- Email: [email protected]
T027 tACS and tDCS for vision restoration
e8
Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
processing unit for associative memories. Interestingly, when applying constant current stimulation, the enhancement of gamma activity and neuronal firing outlast the period of stimulation by several minutes, suggesting plastic effects of DC stimulation on this important associative neuronal network. doi:10.1016/j.clinph.2016.10.123
T025 Optimizing logical coupling between brain stimulation and pharmacotherapy with use of animal models—A. Rotenberg (Boston Children’s Hospital/Harvard Medical School, Neurology, Neuromodulation Program, Boston, MA, United States) Adaptations of noninvasive brain stimulation protocols to animal models offers opportunities for insight into the molecular and cellular consequences of techniques such as rTMS and tDCS. Beyond identifying mechanisms by which these and related protocols alter brain function, in vivo and in vitro translational experiments can uncover signalling pathways that are both engaged by noninvasive brain stimulation and also contain therapeutic drug targets. Thus paired drug-device combinations may be tested in preclinical experiments where relatively high-throughput systematic manipulation of stimulation parameters and drug choice and dose is much more practical than in clinical studies. Accordingly this presentation summarizes experiments aimed to address practical gaps in knowledge that may be encountered in the clinical arena, where in many disease states a patient is unlikely to undergo stimulation without concomitant drug treatment, and where the therapeutic efficacy of noninvasive brain stimulation may be incomplete and can be improved by selective drug treatment. doi:10.1016/j.clinph.2016.10.124
T027 tACS and tDCS for vision restoration—B.A. Sabel, R. Alber (Ottovon-Guericke University, Institute of Medical Psychology, Magdeburg, Germany) Alternating current stimulation (tACS), when applied near the eye, forces retinal ganglion cells to fire at predetermined frequencies. Repeating this for extended time periods might strengthen the synaptic connectivity through mechanisms of neuroplasticity and thus induce long-lasting after-effects of brain synchronization. To check clinical efficacy in the treatment of vision loss, patients suffering from optic nerve damage received tACS for 10 days (20–40 min daily, AC–current bursts of. doi:10.1016/j.clinph.2016.10.125
Against T028 Efficacy is not equal to effectiveness: Transcranial magnetic stimulation in the treatment of depressive disorder—D. Schutter (Donders Institute, Brain Stimulation and Motivtrional Control, Nijmegen, The Netherlands) Administering transcranial magnetic stimulation to the prefrontal cortex is efficacious for the management of depressive symptoms. Data demonstrating efficacy are often assumed to be similar to
effectiveness data, but this assumption is not correct. Efficacy is the extent to which a treatment does more good than harm under experimentally controlled conditions, whereas effectiveness is the extent to which a treatment does more good than harm when provided under the usual conditions of health care practice. Efficacy studies often overestimate the effect of treatment when implemented in clinical practice effectiveness research accounts for additional variability, including patient characteristics and suboptimal TMS dosage, that moderate treatment effect (Eichler et al., 2011). While the main clinical outcome measure in TMS efficacy studies is the baseline adjusted change score on established clinical ratings scales, assessment of health outcomes including quality adjusted life years has not been extensively studied. In fact, cost-utility analyses are critical to establish external validity by showing that the efficacy in randomized controlled trials reflects clinical practice. Together with the absence of mechanistic neurophysiological explanations and lack of insight into the duration of the effects, the effectiveness of TMS in the treatment of depression remains an open question (Gartlehner et al., 2006). TMS improve symptoms of depression, but due to the multifactorial nature of the intervention, the overall effectiveness of TMS for the treatment of depression remains unclear (Canadian Agency for Drugs and Technologies in Health, 2014). Effectiveness studies are needed in order to consider TMS a realistic option for health-care decisions by practitioners and policy-makers in the treatment of depressive disorder. References Canadian Agency for Drugs and Technologies in Health (2014). Transcranial magnetic stimulation for the treatment of adults with PTSD, GAD, or depression: A review of clinical effectiveness and guidelines. Rapid Response Report: Summary with Critical Appraisal. Ottawa (ON): CADTH. Eichler HG, Abadie E, Breckenridge A, Flamion B, Gustafsson LL, Leufkens H, Rowland M, Schneider CK, Bloechl-Daum B. Bridging the efficacy-effectiveness gap: a regulator’s perspective on addressing variability of drug response. Nat Rev Drug Discov. 2011;10:495–506. Gartlehner G, Hansen RA, Nissman D, Lohr KN, Caret TS (2006). Criteria for distinguishing effectiveness from efficacy trials in systematic reviews. Tech Rev, 12. Rockville (MD): Agency for Healthcare Research and Quality (US). doi:10.1016/j.clinph.2016.10.126
T029 Where do we stimulate M1? A combined neurophysiological and modelling approach—A. Thielscher (a Technical University of Denmark, Kgs, Lyngby, Denmark , b Danish Research Center for Magnetic Resonance, Copenhagen University Hospital Hvidovre2x1, Hvidovre, Denmark) Much of our knowledge on the physiological mechanisms of transcranial magnetic stimulation (TMS) stems from studies which targeted the human motor cortex. Very surprisingly, however, it is still unclear which part of M1 is stimulated by TMS when a muscle twitch is elicited. Considering that the motor cortex consists of functionally and histologically distinct subareas, this also renders the hypotheses on the physiological TMS effects uncertain. I will report on two recent studies which combined electrophysiological measurements of muscle responses to TMS with realistic estimates of the induced electric field, based on the finite-element method (FEM) and MRI-derived individual head models. In the first study, the orientation of a standard figure 8 coil was systematically varied and the field changes in different subparts of the motor cortex were compared with the electrophysiological threshold changes. In the second study, three figure 8 coils having different field decays were used and the differences in the electrophysiological thresholds were correlated with the differences in the calculated field
Abstracts / Clinical Neurophysiology 128 (2017) e1–e163
processing unit for associative memories. Interestingly, when applying constant current stimulation, the enhancement of gamma activity and neuronal firing outlast the period of stimulation by several minutes, suggesting plastic effects of DC stimulation on this important associative neuronal network. doi:10.1016/j.clinph.2016.10.123
T025 Optimizing logical coupling between brain stimulation and pharmacotherapy with use of animal models—A. Rotenberg (Boston Children’s Hospital/Harvard Medical School, Neurology, Neuromodulation Program, Boston, MA, United States) Adaptations of noninvasive brain stimulation protocols to animal models offers opportunities for insight into the molecular and cellular consequences of techniques such as rTMS and tDCS. Beyond identifying mechanisms by which these and related protocols alter brain function, in vivo and in vitro translational experiments can uncover signalling pathways that are both engaged by noninvasive brain stimulation and also contain therapeutic drug targets. Thus paired drug-device combinations may be tested in preclinical experiments where relatively high-throughput systematic manipulation of stimulation parameters and drug choice and dose is much more practical than in clinical studies. Accordingly this presentation summarizes experiments aimed to address practical gaps in knowledge that may be encountered in the clinical arena, where in many disease states a patient is unlikely to undergo stimulation without concomitant drug treatment, and where the therapeutic efficacy of noninvasive brain stimulation may be incomplete and can be improved by selective drug treatment. doi:10.1016/j.clinph.2016.10.124
T027 tACS and tDCS for vision restoration—B.A. Sabel, R. Alber (Ottovon-Guericke University, Institute of Medical Psychology, Magdeburg, Germany) Alternating current stimulation (tACS), when applied near the eye, forces retinal ganglion cells to fire at predetermined frequencies. Repeating this for extended time periods might strengthen the synaptic connectivity through mechanisms of neuroplasticity and thus induce long-lasting after-effects of brain synchronization. To check clinical efficacy in the treatment of vision loss, patients suffering from optic nerve damage received tACS for 10 days (20–40 min daily, AC–current bursts of. doi:10.1016/j.clinph.2016.10.125
Against T028 Efficacy is not equal to effectiveness: Transcranial magnetic stimulation in the treatment of depressive disorder—D. Schutter (Donders Institute, Brain Stimulation and Motivtrional Control, Nijmegen, The Netherlands) Administering transcranial magnetic stimulation to the prefrontal cortex is efficacious for the management of depressive symptoms. Data demonstrating efficacy are often assumed to be similar to
effectiveness data, but this assumption is not correct. Efficacy is the extent to which a treatment does more good than harm under experimentally controlled conditions, whereas effectiveness is the extent to which a treatment does more good than harm when provided under the usual conditions of health care practice. Efficacy studies often overestimate the effect of treatment when implemented in clinical practice effectiveness research accounts for additional variability, including patient characteristics and suboptimal TMS dosage, that moderate treatment effect (Eichler et al., 2011). While the main clinical outcome measure in TMS efficacy studies is the baseline adjusted change score on established clinical ratings scales, assessment of health outcomes including quality adjusted life years has not been extensively studied. In fact, cost-utility analyses are critical to establish external validity by showing that the efficacy in randomized controlled trials reflects clinical practice. Together with the absence of mechanistic neurophysiological explanations and lack of insight into the duration of the effects, the effectiveness of TMS in the treatment of depression remains an open question (Gartlehner et al., 2006). TMS improve symptoms of depression, but due to the multifactorial nature of the intervention, the overall effectiveness of TMS for the treatment of depression remains unclear (Canadian Agency for Drugs and Technologies in Health, 2014). Effectiveness studies are needed in order to consider TMS a realistic option for health-care decisions by practitioners and policy-makers in the treatment of depressive disorder. References Canadian Agency for Drugs and Technologies in Health (2014). Transcranial magnetic stimulation for the treatment of adults with PTSD, GAD, or depression: A review of clinical effectiveness and guidelines. Rapid Response Report: Summary with Critical Appraisal. Ottawa (ON): CADTH. Eichler HG, Abadie E, Breckenridge A, Flamion B, Gustafsson LL, Leufkens H, Rowland M, Schneider CK, Bloechl-Daum B. Bridging the efficacy-effectiveness gap: a regulator’s perspective on addressing variability of drug response. Nat Rev Drug Discov. 2011;10:495–506. Gartlehner G, Hansen RA, Nissman D, Lohr KN, Caret TS (2006). Criteria for distinguishing effectiveness from efficacy trials in systematic reviews. Tech Rev, 12. Rockville (MD): Agency for Healthcare Research and Quality (US). doi:10.1016/j.clinph.2016.10.126
T029 Where do we stimulate M1? A combined neurophysiological and modelling approach—A. Thielscher (a Technical University of Denmark, Kgs, Lyngby, Denmark , b Danish Research Center for Magnetic Resonance, Copenhagen University Hospital Hvidovre2x1, Hvidovre, Denmark) Much of our knowledge on the physiological mechanisms of transcranial magnetic stimulation (TMS) stems from studies which targeted the human motor cortex. Very surprisingly, however, it is still unclear which part of M1 is stimulated by TMS when a muscle twitch is elicited. Considering that the motor cortex consists of functionally and histologically distinct subareas, this also renders the hypotheses on the physiological TMS effects uncertain. I will report on two recent studies which combined electrophysiological measurements of muscle responses to TMS with realistic estimates of the induced electric field, based on the finite-element method (FEM) and MRI-derived individual head models. In the first study, the orientation of a standard figure 8 coil was systematically varied and the field changes in different subparts of the motor cortex were compared with the electrophysiological threshold changes. In the second study, three figure 8 coils having different field decays were used and the differences in the electrophysiological thresholds were correlated with the differences in the calculated field