Recent increased interest in the electricity-based brain stimulation method of transcranial direct-current stimulation (tDCS) as a means of improving cognitive ability has some experts raising concerns about the neuroethical issues surrounding the technique — particularly its ease of use as a make-it-yourself home device.
The technique, in which small surges of electricity are delivered to the brain, is about as low-tech as they come, requiring only, as shown in easy-to-find Internet instructions, little more than a 9-volt battery and some electric wire This means do-it-yourselfers can cheaply and relatively easily assemble their own devices and deliver their own brain stimulation.
Those wishing to play it a little safer can opt to purchase an already assembled headset online for about $249, which comes with the promise of improving computer and video game performance.
With the click of a button, the headset sends a surge of electricity rippling across the prefrontal cortex, allowing synapses to fire faster.
Although the only indication showing relatively solid evidence of improvement with the device is depression, smaller studies looking at cognitive improvement appear to have been the key drivers of increased interest among researchers and the lay public in the technology's potential.
But with scant solid evidence in support of that potential, scientists need to temper their enthusiasm over the possibilities with caution, particularly emphasizing the "do not try this at home" message, explained the authors of an editorial in the June 20 issue of Nature.
"Such home use of experimental laboratory kits puts neuroethicists, and journals such as Nature, in a bind," they write.
"To draw attention to it could promote and accelerate its use, and so increase the risk of a mishap. To ignore it leaves the risks unexplored."
Ethical Dilemma
Despite several recent published editorials and papers on the issue, the exact extent of use of home tDCS devices is unknown, and with the additional lack of evidence on benefits and potential risks, Peter Reiner, PhD, who coauthored one of the papers, published in the Journal of Medical Ethics, said that he and his colleagues had strong reservations about even publishing their paper.
"This device is moving very rapidly from concept to implementation and while we don't know how widely it's being used as a do-it-yourself at-home device, we have a responsibility not make that problem worse by reporting upon it," said Dr. Reiner, from the National Core for Neuroethics at the University of British Columbia in Vancouver, Canada.
"So we thought very long and hard before publishing this with concern about whether we were really going to draw so much attention to it that people would wind up taking it up," he told Medscape Medical News.
"But we have seen more Web sites selling this and more commercial outfits either preparing to launch or launching this, so we thought the time was right."
The most intriguing aspect of tDCS is also what makes it particularly worrisome — the potential for long-term manipulation of neuroplasticity.
In a recent small study, researchers trained participants for 6 days with numeric symbols while concurrent tDCS was applied to the parietal lobes. They found sustained improvements in numeric proficiency as much as 6 months after the training (Curr Biol. 2010;20:2016-2020).
"The specificity and longevity of tDCS on numerical abilities establishes tDCS as a realistic tool for intervention in cases of atypical numerical development or loss of numerical abilities because of stroke or degenerative illnesses," those authors wrote.
Acknowledging such potentially long-term effects of tDCS, Dr. Reiner and his colleagues compared the potential benefits to that of functional MRI.
"Much as functional MRI has fuelled a revolution in measuring brain activity, tDCS seems poised to radically change our ability to manipulate brain activity in living humans," the authors write.
"Neither technique has the resolution that the synaptically oriented neurocognoscenti might wish for, but what they lack in specificity they make up for in versatility."
"Together, these are the Swiss Army knives of human neuroscience," they add.
Double-Edged Sword
But concerns of the possible risks suggest more of a double-edged sword. While the specific risks have not been well documented, their absence doesn't mean the technique is benign, Dr. Reiner emphasized in his paper.
Some possibilities of risks that are particularly a concern with home use include improper placement of electrodes (due to issues such as left-handed or other neuroanatomic differences); reversing polarity, which could impair function; interaction with pharmacologic agents; and unintended and undesirable effects that could be long-lasting, the authors explained.
The logical solution of tougher regulation of the devices, however, could only place users more at risk, Dr. Reiner said.
"The bottom line is there are some challenges here and we think it would be a mistake if the regulatory authorities were to come down hard and say this could only be used under medical supervision," he said.
"That could easily result in a substantial black market, and experts would not be gaining insights from the proper usage of the device."
In the opinion piece, Dr. Reiner also cautioned that care should even be taken in the public discussion of tDCS in order to prevent misinterpretations of the technique's safety — starting with refraining from calling the technology "noninvasive."
"Although the electrodes do not penetrate the brain, the electrical current must do so, as otherwise it would have no effect on neural function," the authors write.
"Thus, tDCS is minimally invasive in some meaningful sense. Yet the technically correct descriptor 'non-invasive' carries substantial rhetorical power with regard to safety, an issue that is particularly relevant when considering DIY users."
Roi Cohen Kadosh, PhD, who has also published recent research on concerns about tDCS and other brain stimulation techniques, noted that little is known about the potential risks of the devices because research so far mainly involved controlled settings.
"At the moment, work at labs has used more strict criteria to avoid damage, and we exclude subjects with some medical conditions, such as a history of epilepsy or taking recreational drugs," said Dr. Cohen Kadosh, a junior research fellow in psychology at the University of Oxford, United Kingdom.
"But people might stimulate without being aware of this, or [use the device] with the attitude of 'more is better,'" he said. "This might lead to side effects, and in the worse case scenario, depending on the intensity and duration, neuronal damage," he told Medscape Medical News.
Bad Timing
John C. Rothwell, PhD, who has also published a paper on potential clinical applications of electrical stimulation, said he felt the evidence on tDCS is simply not strong enough to draw any conclusions either way.
"All of these studies so far have been extremely small and many don't have any affect whatsoever on most of the subjects — good or bad," said. Dr. Rothwell, from the University College London Institute of Neurology in the United Kingdom.
"There is this hype about the methods, but the results so far have been weak," he told Medscape Medical News.
"There have been useful effects on depression shown, but even that is only if it is used everyday for at least 6 weeks," he added, noting that the only adverse effect shown to be a concern is that of skin burns related to placement of the electrodes.
With such scant evidence, Dr. Rothwell even questioned whether the issue should have been brought up in the Nature editorial.
"I think the article in Nature was extremely badly timed," he said. "It generates publicity to techniques that have dubious effectiveness, giving the techniques more credence than they deserve."
Dr. Reiner, Dr. Cohen-Kadosh, and Dr. Rothwell have disclosed no relevant financial relationships.
Nature. 2013;498:271-272. Full text
J Med Ethics. Published online June 3, 2013. Full text
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Cite this: DIY Brain Stimulation Raises Concerns - Medscape - Jul 10, 2013.
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