Category Archives: Paper

Weekend tDCS Insights – Chi & Snyder, SpeakWisdom, Carlo Miniussi

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Some very excellent tDCS-related documents came to my attention over the weekend. I’m pretty sure I’d looked for at least one of them before, but that it was behind a paywall. I’ll provide links to the pdfs here, but suggest that (as has happened elsewhere on the blog) pdf links frequently go bad so ‘get em while they’re hot’.

Brain stimulation enables the solution of an inherently difficult problem (pdf)
This is the paper by Alan Snyder and Richard Chi that is frequently referenced in ‘unlock your inner savant’ articles on various pop-sci sites. (See also) Spoiler alert! Gives the answer to the ‘9 dot’ problem and once you’ve seen it it will be impossible to discover how ‘savant-like’ you are (at least according to this test).

ninedot …we applied cathodal tDCS (1.6mA) at the left anterior temporal lobe (ATL) together with anodal tDCS at the right ATL for approximately 10 min… None of the 22 participants in the main experiment solved the nine-dot problem before stimulation. But with 10 min of right lat- eralizing transcranial direct current stimulation (tDCS), we found that more than 40% of participants could do so.

speakWisdomTakeapartDr. Brent Williams, at his SpeakWisdom blog, published another excellent tDCS post updating his DIY device, and adding a .doc that outlines his recommended (For Discussion) protocols for depression, ‘Savant Learning’, memorization, and chronic pain.
His protocol describes directions for use with either his ‘User-Built tDCS Research Device’, or the ActivaDose II.

Transcranial Magnetic and Electric Stimulation in Perception and Cognition Research (pdf)
This is a fascinating paper (Carlo Miniussi et al) that brings us up to date (2012) on applications of tDCS, TMS tACS (transcranial alternating current), and tRNS (transcranial random noise stimulation), especially in relation to cognition and learning. What really caught my eye was this entry about tRNS…

 tRNS consists of the application of a random electrical oscillation spectrum over the cortex. tRNS can be applied at different frequency band ranges over the entire spectrum from 0.1 to 640 Hz…They applied tRNS to the visual cortices of healthy subjects and observed a significant improvement in the performance of healthy subjects in a visual perceptual learning task. This improvement was significantly higher than the improvement obtained with anodal tDCS…

And that folks, is how a weekend disappears down the rabbit hole!

Recent tDCS Papers of Interest

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  1. Acute working memory improvement after tDCS in antidepressant-free patients with Major Depressive Disorder. All effect sizes were large. In other words, one session of tDCS acutely enhanced WM in depressed subjects…(Paywall)
  2. Neurobiological Effects of Transcranial Direct Current Stimulation: A Review The purpose of this systematic review is to summarize the current knowledge regarding the neurobiological mechanisms involved in the effects of tDCS. (pdf)
  3. Modulating Human Procedural Learning by Cerebellar Transcranial Direct Current Stimulation. Our finding that anodal cerebellar tDCS improves an implicit learning type essential to the development of several motor skills or cognitive activity suggests that the cerebellum has a critical role in procedural learning. (Paywall)
  4. Neuroenhancement of the aging brain: Restoring skill acquisition in old subjects. These results suggest noninvasive brain stimulation as a promising and safe tool to potentially assist functional independence of aged individuals in daily life. (Paywall)
  5. Examining transcranial direct-current stimulation (tDCS) as a treatment for hallucinations in schizophrenia. Although this study is limited by the small sample size, the results show promise for treating refractory auditory verbal hallucinations and other selected manifestations of schizophrenia. (Paywall)
  6. Modulation of training by single-session transcranial direct current stimulation to the intact motor cortex enhances motor skill acquisition of the paretic hand.These results indicate that tDCS is a promising tool to improve not only motor behavior, but also procedural learning. (Paywall)
  7. Interactions between transcranial direct current stimulation (tDCS) and pharmacological interventions in the Major Depressive Episode: Findings from a naturalistic study. tDCS over the DLPFC acutely improved depressive symptoms. Besides the inherent limitations of our naturalistic design, our results suggest that tDCS effects might vary according to prior pharmacological treatment… (Paywall)
  8. Amelioration of Cognitive Control in Depression by Transcranial Direct Current Stimulation. Deficient cognitive control over emotional distraction is a central characteristic of major depressive disorder (MDD). The present study demonstrates that anodal tDCS applied to the left dlPFC improves deficient cognitive control in MDD. (Paywall)
  9. Comparing immediate transient tinnitus suppression using tACS and tDCS: a placebo-controlled study. Our main result was that bifrontal tDCS modulates tinnitus annoyance and tinnitus loudness… (Paywall)
  10. Review of transcranial direct current stimulation in poststroke recovery. In this review, we summarize characteristics of tDCS (method of stimulation, safety profile, and mechanism) and its application in the treatment of various stroke-related deficits… (Paywall)
  11. Enhancing vigilance in operators with prefrontal cortex transcranial direct current stimulation (tDCS). These findings indicate that tDCS may be well-suited to mitigate performance degradation in work settings requiring sustained attention or as a possible treatment for neurological or psychiatric disorders involving sustained attention. (Paywall)

 

NIBS Non-Invasive Brain Stimulation – The Air Force Research Laboratory and tDCS

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NIBS Non-Invasive Brain Stimulation

Every military application of tDCS I’ve seen so far specifically mentions drones and drone pilot training. This logo has a drone in it! For the record, I think the use of drones is illegal and immoral, and that the deaths of innocents is un-American and unacceptable. That said, the tDCS research coming out of this sector is fascinating and will no doubt have an impact beyond military training.

[Update 7/30/14 I’ve replaced the old (broken) link with an active one that comes via Ryan (see comment below)] http://colonyofcommodus.files.wordpress.com/2013/02/2012-afosr-review-mckinley.pdf it was a public document. It appears to be a set of slides used in a presentation. It documents the most aggressive use of tDCS for the purpose of learning and cognitive enhancement I’ve seen. You will conclude, after reading this, that the Air Force is not fooling around.

Air Force Research Laboratory Skill Learning tDCS

Here is one of the more shocking aspects of the research: The notion that cathodal stimulation can have a positive effect by depressing ‘competing memory’. What? The plot thickens.

Air Force Research Laboratory Skill Learning tDCS

There is weeks of research ahead for anyone diving deeply into this paper. A lot of new questions to answer.

tDCS Recent Activity 12/12 – 1/13

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A lot of the ‘pop sci’ articles are drawing on the results of only a few studies. Hopefully we’ll get affirmation of the efficacy of tDCS in cognitive enhancement soon.

Does Passing A Small Current Through Your Brain Really Make You Smarter?

Excellent update from Giulio Ruffini of Neuroelectrics. Full of links to relevant papers.

tDCS and Stroke: What We Know So Far (Jan 2013)

As far as I can tell, this is a new development in understanding the mechanism for the mediation of pain using tDCS.

Immediate effects of tDCS on the μ-opioid system of a chronic pain patient
To our knowledge, we provide data for the first time in vivo that there is possibly an instant increase of endogenous μ-opioid release during acute motor cortex neuromodulation with tDCS.
(And the pop-sci media follow-up Electrical Current Can Unlock The Seriously Good Drugs In Your Brain and Happiness Is a Warm Transcranial Direct Current Electrode)

A lot of research is going on right now into understanding where exactly, current if flowing.

The electric field in the cortex during transcranial current stimulation
The aim of this study was to investigate the effect of tissue heterogeneity and of the complex cortical geometry on the electric field distribution.

Some context.

A pioneer work on electric brain stimulation in psychotic patients. Rudolph Gottfried Arndt and his 1870s studies.
Today’s brain stimulation methods are commonly traced back historically to surgical brain operations. With this one-sided historical approach it is easy to overlook the fact that non-surgical electrical brain-stimulating applications preceded present-day therapies.

Mental Practice, or MP is practicing doing something without actually doing it. A musician imagining playing their instrument for instance. This study measured quality of handwriting with the non-dominant hand while using tDCS.

Site-specific effects of mental practice combined with transcranial direct current stimulation on motor learning
In conclusion, our results suggest that MP-induced effects in improving motor performance can be successfully consolidated by excitatory non-invasive brain stimulation on the M1 and left DLPFC.

Anodal transcranial direct current stimulation of prefrontal cortex enhances working memory – Springer

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[Update 12/17/2012 Another paper discussing the efficacy of using tDCS to enhance working memory. Transcranial direct current stimulation of the prefrontal cortex modulates working memory performance: combined behavioural and electrophysiological evidence]

Working memory, as associated with ‘brain training’ and ‘plasticity‘, is often expressed as what one would wish to have more of, or at the very least, what one hopes not to lose as we age. (For a great overview of working memory and the how’s of enhancing it, see this fascinating post from neuroscientist Bradley Voytek’s blog  Working memory and cognitive enhancement.)

Our aim was to determine whether anodal transcranial direct current stimulation, which enhances brain cortical excitability and activity, would modify performance in a sequential-letter working memory task when administered to the dorsolateral prefrontal cortex DLPFC. Fifteen subjects underwent a three-back working memory task based on letters. This task was performed during sham and anodal stimulation applied over the left DLPFC. Moreover seven of these subjects performed the same task, but with inverse polarity cathodal stimulation of the left DLPFC and anodal stimulation of the primary motor cortex M1. Our results indicate that only anodal stimulation of the left prefrontal cortex, but not cathodal stimulation of left DLPFC or anodal stimulation of M1, increases the accuracy of the task performance when compared to sham stimulation of the same area. This accuracy enhancement during active stimulation cannot be accounted for by slowed responses, as response times were not changed by stimulation. Our results indicate that left prefrontal anodal stimulation leads to an enhancement of working memory performance. Furthermore, this effect depends on the stimulation polarity and is specific to the site of stimulation. This result may be helpful to develop future interventions aiming at clinical benefits.

via Anodal transcranial direct current stimulation of prefrontal cortex enhances working memory – Springer.
full pdf

This 2011 paper does confirm positive results of tDCS in a similar application and test setup. Improving working memory: exploring the effect of transcranial random noise stimulation and transcranial direct current stimulation on the dorsolateral prefrontal cortex.

However, the study does provide confirmation of previous findings that anodal tDCS enhances some aspects of DLPFC functioning.

PLOS ONE: Transcranial Direct Current Stimulation Augments Perceptual Sensitivity and 24-Hour Retention in a Complex Threat Detection Task

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Vincent Clark is an author on this paper. He’s associated with the Mind Research Network. We earlier covered work by Michael Weisend, also from MRN around a Jan. 2012 paper. This paper offers further details and is available to the public.

Transcranial Direct Current Stimulation Procedures

TDCS was applied using an ActivaDose II Iontophoresis Delivery Unit, which provides for delivery of a constant low level of direct current. Square-shaped (11 cm2) saline-soaked (0.9% sodium saline solution) sponge electrodes were attached to the participant with self-adhesive bandage strips. The anode was placed near electrode site F10 in the 10-10 EEG system, over the right sphenoid bone. The cathode was placed on the contralateral (left) upper arm. The site of the anode was selected based on our previous fMRI results showing that this brain region was the primary locus of neural activity associated with performance this task [23].

Anodal 2 mA current was applied to the scalp electrode site F10 in the 10-10 EEG system. The resulting enhancement of performance in the threat detection task is consistent with our previous fMRI results [23] showing that the right inferior frontal cortex is a major locus of a distributed brain network that mediates performance on this task. The right parietal cortex is a part of this network and could also be a target for stimulation.
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One possible explanation for the improvement in detection performance (hit rate) in the threat detection task is that tDCS increases general arousal, thereby leading to a change in response bias in the more liberal direction [25], which would increase the hit rate. However, computation of signal detection metrics showed that there were no significant effects of tDCS on the ß measure of response bias. Instead, the effect of brain stimulation was to enhance perceptual sensitivity, d′.

The improvement in perceptual sensitivity suggests that participants receiving tDCS were better able to encode stimulus features that distinguished targets and non-targets, which in turn led to accelerated learning and improved retention.

via PLOS ONE: Transcranial Direct Current Stimulation Augments Perceptual Sensitivity and 24-Hour Retention in a Complex Threat Detection Task.

tDCS – Building Research tDCS Units « SpeakWisdom

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This bubbled up today. He explores some choices he made in building his DIY kit in a series of blog posts on tDCS.

Just to see how easily it could be done, I built a couple of tDCS units for about $30 each using common parts. The meters were purchased from EBay for about $7 each and all the remaining components came from a local Radio Shack, including the case, voltage regulator, resistors, etc. The tDCS units feature a potentiometer to make it possible to adjust current for treatment specifics or pad variations.

20120902-214144.jpg
(Two tDCS units built in about 3 hours for well less than $100)

 

via tDCS – Building Research tDCS Units « SpeakWisdom.

Transcranial Direct Current Stimulation Intensity and Duration Effects on Tinnitus Suppression

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Tinnitus has been a part of my life for so long I can’t remember not having it. While it doesn’t seem to bother me the way it does others, it can be very annoying, especially when I’m in a very quiet environment, camping for instance. So it would be incredible if a breakthrough in tinnitus treatment were to come along.

Background. Perception of sound in the absence of an external auditory source is called tinnitus, which may negatively affect quality of life. Anodal transcranial direct current stimulation tDCS of the left temporoparietal area LTA was explored for tinnitus relief. Objective. This pilot study examined tDCS dose current intensity and duration and response effects for tinnitus suppression. Methods. Twenty-five participants with chronic tinnitus and a mean age of 54 years took part. Anodal tDCS of LTA was carried out. Current intensity 1 mA and 2 mA and duration 10 minutes, 15 minutes, and 20 minutes were varied and their impact on tinnitus measured. Results. tDCS was well tolerated. Fifty-six percent of participants 14 experienced transient suppression of tinnitus, and 44% of participants 11 experienced long-term improvement of symptoms overnight—less annoyance, more relaxed, and better sleep. There was an interaction between duration and intensity of the stimulus on the change in rated loudness of tinnitus, F2, 48 = 4.355, P = .018, and clinical global improvement score, F2, 48 = 3.193, P = .050, after stimulation. Conclusions. Current intensity of 2 mA for 20 minutes was the more effective stimulus parameter for anodal tDCS of LTA. tDCS can be a potential clinical tool for reduction of tinnitus, although longer term trials are needed.

Again, this study begs the question: If 2 mA was more effective than 1 mA, why not 3?
P.S. Thanks you know who you are!

via Transcranial Direct Current Stimulation Intensity and Duration Effects on Tinnitus Suppression.

Where To Find More Information

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I’m calling this the deep data page. I’ll collect links to collections of papers and abstracts that cover tDCS. There is really, a LOT, of information out there and lots more is on the way. I’ll update this page as I come across more articles. If you have a favorite tDCS stash, please share it in the comments.

Vincent Walsh TMS > tDCS & Migraine

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Towards the end of the video (The Daily Telegraph 2008) Professor Vincent Walsh, (now of University of California Davis) discusses tDCS and its potential for therapeutic use. Especially of interest is the information on migraine headaches:

So, some migraines are caused by having too much activity in the visual brain area, and some are by having too little activity. And we hope that this can balance out, reverse that relative inactivity in the brain.

Could this imply that one person’s migraine could be mitigated with Cathodal (-) tdcs while another’s might benefit from Anodal (+) application of tDCS? And conversely, does it imply that improper stimulation would lead to MORE migraines?

If I suffered from migraines and wanted to test tDCS, here’s where I’d start:
Check the FisherWallace  Find A Doctor search page for an electrotherapist in your area.
If they will treat you for migraine, try a few sessions. If it works, and your doctor will authorize a purchase, you can buy your own unit (for $700). A FisherWallace device may qualify for insurance coverage.

Alternately, I would monitor the ClinicalTrials.gov site and keep an eye out for new studies testing tDCS for migraine. And lastly, I would contact manufacturers of other tDCS devices and ask if they knew of any electrotherapy practitioners in your area working with migraine. Here’s my short list of manufacturers to contact:

  • Soterix Medical: Are on the cutting edge of all things tDCS and in some of their literature I have seen them mention migraine.
  • MagStim: Another medical-level producer, although I’m not sure these devices are approved for use in the U.S. yet.
  • Alpha-Stim: While they don’t advertize the use of their device for migraine, they do offer many testimonials from people who state they found it beneficial. I have not seen this company associated with any scientific studies or papers.

Induction of visual dream reports after transcranial direct current stimulation (tDCs) during Stage 2 sleep – JAKOBSON – 2012 – Journal of Sleep Research

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This is encouraging because a previous study showed minimal effect on dreaming using tDCS.

In both experiments a significantly greater number of imagery reports were found on awakening after tDCs (cathodal–frontal, anodal–parietal), compared to the blank control conditions. However, in Experiment 2 the frequency of imagery reports from the tDCs (cathodal–frontal, anodal–parietal) was not significantly different from the other two tDC conditions, suggesting a non-specific effect of tDCs. Overall, it was concluded that tDCs (cathodal–frontal, anodal–parietal) increased the frequency of dream reports with visual imagery, possibly via a general arousing effect and/or recreating specific cortical neural activity involved in dreaming.

via Induction of visual dream reports after transcranial direct current stimulation (tDCs) during Stage 2 sleep – JAKOBSON – 2012 – Journal of Sleep Research – Wiley Online Library. Full pdf.

Amping Up Brain Function: Transcranial Stimulation Shows Promise in Speeding Up Learning: Scientific American

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Another group of researchers hot on the trail how tDCS might be used to enhance brain function is the (non-profit) Mind Research Network of Albuquerque, NM. A lot of their work is funded by NiH, but what I’ve seen around their tDCS research pertains to increasing soldier’s ability to detect danger, and is funded by DOA (2010 Research Report pdf) Unfortunately I was not able to find a full version of the paper not behind a pay wall. The abstract is here and from a Scientific America article…

Subjects definitely register the stimulation, but it is not unpleasant. “It feels like a mild tickling or slight burning,” says undergraduate student Lauren Bullard, who was one of the subjects in another study on TDCS and learning reported at the meeting, along with her mentors Jung and Michael Weisend and colleagues of the Mind Research Network in Albuquerque. “Afterward I feel more alert,” she says. But why?

Bullard and her co-authors sought to determine if they could measure any tangible changes in the brain after TDCS, which could explain how the treatment accelerates learning. The researchers looked for both functional changes in the brain (altered brain-wave activity) and physical changes (by examining MRI brain scans) after TDCS.

They used magnetoencephalography (MEG) to record magnetic fields (brain waves) produced by sensory stimulation (sound, touch and light, for example), while test subjects received TDCS. The researchers reported that TDCS gave a six-times baseline boost to the amplitude of a brain wave generated in response to stimulating a sensory nerve in the arm. The boost was not seen when mock TDCS was used, which produced a similar sensation on the scalp, but was ineffective in exciting brain tissue. The effect also persisted long after TDCS was stopped. The sensory-evoked brain wave remained 2.5 times greater than normal 50 minutes after TDCS. These results suggest that TDCS increases cerebral cortex excitability, thereby heightening arousal, increasing responses to sensory input, and accelerating information processing in cortical circuits.

Remarkably, MRI brain scans revealed clear structural changes in the brain as soon as five days after TDCS. Neurons in the cerebral cortex connect with one another to form circuits via massive bundles of nerve fibers (axons) buried deep below the brain’s surface in “white matter tracts.” The fiber bundles were found to be more robust and more highly organized after TDCS. No changes were seen on the opposite side of the brain that was not stimulated by the scalp electrodes.

via Amping Up Brain Function: Transcranial Stimulation Shows Promise in Speeding Up Learning: Scientific American.

Cerebellum and processing of negative facial emotions…

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Cerebellum and processing of negative facial emotions: Cerebellar transcranial DC stimulation specifically enhances the emotional recognition of facial anger and sadness.

Abstract
Some evidence suggests that the cerebellum participates in the complex network processing emotional facial expression. To evaluate the role of the cerebellum in recognising facial expressions we delivered transcranial direct current stimulation (tDCS) over the cerebellum and prefrontal cortex. A facial emotion recognition task was administered to 21 healthy subjects before and after cerebellar tDCS; we also tested subjects with a visual attention task and a visual analogue scale (VAS) for mood. Anodal and cathodal cerebellar tDCS both significantly enhanced sensory processing in response to negative facial expressions (anodal tDCS, p=.0021; cathodal tDCS, p=.018), but left positive emotion and neutral facial expressions unchanged (p>.05). tDCS over the right prefrontal cortex left facial expressions of both negative and positive emotion unchanged. These findings suggest that the cerebellum is specifically involved in processing facial expressions of negative emotion.

via Cerebellum and processing of negative facial emoti… [Cogn Emot. 2012] – PubMed – NCBI.

Unleashing Potential: Transcranial Direct Current Stimulation over the Right Posterior Parietal Cortex Improves Change Detection in Low-Performing Individuals

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This is pretty fascinating. If I’m getting it, it implies that for this particular brain function there is an upward bounded capability. If you’re already there (say, genius level) tDCS won’t improve your performance, but it will if you’re not already wired at the upper bound! I know from my CambridgeBrainScience.com tests, that I’m especially weak in the VSTM (visual short-term memory) area. [Unfortunately there’s a paywall around this and most other journal paper.] Paper originates from the Institute of Cognitive Neuroscience at the National Central University, Taiwan.

Here we show that artificially elevating parietal activity via positively charged electric current through the skull can rapidly and effortlessly improve people’s VSTM performance.

…The high performers, however, did not benefit from tDCS as they showed equally large waveforms in N2pc and CDA, or SPCN (sustained parietal contralateral negativity), before and after the stimulation such that electrical stimulation could not help any further, which also accurately accounts for our behavioral observations. Together, these results suggest that there is indeed a fixed upper limit in VSTM, but the low performers can benefit from neurostimulation to reach that maximum via enhanced comparison processes, and such behavioral improvement can be directly quantified and visualized by the magnitude of its associated electrophysiological waveforms.

via Unleashing Potential: Transcranial Direct Current Stimulation over the Right Posterior Parietal Cortex Improves Change Detection in Low-Performing Individuals.