tDCS - Science topic

Over the past two decades, many studies have been conducted with the aim of finding a way to moderate chronic tinnitus. In these studies, various methods such as transcranial magnetic stimulation have been used.

An important factor in choosing the right treatment method is that it has longer lasting effects. Among the methods of rTMS,TENS, tDCS and VNS, which one does have more long-term effects?

There are dozens of studies that investigate the effect of tdcs on depression, but not on anxiety (generalized anxiety disorder).

I have found two randomized controlled trials, and two case studies. (studies that perform multiple sessions, there might be more of them but still much less than depression studies)

This is strange since anxiety disorders have a higher prevalence than depression, and are also quite debilitating.

What explains this relative lack of studies ? Might it be that tdcs is not very effective in this disorder so that studies that fail to find an effect don't get published ?

When I look up studies about tdcs, it is always assumed that the electrical current produces polarisation only at the electrode surface. I have never been able to find any studies who clarify exactly why that happens.

If I have understood it correctly it has something to do with the fact that the current is either entering the brain or leaving it, but I don't understand why the current would have no effect "in" the brain.

Also if you perform a bihemispherical montage (such as a bitemporal or bifrontal montage), would the current stimulate areas along the longitudinal fissure, since the current is going out and into the brain at that spot.

I have used TNS & TMS & TACS systems which resulted in the patients awakening.TDCS was a bit effective but even this caused the patient to wake up after some time .

Which of the following methods can be applied for evaluating the cognition process of an interpreter while interpreting/speaking?

fMRI, EEG, MEG, tDCS, PET, fNIRS, or…..?

I had a problem that I failed to draw a head-model by "Draw Head-Model" button (error message below), when I lunched COMETS2, pressed "preprocessing" button, and read "testmodel.node" .

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Error using fread

Invalid file identifier. Use fopen to generate a valid file identifier.

Error in CONE_tDCS

Error in gui_mainfcn (line 95)

feval(varargin{:});

Error in CONE_tDCS

Error in matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)CONE_tDCS('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback.

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[My environment]

OS: win7 professional sp1 64bit

RAM: 8GB

MATLAB ver: R2017a (I tested it on R2018a and R2015b. But there was same trouble.)

Could you tell me the way I can run COMETS2 ?

Do you think that ganglion cell axonal regeneration may be stimulated in a 54 year old patient who became blind after suffering encephalitis in 2014, and subsequently lost almost all of his optic nerves (from the eye to the optic chiasm)? Recent MRI with DTI analyses revealed intact occipital lobes and optic tract up to the optic chiasm, but pathologic MRI signal of the optic chiasm with optic nerve atrophy. We have been able to increase his perception of phosphenes using tDCS, and wonder if we can amplify this effect.

This study will be relatively small-scale, and will form part of my doctoral thesis. I am hoping to bilaterally stimulate the DLPFC in a group of cannabis users for a short duration, in order to assess whether craving can be temporarily modulated.

In much of the tDCS literature I have reviewed so far, the position of M1 for anodal tDCS is given as coincident with C3/C4. Likewise, the positon of primary somatosensory cortex S1 for cathodal tDCS is given as 2 cm posterior or occipital to C3/C4. But now I am reading "the course of the central sulcus (rolandic fissure) which separates the frontal lobe from the parietal lobe corresponds to thin lines touching CPz-C2-C4 and CPz-C1-C3, respectively, [& actually courses through the centers of C4 & C3, respectively.] The two gyri immediately neighboring the central sulcus are the primary motor cortex (in frontal direction), and primary sensory cortex (in occipital direction)."

If it is true that it is the central sulcus itself that is coincident with the C3/C4 positions and that primary sensory cortex is estimated at approx. 2 cm occipital/posterior, then why is primary motor cortex not estimated as 2 cm frontal / anterior? I have not seen this discussed anywhere in the literature I've reviewed so far.

I am also trying to match up the M1 & S1 homoncular maps with their approximately corresponding electrode positions, understanding that only one electrode position each intended to stimulate all of M1 or S1 is much too coarse for the application we have in mind. Does anyone have a reference they would be willing to share which ideally would match up the 10-20 electrode positions in the vicinity of C3/C4 with their approximately corresponding somatosensory & somatomotor functional homunculi with higher resolution & greater specificity?

Quite a few published researchers are using Amrex branded sponge electrodes with banana jack connections for 1x1 low resolution tDCS. We have attempted to use them & have encountered several problems including one serious safety problem.

The electrode in question is a 3" by 3" square non-conductive rubber frame containing conductive wire mesh overlaid with a removable coarse kitchen-type sponge that protrudes out of a 2" by 2" aperture when soaked in saline. The rubber frame is stiff & does not conform well to the curvature of the cranium, especially with smaller subjects. This in turn results in difficulty placing it accurately & reproducibly & also in making good & uniform electrical contact. Though the maximum contact area of the sponge on the scalp is ideally 4 in² (25 cm²), in practice it is considerably less & variable with only a central area of contact which can be approximated as a circular disc inscribed within the 2" by 2" square aperture. This leads in turn to the most serious problem:

Injected current levels up to 2.0 mA are routine in tDCS research. The research community generally accepts a current density limit of .08 mA/cm² for the safety of the subject's skin in contact with the electrode & also to minimize potential damage to the underlying brain tissue. Even if the 2" by 2" sponge made perfect contact with the skin, at the 2.0 mA injected current level the current density limit is reached, exactly, as bulk current density = current / cross-sectional contact area = 2.0 mA / 25 cm² = .08 mA/cm². But these electrodes do not make perfect contact even when the they are secured tightly because of the rigid frames enclosing the sponges. So the contact area is rather less, resulting in the denominator being smaller and the current density necessarily exceeding the safety limit. Even at somewhat lower levels of injected current, taking the variable contact area of the sponges into account, the current density could easily exceed the safety limit. Furthermore, this is a very coarse bulk analysis. Taking nonhomogeneity, edge & corner effects into account, local areas of unacceptably high current density are unavoidable & can be demonstrated convincibly with a more sophisticated analysis (one using finite element methods for example).

Yet another practical problem with these electrodes is they have a strong & pungent odor which research subjects find objectionable, penetrates their hair & endures on the electrodes even after successive washings. If one electrode is placed supraorbitally, as is a common position in tDCS, the obnoxious smell in close proximity to the subject's nose even has the potential to affect the outcome of the experiment because it induces stress & stress-related neurological activity that has the potential to confound results.

These areas were stimulated in mice in a work by Moshel et al (2005) and I would like to understand where the corresponding areas are exactly situated in human.

We are using an experimental paradigm that involves a study phase of about one hour and we want to inhibit the DLPFC during learing. However, all the transcranial direct current stimulation (tDCS) protocols we are aware of do only last for about 30 min -- plus it takes time to build up their effectivity.

In specific could stimulation of the right DLPFC have a different effect to stimulation of the left hemisphere?

A question to all you stroke and tDCS / TMS researchers.

I want to visualize the lesion location of my participants in relationship to the stimulation site. In my case I have the lesions as ROIs normalised to the MNI standard space. Now I would like to create a 3 D image with the lesion mask as volume and mark position P4 on top. My objective is to see whether I actually tried to stimulate healthy or affected tissue with my tDCS protocol.

Alternatively marking P4 on the 2D slices would be fine as well. I just don't know how. I found the paper by Okamoto et al, 2004 ( ) which gives coordinates for the MNI templates.

Thank everyone for advice.

I am currently testing for my undergraduate dissertation looking at TDCS . I was wondering if what was done/thought/spoken about during the stimulation would change the effect of the TDCS at all?

In a study looking at effects ofTDCS delivered at rest, would having a programme for the duration of stimulation (20 minutes) be a useful means of control?

Any advice or relevant literature suggestions would be greatly appreciated

Palm et al., (DOI: 10.1016/j.brs.2008.04.003) suggest to disinfect the sponge electrodes regularly to reduce the occurrence of skin lesions, but there is few information to do it. 

Kuritani et al., (PMID: 8509738) suggest the use of autoclave and chemiclave for endodontic sponges. This could be a good option to treat tDCS sponges.

Another tip is to introduce wet sponges in microwave oven for 2 minutes, but it is only used in kitchen sponges.

According to your clinical and/or research experience. What do you suggest me?

tDCS = Transcranial direct current stimulation

Polhemus Liberty has great specs / spatio-temporal accuracy and no sensor occlusion, but compensates for static field distortions only, which excludes the concurrent use of magnetic or alternating current stimulation, or even EEG (cable movement).

Polhemus Liberty specs:

-Capture frequency: 240Hz

-Spatial resolution: 0.005mm at a distance of 60cm

Is there any motion capture alternatives with similar specs as Polhemus compatible with concurrent TMS/tDCS/EEG?

Thanks!

Has someone heard about unexpected effects of sham when using tDCS? We are observing what seems to be a systematic inhibitory effect of 2 mA (30 sec ramp up + 30 sec ramp down) cathodal sham stimulation. We are stimulating the right ventrolateral prefrontal cortex. I did not believe this putative effect at the very begining of the experiment, but after running a lot of participants with an experimental task I know very very well, I am now about to claim that our sham condition is playing a role...

Is tDCS able to change the structure, wiring and the organization of the brain neural networks? How about DBS? How long does it take?

I work in a neurorehabilitation center and I am interested in incorporating tDCS for patients with disorders of consciousness, cerebral palsy, spinal cord injuries, neurodegenerative diseases...

I would like to know what is the maximum recommended number of sessions (number of days/weeks/months) and if there is any colleague who has a protocolized number of sessions.

I have seen many articles but they are very heterogeneous so I would like to know the opinion of experts. In fact I even read a case report of a patient with disorders of consciousness treated for 6 months.

I would also like to know if once stimulation has been applied how long the «rest period» would a patient have before resuming electrostimulation.

Thanks in advance.

In your opinion, in a program of rehabilitation of motor deficit with tDCS, a condition of neoformation or tumor removal is a criteria of exclusion?

Hi everyone,

We are conducting a meta-analysis with a focus on single–session tDCS effects on working memory. If there is anyone who is willing to share their unpublished work or manuscript not yet appeared in the following databases: MEDLINE, SCOPUS, ScienceDirect, PsycARTICLES or CENTRAL, we would be happy to include it in our study. Also, research with data on WM measure following single–session tDCS (e.g. N –back), without that necessarily being a prime focus of a study, would be of great value for us. We would also like to include data from a PhD or master thesis, so please feel free to share it as well.

If you have any further questions, I am happy to answer.

I am planning to conduct a study to compare between two different tDCS montages over two different cortical areas, and the study will be controlled using sham group. What would be the tDCS montage for the sham group?

I did two a two way repeated measures ANOVA for a within-subjects cross over study to evaluate the effect of tDCS on HRV over time (40 minutes) in patients with Alcohol Use Disorder. With tDCS put on for 20 minutes between 10-30.

My within subject subjects factors are treatment (sham and real) and time (8 periods of 5 mins). I found only significance for time and not for treatment nor treatment*time.

I want to analyze between which moments in time their is a significant difference. But the pairwise comparisons don't show any significance between periods.

Can I do one way anova seperate for sham and real?

Do I use paired students t-test to evaluate difference in time points?

any other suggestions...

Thank you,

student

I have run an experiment investigating the effect of tDCS as treatment for alcoholism on rats. to measure effect I have compared how much rats drink before (baseline) and efter (deprivation effect) deprivation.

I get percentages such as 71 % for treatment and 133.65 % for control and 200% for treatment and 350 % for control. n-numbers are low, between 4-8. std are very high.

Is it possible to talk about a trend when p-values are really high?

Since tDCS is noninvasive technique of stimulation and has mainly modulating effects on brain tissue, the direct measurement is not possible. Is anyone aware of some simulation or biophysics study (beside Miranda) which determined the amount of electricity ( I read about the approximately 1 micro Coulomb) which is moved by this application. Thank you!

TACS is a device that imports frequencies to your brain in order to persuade your brain’s neurons oscillate by them.

Is it possible to enhance the skills of people with usual intelligence and make them smart by importing gamma ray to their brain?

Does the mechanism have long lasting effects?

Have you ever read something about it?

tDCS and tACS are forms of neurostimulation that  delivered via electrodes on the head and have therapeutic effects.

I want to know which one has a longer-lasting effect.

Hello everybody,

Does anybody know how to convert given MNI coordinates (e.g., peak coordinates from an fMRI paper) into "electrode space", i.e., electrode positions according to the 10/20 system? Would be needed for targeted electrical neurostimulation (tDCS).

Maybe there is an offline or online conversion tool? Or some function in FSL?

Thanks,

Stefan

Brain stimulation therapies include Electroconvulsive Therapy (ECT), Vagus Nerve Stimulation (VNS), Deep Brain Stimulation (DBS), Transcranial Direct Current Stimulation (tDCS) and repetitive transcranial magnetic stimulation. Brain stimulation therapies such as ECT should be reassessed with relevance to dose and frequency for the treatment of psychiatric and behavioral disorders. The major concern with ECT is associated with excessive heat generation and inactivation of genes required for neuron survival. Brain stimulation therapies such as ECT, VNS, DBS, tDCS and rTMS that use direct electrical currents to stimulate specific parts of the brain may be therapeutic when drug treatment is ineffective in diabetes and neurodegenerative diseases.

RELEVANT REFERENCE:

Martins IJ (2018) S Brain Stimulation Therapies in Neuropsychiatric and Neurodegenerative Diseases. Int J Genom Data Min: IJGD-127. DOI: 10.29011/ 2577-0616. 000027

Hello,

I would like to ask whether there is anybody with tDCS modeling software who would be so kind to help us to optimize the placent of cathodal electrode.

The aim is to stimulate prefrontal cortex with standard 7x5cm anode over (roughly) F3, AF3 and AF7 of the 10-10 EEG system. However, since the gradient of stimulation intensity depends on the placement of cathode, we would like to know where to put it to maintain peak stimulation aproximately under (and between) these electrode positions.

Candidate cathodal  placement we would like to check:

(1) Extra-cefalic - e.g. shoulder; (2) Left Wernicke area (roughly CP5); (3) Motor cortex.

Dear ResearchGate,

Im in the look out for a highly viscous eeg/tACS gel and donut shaped tCS rubber carbon electrodes needed for my sleep study. Both of these are demonstrated in https://www.jove.com/video/53527/concurrent-electroencephalography-recording-during-transcranial

In regards to the donut shaped tCS electrodes i can't find them anywhere. Does anyone know who sells them? Additionally, is it safe to make them by hole punching a circular tCS electrode?

In regards to viscuous gel i've found some options but they either dont show/tell how viscuous it is or . Does anyone have any recommended brands?

Thank you for your help!

Regards,

Achilleas

Is EEG conductive paste suitable to use with current inducing electrodes? It would help a lot for my sleep study. I'm using STARSTIM EEG/tES from Neuroelectrics.

Currently have this EEG paste http://www.weaverandcompany.com/ten20.html

And using these type of EEG/tACS electrodes http://www.neuroelectrics.com/products/electrodes/pistim/

Thank you for your help!

Dear tACS community, dear physicists and electrical engineers

I would be very grateful if somebody with the appropriate training could please clarify how to calculate the current density under the stimulation electrode for an alternating current? Based on the standard set by tDCS research (direct current stimulation), some researchers variably divide either the half peak maximum amplitude or the peak-to-peak amplitude by the electrode area, while others say that this measure is inappropriate for AC currents. What is the correct measure that relates injected current and electrode surface area?

Like most researchers in the tDCS community, I'm looking to induce persistent LTP-like effects.

The current literature is informative insofar as highlighting that multiple sessions of tDCS appear to enhance the strength and prolong the duration of resulting after-effects. The time at which repeat stimulation is administered also appears to be crucial but as yet there is little-to-no consensus on the most optimal parameters to use, including appropriate inter-stimulation-intervals. More recently, there seems to be a suggestion that implementing within-session intervals instead of continuous stimulation could be the way to go, however, the related studies only cover single sessions and don't comment on the frequency at which subsequent sessions of stimulation should be delivered.

Does anyone have any experience of attempting to induce longer lasting modulations - successful or otherwise? I'd appreciate advice on what to trial, what to avoid and whether you've noted differences between target populations (healthy/clinical, young/old etc) with regard to the parameters that show the most potential.

Thanks in advance!

Hello,

 I  was looking for some tDCS stimulation software and fortunately found COMETS (http://cone.hanyang.ac.kr/BioEST/Kor/Comets.html) . I would like to dig bit deep into it and started to examine the output file POTENT.OUT and other files. Could someone please help me with the following questions.

1)      The file POTENT.OUT has voxels and associated with a number, I am presuming that value as current. Am I correct here or is it Electric field, if so what are the units for that value?

2)      I happen to open POTENT.OUT file in Notepad and found 13,194 voxels and with corresponding current in each of them( example  1   0.00003467) which has 3D co-ordinates associated with those 13,194 voxels in xyz.dat file. The problem I am facing is , I couldn’t find out the boundaries associated with these voxels, like voxel number 1-1000 belong to frontal lobe, 10000-5000 belong to Parietal Lobe etc.

3)      I used MESH VIEWER to view .PLY files, the only thing I can see is brain model  but not the stimulated region in it.

4)      I would like to build my own head models, so all I need to do is get fMRI Images and get them into CURRY 7 and create boundary conditions. Is that all I need to do or any other software I need to use other than this?

 Any help is very much appreciated.

Many thanks in advance.

Regards,

Sri.

Bilinguals have been shown to perform better in a vast pallet of tasks hinting at having a better developed and more effective executive control network. 

The advantages range from superior inhibition of irrelevant information, enhanced decision making to faster problem solving and shifting between mental sets and even improved creativity. 

Because everything in the brain is connected and for bilinguals has been shown that they can compensate and use some are differently or more efficiently (less activation-better performance), we would like to know if this extends to the field of salience perception.   ??

Typically, the area investigated and involved in salience guided attention is posterior parietal cortex (PPC). LEFT is critically involved in attention for low-salience stimuli in the presence of highly salient distractors and the RIGHT one is involved in attending to more salient stimuli.

We would really appreciate any suggestion on how an experimental paradigm could be created using TMS or tDCS to test whether bilinguals are better (faster, more accurate) at a global-local salience task.

My area of research is effect tDCS (Trans-Cranial Direct Current Stimulation) on brain potentials.

I don’t have a good knowledge in tDCS modelling but would like use it a bit in my thesis. As I have already completed 2 years of my PHD I don’t want drift into new field or code the stuff for modelling. I would like to observe how current flows into brain when tDCS is applied. I looked for tDCS modelling software and couldn’t find many in my search. I found one named SPHERES (http://neuralengr.com/spheres/?page_id=17), which doesn’t have human brain model instead have a sphere but can play with parameters (amount of current, electrodes location where tDCS is applied etc).

Could anyone please help me with a simulation software where I can play with parameters like amount of current, electrodes location where tDCS is applied etc. Any help would be really appreciated.

Would like (a) screening questionnaire for participants prior to participation and, (b) post-activity questionnaire to ascertain adverse effects resulting from stimulation protocol.

I want to design an electronic circuit for TDCS, with the range of current that is given, I=0-2mA. how can I do it.

I'm glad if you can help me

I am submitting an IDE to the FDA for a study using the NeuroConn DC Stimulator. If anyone has had experience with this, I would greatly appreciate any pearls of wisdom you are willing to share. It would also be quite helpful to see an IDE application that was accepted by the FDA. 

Previous studies presumed that individual's cognitive functions could be improved by anodal tDCS, while cathodal tDCS made one's cognitive functions decrease.But when it comes to a result that motor or visual function is enhanced with cathodal tDCS, how to comprehend it?

I am specifically looking for advise concerning the type of stimulator that can be used in rodents. Would it be feasible to build our own stimulator, if yes, which technical aspects should be considered.

As we know it will take a long time for us to make subjects' resistance down before having an EEG test, while the aftereffect of tDCS may not last for a long time for some tasks.

For example: different people may have a different skin conductance and resistance. It may also not be possible to control the exact amount of saline. Are these differences important or not?

A few recent studies have concluded that a current level of 2mA was more effective (in creating desired outcome) than 1mA. I'm wondering why higher (but safe) current levels aren't being tested.