According to IEEE Spectrum:
“A handful of athletes competing at the Summer Olympic Games in Rio next week will arrive having tried to boost their performance using an unconventional (and not-yet-banned) technology: brain stimulation. The technique, called transcranial direct current stimulation (tDCS), involves channeling a tiny current through specific regions of the brain, making neurons in that area more likely to fire.”
The athletes are using the Halo tDCS device. Here is the promotional video:
Before you run out and buy one of these devices, I suggest you read “An open letter concerning do-it-yourself users of transcranial direct current stimulation” published in The Annals of Neurology.
A paper in the journal Psychosomatic Medicine reviews the research on Brain Stimulation as a treatment for food cravings. The findings suggest that repetitive transcranial magnetic stimulation might be helpful. On the other hand, transcranial direct current stimulation did not seem to have a significant effect.
Here is a video on TMS:
Here is the abstract:
Objective: The primary aim of this review was to evaluate the effectiveness of noninvasive brain stimulation to the dorsolateral prefrontal cortex (dlPFC) for modulating appetitive food cravings and consumption in laboratory (via meta-analysis) and therapeutic (via systematic review) contexts.
Methods: Keyword searches of electronic databases (PubMed, Scopus, Web of Science, PsychoInfo, and EMBASE) and searches of previous quantitative reviews were used to identify studies (experimental [single-session] or randomized trials [multi-session]) that examined the effects of neuromodulation to the dlPFC on food cravings (n = 9) and/or consumption (n = 7). Random-effects models were employed to estimate the overall and method-specific (repetitive transcranial magnetic stimulation [rTMS] and transcranial direct current stimulation [tDCS]) effect sizes. Age and body mass index were examined as potential moderators. Two studies involving multisession therapeutic stimulation were considered in a separate systematic review.
Results: Findings revealed a moderate-sized effect of modulation on cravings across studies (g, -0.516; p = .037); this effect was subject to significant heterogeneity (Q, 33.086; p < .001). Although no statistically significant moderators were identified, the stimulation effect on cravings was statistically significant for rTMS (g, -0.834; p = .008) but not tDCS (g, -0.252; p = .37). There was not sufficient evidence to support a causal effect of neuromodulation and consumption in experimental studies; therapeutic studies reported mixed findings.
Conclusions: Stimulation of the dlPFC modulates cravings for appetitive foods in single-session laboratory paradigms; when estimated separately, the effect size is only significant for rTMS protocols. Effects on consumption in laboratory contexts were not reliable across studies, but this may reflect methodological variability in delivery of stimulation and assessment of eating behavior. Additional single- and multi-session studies assessing eating behavior outcomes are needed.
Another account of György Buzsáki’s tDCS experiment:
“Buzsáki set up the system on a cadaver and measured how much of the current penetrated the skull and made it into the brain. Not much, so it would seem. He is still writing up his results for peer review, but presented an outline at the annual meeting of the Cognitive Neuroscience Society in New York early last month. In his talk, he explained that so little electrical charge gets through the skull and into the brain that stimulating neurons to fire would require applying roughly twice the current that most commercial devices supply.”
Here are the counterarguments:
“Buzsáki’s critics have two responses. First, they suggest that living tissue has fundamentally different electrical characteristics, and so experiments on dead tissue tell us nothing. Buzsáki disagrees: if anything, more current will make it into the inactive tissue of a cadaver’s brain than into the brain of a live person, he says.
Second, critics argue that there need not be enough current to make neurons fire, just enough to bring them closer to the threshold for firing.”
You can read about dead salmons here.
I have been following the research on transcranial direct current stimulation of the brain, with great interest. Many papers have reported positive results, suggesting that the procedure may have real benefits as a cognitive enhancer.
But now a demonstration by György Buzsáki raises questions:
“When Buzsáki and his colleague, Antal Berényi, of the University of Szeged in Hungary, mimicked an increasingly popular form of brain stimulation by applying alternating electrical current to the outside of the cadaver’s skull, the electrodes inside registered little. Hardly any current entered the brain. On closer study, the pair discovered that up to 90% of the current had been redirected by the skin covering the skull, which acted as a “shunt,” Buzsáki said.
The new, unpublished cadaver data make dramatic effects on neurons unlikely, Buzsáki says. Most tDCS and tACS devices deliver about 1 to 2 milliamps of current. Yet based on measurements from electrodes inside multiple cadavers, Buzsaki calculated that at least 4 milliamps—roughly equivalent to the discharge of a stun gun—would be necessary to stimulate the firing of living neurons inside the skull. Buzsáki notes he got dizzy when he tried 5 milliamps on his own scalp. “It was alarming,” he says, warning people not to try such intense stimulation at home.”
It is still possible that lower levels of current may be alter the threshold of neuron firing, but, there is now reason for increased skepticism.
A nice video explaining the science of non-invasive brain stimulation is now available at Meaning of Life TV.
WordPress doesn’t allow me to embed videos from Meaning of Life TV, so you have to watch it here.
I know it’s tempting, but here’s another reason not to rush into transcranial direct current stimulation:
‘To better understand the effects of current on the brain the researchers used only 0.8V , about half the amount found in a 1.5 volt battery. Recent research published in the American Chemical Society publication Langmuir provided evidence that even at such a low voltage, the current could cause significant changes in the conformation of the proteins tested in the laboratory.
“What is happening in neurons is key because we know information is sent through electrical signals and if you apply external fields, there might be some important interruption that affects the normal functionality of neurons,” said Marucho. “Maybe you could enhance memory and other activities in the short term, but maybe you are also affecting some other important functions of neurons in the long term. We don’t know–and I don’t think anybody knows the long term effects of these applications.”’
The paper can be found here.
Proteins under the influence of an electric field