scholarly journals Effects of electrodes length and insulation for transcranial electric stimulation

2019 ◽  
Vol 10 ◽  
pp. 111
Author(s):  
Ryosuke Tomio
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Subcutaneous Fat ◽  
Motor Evoked Potential ◽  
Threshold Level ◽  
Lower Threshold ◽  
The Finite Element Method ◽  
Stimulation Threshold ◽  
Transcranial Electric Stimulation ◽  
The Brain

Background: The aim of this study is to investigate the effects of length and insulation of the corkscrew electrodes for transcranial motor evoked potential (tMEP) monitoring. Methods: We used the finite element method to visualize the electric field in the brain, which was generated by electrodes of different lengths (4, 7, and 12 mm). Two types of head models were generated: A model that included a subcutaneous fat layer and another without a fat layer. Two insulated needle types of conductive tip (5 and 2 mm) were studied. The stimulation threshold levels of hand tMEP were measured in a clinical setting to compare normal corkscrew and insulated 7-mm depth corkscrew. Results: The electric field in the brain depended on the electrode depths in the no fat layer model. The deeper the electrodes reached, the stronger the electric fields generated. Electrode insulation made a difference in the fat layer models. The threshold level recordings of tMEP revealed that the 7-mm insulated electrodes showed a lower threshold than the normal electrodes by one-side replacement in each patient: 33.6 ± 9.6 mA and 36.3 ± 11.0 mA (n =16, P < 0.001), respectively. The 7-mm insulated electrodes also showed a lower threshold than the normal electrodes when both sides, electrodes were replaced: 34.4 ± 8.6 mA and 37.5 ± 9.2 mA (n =10, P = 0.003), respectively. Conclusions: The electrodes depth reached enough to skull is considered to be efficient. Insulation of the electrodes with a conductive tip is efficient when there is subcutaneous fat layer.

Effects of transcranial stimulating electrode montages over the head for lower-extremity transcranial motor evoked potential monitoring

2016 ◽  
Vol 126 (6) ◽  
pp. 1951-1958 ◽  
Author(s):  
Ryosuke Tomio ◽  
Takenori Akiyama ◽  
Takayuki Ohira ◽  
Kazunari Yoshida
Keyword(s):  
Finite Element ◽  
Lower Extremity ◽  
Electric Field ◽  
Motor Evoked Potentials ◽  
Motor Evoked Potential ◽  
Threshold Level ◽  
Lower Threshold ◽  
Transcranial Electrical Stimulation ◽  
Head Model ◽  
The Brain

OBJECTIVEThe aim of this study was to determine the most effective electrode montage to elicit lower-extremity transcranial motor evoked potentials (LE-tMEPs) using a minimum stimulation current.METHODSA realistic 3D head model was created from T1-weighted images. Finite element methods were used to visualize the electric field in the brain, which was generated by transcranial electrical stimulation via 4 electrode montage models. The stimulation threshold level of LE-tMEPs in 52 patients was also studied in a practical clinical setting to determine the effects of each electrode montage.RESULTSThe electric field in the brain radially diffused from the brain surface at a maximum just below the electrodes in the finite element models. The Cz-inion electrode montage generated a centrally distributed high electric field with a current direction longitudinal and parallel to most of the pyramidal tract fibers of the lower extremity. These features seemed to be effective in igniting LE-tMEPs.Threshold level recordings of LE-tMEPs revealed that the Cz-inion electrode montage had a lower threshold on average than the C3–C4 montage, 76.5 ± 20.6 mA and 86.2 ± 20.6 mA, respectively (31 patients, t = 4.045, p < 0.001, paired t-test). In 23 (74.2%) of 31 cases, the Cz-inion montage could elicit LE-tMEPs at a lower threshold than C3–C4.CONCLUSIONSThe C3–C4 and C1–C2 electrode montages are the standard for tMEP monitoring in neurosurgery, but the Cz-inion montage showed lower thresholds for the generation of LE-tMEPs. The Cz-inion electrode montage should be a good alternative for LE-tMEP monitoring when the C3–C4 has trouble igniting LE-tMEPs.

scholarly journals Spatiotemporal structure of intracranial electric fields induced by transcranial electric stimulation in human and nonhuman primates

2016 ◽  
Author(s):  
Alexander Opitz ◽  
Arnaud Falchier ◽  
Chao-Gan Yan ◽  
Erin Yeagle ◽  
Gary Linn ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Electric Stimulation ◽  
Brain Regions ◽  
Electrode Arrays ◽  
Non Invasive ◽  
Crucial Information ◽  
Cebus Monkeys ◽  
Transcranial Electric Stimulation ◽  
The Brain

AbstractTranscranial electric stimulation (TES) is an emerging technique, developed to non-invasively modulate brain function. However, the spatiotemporal distribution of the intracranial electric fields induced by TES remains poorly understood. In particular, it is unclear how much current actually reaches the brain, and how it distributes across the brain. Lack of this basic information precludes a firm mechanistic understanding of TES effects. In this study we directly measure the spatial and temporal characteristics of the electric field generated by TES using stereotactic EEG (s-EEG) electrode arrays implanted in cebus monkeys and surgical epilepsy patients. We found a small frequency dependent decrease (10%) in magnitudes of TES induced potentials and negligible phase shifts over space. Electric field strengths were strongest in superficial brain regions with maximum values of about 0.5 mV/mm. Our results provide crucial information for the interpretation of human TES studies and the optimization and design of TES stimulation protocols. In addition, our findings have broad implications concerning electric field propagation in non-invasive recording techniques such as EEG/MEG.

scholarly journals Design of Cable Termination for AC Breakdown Voltage Tests

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3075 ◽  
Author(s):  
Arthur F. Andrade ◽  
Edson G. Costa ◽  
Filipe L.M. Andrade ◽  
Clarice S.H. Soares ◽  
George R.S. Lira
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Breakdown Voltage ◽  
Electric Field Distribution ◽  
International Standards ◽  
The Finite Element Method ◽  
Cable Model ◽  
Voltage Measurement ◽  
Insulating Material ◽  
Purpose Computer

International standards prescribe overvoltage tests to evaluate the insulating material performance of high-voltage cables. However, it is difficult to manage the electric fields at the cable ends when laboratory measurements are carried out because surface and external discharges occur at the cable termination. Therefore, this paper presents a procedure for designing cable terminations to reduce the electric field at the cable ends to appropriate levels even in the case of overvoltage tests. For this purpose, computer simulations of electric field distribution using the finite element method (FEM) were performed. A 35 kV cable model was employed as a sample. An voltage with RMS (root mean square) value of 300 kV was used as an overestimate of breakdown voltage for the internal insulating material. The cable termination model obtained through the proposed methodology allows an electric field reduction in air, preventing the occurrence of external discharges, and thus permitting the breakdown voltage measurement of the cable’s inner insulation.

scholarly journals Electric field dynamics in the brain during multi-electrode transcranial electric stimulation

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Ivan Alekseichuk ◽  
Arnaud Y. Falchier ◽  
Gary Linn ◽  
Ting Xu ◽  
Michael P. Milham ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Stimulation ◽  
Transcranial Electric Stimulation ◽  
The Brain

Analysis of 50Hz Electric Fields Generated by Multi-Circuit Transmission Lines on the Same Tower

2014 ◽  
Vol 700 ◽  
pp. 67-70 ◽  
Author(s):  
Bin Liu ◽  
Tao Wang ◽  
Fei Gu ◽  
Jie Wei ◽  
Hong Wei Cui ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Transmission Lines ◽  
The Finite Element Method ◽  
Protection Measures ◽  
Overhead Transmission Lines ◽  
Domestic Security ◽  
Phase Sequence ◽  
The Cross ◽  
Security Standards

The finite element method has been applied to calculate the 50Hz electric fields nearby the transmission lines. The electric field strengths nearby multi-circuit transmission lines on the same tower under different arrangement of phase sequence, nearby the cross-arm are calculated. According to the foreign and domestic security standards of 50Hz electric field, the impacts of overhead transmission lines on environment are evaluated and the adoptable measures to reduce electric field strength are proposed. Meanwhile the distributing pattern of the electric field nearby the cross-arm is analyzed and proposals for further protection measures during maintenance operation are provided.

scholarly journals Modelling of the Electric Field Distribution in Deep Transcranial Magnetic Stimulation in the Adolescence, in the Adulthood, and in the Old Age

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Serena Fiocchi ◽  
Michela Longhi ◽  
Paolo Ravazzani ◽  
Yiftach Roth ◽  
Abraham Zangen ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Stimulation ◽  
Depressive Disorders ◽  
Brain Structures ◽  
Increasing Demand ◽  
And Gender ◽  
Aging People ◽  
The Brain

In the last few years, deep transcranial magnetic stimulation (dTMS) has been used for the treatment of depressive disorders, which affect a broad category of people, from adolescents to aging people. To facilitate its clinical application, particular shapes of coils, including the so-called Hesed coils, were designed. Given their increasing demand and the lack of studies which accurately characterize their use, this paper aims to provide a picture of the distribution of the induced electric field in four realistic human models of different ages and gender. In detail, the electric field distributions were calculated by using numerical techniques in the brain structures potentially involved in the progression of the disease and were quantified in terms of both amplitude levels and focusing power of the distribution. The results highlight how the chosen Hesed coil (H7 coil) is able to induce the maxima levels ofEmainly in the prefrontal cortex, particularly for the younger model. Moreover, growing levels of induced electric fields with age were found by going in deep in the brain, as well as a major capability to penetrate in the deepest brain structures with an electric field higher than 50%, 70%, and 90% of the peak found in the cortex.

scholarly journals Integrating electric field modelling and neuroimaging to explain inter-individual variability of tACS effects

2019 ◽  
Author(s):  
Florian H. Kasten ◽  
Katharina Duecker ◽  
Marike C. Maack ◽  
Arnd Meiser ◽  
Christoph S. Herrmann
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Individual Variability ◽  
Transcranial Electrical Stimulation ◽  
Field Modelling ◽  
Novel Approach ◽  
Before And After ◽  
Transcranial Alternating Current Stimulation ◽  
The Brain ◽  
Field Variability

AbstractUnderstanding variability of transcranial electrical stimulation (tES) effects is one of the major challenges in the brain stimulation community. Promising candidates to explain this variability are individual anatomy and the resulting differences of electric fields inside the brain. We integrated individual simulations of electric fields during tES with source-localization to predict variability of transcranial alternating current stimulation (tACS) aftereffects on α-oscillations. In two experiments, participants received 20 minutes of either α-tACS (1 mA) or sham stimulation. Magnetoencephalogram was recorded for 10 minutes before and after stimulation. tACS caused a larger power increase in the α-band as compared to sham. The variability of this effect was significantly predicted by measures derived from individual electric field modelling. Our results directly link electric field variability to variability of tACS outcomes, stressing the importance of individualizing stimulation protocols and providing a novel approach to analyze tACS effects in terms of dose-response relationships.

16 Noninvasive deep brain stimulation via delivery of temporally interfering electric fields

2020 ◽  
Vol 91 (8) ◽  
pp. e6.3-e7
Author(s):  
Nir Grossman
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Brain Stimulation ◽  
Dynamic Range ◽  
Imperial College ◽  
Network Activity ◽  
Massachusetts Institute Of Technology ◽  
Neural Firing ◽  
Institute Of Technology ◽  
The Brain

Nir is a Lecturer (Assistant Professor) at Imperial College London and a founding fellow of the UK Dementia Research Institute (UK-DRI). The long-term goal of his research is to develop neuromodulatory interventions for neurodegenerative diseases by direct modulation of the underlying aberrant network activity. Nir received a BSc in Physics from the Israeli Institute of Technology (Technion), an MSc in Electromagnetic Engineering from the Technical University of Hamburg-Harburg, and a PhD in Neuroscience from Imperial College London. He then completed a postdoc training, as a Wellcome Trust Fellow, at the Massachusetts Institute of Technology (MIT) and Harvard University. Nir was recently awarded the prestige prize for Neuromodulation from the Science magazine for describing how temporal interfering of kHz electric fields can non-invasively stimulate focal neural structures deep in the brain.Electrical brain stimulation is a key technique in research and clinical neuroscience studies, and also is in increasingly widespread use from a therapeutic standpoint. However, to date all methods of electrical stimulation of the brain either require surgery to implant an electrode at a defined site, or involve the application of non-focal electric fields to large fractions of the brain. We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice.

scholarly journals Effects of Pulsed Electric Fields on Yeast with Prions and the Structure of Amyloid Fibrils

2021 ◽  
Vol 11 (6) ◽  
pp. 2684
Author(s):  
Justina Jurgelevičiūtė ◽  
Nedas Bičkovas ◽  
Andrius Sakalauskas ◽  
Vitalij Novickij ◽  
Vytautas Smirnovas ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Electrostatic Interactions ◽  
Amyloid Fibrils ◽  
Translation Termination ◽  
Yeast Prions ◽  
Amyloid Aggregates ◽  
Perfect Model ◽  
Noncovalent Bonds ◽  
The Brain

Prions are misfolded, self-replicating, and transmissible proteins capable of causing different conditions that affect the brain and nervous system in humans and animals. Yeasts are the perfect model to study prion formation, dissemination, and the structure of protein aggregates. Yeast prions are related to stress resistance, cell fitness, and viability. Applying a pulsed electric field (PEF) as a factor capable of disintegrating the amyloid aggregates arises from the fact that the amyloid aggregates form via noncovalent bonds and stabilize via electrostatic interactions. In this research, we applied 2–26 kV/cm PEF delivered in sequences of 5 pulses of 1 ms duration to the Saccharomyces cerevisiae cell without prions and containing strong and weak variants of the [PSI+] prion (prion form of Sup35 translation termination factor). We determined that prions significantly increase cell survivability and resistance to PEF treatment. The application of PEF to the purified Sup35NM fibrils showed that the electric field causes significant reductions in the length of fibrils and the full disintegration of fibrils to Sup35 oligomers can be achieved in higher fields.

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