scholarly journals Electric field dependent effects of motor cortical TDCS

2018 ◽  
Author(s):  
Ilkka Laakso ◽  
Marko Mikkonen ◽  
Soichiro Koyama ◽  
Daisuke Ito ◽  
Tomofumi Yamaguchi ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Brain Anatomy ◽  
After Effects ◽  
Neuropsychiatric Diseases ◽  
Motor Cortical ◽  
The Individual ◽  
The Brain

AbstractTranscranial direct current stimulation (TDCS) can modulate motor cortical excitability. However, its after-effects are highly variable between individuals. Individual cranial and brain anatomy may contribute to this variability by producing varying electric fields in each subject’s brain. Here we show that these fields are related to excitability changes following anodal TDCS of the primary motor cortex (M1). We found in two experiments (N=28 and N=9) that the after-effects of TDCS were proportional to the individual electric field in M1, calculated using MRI-based models. Individuals with the lowest and highest local electric fields in M1 tended to produce opposite changes in excitability. Furthermore, the effect was field-direction dependent and non-linear with stimulation duration or other experimental parameters. The electric field component pointing into the brain was negatively proportional to the excitability changes following 1 mA 20 min TDCS of right M1 (N=28); the effect was opposite after 1 mA 10 min TDCS of left M1 (N=9). Our results demonstrate that a large part of variability in the after-effects of motor cortical TDCS is due to inter-individual differences in the electric fields. We anticipate that individualized electric field dosimetry could be used to control the neuroplastic effects of TDCS, which is increasingly being explored as a treatment for various neuropsychiatric diseases.

scholarly journals Dose-controlled tDCS reduces electric field intensity variability at a cortical target site

2019 ◽  
Author(s):  
Carys Evans ◽  
Clarissa Bachmann ◽  
Jenny Lee ◽  
Evridiki Gregoriou ◽  
Nick Ward ◽  
...  
Keyword(s):  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Primary Motor Cortex ◽  
Target Site ◽  
Fixed Dose ◽  
Brain Scans ◽  
Human Connectome Project ◽  
Dose Control ◽  
The Brain

AbstractBackgroundVariable effects limit the efficacy of transcranial direct current stimulation (tDCS) as a research and therapeutic tool. Conventional application of a fixed-dose of tDCS does not account for inter-individual differences in anatomy (e.g. skull thickness), which varies the amount of current reaching the brain. Individualised dose-control may reduce the variable effects of tDCS by reducing variability in electric field intensities at a cortical target site.ObjectiveTo characterise the variability in electric field intensity at a cortical site (left primary motor cortex; M1) and throughout the brain for conventional fixed-dose tDCS, and individualised dose-controlled tDCS.MethodsThe intensity and distribution of the electric field during tDCS was estimated using Realistic Volumetric Approach to Simulate Transcranial Electric Stimulation (ROAST) in 50 individual brain scans taken from the Human Connectome Project, for fixed-dose tDCS (1mA & 2mA) and individualised dose-controlled tDCS targeting left M1.ResultsWith a fixed-dose (1mA & 2mA), E-field intensity in left M1 varied by more than 100% across individuals, with substantial variation observed throughout the brain as well. Individualised dose-controlled ensured the same E-field intensity was delivered to left M1 in all individuals. Its variance in other regions of interest (right M1 and area underneath the electrodes) was comparable with fixed- and individualised-dose.ConclusionsIndividualized dose-control can eliminate the variance in electric field intensities at a cortical target site. Assuming that the current delivered to the brain directly determines its physiological and behavioural consequences, this approach may allow for reducing the known variability of tDCS effects.

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.

Transcranial brain stimulation: potential and limitations

e-Neuroforum ◽  
2014 ◽  
Vol 20 (2) ◽  
Author(s):  
W. Paulus
Keyword(s):  
Electric Fields ◽  
Magnetic Stimulation ◽  
Near Infrared ◽  
Brain Activity ◽  
Electrical Energy ◽  
After Effects ◽  
Network Characteristics ◽  
Neuronal Membranes ◽  
Transcranial Brain Stimulation ◽  
The Brain

AbstractThe brain adapts to new requirements in response to activity, learning or reactions to environmental stimuli by continuous reorgani­zation. These reorganization processes can be facilitated and augmented, or also inhibit­ed and prevented, by transcranial neurostim­ulation. The most common methods are electrical or magnetic stimulation. However, few studies have dealt with the newer methods using near infrared or ultrasound stimulation.Transcranial magnetic stimulation (TMS) allows the pain-free transfer of very short bursts of high intensity electrical energy through the skull and can induce action po­tentials. By varying the number and intensity of the stimuli, and the stimulus sequence, repetitive TMS (rTMS) can induce either inhib­itory or facilitatory effects in the brain. A differentiation is made between short-lived interference with ongoing brain activity, and plastic changes that persist for a longer period beyond the end of the stimulation.Weaker electric fields in the 1 mA range can be applied painlessly through the skull. These probably exert their effects by modulating neuronal membranes and influencing the spontaneous firing rate of cortical neu­rons. They encompass the range from tran­scranial direct current stimulation (tDCS) to high frequency alternating current stimulation (tACS) in the kilohertz range. In view of the multitude of physically possible stimulation algorithms, hypothesis-driven protocols based on cellular or neuronal network characteristics are particularly popular, in the effort to narrow the choices in a meaningful manner. Examples are theta burst stimulation or tACS in the so-called “ripple” frequen­cy range. It is, of course, not possible to selectively stimulate individual neurons using transcranial stimulation techniques; however selective after-effects can be achieved when used in combination with neuropharmacologically active drugs. The use of these methods for neuroenhancement is now a topic of intense discussion.

NMDA Receptor-Mediated Motor Cortex Plasticity After 20 Hz Transcranial Alternating Current Stimulation

2018 ◽  
Vol 29 (7) ◽  
pp. 2924-2931 ◽  
Author(s):  
M Wischnewski ◽  
M Engelhardt ◽  
M A Salehinejad ◽  
D J L G Schutter ◽  
M -F Kuo ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Alternating Current ◽  
Beta Oscillations ◽  
Human Motor Cortex ◽  
After Effects ◽  
Transcranial Alternating Current Stimulation ◽  
Human Motor ◽  
Motor Cortex Plasticity

Abstract Transcranial alternating current stimulation (tACS) has been shown to modulate neural oscillations and excitability levels in the primary motor cortex (M1). These effects can last for more than an hour and an involvement of N-methyl-d-aspartate receptor (NMDAR) mediated synaptic plasticity has been suggested. However, to date the cortical mechanisms underlying tACS after-effects have not been explored. Here, we applied 20 Hz beta tACS to M1 while participants received either the NMDAR antagonist dextromethorphan or a placebo and the effects on cortical beta oscillations and excitability were explored. When a placebo medication was administered, beta tACS was found to increase cortical excitability and beta oscillations for at least 60 min, whereas when dextromethorphan was administered, these effects were completely abolished. These results provide the first direct evidence that tACS can induce NMDAR-mediated plasticity in the motor cortex, which contributes to our understanding of tACS-induced influences on human motor cortex physiology.

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.

scholarly journals Comparative Modeling of Transcranial Magnetic and Electric Stimulation in Mouse, Monkey, and Human

2018 ◽  
Author(s):  
Ivan Alekseichuk ◽  
Kathleen Mantell ◽  
Sina Shirinpour ◽  
Alexander Opitz
Keyword(s):  
Finite Element ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Mouse Brain ◽  
Electric Stimulation ◽  
Human Model ◽  
Brain Anatomy ◽  
List Type

ABSTRACTTranscranial magnetic stimulation (TMS) and transcranial electric stimulation (TES) are increasingly popular methods to noninvasively affect brain activity. However, their mechanism of action and dose-response characteristics remain under active investigation. Translational studies in animals play a pivotal role in these efforts due to a larger neuroscientific toolset enabled by invasive recordings. In order to translate knowledge gained in animal studies to humans, it is crucial to generate comparable stimulation conditions with respect to the induced electric field in the brain. Here, we conduct a finite element method (FEM) modeling study of TMS and TES electric fields in a mouse, capuchin monkey, and human model. We systematically evaluate the induced electric fields and analyze their relationship to head and brain anatomy. We find that with increasing head size, TMS-induced electric field strength first increases and then decreases according to a two-term exponential function. TES-induced electric field strength strongly decreases from smaller to larger specimen with up to 100x fold differences across species. Our results can serve as a basis to compare and match stimulation parameters across studies in animals and humans.HIGHLIGHTSTranslational research in brain stimulation should account for large differences in induced electric fields in different organismsWe simulate TMS and TES electric fields using anatomically realistic finite element models in three species: mouse, monkey, and humanTMS with a 70 mm figure-8 coil creates an approximately 2-times weaker electric field in a mouse brain than in monkey and human brains, where electric field strength is comparableTwo-electrode TES creates an approximately 100-times stronger electric field in a mouse brain and 3.5-times stronger electric field in a monkey brain than in a human brain

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.

The brain of the honeybee Apis mellifera . I. The connections and spatial organization of the mushroom bodies

1982 ◽  
Vol 298 (1091) ◽  
pp. 309-354 ◽  
Keyword(s):  
Visual Information ◽  
Spatial Organization ◽  
Short Term Memory ◽  
Single Layer ◽  
Mushroom Bodies ◽  
After Effects ◽  
Kenyon Cells ◽  
The Individual ◽  
Polar Organization ◽  
The Brain

The mushroom bodies of the bee are paired neuropils in the dorsal part of the brain. Each is composed of the arborizations of over 17 x 10 4 small interneurons of similar architecture called Kenyon cells. Golgi staining demonstrates that these neurons can be divided into five groups distinguished on the basis of their dendritic specializations and geometry. The mushroom body neuropils each consist of a pair of cup-shaped structures, the calyces, connected by two short fused stalks, the pedunculus, to two lobes, the α- and β-lobes. Each calyx is formed from three concentric neuropil zones, the basal ring, the collar and the lip. The calyces are organized in a polar fashion; within the calyces each of the five categories of Kenyon cell has a distribution limited to particular polar contours. The dendritic volumes of neighbouring Kenyon cells arborizing within each individual contour are greatly overlapped. Fibres from groups of neighbouring cells within a calycal contour are gathered into bundles that project into the pedunculus, each fibre dividing to enter both the the α- and β-lobes. The pedunculus and the lobes are conspicuously layered. Kenyon cells with neighbouring dendritic fields within the same calycal contour occupy a single layer in the pedunculus and lobes. Thus the two- polar organization of the calyces is transformed into a Cartesian map within the pedunculus, which continues into the α- and β-lobes. The calyx receives input fibres from both the antennal lobes and the optic neuropils. The branching patterns of these cells reflect the polar organization of the calyces as their terminals are restricted to one or more of the three gross compartments of the calycal neuropil. The course of these tracts and the morphologies of the fibres that they contain are described. Cells considered to represent outputs from the mushroom bodies arborize in the pedunculus and α- and β-lobes. Generally the arborizations of the output neurons reflect the layered organization of these neuropils. Fibres from the two lobes run to the anterior median and lateral protocerebral neuropil, and the anterior optic tubercle. Additionally there is an extensive network of feedback interneurons that inter- connect the α- and β-lobes with the ipsi- and contralateral calyces. Many individual neurons have branches in both the α- and β-lobes and in the pedunculus. The pathways and geometries of the fibres subserving the two lobes are described. The hypothesis of Vowles (1955) that the individual lobes represent a separation of sensory and motor output areas is shown to be incorrect. The anatomy of the bee’s mushroom bodies suggests that they process second-order antennal and fourth- and higher-order visual information. The feedback pathways are discussed as possible means of creating long-lasting after-effects which may be important in complex timing processes and possibly the formation of short-term memory.

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.

scholarly journals Differences between motor execution and motor imagery of grasping movements in the motor cortical excitatory circuit

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5588 ◽  
Author(s):  
Hai-Jiang Meng ◽  
Yan-Ling Pi ◽  
Ke Liu ◽  
Na Cao ◽  
Yan-Qiu Wang ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Motor Imagery ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Short Interval ◽  
Corticospinal Excitability ◽  
Motor Execution ◽  
Human Motor Cortex ◽  
Motor Cortical ◽  
The Right

Background Both motor imagery (MI) and motor execution (ME) can facilitate motor cortical excitability. Although cortical excitability is modulated by intracortical inhibitory and excitatory circuits in the human primary motor cortex, it is not clear which intracortical circuits determine the differences in corticospinal excitability between ME and MI. Methods We recruited 10 young healthy subjects aged 18−28 years (mean age: 22.1 ± 3.14 years; five women and five men) for this study. The experiment consisted of two sets of tasks involving grasp actions of the right hand: imagining and executing them. Corticospinal excitability and short-interval intracortical inhibition (SICI) were measured before the interventional protocol using transcranial magnetic stimulation (baseline), as well as at 0, 20, and 40 min (T0, T20, and T40) thereafter. Results Facilitation of corticospinal excitability was significantly greater after ME than after MI in the right abductor pollicis brevis (APB) at T0 and T20 (p < 0.01 for T0, and p < 0.05 for T20), but not in the first dorsal interosseous (FDI) muscle. On the other hand, no significant differences in SICI between ME and MI were found in the APB and FDI muscles. The facilitation of corticospinal excitability at T20 after MI correlated with the Movement Imagery Questionnaire (MIQ) scores for kinesthetic items (Rho = −0.646, p = 0.044) but did not correlate with the MIQ scores for visual items (Rho = −0.265, p = 0.458). Discussion The present results revealed significant differences between ME and MI on intracortical excitatory circuits of the human motor cortex, suggesting that cortical excitability differences between ME and MI may be attributed to the activation differences of the excitatory circuits in the primary motor cortex.

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