scholarly journals Modeling implanted metals in electrical stimulation applications

2021 ◽  
Author(s):  
Borja Mercadal ◽  
Ricardo Salvador ◽  
Maria Chiara Biagi ◽  
Fabrice Bartolomei ◽  
Fabrice Wendling ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Electric Fields ◽  
Strong Field ◽  
Numerical Models ◽  
The Body ◽  
Transcranial Electrical Stimulation ◽  
Head Model ◽  
Perfect Conductor ◽  
Theoretical Argument ◽  
Metal Implants

AbstractBackgroundMetal implants impact the dosimetry assessment in electrical stimulation techniques. Therefore, they need to be included in numerical models. While currents in the body are ionic, metals only allow electron transport. In fact, charge transfer between tissues and metals requires electric fields to drive the electrochemical reactions at the interface. Thus, metal implants may act as insulators or as conductors depending on the scenario.Objective/HypothesisThe aim of this paper is to provide a theoretical argument that guides the choice of the correct representation of metal implants using purely electrical models but considering the electrochemical nature of the problem in the technology of interest.MethodsWe built a simple model of a metal implant exposed to a homogeneous electric field of various magnitudes to represent both weak (e.g., tDCS), medium (TMS) or strong field stimulation. The same geometry was solved using two different models: a purely electric one (with different conductivities for the implant), and an electrochemical one. As an example of application, we also modeled a transcranial electrical stimulation (tES) treatment in a realistic head model with a skull plate using a high and low conductivity value for the plate.ResultsMetal implants generally act as electric insulators when exposed to electric fields up to around 100 V/m (tES and TMS range) and they only resemble a perfect conductor for fields in the order of 1000 V/m and above. The results are independent of the implant’s metal, but they depend on its geometry.Conclusion(s)Metal implants can be accurately represented by a simple electrical model of constant conductivity, but an incorrect model choice can lead to large errors in the dosimetry assessment. In particular, tES modeling with implants incorrectly treated as conductors can lead to errors of 50% in induced fields or more. Our results can be used as a guide to select the correct model in each scenario.

scholarly journals Multi-channel transorbital electrical stimulation for effective stimulation of posterior retina

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sangjun Lee ◽  
Jimin Park ◽  
Jinuk Kwon ◽  
Dong Hwan Kim ◽  
Chang-Hwan Im
Keyword(s):  
Electrical Stimulation ◽  
Electric Field ◽  
Electric Fields ◽  
Anterior Part ◽  
Posterior Part ◽  
Human Head ◽  
Electrical Current ◽  
Field Analysis ◽  
Head Model ◽  
Stimulation Of

AbstractTransorbital electrical stimulation (tES) has been studied as a new noninvasive method for treating intractable eye diseases by delivering weak electrical current to the eye through a pair of electrodes attached to the skin around the eye. Studies have reported that the therapeutic effect of tES is determined by the effective stimulation of retinal cells that are densely distributed in the posterior part of the retina. However, in conventional tES with a pair of electrodes, a greater portion of the electric field is delivered to the anterior part of the retina. In this study, to address this issue, a new electrode montage with multiple electrodes was proposed for the effective delivery of electric fields to the posterior retina. Electric field analysis based on the finite element method was performed with a realistic human head model, and optimal injection currents were determined using constrained convex optimization. The resultant electric field distributions showed that the proposed multi-channel tES enables a more effective stimulation of the posterior retina than the conventional tES with a pair of electrodes.

scholarly journals Unification of optimal targeting methods in Transcranial Electrical Stimulation

2019 ◽  
Author(s):  
Mariano Fernandez-Corazza ◽  
Sergei Turovets ◽  
Carlos Muravchik
Keyword(s):  
Electrical Stimulation ◽  
Optimization Problem ◽  
Linear Optimization ◽  
Region Of Interest ◽  
Extreme Case ◽  
Transcranial Electrical Stimulation ◽  
Head Model ◽  
Dose Limit ◽  
Safety Constraints ◽  
Complete Optimization

AbstractOne of the major questions in high-density transcranial electrical stimulation (TES) is: given a region of interest (ROI), and given electric current limits for safety, how much current should be delivered by each electrode for optimal targeting? Several solutions, apparently unrelated, have been independently proposed depending on how “optimality” is defined and on how this optimization problem is stated mathematically. Among them, there are closed-formula solutions such as ones provided by the least squares (LS) or weighted LS (WLS) methods, that attempt to fit a desired stimulation pattern at ROI and non-ROI, or reciprocity-based solutions, that maximize the directional dose at ROI under safety constraints. A more complete optimization problem can be stated as follows: maximize directional dose at ROI, limit dose at non-ROI, and constrain total injected current and current per electrode (safety constraints). To consider all these constraints (or some of them) altogether, numerical convex or linear optimization solvers are required. We theoretically demonstrate in this work that LS, WLS and reciprocity-based closed-form solutions are particular solutions to the complete optimization problem stated above, and we validate these findings with simulations on an atlas head model. Moreover, the LS and reciprocity solutions are the two opposite cases emerging under variation of one parameter of the optimization problem, the dose limit at non-ROI. LS solutions belong to one extreme case, when the non-ROI dose limit is strictly imposed, and reciprocity-based solutions belong to the opposite side, i.e., when this limit is loose. As we couple together most optimization approaches published so far, these findings will allow a better understanding of the nature of the TES optimization problem and help in the development of advanced and more effective targeting strategies.

scholarly journals Inter-individual and age-dependent variability in simulated electric fields induced by conventional transcranial electrical stimulation

NeuroImage ◽  
2021 ◽  
Vol 224 ◽  
pp. 117413
Author(s):  
Daria Antonenko ◽  
Ulrike Grittner ◽  
Guilherme Saturnino ◽  
Till Nierhaus ◽  
Axel Thielscher ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Electric Fields ◽  
Transcranial Electrical Stimulation ◽  
Age Dependent

scholarly journals Electrical neuromodulation biases brightness perception of flickering light

2021 ◽  
Author(s):  
Marina Fiene ◽  
Jan-Ole Radecke ◽  
Jonas Misselhorn ◽  
Malte Sengelmann ◽  
Christoph S. Herrmann ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Electric Fields ◽  
Subjective Experience ◽  
Phase Synchronization ◽  
Temporal Dynamics ◽  
Cortical Excitability ◽  
Brightness Discrimination ◽  
Transcranial Electrical Stimulation ◽  
Subjective Perception ◽  
Brightness Perception

Human brightness estimation often pronouncedly dissociates from objective viewing conditions. Yet, the physiological substrate underlying subjective perception is still poorly understood. Rather than physical illumination, the subjective experience of brightness has been shown to correlate with temporal dynamics in the amplitude of cortical neural responses. Here, we aimed to experimentally manipulate visual flicker-evoked steady-state responses and related perception via concurrent modulation of cortical excitability by transcranial alternating current stimulation. Participants performed a brightness discrimination task of two visual flicker stimuli, one of which was targeted by same-frequency electrical stimulation at varying phase shifts. Transcranial electrical stimulation was applied with an occipital and a periorbital active control montage, based on finite-element method simulations of electric fields. Experimental results reveal that flicker brightness perception is modulated dependent on the phase shift between sensory and electrical stimulation, solely under stable flicker entrainment and exclusively under occipital electrical stimulation. The degree of induced brightness modulation was positively correlated with the strength of neuronal phase locking to the flicker, recorded prior to electrical stimulation. This finding was corroborated by a neural network model, demonstrating a comparable dependency between flicker-evoked phase synchronization and amplitude modulations of entrained neural rhythms by phase shifted visual and electric inputs. Our data suggest a causal role of the amplitude of neural activity in visual cortex for brightness perception in humans. This finding provides an important step towards understanding the basis of visual perception and further confirms electrical stimulation as a tool for advancing controlled modulations of neural excitability and related behavior.

scholarly journals Transcranial Electrical Stimulation generates electric fields in deep human brain structures

2021 ◽  
Author(s):  
Samuel Louviot ◽  
Louise Tyvaert ◽  
Louis G. Maillard ◽  
Sophie Colnat-Coulbois ◽  
Jacek Dmochowski ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Human Brain ◽  
Electric Fields ◽  
Brain Structures ◽  
Transcranial Electrical Stimulation

scholarly journals Assessment of the state of personal and situational anxiety and indicators of stress-implementing and stress-limiting systems of the organism as marker efficiency the antenatal preparation

2021 ◽  
pp. 17-22
Author(s):  
N.Y. Skripchenko ◽  
◽  
Y.V. Nevyshna ◽  
Keyword(s):  
Electrical Stimulation ◽  
Pain Relief ◽  
Pain Tolerance ◽  
The State ◽  
The Body ◽  
Control Group ◽  
Transcranial Electrical Stimulation ◽  
Healthy Women ◽  
Situational Anxiety ◽  
Transcranial Electrostimulation

As a result of research conducted on the basis of the State Institution «Institute of Pediatrics, Obstetrics and Gynecology named after academician O.M. Lukyanova NAMS of Ukraine», the issue of the transcranial electrostimulation introduction in preparation for partnership labor was shown. Purpose — to study the features of changes in the state of personal and situational anxiety, stress-implementing and stress-limiting systems of the body in healthy women depending on the method of prenatal training. Materials and methods. 120 somatically healthy women without severe extragenital and obstetric pathology with a physiological course of singleton pregnancy were examined. In the first group — 45 women set up for partner childbirth, the second group also included 45 patients who underwent a course of transcranial electrical stimulation (TES) of mesodiencephalic structures of the brain in comprehensive preparation for partner childbirth. The control group included 30 women who did not receive prenatal training, did not have individual support in childbirth and were tuned to traditional methods of pain relief as needed. Results. Following the results of the determination of pain rate in the dynamic of the TES procedure, a progressive growth of the pain tolerance threshold was recorded with the subsequent stabilization of this value after the 5th procedure of electrical stimulation. Methods of psychophysical preparation for childbirth using transcranial electrostimulation and partner support made it possible to reduce medical induced pain relief during childbirth, which is what the data we obtained indicate. Conclusions. The use of TES in complex prenatal preparation for partner labor allows to achieve and maintain a stable psycho-emotional adaptation of pregnant women and increases the tolerance of the consonant to labor pain without additional medication load, which helps to make more physiological course of labor. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: labor, prenatal preparation, transcranial electrostimulation, pain threshold, anesthesia, partnership labor.

scholarly journals Intracranial Electric Field Recording During Multichannel Transcranial Electrical Stimulation

2021 ◽  
Author(s):  
Minmin Wang ◽  
Jiawei Han ◽  
Hongjie Jiang ◽  
Junming Zhu ◽  
Wuwei Feng ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Simulation Model ◽  
Electric Fields ◽  
Simulation Models ◽  
Transcranial Electrical Stimulation ◽  
Induced Voltage ◽  
Linear Superposition ◽  
In Vivo Measurements ◽  
Highly Correlated

Background: Multichannel transcranial electrical stimulation (tES) modeling and optimization have been widely studied in recent years. Its theoretical bases include quasi-static assumption and linear superposition. However, there is still a lack of direct in vivo evidence to validate the simulation model and theoretical assumptions. Methods: We directly measured the multichannel tES-induced voltage changes with implanted stereotactic-electroencephalographic (sEEG) electrodes in 12 epilepsy subjects. By combining these measured data, we investigate the linear superposition and prediction accuracy of simulation models for multi-electrode stimulation and further compare the induced EF differences between transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS). Results: Our in vivo measurements demonstrated that the multi-electrode tES-induced voltages were almost equal to the sum of the voltages generated independently by bipolar stimulation. Both measured voltages and electric fields obtained in vivo were highly correlated with the predicted values in our cohort (Voltages: r = 0.92, p < 0.001; electric fields: r = 0.74, p < 0.001). Under the same stimulation intensity, the tDCS-induced peak-zero voltages were highly correlated with the values of tACS (r = 0.99, p < 0.001; s = 0.99). Conclusions: The in vivo measurements provides confirmatory results for linear superposition and quasi-static assumption within the human brain. Furthermore, we found that the individualized simulation model reliably predicted the multi-electrode tES-induced electric fields.

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