Posts Tagged tDCS

[NEWS] Brain stimulation improves depression symptoms, restores brain waves in clinical study — ScienceDaily

Date: March 11, 2019

Source: University of North Carolina Health Care

Summary: With a weak alternating electrical current sent through electrodes attached to the scalp, researchers successfully targeted a naturally occurring electrical pattern in a specific part of the brain and markedly improved depression symptoms in about 70 percent of participants in a clinical study.

FULL STORY

With a weak alternating electrical current sent through electrodes attached to the scalp, UNC School of Medicine researchers successfully targeted a naturally occurring electrical pattern in a specific part of the brain and markedly improved depression symptoms in about 70 percent of participants in a clinical study.

The research, published in Translational Psychiatry, lays the groundwork for larger research studies to use a specific kind of electrical brain stimulation called transcranial alternating current stimulation (tACS) to treat people diagnosed with major depression.

“We conducted a small study of 32 people because this sort of approach had never been done before,” said senior author Flavio Frohlich, PhD, associate professor of psychiatry and director of the Carolina Center for Neurostimulation. “Now that we’ve documented how this kind of tACS can reduce depression symptoms, we can fine tune our approach to help many people in a relatively inexpensive, noninvasive way.”

Frohlich, who joined the UNC School of Medicine in 2011, is a leading pioneer in this field who also published the first clinical trials of tACS in schizophrenia and chronic pain.

His tACS approach is unlike the more common brain stimulation technique called transcranial direct stimulation (tDCS), which sends a steady stream of weak electricity through electrodes attached to various parts of the brain. That approach has had mixed results in treating various conditions, including depression. Frohlich’s tACS paradigm is newer and has not been investigated as thoroughly as tDCS. Frohlich’s approach focuses on each individual’s specific alpha oscillations, which appear as waves between 8 and 12 Hertz on an electroencephalogram (EEG). The waves in this range rise in predominance when we close our eyes and daydream, meditate, or conjure ideas — essentially when our brains shut out sensory stimuli, such as what we see, feel, and hear.

Previous research showed that people with depression featured imbalanced alpha oscillations; the waves were overactive in the left frontal cortex. Frohlich thought his team could target these oscillations to bring them back in synch with the alpha oscillations in the right frontal cortex. And if Frohlich’s team could achieve that, then maybe depression symptoms would be decreased.

His lab recruited 32 people diagnosed with depression and surveyed each participant before the study, according to the Montgomery-Åsberg Depression Rating Scale (MADRS), a standard measure of depression.

The participants were then separated into three groups. One group received the sham placebo stimulation — a brief electrical stimulus to mimic the sensation at the beginning of a tACS session. A control group received a 40-Hertz tACS intervention, well outside the range that the researchers thought would affect alpha oscillations. A third group received the treatment intervention — a 10-Hertz tACS electrical current that targeted each individual’s naturally occurring alpha waves. Each person underwent their invention for 40 minutes on five consecutive days. None of the participants knew which group they were in, and neither did the researchers, making this a randomized double-blinded clinical study — the gold standard in biomedical research. Each participant took the MADRS immediately following the five-day regimen, at two weeks, and again at four weeks.

Prior to the study, Frohlich set the primary outcome at four weeks, meaning that the main goal of the study was to assess whether tACS could bring each individual’s alpha waves back into balance and decrease symptoms of depression four weeks after the five-day intervention. He set this primary outcome because scientific literature on the study of tDCS also used the four-week mark.

Frohlich’s team found that participants in the 10-Hertz tACS group featured a decrease in alpha oscillations in the left frontal cortex; they were brought back in synch with the right side of the frontal cortex. But the researchers did not find a statistically significant decrease in depression symptoms in the 10-Hertz tACS group, as opposed to the sham or control groups at four weeks.

But when Frohlich’s team looked at data from two weeks after treatment, they found that 70 percent of people in the treatment group reported at least a 50 percent reduction of depression symptoms, according to their MADRS scores. This response rate was significantly higher than the one for the two other control groups. A few of the participants had such dramatic decreases that Frohlich’s team is currently writing case-studies on them. Participants in the placebo and control groups experienced no such reduction in symptoms.

“It’s important to note that this is a first-of-its kind study,” Frohlich said. “When we started this research with computer simulations and preclinical studies, it was unclear if we would see an effect in people days after tACS treatment — let alone if tACS could become a treatment for psychiatric illnesses. It was unclear what would happen if we treated people several days in a row or what effect we might see weeks later. So, the fact that we’ve seen such positive results from this study gives me confidence our approach could help many people with depression.”

Frohlich’s lab is currently recruiting for two similar follow-up studies.

Other authors of the Translational Psychiatry paper are co-first authors Morgan Alexander, study coordinator and graduate student, and Sankaraleengam Alagapan, PhD, a postdoctoral fellow, both in the department of psychiatry at UNC-Chapel Hill; David Rubinow, MD, the Assad Meymandi Distinguished Professor and Chair of Psychiatry at the UNC School of Medicine; former UNC postdoctoral fellow Caroline Lustenberger, PhD; and Courtney Lugo and Juliann Mellin, both study coordinators at the UNC School of Medicine.

This research was funded through grants from the Brain Behavior Research Foundation, National Institutes of Health, the BRAIN Initiative, and the Foundation of Hope.

Frohlich holds joint appointments at UNC-Chapel Hill in the department of cell biology and physiology and the Joint UNC-NC State Department of Biomedical Engineering. He is also a member of the UNC Neuroscience Center.

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Materials provided by University of North Carolina Health CareNote: Content may be edited for style and length.


Journal Reference:

  1. Morgan L. Alexander, Sankaraleengam Alagapan, Courtney E. Lugo, Juliann M. Mellin, Caroline Lustenberger, David R. Rubinow, Flavio Fröhlich. Double-blind, randomized pilot clinical trial targeting alpha oscillations with transcranial alternating current stimulation (tACS) for the treatment of major depressive disorder (MDD)Translational Psychiatry, 2019; 9 (1) DOI: 10.1038/s41398-019-0439-0

 

via Brain stimulation improves depression symptoms, restores brain waves in clinical study — ScienceDaily

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[WEB SITE] Depression: Brain stimulation may be a good alternative treatment

A new review, which appears in The BMJ journal, examines the benefits of non-invasive brain stimulation for treating major depression and finds that the technique is a valid alternative to existing treatments.

doctor talking to patient

Doctors should consider brain stimulation as an alternative treatment for people living with severe depression, finds a new review

Over 17 million adults in the United States have had an episode of major depression at one point in their lives.

Some of these people have treatment-resistant depression, which means common prescription drugs do not alleviate the symptoms.

Recent studies have pointed to alternative treatment methods for major depression, such as non-invasive brain stimulation techniques.

For instance, a study that appeared at the end of last year showed that using small electric currents to stimulate a brain area called the orbitofrontal cortex significantly improves the mood of people who did not benefit from conventional antidepressants.

An even more recent trial of a form of brain stimulation called “transcranial alternating current stimulation” (tACS) found that the technique halved depression symptoms in almost 80 percent of the study participants.

Despite such promising results, doctors do not use these techniques widely, as there is not enough data available on their efficacy.

So, a team of researchers led by Julian Mutz at the Institute of Psychiatry, Psychology & Neuroscience at King’s College London, United Kingdom, set out to review some clinical trials that have examined the benefits of non-invasive brain stimulation techniques for people living with depression.

Brain stimulation as additional treatment

Specifically, Mutz and team examined the results of 113 clinical trials. Overall, these trials included 6,750 participants who were 48 years old, on average, and were living with major depressive disorder or bipolar depression.

The original clinical trials involved randomly assigning these participants to 18 treatment interventions or “sham” therapies. The reviewers focussed on the response, or “efficacy” of the treatment, as well as the “discontinuation of treatment for any reason” — or “acceptability” of the therapies. Mutz and colleagues also rated the trials’ risk of bias.

The therapies included in the review were “electroconvulsive therapy (ECT), transcranial magnetic stimulation (repetitive (rTMS), accelerated, priming, deep, and synchronized), theta burst stimulation, magnetic seizure therapy, transcranial direct current stimulation (tDCS), or sham therapy.”

Of these, the treatments that the researchers in the original trial examined most often were high frequency left rTMS and tDCS, which they tested against sham therapy. On the other hand, not many trials covered more recent forms of brain stimulation, such as magnetic seizure therapy and bilateral theta burst stimulation, the review found.

Kutz and his team deemed 34 percent of the trials they reviewed as having a low risk of bias. They considered half of the trials to have an “unclear” risk of bias, and finally, 17 percent to have a high risk of bias. The newer the treatments, the higher was the uncertainty of the trials’ results.

The review found that bitemporal ECT, high dose right unilateral ECT, high frequency left rTMS and tDCS were all significantly more effective than sham therapy both in terms of efficacy and acceptability.

When considering “discontinuation of treatment for any reason,” the researchers found that the participants were not any likelier to discontinue brain stimulation treatments than they were sham therapy. Mutz and colleagues conclude:

These findings provide evidence for the consideration of non-surgical brain stimulation techniques as alternative or add-on treatments for adults with major depressive episodes.”

“These findings also highlight important research priorities in the specialty of brain stimulation, such as the need for further well-designed randomized controlled trials comparing novel treatments, and sham-controlled trials investigating magnetic seizure therapy,” the authors add.

Finally, the researchers also note that their results have clinical implications, “in that they will inform clinicians, patients, and healthcare providers on the relative merits of multiple non-surgical brain stimulation techniques.”

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[WEB PAGE] Transcranial Direct Current Stimulation Promising for Major Depressive Disorder

Transcranial Electrical Stimulation

Transcranial direct current stimulation has produced mixed results in patients with major depressive disorder.

Transcranial direct current stimulation (tDCS) is an investigative modality for major depressive disorder (MDD) that has shown some promising results.1 Though it has a while before it is approved by the US Food and Drug Administration, clinicians and patients have been clamoring for an effective treatment for MDD that is not associated with harmful adverse effects.As 6.7% of the world’s population has MDD, which is resistant to pharmacotherapy in approximately one-third of cases, the push is on to identify treatment with lasting effects to combat this disabling disorder.1

tDCS refers to the use of a noninvasive, weak electrical current (1 to 2 mA) applied to electrodes on the scalp that modify cortical excitability.1,2 tDCS has been tested with favorable outcomes in individuals with stroke, Alzheimer disease, movement disorders, schizophrenia, and addiction.1,2

A Small but Emerging Body of Evidence

tDCS has produced mixed results in patients with MDD.3 Brunoni and colleagues performed a meta-analysis of individual patient data on 289 participants with MDD (mean age, 47.2 years; 62.3% women) in 6 randomized, sham-controlled studies.3 tDCS significantly improved response compared with sham procedures (34% vs 19%, respectively; odds ratio [OR], 2.44; 95% confidence interval [CI], 1.38-4.32; P=.002). Remission rates were also favorable (23.1% vs 12.7%, respectively; OR, 2.38; 95% CI, 1.22-4.64; P=.002). The trials did not uniformly categorize adverse events, but the researchers noted that both the tDCS and sham groups had similar drop-out rates.

“tDCS efficacy is still small, and it should be optimized,” noted lead author André Russowsky Brunoni, MD, PhD, associate professor at the Institute of Psychiatry at the University of São Paulo Medical School in Brazil. “There are some approaches for increasing its efficacy, such as combining with other therapies and/or increasing the dose, although this has not been systematically tested yet.”

Combination tDCS and Antidepressant Therapy

The SELECT-TDCS trial (ClinicalTrials.gov Identifier: NCT01033084) examined the cognitive effects of tDCS on 120 patients with MDD (mean age, 42 years; 68% women) in a 6-week trial of sertraline 50 mg/d vs placebo and tDCS vs sham procedure.4 As assessed by a battery of neuropsychological tests, such as the Mini-Mental Status Exam and the Montreal Cognitive Assessment, patients in the trial neither benefited nor regressed in their cognitive functioning with treatment.

tDCS for Treatment-Resistant MDD

Martin and colleagues sought to determine whether tDCS could be used for patients for whom 2 different pharmacotherapies were ineffective for MDD.5 In the open-label study, 20 patients (mean age, 47.4 years; 50% women) received tDCS during cognitive emotional therapy sessions 3 times a week for 6 weeks. The 17 completers had their mood, cognition, and emotion processing assessed at baseline, 3 weeks, and 6 weeks. At the end of the study, 41% of the participants experienced a ≥50% improvement in their depression score and none reported serious adverse events. During the stimulation, patients reported mild burning, redness, and tingling, which diminished by the end of the study.

“Current evidence suggests that tDCS when given by itself has limited antidepressant efficacy compared to standard medication treatment and that it is also not effective in more treatment-resistant patients,” said lead author Donel Martin, PhD, clinical neuropsychologist from the School of Psychiatry at the University of New South Wales in Sydney, Australia. “What our results suggest is that if patients complete a task during tDCS, which simultaneously activates relevant dysfunctional brain regions instead of doing nothing at all, better antidepressant effects may be achieved.”

Filling the tDCS Research Gaps

Scientists have yet to clearly elucidate the mechanism of action of low-current electrical stimulation with tDCS.2 Still to be discovered: how tDCS modulates neurons, how it affects the neural networks, and how the currents change behavior. When clinicians have a better understanding of the underlying mechanisms, they will be better equipped to select the appropriate patients, administer optimal dosages, pair with synergistic antidepressants, and accurately place the electrodes.

Co-author Opher Donchin, PhD, head of the biomedical engineering department at Ben-Gurion University of the Negev, Be’er Sheva, Israel, acknowledges that researchers and clinicians still need additional information for tDCS to progress. “[Functional magnetic resonance imaging] of the brain region before applying tDCS will assist in delivering tDCS with spatiotemporal accuracy,” he said. “Focal stimulation using small electrodes (with high-definition tDCS) is crucial in intensifying and restricting current flow around the intended region. Also, an individual’s genetic test to assess the sensitivity towards tDCS will determine subject-specific adjustment of stimulation strength.”

In animal studies, tDCS has demonstrated long-term changes in brain plasticity in subjects with depression, but scientists still do not know how this occurs.6 Although many studies extrapolated from depression trials, more needs to be elucidated about depressive phenotypes (eg, anxious, melancholic).

“The goal of the paper was to provide a rigorous framework so that future research may one day impact clinical care,” explained co-author Sarah H. Lisanby, MD, director of the Division of Translational Research and the Noninvasive Neuromodulation Unit at the National Institute of Mental Health in Bethesda, Maryland. “There is a need for better characterization/phenotyping of patients in a heterogeneous disorder, for rigorous trial designs, for optimizing spatial targeting and dosing such that the stimulation delivered to the brain is well characterized, and opportunities for combining tDCS with established efficacious interventions as an augmentation strategy.”

Summary and Clinical Applicability

The application of tDCS may ameliorate depression in patients with MDD. Despite some positive signals, tDCS remains an investigative therapy in the United States. More rigorous studies — including randomized, sham-controlled, and dose-ranging trials — are needed to determine optimal patient selection.

References

  1. Bennabi D, Haffen E. Transcranial direct current stimulation (tDCS): a promising treatment for major depressive disorderBrain Sci.2018;8(5):81.
  2. Das S, Holland P, Frens MA, Donchin O. Impact of transcranial direct current stimulation (tDCS) on neuronal functionsFront Neurosci. 2016;10:550.
  3. Brunoni AR, Moffa AH, Fregni F, et al. Transcranial direct current stimulation for acute major depressive episodes: meta-analysis of individual patient dataBr J Psychiatry. 2016;208(6):522-531.
  4. Brunoni AR, Tortella G, Benseñor IM, Lotufo PA, Carvalho AF, Fregni F. Cognitive effects of transcranial direct current stimulation in depression: results from the SELECT-TDCS trial and insights for further clinical trialsJ Affect Disord. 2016;202:46-52. doi: 10.1016/j.jad.2016.03.066
  5. Martin DM, Teng JZ, Lo TY, et al. Clinical pilot study of transcranial direct current stimulation combined with Cognitive Emotional Training for medication resistant depression. J Affect Disord. 2018;232:89-95.
  6. Bikson M, Brunoni AR, Charvet LE, et al. Rigor and reproducibility in research with transcranial electrical stimulation: an NIMH-sponsored workshopBrain Stimul. 2018;11(3):465-480.

via Transcranial Direct Current Stimulation Promising for Major Depressive Disorder – Psychiatry Advisor

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[VIDEO] What is tDCS? – YouTube

What is tDCS and how tDCS works. To try tDCS or learn more, visit http://www.caputron.com

 

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[WEB SITE] tDCS application for motor rehabilitation

Neuer Inhalt

An increasing number of studies highlight the potential application of transcranial direct current stimulation (tDCS) for motor rehabilitation in neurological diseases as well as in healthy aging. tDCS is a technique where a constant weak electric current is passed through scalp electrodes and has been shown to modulate excitability in both cortical and subcortical brain areas. Although the results of tDCS interventions for motor rehabilitation are still preliminary, they encourage further research to better understand its therapeutic potential and to inform optimal clinical use.

This collection of articles aims to present the most recent advances in tDCS for motor rehabilitation, addressing topics such as theoretical, methodological, and practical approaches to be considered when designing tDCS-based rehabilitation. Submissions of both experimental and review studies is encouraged.

This collection of articles has not been sponsored and articles have undergone the journal’s standard peer-review process overseen by the Editor-in-Chief and Associate Editors. The Editor-in-Chief and Associate Editors declare no competing interests.

  1. Content Type:Review

    Transcranial direct current stimulation for the treatment of motor impairment following traumatic brain injury

    After traumatic brain injury (TBI), motor impairment is less common than neurocognitive or behavioral problems. However, about 30% of TBI survivors have reported motor deficits limiting the activities of daily…

    Authors:Won-Seok Kim, Kiwon Lee, Seonghoon Kim, Sungmin Cho and Nam-Jong Paik

    Citation:Journal of NeuroEngineering and Rehabilitation 2019 16:14

    Published on: 25 January 2019

  2. Content Type:Review

    Transcranial direct current stimulation for promoting motor function in cerebral palsy: a review

    Transcranial direct current stimulation (tDCS) has the potential to improve motor function in a range of neurological conditions, including Cerebral Palsy (CP). Although there have been many studies assessing …

    Authors:Melanie K. Fleming, Tim Theologis, Rachel Buckingham and Heidi Johansen-Berg

    Citation:Journal of NeuroEngineering and Rehabilitation 2018 15:121

    Published on: 20 December 2018

  3. Content Type:Commentary

    Transcranial direct current stimulation (tDCS) for upper limb rehabilitation after stroke: future directions.

    Transcranial Direct Current Stimulation (tDCS) is a potentially useful tool to improve upper limb rehabilitation outcomes after stroke, although its effects in this regard have shown to be limited so far. Addi…

    Authors:Bernhard Elsner, Joachim Kugler and Jan Mehrholz

    Citation:Journal of NeuroEngineering and Rehabilitation 2018 15:106

    Published on: 15 November 2018

  4. Content Type:Research

    Home-based transcranial direct current stimulation plus tracking training therapy in people with stroke: an open-label feasibility study

    Transcranial direct current stimulation (tDCS) is an effective neuromodulation adjunct to repetitive motor training in promoting motor recovery post-stroke. Finger tracking training is motor training whereby p…

    Authors:Ann Van de Winckel, James R. Carey, Teresa A. Bisson, Elsa C. Hauschildt, Christopher D. Streib and William K. Durfee

    Citation:Journal of NeuroEngineering and Rehabilitation 2018 15:83

    Published on: 18 September 2018

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[ARTICLE] Transcranial direct current stimulation for the treatment of motor impairment following traumatic brain injury – Full Text

Abstract

After traumatic brain injury (TBI), motor impairment is less common than neurocognitive or behavioral problems. However, about 30% of TBI survivors have reported motor deficits limiting the activities of daily living or participation. After acute primary and secondary injuries, there are subsequent changes including increased GABA-mediated inhibition during the subacute stage and neuroplastic alterations that are adaptive or maladaptive during the chronic stage. Therefore, timely and appropriate neuromodulation by transcranial direct current stimulation (tDCS) may be beneficial to patients with TBI for neuroprotection or restoration of maladaptive changes.

Technologically, combination of imaging-based modelling or simultaneous brain signal monitoring with tDCS could result in greater individualized optimal targeting allowing a more favorable neuroplasticity after TBI. Moreover, a combination of task-oriented training using virtual reality with tDCS can be considered as a potent tele-rehabilitation tool in the home setting, increasing the dose of rehabilitation and neuromodulation, resulting in better motor recovery.

This review summarizes the pathophysiology and possible neuroplastic changes in TBI, as well as provides the general concepts and current evidence with respect to the applicability of tDCS in motor recovery. Through its endeavors, it aims to provide insights on further successful development and clinical application of tDCS in motor rehabilitation after TBI.

Background

Traumatic brain injury (TBI) is defined as “an alteration in brain function (loss of consciousness, post-traumatic amnesia, and neurologic deficits) or other evidence of brain pathology (visual, neuroradiologic, or laboratory confirmation of damage to the brain) caused by external force” [1]. The incidence and prevalence of TBI are substantial and increasing in both developing and developed countries. TBI in older age groups due to falling has been on the rise in recent years, becoming the prevalent condition in all age groups [23]. TBI causes broad spectrum of impairments, including cognitive, psychological, sensory or motor impairments [45], which may increase the socioeconomic burdens and reduce the quality of life [67]. Although motor impairment, such as limb weakness, gait disturbance, balance problem, dystonia or spasticity, is less common than neurocognitive or behavioral problems after TBI, about 30% of TBI survivors have reported motor deficits that severely limited activities of daily living or participation [8].

Motor impairment after TBI is caused by both focal and diffuse damages, making it difficult to determine the precise anatomo-clinical correlations [910]. According to previous clinical studies, recovery after TBI also seems worse than that after stroke, although the neuroplasticity after TBI may also play an important role for recovery [11]. Therefore, a single unimodal approach for motor recovery, including conventional rehabilitation, may be limiting, and hence, requiring a novel therapeutic modality to improve the outcome after TBI.

Transcranial direct current stimulation (tDCS) – one of the noninvasive brain stimulation (NIBS) methods – can increase or decrease the cortical excitability according to polarity (anodal vs. cathodal) and be used to modulate the synaptic plasticity to promote long-term functional recovery via long-term depression or potentiation [1213]. Recent clinical trials evaluating patients with stroke have reported the potential benefits of tDCS for motor recovery [14]. Neuroplastic changes after TBI and results from animal studies also suggest that tDCS could improve the motor deficit in TBI, although clinical trials using tDCS for motor recovery in TBI are currently lacking [14].

In this review, we will cover (1) the pathophysiology and possible neuroplastic changes in TBI; (2) physiology of tDCS; (3) current clinical evidence of tDCS in TBI for motor recovery; (4) general current concept of tDCS application for motor recovery; and (5) the future developments and perspectives of tDCS for motor recovery after TBI. Although the scope of motor recovery is wide, this review will focus primarily on the recovery of limb function, especially that of the upper limb. We expect that this review can provide insights on further successful development and clinical application of tDCS in motor rehabilitation after TBI.[…]

 

Continue —> Transcranial direct current stimulation for the treatment of motor impairment following traumatic brain injury | Journal of NeuroEngineering and Rehabilitation | Full Text

Fig. 3Schematic classification of personalized tDCS for motor recovery. Depending on electrode size, shape, and arrangement, tDCS can be broadly classified into a Conventional tDCS, b Customized Electrode tDCS, and c Distributed Array or High-Definition tDCS. Red color represents anodes and blue color represents cathodes

Fig. 5Merged system with tDCS and virtual reality. Patient with TBI can use this system in the hospital setting with the supervision of clinican (a) and can continue to use it at their home with tele-monitored system (b)

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[Abstract] Sham tDCS: A hidden source of variability? Reflections for further blinded, controlled trials

Abstract

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly used to modulate neural activity in the living brain. In order to establish the neurophysiological, cognitive or clinical effects of tDCS,tDCS most studies compare the effects of active tDCS to those observed with a sham tDCS intervention. In most cases, sham tDCS consists in delivering an active stimulation for a few seconds to mimic the sensations observed with active tDCS and keep participants blind to the intervention. However, to date, sham-controlled tDCS studies yield inconsistent results, which might arise in part from sham inconsistencies. Indeed, a multiplicity of sham stimulation protocols is being used in the tDCS research field and might have different biological effects beyond the intended transient sensations. Here, we seek to enlighten the scientific community to this possible confounding factor in order to increase reproducibility of neurophysiological, cognitive and clinical tDCS studies.

via Sham tDCS: A hidden source of variability? Reflections for further blinded, controlled trials – Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation

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[WEB SITE] Transcranial Direct Current Stimulation – Video

People have investigated brain stimulation since very early times, in ancient Rome torpedo fish were applied to the heads of some patients to relieve headaches, for instance, by their electrical currents. In 1802, Aldini of Italy applied electrical current to the exposed cortex of the human brain and attempted also to treat melancholia with a voltaic pile.

Human brain connected to cables and computer chips. Image Credit: Mopic / Shutterstock

Human brain connected to cables and computer chips. Image Credit: Mopic / ShutterstockEnter a caption

The voltaic pile led to accelerated interest in electrical brain stimulation to treat various disorders, including mental illness. The results were not always encouraging, of course, and it wasn’t until much later, in the middle of the 20th century, that direct current stimulation was used to alter the excitable patterns of the brain. This led to increased interest in using direct current to treat mania or depression. There was a brief upsurge in the use of electroconvulsive therapy to treat schizophrenia and other mental illnesses, but it came to an end in the last decade of the 20th century. Electrical stimulation of the brain became stigmatized and drug therapy took center stage as far as psychiatric treatment was concerned.

Recently, interest has arisen in electrical stimulation of the brain because of the finding that weak transcranial direct current stimulation (tDCS) of the brain produced changes in polarization and excitable thresholds of the neurons, which lasted long beyond the period of stimulation. This has led many to investigate the nature of the changes and the potential applications of this technique to major depressive disorder, schizophrenia, obsessive-compulsive disorder and other disorders of the mind with a basis in brain functioning.

Transcranial Direct Current Stimulation Method

The technique of tDCS depends upon non-invasive stimulation of the brain through the skull, by a small constant current applied through scalp electrodes to the head. This leads to currents flowing through the superficial cortex. The strength of the current is so low that it does not directly cause an action potential in the brain neurons, and so instead regulates the excitability of the brain by making them more or less refractory to other endogenous stimulation according to the polarity of the electrodes. Anodal current is generally stimulatory by inducing increased excitability, but cathodal current reduces it. The effect of a single stimulus lasts for 30-120 minutes.

The way in which the current acts depends upon the polarity and the orientation of the cells. Anodal tDCS produces an inflow of current directed inwardly, which hyperpolarizes the apical dendrites of neurons in the pyramidal cortex, but depolarizes those of the somatic areas. Cathodal tDCS on the other hand leads to the reverse effect. The third factor determining the effect of the current is its dose. The strength of the electrical stimulation may lie between 0.5 and 2 mA, its duration is between 5-40 minutes, and the electrode size ranges from 3-100 cm. By altering these variables, it is possible to regulate the current density and total charge, but it may still be difficult to exactly quantify the total current delivered to the brain because of other factors outside the experimental field, such as scalp and cranial impedance.

The electrodes are placed in accordance with the international Electroencephalogram

System, so that one is on the scalp (the active electrode) and the other on the scalp (bipolar or bicephalic placement) or another part of the body, most commonly the upper arm or the shoulder (termed unipolar or monocephalic placement). The current traces a path from the anode, scalp, cranium, cortex, subcortical region, and cathode, stimulating not only the cortex but deeper structures, both in the deep brain and in the midbrain and spinal cord if unipolar placement is adopted. Secondly, the area stimulated is not confined to that near the electrodes because the current flows into adjoining regions in between and around the electrodes.

Mechanism of tDCS

Electrical stimulation with tDCS seems to produce a two-way modification of post-synaptic neuronal connections which results in the same effects as long-term potentiation or long-term depression of cortical excitability does. This is mediated through NMDA receptors. Glutamate antagonists prevent these long-term effects, while NMDAR agonists increase theiramplitude. Work is still going on as to whether repetitive tDCS could cause a more prolonged alteration of behavior. The stimulation has been found to change motor and emotional functioning, as well as sensory, attention-related, and cognitive responses. It is therefore likely to be useful in several psychiatric disorders. It has been found that glutamate antagonists abolish tDCS after-effects, while NMDA-agonists enhance them.

The Advantages and Disadvantages of tDCS

The technique of tDCS is easy to use, in fact, capable of application at home. It is noninvasive and inexpensive. No serious adverse effects have been noted so far. On the other hand, this very ease of use lends itself to a high potential for misuse, such as recreational use, unsupervised medical use, and unethical use as, for instance, to improve one’s attention span while studying. Its long-term effects are also not well established. Thus while the potential has long been recognized, the implementation of this technique is still not widespread pending proper regulation of its use worldwide.

Further Reading

via Transcranial Direct Current Stimulation

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[Abstract] Realistic modeling of transcranial current stimulation: The electric field in the brain

Highlights

  • Computational models are required to optimize the electric field in the brain.
  • tCS pipelines allow for fast and semi-automatic production of realistic head models.
  • In-vivo validation studies corroborate electric field predictions from tCS models.
  • tCS modeling could help identify the causes for intra and inter-subject variability.
  • Successful application of multi-electrode montages strongly depends on tCS models

Abstract

Computational models of transcranial current stimulation (tCS) derived from MRI predict the electric field distribution in individual brains with reasonable accuracy and should be used to guide the selection of optimal stimulation parameters. Some recent advances that support this claim are: free toolboxes to generate individual head models for electric field calculations, the validation of model predictions in comparison to in-vivomeasurements, and new algorithms to optimize the electric field at the target with multi-electrode stimulation. Electrical impedance tomography may provide subject-specific estimates of the electric conductivity of the scalp and skull, thereby improving the accuracy of the electric field calculations. In the future, electric field models should be coupled with electrophysiological models to predict experimental outcomes.

Graphical abstract

Image 1 

via Realistic modeling of transcranial current stimulation: The electric field in the brain – ScienceDirect

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[Abstract + References] Transcranial Direct Current Stimulation for Poststroke Motor Recovery: Challenges and Opportunities – PM&R

Abstract

There has been a renewed research interest in transcranial direct current stimulation (tDCS) as an adjunctive tool for poststroke motor recovery as it has a neuro-modulatory effect on the human cortex. However, there are barriers towards its successful application in motor recovery as several scientific issues remain unresolved, including device-related issues (ie, dose-response relationship, safety and tolerability concerns, interhemispheric imbalance model, and choice of montage) and clinical trial-related issues (ie, patient selection, timing of study, and choice of outcomes). This narrative review examines and discusses the existing challenges in using tDCS as a brain modulation tool in facilitating recovery after stroke. Potential solutions pertinent to using tDCS with the goal of harnessing the brains plasticity are proposed.

References

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via Transcranial Direct Current Stimulation for Poststroke Motor Recovery: Challenges and Opportunities – PM&R

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