- Email: [email protected]
tACS- What goes on inside? The neural consequences of transcranial alternating current stimulation
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Abstracts / Brain Stimulation 7 (2014) e1ee16
[7] Eran Dayan, Nitzan Censor, Ethan R Buch, Marco Sandrini, and Leonardo G Cohen. Noninvasive brain stimulation: from physiology to network dynamics and back. Nature neuroscience, 16(7):838e844, 2013. [8] Mario Dipoppa and Boris S Gutkin. Flexible frequency control of cortical oscillations enables computations required for working memory. Proceedings of the National Academy of Sciences, 2013. [9] Oded Meiron and Michal Lavidor. Prefrontal oscillatory stimulation modulates access to cognitive control references in retrospective metacognitive commentary. Clinical Neurophysiology, 2013. [10] Cornelia Pirulli, Anna Fertonani, and Carlo Miniussi. The role of timing in the induction of neuromodulation in perceptual learning by transcranial electric stimulation. Brain stimulation, 2013. [11] Albert Snowball, Ilias Tachtsidis, Tudor Popescu, Jacqueline Thompson, Margarete Delazer, Laura Zamarian, Tingting Zhu, and Roi Cohen Kadosh. Long-term enhancement of brain function and cognition using cognitive training and brain stimulation. Current Biology, 2013.
38 Safety of transcranial Direct Current Stimulation in Pediatric Hemiparesis: Determination of the Method for Locating the Optimal Stimulation Site B.T. Gillick a,*, T. Feyma b, J. Menk c, L.E. Krach d a Brain Plasticity Laboratory, Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Minneapolis, MN b Department of Pediatric Neurology, Gillette Children’s Specialty Healthcare, St Paul, MN c Clinical and Translational Science Institute, Biostatistical Design and Analysis Center, University of Minnesota Medical School, Minneapolis, MN d Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Minneapolis, MN *E-mail: [email protected]. Background/Objectives: Transcranial direct current stimulation has the potential to maximize neuro recovery in children with unilateral congenital lesions and resultant hemiparesis. To investigate this device, optimal electrode location must be verified. Current tDCS treatments rely on traditional EEG landmarks but, in children with unilateral lesions, the location of the motor hotspot may vary. Hypothesis: Conventional EEG landmarks differ from the motor hotspot in both the ipsilesional and contralesional hemisphere in children with congenital hemiparesis. Design: Exploratory Cohort Study Participants and Setting: Ten children with congenital hemiparesis due to a unilateral lesion at an academic facility (mean age 14.0 years, SD 3.67). Materials/Methods: Using transcranial magnetic stimulation (TMS), motor threshold was found in each hemisphere with the first dorsal interosseous (FDI) muscle at rest. Using the conventional EEG measurement system, C3 (left hemisphere) and C4 (right hemisphere) motor landmarks were found. Measurements were then made between the two points. Results: The average distance between the ipsilesional and contralesional TMS hotspots and EEG landmarks were 3.2 3.1 cm and 2.9 1.9 centimeters, respectively. The proportion and 95% confidence interval for agreement of the ipsilesional and contralesional TMS hotspots and EEG landmarks were 0.3, [0.07, 0.65] and 0.2, [0.03, 0.56], respectively. Conclusions/Significance: Our research indicates that EEG landmarks do not consistently indicate the optimal site of tDCS motor cortex stimulation in children with unilateral lesions. This variation can directly aff5ct the optimal electrode placement and the
intended target area of application of tDCS with functional or anatomic reorganization.
39 Impact of baseline excitability on tDCS-induced plasticity S. Fresnoza , M.-F. Kuo , W. Paulus , M.A. Nitsche Dept. Clinical Neurophysiology, University Medical Center, GeorgAugust-University, Goettingen, Germany *E-mail: [email protected]. Neuroplastic alterations of cortical excitability can be accomplished by non-invasive brain stimulation with transcranial direct currents (tDCS). Excitability alterations can last from some minutes for up to more than 24h after plasticity induction. However, substantial interindividual variability does exist with regard to the duration and magnitude of the effects. The reasons for this variability have not been systematically explored. In a retrospective analysis in 22 healthy humans, we analyzed the dependence of tDCS-induced motor cortex plasticity from baseline excitability, as defined by the transcranial magnetic stimulation (TMS) intensity required to induce motor evoked potential amplitudes (MEP) of the size of 1 mV. Lower TMS intensity was associated with larger magnitude of tDCS-induced plasticity for both, the aftereffects of anodal, and cathodal tDCS. We conclude that baseline excitability is an important factor for determination of the efficacy of tDCS at the individual level. The physiological, and anatomical reasons for this association, as well as the opportunity to use this factor for optimizing tDCS effect, should be explored in future studies.
40 tACS- What goes on inside? The neural consequences of transcranial alternating current stimulation Kohitij Kar , Jacob Duijnhouwer , Bart Krekelberg Department of Neuroscience, Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, USA *E-mail: [email protected]. There is considerable evidence for clinical and behavioral efficacy of transcranial alternating current stimulation (tACS). The effects range from suppressing Parkinsonian tremors to augmenting human learning and memory. Despite widespread use, the neurobiological mechanism of actions of tACS on the brain is unclear. We have taken a threefold approach to probe tACS mechanisms. First, we examined the behavioral effects of tACS on human motion perception. Second, we used known motion models to generate predictions about neural mechanisms that could produce the effects. Third, we tested these predictions by directly measuring tACS-induced neural activity changes in the macaque brain. In human subjects, we found that tACS (10 Hz, 0.5 mA) applied over area hMT+, during coarse motion direction discrimination, increases observers’ sensitivity. Based on reports suggesting that tACS interacts with mechanisms of plasticity, we hypothesized that a reduction in adaptation might cause this effect. We tested this hypothesis by applying tACS during visual motion adaptation. tACS over contralateral but not ipsilateral hMT+ mitigated the motion aftereffect and sensitivity changes induced by adaptation. These results suggest that tACS-induced membrane voltage modulations reduce adaptation in the motion-selective neurons. Tuning curve estimates of macaque MT neurons showed that tACS attenuated the effects of motion adaptation on tuning amplitude and width. In addition to single cell measures, tACS also mitigated adaptationinduced changes in evoked LFP responses. Our results provide novel insight into how tACS interacts with neural activity and establishes the awake, behaving macaque as an in-vivo animal model to study tACS mechanisms.
Abstracts / Brain Stimulation 7 (2014) e1ee16
[7] Eran Dayan, Nitzan Censor, Ethan R Buch, Marco Sandrini, and Leonardo G Cohen. Noninvasive brain stimulation: from physiology to network dynamics and back. Nature neuroscience, 16(7):838e844, 2013. [8] Mario Dipoppa and Boris S Gutkin. Flexible frequency control of cortical oscillations enables computations required for working memory. Proceedings of the National Academy of Sciences, 2013. [9] Oded Meiron and Michal Lavidor. Prefrontal oscillatory stimulation modulates access to cognitive control references in retrospective metacognitive commentary. Clinical Neurophysiology, 2013. [10] Cornelia Pirulli, Anna Fertonani, and Carlo Miniussi. The role of timing in the induction of neuromodulation in perceptual learning by transcranial electric stimulation. Brain stimulation, 2013. [11] Albert Snowball, Ilias Tachtsidis, Tudor Popescu, Jacqueline Thompson, Margarete Delazer, Laura Zamarian, Tingting Zhu, and Roi Cohen Kadosh. Long-term enhancement of brain function and cognition using cognitive training and brain stimulation. Current Biology, 2013.
38 Safety of transcranial Direct Current Stimulation in Pediatric Hemiparesis: Determination of the Method for Locating the Optimal Stimulation Site B.T. Gillick a,*, T. Feyma b, J. Menk c, L.E. Krach d a Brain Plasticity Laboratory, Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Minneapolis, MN b Department of Pediatric Neurology, Gillette Children’s Specialty Healthcare, St Paul, MN c Clinical and Translational Science Institute, Biostatistical Design and Analysis Center, University of Minnesota Medical School, Minneapolis, MN d Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Minneapolis, MN *E-mail: [email protected]. Background/Objectives: Transcranial direct current stimulation has the potential to maximize neuro recovery in children with unilateral congenital lesions and resultant hemiparesis. To investigate this device, optimal electrode location must be verified. Current tDCS treatments rely on traditional EEG landmarks but, in children with unilateral lesions, the location of the motor hotspot may vary. Hypothesis: Conventional EEG landmarks differ from the motor hotspot in both the ipsilesional and contralesional hemisphere in children with congenital hemiparesis. Design: Exploratory Cohort Study Participants and Setting: Ten children with congenital hemiparesis due to a unilateral lesion at an academic facility (mean age 14.0 years, SD 3.67). Materials/Methods: Using transcranial magnetic stimulation (TMS), motor threshold was found in each hemisphere with the first dorsal interosseous (FDI) muscle at rest. Using the conventional EEG measurement system, C3 (left hemisphere) and C4 (right hemisphere) motor landmarks were found. Measurements were then made between the two points. Results: The average distance between the ipsilesional and contralesional TMS hotspots and EEG landmarks were 3.2 3.1 cm and 2.9 1.9 centimeters, respectively. The proportion and 95% confidence interval for agreement of the ipsilesional and contralesional TMS hotspots and EEG landmarks were 0.3, [0.07, 0.65] and 0.2, [0.03, 0.56], respectively. Conclusions/Significance: Our research indicates that EEG landmarks do not consistently indicate the optimal site of tDCS motor cortex stimulation in children with unilateral lesions. This variation can directly aff5ct the optimal electrode placement and the
intended target area of application of tDCS with functional or anatomic reorganization.
39 Impact of baseline excitability on tDCS-induced plasticity S. Fresnoza , M.-F. Kuo , W. Paulus , M.A. Nitsche Dept. Clinical Neurophysiology, University Medical Center, GeorgAugust-University, Goettingen, Germany *E-mail: [email protected]. Neuroplastic alterations of cortical excitability can be accomplished by non-invasive brain stimulation with transcranial direct currents (tDCS). Excitability alterations can last from some minutes for up to more than 24h after plasticity induction. However, substantial interindividual variability does exist with regard to the duration and magnitude of the effects. The reasons for this variability have not been systematically explored. In a retrospective analysis in 22 healthy humans, we analyzed the dependence of tDCS-induced motor cortex plasticity from baseline excitability, as defined by the transcranial magnetic stimulation (TMS) intensity required to induce motor evoked potential amplitudes (MEP) of the size of 1 mV. Lower TMS intensity was associated with larger magnitude of tDCS-induced plasticity for both, the aftereffects of anodal, and cathodal tDCS. We conclude that baseline excitability is an important factor for determination of the efficacy of tDCS at the individual level. The physiological, and anatomical reasons for this association, as well as the opportunity to use this factor for optimizing tDCS effect, should be explored in future studies.
40 tACS- What goes on inside? The neural consequences of transcranial alternating current stimulation Kohitij Kar , Jacob Duijnhouwer , Bart Krekelberg Department of Neuroscience, Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, USA *E-mail: [email protected]. There is considerable evidence for clinical and behavioral efficacy of transcranial alternating current stimulation (tACS). The effects range from suppressing Parkinsonian tremors to augmenting human learning and memory. Despite widespread use, the neurobiological mechanism of actions of tACS on the brain is unclear. We have taken a threefold approach to probe tACS mechanisms. First, we examined the behavioral effects of tACS on human motion perception. Second, we used known motion models to generate predictions about neural mechanisms that could produce the effects. Third, we tested these predictions by directly measuring tACS-induced neural activity changes in the macaque brain. In human subjects, we found that tACS (10 Hz, 0.5 mA) applied over area hMT+, during coarse motion direction discrimination, increases observers’ sensitivity. Based on reports suggesting that tACS interacts with mechanisms of plasticity, we hypothesized that a reduction in adaptation might cause this effect. We tested this hypothesis by applying tACS during visual motion adaptation. tACS over contralateral but not ipsilateral hMT+ mitigated the motion aftereffect and sensitivity changes induced by adaptation. These results suggest that tACS-induced membrane voltage modulations reduce adaptation in the motion-selective neurons. Tuning curve estimates of macaque MT neurons showed that tACS attenuated the effects of motion adaptation on tuning amplitude and width. In addition to single cell measures, tACS also mitigated adaptationinduced changes in evoked LFP responses. Our results provide novel insight into how tACS interacts with neural activity and establishes the awake, behaving macaque as an in-vivo animal model to study tACS mechanisms.