS was well tolerated. The general finding of present study is that sensitivity to sham stimulation has impact on effect of tRNS; namely, ‘Excitatory group’ resulted in inhibition of tRNS, whereas inhibitory group shows excitation of tRNS. For ‘Non responder group’ the 1 mA tRNS resulted in a significant increase of MEP amplitudes compared to sham stimulation, which is consistent with the literature Conclusion: Accounting for variation in individual sensitivity to sham stimulation, stimulation may influence the utility of tRNS as a tool for understanding brain-behavior interactions and as a method for clinical interventions. References Oldfield RC. The assessment and analysis of handedness: the Edinburgh inventory. Neuropsychologia 1971;9:97–113. Terney D, Chaieb L, Moliadze V, Antal A, Paulus W. Increasing human brain excitability by transcranial high-frequency random noise stimulation. J Neurosci 2008;28:14147–55. doi:10.1016/j.clinph.2016.05.174
EP 135. Boosting cognitive control with transcranial alternating current stimulation—S.E. Peter *, D. Mederer, N. Habboush, E. Lyzhko, M. Siniatchkin, V. Moliadze (Schleswig-Holstein University Hospital (UK-SH), Christian-Albrechts-University, Kiel, Department of Medical Psychology and Medical Sociology, Kiel, Germany) ⇑
Corresponding author.
Background and aims: The anatomical borders of eloquent speech areas, e.g. Broca’s area, have been vaguely defined and exhibit high inter-subject variability (Amunts and Zilles, 2012), mainly due to inconsistent morphology of the inferior frontal gyrus (IFG) (Ebeling et al., 1989) and small-scale incongruity of functional segregation with respect to anatomical landmarks (Garrett et al., 2012; Quiñones-Hinojosa et al., 2003). However, knowing the exact boundaries of the eloquent cortex became clinically important in preventing postoperative deficits after brain surgery (Garrett et al., 2012; Hollon et al., 2015). The awake electrical stimulation mapping (ESM) has become the preferred method to delineate the speech cortex, as the current non-invasive alternatives lack specificity and spatial resolution (Garrett et al., 2012; Hollon et al., 2015). Since the structural connectivity-based parcellation using diffusion tensor imaging (DTI) has been shown to closely relate to the cytoarchitectonics in the IFG (Klein et al., 2007), we tested whether the location of eloquent cortex could be better predicted by preoperative DTI rather than by its relation to gyrification. Methods: Seventeen patients (8 males, median age 33, range 18– 63) suffering from primary brain tumor underwent pre-operative 3T MRI scanning using a high resolution T1 MPRAGE and a single shell diffusion weighted imaging (DWI) sequence (60 directions, b = 1000 s/mm2, resolution 2 2 2 mm), and intraoperative direct cortical electrical stimulation with a bipolar Ojemann electrode during awake language mapping. After standard preprocessing, probabilistic fiber tracking (PROBTRACKX in FSL (Behrens et al., 2007)) was carried out using 5 mm spheres as cortico-subcortical seeds placed at the intraoperatively defined positive stimulation sites. The resulting cortical projections were then overlaid onto the individual cortex surface (Freesurfer) and compared visually and using binary logical operations. Results: A variety of stimulation-positive functional sites was detected, producing anomia, counting, speech and motor arrest. Anomia sites were found both in the pars triangularis and pars opercularis of the inferior frontal gyrus (also in individual patients). Even opercular anomia sites followed the connectivity pattern of triangular anomia sites and had stronger connections to the rostral parts of the mesial prefrontal cortex and pre-supplementary motor area (pre-SMA) than to the precentral gyrus and SMA proper, as opposed to opercular speech or counting arrest sites which also connected more strongly to more posterior parts of the brain, mostly posterior temporal cortex. Thus, even adjacent sites on the same gyrus that differed in function showed dissociable structural connectivity. Conclusions: Our results suggest that structure–function relationships are more evident between function and structural connectivity than between function and gyrification. Acknowledgement: This study was supported by the German Research Foundation, the European Union, and the German Academic Exchange Service (DAAD). References Amunts, Zilles. Trends Cogn Sci 2012;16(8):418–26. Ebeling et al. AJNR Am J Neuroradiol 1989;10(5):937–42. Garrett et al. Neurosurg Clin N Am 2012;23(3):497–506. Quiñones-Hinojosa et al. J Neurosurg 2003;99(2):311–8. Hollon et al. Semin Radiat Oncol 2015;25(3):181–8. Klein et al. NeuroImage 2007;34(1):204–11. Behrens et al. NeuroImage 2007;34(1):144–55. doi:10.1016/j.clinph.2016.05.173
e297
EP 134. Effect of transcranial random noise stimulation depends on sensitivity to sham stimulation—V. Kortüm *, M. Brede, K. Parkosadze, M. Siniatchkin, V. Moliadze (Schleswig-Holstein University Hospital (UK-SH), Christian-Albrechts-University, Kiel, Department of Medical Psychology and Medical Sociology, Kiel, Germany) ⇑
Corresponding author.
Introduction: Tranccranial random noise stimulation (tRNS) induces a consistent excitability increase lasting at least 60 min after 10 min of stimulation, as demonstrated by both physiological measures and behavioural Tasks (Terney et al., 2008). The present study tests whether the tRNS-induced changes in corticospinal excitability varies as a function of individual differences in sensitivity to sham stimulation. Methods: The study was approved by the Ethic Committee of the Faculty of Medicine Christian-Albrechts University Kiel. 24 participants, aged between 18 and 30 years, participated in the study. All subjects were right-handed according to the Edinburgh handedness inventory (Oldfield, 1971). Stimulation techniques: tRNS (1 mA, 10 min) was applied through a pair of saline-soaked surface sponge electrodes (5 7 cm). The minimum period between sessions for a single subject was 7 days, and sessions were applied in randomized order. Monitoring of motor cortical excitability: To examine changes in corticospinal excitability, motor evoked potentials (MEPs) of the right first dorsal interosseous muscle (FDI) were recording following stimulation of its motor-cortical representation field by single-pulse TMS. For further analysis we divided three subgroups according to excitatory (‘Excitatory group’, n = 9), inhibitory (‘Inhibitory group’, n = 7) or no respond (‘Non responder group’, n = 8) to sham- stimulation (Wilcoxon signed-rank test for dependent sampling). For this, we compared the MEP-amplitude in mean of the three time points after stimulation with the MEP-amplitude in mean before. Results: In all subjects the tRNS was well tolerated. The general finding of present study is that sensitivity to sham stimulation has impact on effect of tRNS; namely, ‘Excitatory group’ resulted in inhibition of tRNS, whereas inhibitory group shows excitation of tRNS. For ‘Non responder group’ the 1 mA tRNS resulted in a significant increase of MEP amplitudes compared to sham stimulation, which is consistent with the literature Conclusion: Accounting for variation in individual sensitivity to sham stimulation, stimulation may influence the utility of tRNS as a tool for understanding brain-behavior interactions and as a method for clinical interventions. References Oldfield RC. The assessment and analysis of handedness: the Edinburgh inventory. Neuropsychologia 1971;9:97–113. Terney D, Chaieb L, Moliadze V, Antal A, Paulus W. Increasing human brain excitability by transcranial high-frequency random noise stimulation. J Neurosci 2008;28:14147–55. doi:10.1016/j.clinph.2016.05.174
EP 135. Boosting cognitive control with transcranial alternating current stimulation—S.E. Peter *, D. Mederer, N. Habboush, E. Lyzhko, M. Siniatchkin, V. Moliadze (Schleswig-Holstein University Hospital (UK-SH), Christian-Albrechts-University, Kiel, Department of Medical Psychology and Medical Sociology, Kiel, Germany) ⇑
Corresponding author.