Evaluation of a Modified High-Definition Electrode Montage for Transcranial Alternating Current Stimulation (tACS) of Pre-Central Areas

Heise, Kirstin; Kortzorg, Nick; Saturnino, Guilherme B.; Fujiyama, Hakuei; Cuypers, Koen; Thielscher, Axel; Swinnen, Stephan P.

doi:10.1016/j.brs.2016.04.009

Cited by 53 publications

(38 citation statements)

References 30 publications

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“…Work in brain slices shows that similarly weak electric fields polarize the membrane potential in cortical neurons 3 , while animal studies show that these fields can entrain firing patterns in cortical neurons 4 . When applied to healthy volunteers, tACS modulates brain oscillations 5 , 6 which are believed to then modulate perception 7 , cognition 8 , and motor function 9 , 10 . The mechanisms of membrane polarization, followed by spike entrainment are assumed to underpin the human behavioral effects.…”

Section: Introductionmentioning

confidence: 99%

Using high-amplitude and focused transcranial alternating current stimulation to entrain physiological tremor

Khatoun

Breukers

Beeck

et al. 2018

Sci Rep

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Transcranial alternating current stimulation (tACS) is a noninvasive neuromodulation method that can entrain physiological tremor in healthy volunteers. We conducted two experiments to investigate the effectiveness of high-amplitude and focused tACS montages at entraining physiological tremor. Experiment 1 used saline-soaked sponge electrodes with an extra-cephalic return electrode and compared the effects of a motor (MC) and prefrontal cortex (PFC) electrode location. Average peak-amplitude was 1.925 mA. Experiment 2 used gel-filled cup-electrodes in a 4 × 1 focused montage and compared the effects of MC and occipital cortex (OC) tACS. Average peak-amplitude was 4.45 mA. Experiment 1 showed that unfocused MC and PFC tACS both produced phosphenes and significant phase entrainment. Experiment 2 showed that focused MC and OC tACS produced no phosphenes but only focused MC tACS caused significant phase entrainment. At the group level, tACS did not have a significant effect on tremor amplitude. However, with focused tACS there was a significant correlation between phase entrainment and tremor amplitude modulation: subjects with higher phase entrainment showed more tremor amplitude modulation. We conclude that: (1) focused montages allow for high-amplitude tACS without phosphenes and (2) high amplitude focused tACS can entrain physiological tremor.

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Section: Introductionmentioning

confidence: 99%

Using high-amplitude and focused transcranial alternating current stimulation to entrain physiological tremor

Khatoun

Breukers

Beeck

et al. 2018

Sci Rep

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“…Additionally, these montages stimulate large areas, which makes it difficult to attribute an experimental outcome to the stimulation of a particular brain region. In this context, pseudo-monopolar montages (i.e., ring montages or 4x1 montages) have been recently introduced in order to produce more focal stimulation effects than the classical bi-polar two-electrode montages using a single anode and cathode (Heise et al, 2016;Kuo et al, 2013). In addition, modelling the electric fields might help to reduce the uncertainty of the affected brain areas, allowing more careful planning of individualized electrode montages for targeting a given area of interest.…”

Section: Introductionmentioning

confidence: 99%

Accessibility of cortical regions to focal TES: Dependence on spatial position, safety, and practical constraints

et al. 2019

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Transcranial electric stimulation (TES) can modulate intrinsic neural activity in the brain by injecting weak currents through electrodes attached to the scalp. TES has been widely used as a neuroscience tool to investigate how behavioural and physiological variables of brain function are modulated by electric stimulation of specific brain regions. For an unambiguous interpretation of TES experiments, it is important that the electric fields can be steered towards one or several brain regions-of-interest. However, the conductive proprieties of the human head impose inherent physical limitations on how focal the electric fields in the brain produced by multi-electrode TES can be. As a rule of thumb, it is not feasible to selectively target deep brain areas with TES, although focusing the field in some specific deeper locations might be possible due to favourable conductive properties in the surrounding tissue. In the present study, we first propose a computationally efficient method for the automatic determination of electrode placements and stimulation intensities to optimally affect a given target position. We provide a computationally efficient and robust implementation of the optimization procedure that is able to adhere to safety constraints, while explicitly controlling both the number of active electrodes and the angular deviation of the field in the target area relative to the desired field direction. Leveraging the high computational efficiency of our method, we systematically assess the achievable focality of multi-electrode TES for all cortex positions, thereby investigating the dependence on the chosen constraints. Our results provide comprehensive insight into the limitations regarding the achievable TES dose and focality that are imposed by the biophysical constraints and the safety considerations of TES. version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ 2012; Ruffini et al., 2014;Wagner et al., 2015;Guler et al., 2016a). These methods share the same basic approach to employ grids of fixed electrode positions, but they differ, among others, in the way the optimization problems are set-up and how they account for the constraints set by the safety limits for TES and for other practical aspects such as a limited number of available stimulation channels. For example, in © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ 6 where vector − = [ 1 1 ⋯ 1 ] 1 −1 and the matrix −1 −1 is the ( − 1) ( − 1) identity matrix. Applying and its pseudo inverse † to Eq. 5, we obtain © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ 7

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“…In their study, none of the participants had any adverse events (Naro et al, 2016a). Heise et al (2016) reported that sensory discomfort was milder with the center-ring montage than with the classical electrode montage in tACS (20 Hz, 0.4 mA, 10 minutes) (Heise et al, 2016). In the center-ring montage, the target electrode is placed over the hand motor area and surrounded by the ring electrode; in the classical electrode montage, two electrodes are placed between the hand motor area and the contralateral supraorbital area.…”

Section: Introductionmentioning

confidence: 99%

Adverse events of tDCS and tACS: A review

Matsumoto

Ugawa

2017

Clinical Neurophysiology Practice

264

160

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Evaluation of a Modified High-Definition Electrode Montage for Transcranial Alternating Current Stimulation (tACS) of Pre-Central Areas

Abstract: In comparison to the classic montage, the M1 centre-ring montage enables a more focal stimulation of the target area and, at the same time, significantly reduces neurosensory side effects, essential for placebo-controlled study designs.

Cited by 53 publications

References 30 publications

Using high-amplitude and focused transcranial alternating current stimulation to entrain physiological tremor

Using high-amplitude and focused transcranial alternating current stimulation to entrain physiological tremor

Accessibility of cortical regions to focal TES: Dependence on spatial position, safety, and practical constraints

Adverse events of tDCS and tACS: A review

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