You may have noticed that I’ve not been posting as much to the blog lately. The blog is already so full of useful content for anyone looking into tDCS that I’m inclined to only post significant information that would move our current understanding of tDCS and neurostimulation forward. This article/paper describing a new technique using ‘HD tACS’ to synchronize (brainwaves) parts of the brain definitely looks intriguing and has implications for anyone paying attention to DIY neurostimulation. Very early, but very interesting.
“These (medial frontal cortex & lateral prefrontal cortex) are maybe the two most fundamental brain areas involved with executive function and self-control,” says Reinhart, who used a new technique called high-definition transcranial alternating current stimulation (HD-tACS) to stimulate these two regions with electrodes placed on a participant’s scalp. Using this new technology, he found that improving the synchronization of brain waves, or oscillations, between these two regions enhanced their communication with each other, allowing participants to perform better on laboratory tasks related to learning and self-control. Conversely, de-synchronizing or disrupting the timing of the brain waves in these regions impaired participants’ ability to learn and control their behavior, an effect that Reinhart could quickly fix by changing how he delivered the electrical stimulation. The work, published October 9, 2017, in the journal Proceedings of the National Academy of Sciences (PNAS), suggests that electrical stimulation can quickly—and reversibly—increase or decrease executive function in healthy people and change their behavior.
Here’s the paper (paywall): Disruption and rescue of interareal theta phase coupling and adaptive behavior. The supplemental pdf. describes the equipment used in the experiment. High definition transcranial alternating current stimulation ( HD- tACS ). The alternating current stimulation was administered noninvasively using an MxN9-3 channel high definition transcranial electrical current stimulator from Soterix Medical (New York, NY). Eight sintered Ag/AgCl electrodes were attached to high-definition plastic holders, filled with conductive gel, and embedded in the Biosemi EEG cap. HD-tACS electrode placement was guided by current-flow modeling using HD- Explore and HD-Targets (Soterix Medical), with the goal of targeting the MFC and lPFC to facilitate the synchronization of neural activity between these regions (the in phase protocol ) or disrupt the signals being conveyed between the MFC and lPFC (the antiphase protocol ).
Listen to Bob McDonald discuss HD tACS with Prof Rob Reinhart on the always interesting Quirks and Quarks.
Each day for two weeks, Bennett would don a headband equipped with moistened sponges and attached to what she called a “big cellphone”—a tDCS stimulator. When she was ready to start the session, a clinician would give her a four-digit code to enter on a keypad, and the current would surge through the wires and into her brain.
This paper proposes combining tDCS with fNIRS (functional near infrared spectroscopy) for the purpose of monitoring effects of tDCS especially in the context of enhancing cognition, i.e. immediate and direct feedback that tDCS is ‘working’.
Using fNIRS to Monitor the Relationship of Cognitive Workload and Brain Dynamics fNIRS provides an attractive method for continuous monitoring of brain dynamics in both seated or mobile participants. fNIRS is safe, highly portable, user-friendly and relatively inexpensive, with rapid application times and near-zero run-time costs. The most commonly used form of fNIRS uses infrared light, introduced at the scalp, to measure changes in blood oxygenation as oxy-hemoglobin converts to deoxy-hemoglobin during neural activity, i.e., the cerebral hemodynamic response. fNIRS uses specific wavelengths of light to provide measures of cerebral oxygenated and deoxygenated hemoglobin that are correlated with the fMRI BOLD signal. Below we briefly review fNIRS studies of cognitive workload.
To clarify the takeaway message: we weren’t actually training fluid intelligence. Fluid intelligence has been shown to rely on fundamental cognitive abilities like working memory and attention, and the games were designed to train those underlying abilities. Training on fluid intelligence tasks would be like teaching to the test.
In a talk, “Can HD-tDCS Enhance Cognitive Training”, Aldis Sipolins describes a ‘wildly ambitious’ cognitive training study called the INSIGHT Project. Funded by IARPA, the study combined rigorous exercise and HD-tDCS-enhanced cognitive training in an attempt to increase ‘fluid intelligence’. 518 subjects, half of whom underwent pre and post fMRI scanning, undertook a 16 week course of combined exercise and brain training. The results? Anodal HD-tDCS improved performance on 3 of 6 brain-training video games but had no effect on transfer, i.e. the improvements did not transfer to general intelligence. As a result tDCS will not be a part of the study moving forward.
Partnered with Aptima to create a suite of six brain-training games. Games were ‘adaptive’, i.e they increased in difficulty as the subject’s performance improved.
Montage used was 2 x 2 (4 electrodes) designed by Soterix to affect DLPFC (dorsalateral prefrontal cortex). Dosage was 2mA for 30 minutes. Training started once current ramped up.
BOMAT (bochumer matrices) test was used to determine whether enhanced game performance transferred to fluid intelligence.
A future study on the INSIGHT Project will include a Mindfulness meditation segment and include nutritional supplements (brain shake).
In a recent Reddit thread when asked what he’d do differently, Aldis Sipolins said:
1) Include a cathodal group, with the hope that it impairs performance. Vince Clark suggested that impairing performance during cognitive training may have led to greater transfer. Kind of like how strapping weights to your body when you train makes it easier to move once you take them off.
2) Include a tDCS group that doesn’t complete the exercise intervention. It’s possible that exercise masked the effects of tDCS.
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:
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.
Soterix is the company Marom Bikson is part of. As far as I can see, Soterix is the only company currently pursuing the idea of HD tDCS, where multiple anodes allow for a more clearly defined flow of current. Both these videos are simply demonstrating how to set up the Soterix brand electrodes.