Of Batteries and Brains: Self-Help with tDCS

Posted by Xi Jiang on April 2, 2015 in Cognition | Leave a comment

A Gratuitous Freudian Introduction

When the renowned (if controversial) psychoanalyst and crayfish neurobiologist Sigmund Freud exclaimed that “Man has, as it were, become a kind of prosthetic God” [1], he was concerned that fast technological progress, while enabling us to modify and control the world around us to a magnificent degree, also made us ill-adjusted to the sheer power we wielded. While Freud did foretell that “great advances” will attenuate the resulting internal conflicts and displeasures, his committed pursuit of psychoanalytic methods seems to suggest that his foresight did not include our recent attempts–and growing capacity–to modify and control the world inside us through more physical means. One such novel means is transcranial (i.e. across-the-skull) direct current stimulation, or tDCS for short, whereby it may cost only ~$5 and some button presses to purposefully access one’s brain without the often fatal inconvenience of opening the skull and exploring the insides.

A gratuitous picture of Freud. The cigar may have something to do with his subconscious.

A Short History of Barely Anything, Except Brain Stimulation

It is not an entirely novel idea, of course, to stimulate and/or alter the mind, sometimes alongside bodily senses and functions (for good or ill), by influencing the brain without invading the cranium. Exercise [2], meditation [3], rituals [4], psychoactive substances [5], and even electric rays/torpedo fish have been in use since ancient times to guide human brains towards more desirable conditions. Brain stimulation via electricity–but without the cooperation of angry fish–took place as early as the 18th century, in the form of electroconvulsive therapy attempts [12]. The then-nascent field of electrophysiology–the study of electrical properties in biological matter–would eventually become a pillar of modern neuroscience, and brain stimulation would prosper as a branch of clinical electrophysiology, leading to the birth of tDCS in the 1980s [6].

A fine specimen of electric ray, whose species once suffered abuse at the gouty feet of Romans.

What makes tDCS special now instead of then, perhaps, is not groundbreaking discoveries in the field of galvanism, but the environment it finds itself in: near-universal electricity, a new generation of technophiles, and the somewhat unseemly modern spirit (which is by no means country-exclusive [13]) of pursuing immediate and easy gratification. Though clinical in origin [6] and less successful in the U.S. in terms of regulatory approval than its fancier cousin TMS (transcranial magnetic stimulation), tDCS devices are much cheaper and easier to build, leading to widespread research, industrial, and public interest [7].

A Brief Explanation of How tDCS Works

The principle of tDCS is straight-forward: by introducing peri/sub-milliamperes (i.e. a barely-felt level) of electric current over the scalp to change neuronal populations’ membrane potential, said populations will become more or less inclined to fire due to changes in resting potentials, depending on the current flow direction/intensity [6]. The hope is that, with tDCS being applied in new and imaginative ways/places, one can improve one’s cognitive performance and/or receive therapeutic effects for physical and mental debilitations. Such improvements are purported to last hours, while requiring only a few minutes of investment [14]. From attention boosts to depression relief to (somewhat dubious) mathematical insights, the promises of tDCS appear tremendous [9], if not altogether consistent [8,15].

As its simple mechanism suggests, a tDCS can be assembled with only a few parts: two electrodes and a battery-powered constant current source are about all one needs, beside the switches/buffer amplifiers/attenuators for current amplitude manipulation [17] and the bells/whistles for individual vanity. When in use, one of the two electrodes can be considered the “cathode”, and the other “anode”; electric current (as defined by arcane physics convention) flows from the anode to the neural tissue beneath the scalp and back up towards the cathode, completing a circuit. At the cortical level, the current flow is created by the extracellular ions, which in turn leads to the aforementioned changes in membrane potential [6]. It is not the increased sophistication of electrical technology, but the improved understanding of neurobiological complexities, that lends tDCS its still-sharpening edge.

A fascinating (if modestly delivered and technical) account of tDCS research for cognitive enhancement by Prof. Vince Clark at the University of New Mexico.

A Strange Tale of Pioneers in the Probably-Not-Final Frontier

According to an article in March 7th, 2015’s The Economist, tDCS has been developed to the point where enticing (and abundant) preliminary research results [8] over about two decades have led to the emergence of a fair-sized brain-tinkering community. Three days after The Economist’s article, VICE media’s Motherboard magazine published a piece on “electro-ceuticals”, highlighting the attraction of tDCS as a new and accessible playground occupied by both DIYers and corporations. Despite the looming regulation concerns described by The Economist  in light of the ease with which tDCS equipment can be produced by amateurs, companies in the U.S. and elsewhere have already begun pioneering the wild and savage markets. As further testament to the technique’s newfound popularity, Reddit, a well-known U.S.-based online news hub/forum, has an active topic dedicated to the application (and science, according to its disclaimers) of tDCS.

A tutorial for building your very own tDCS device. This embedding does not carry the author’s or this website’s endorsement of the methodology or the commercial products shown in the video. However, the preceding sentence should not be construed as a warning against adventurous souls.

Before it becomes routine to purchase tDCS devices in corner shops, however, some safety and efficacy concerns ought to be addressed, given the variable and occasionally contradictory (e.g. on working memory benefits) experimental outcomes. Adverse effects seldom go beyond mild headaches in laboratory settings [16], but long-term detriments, if any, remain obscure. Dr. Roi Kadosh, an Oxford researcher interviewed in the Economist article, cautioned in his recent review paper that in addition to result-compromising issues (relatively small sample sizes, individual differences, and inconsistent experimental protocols), there has been very little effort in whether local non-invasive interventions induce cognitive costs outside the area of stimulation/enhancement [15]. Thus it is understandable that, while overshadowed by the general cautious–and some not so cautious–optimism, vocal resistance and outright confusion/hostility (see these two comment sections) towards tDCS have also made their appearances.

The history of science, unfortunately, tends to agree with Freud’s opinion that our discomfort with what we are capable of can lead to enduring misery, and the mainstream emergence of the brain-tinkering community might be difficult to achieve while avoiding the (perhaps inevitable) setbacks due to unrealized promises and/or self-perpetuating ignorance. In the case of vaccination [10] and arguably GMO controversies, for instance, once-legitimate concerns begat irrational fears, and irrational fears begat obstructive denialism [11]. One can only hope that, through the ongoing drive for reproducible research and the future efforts of scientific communication, tDCS devices will be evaluated according to their own merit (or lack thereof) instead of conformity pressure or existing bias.

References;

[1] Freud S. Civilization and its Discontents (1930). Available here.

[2] Berryman JW. Motion and rest: Galen on exercise and health. The Lancet (2012), 380:210-1.

[3] Lutz A et al. Attention regulation and monitoring in meditation. Trends in Cognitive Sciences (2008), 12:163-9.

[4] Graybiel AM. Habits, rituals, and the evaluative brain. Annual Review of Neuroscience (2008), 31:359-87.

[5] Merlin MD. Archaeological evidence for the tradition of psychoactive plant use in the Old World. Economic Botany (2003), 57;295-323.

[6] Rossini PM et al. Non-invasive electrical and magnetic stimulation of the brain, spinal cord and roots: basic principles and procedures for routine clinical application. Report of an IFCN committee. Electroencephalography and clinical Neurophysiology (1994). 91:79-92.

[7] Brunoni AR et al. Clinical research with transcranial direct current stimulation (tDCS): challenges and future directions. Brain Stimulation (2012). 5:175-95.

[8] Shin Y et al. Transcranial direct current stimulation (tDCS) – Application in neuropsychology. Neuropsychologia (2015). 69:154-75.

[9] Horvath et al. Evidence that transcranial direct current stimulation (tDCS) generates little-to-no reliable neurophysiologic effect beyond MEP amplitude modulation in healthy human subjects: A systematic review. Neuropsychologia (2015). 66:213-36.

[10] Wolfe RM, Sharp LK. Anti-vaccinationists past and present. British Medical Journal (2002). 325:430-2.

[11] Diethelm P, McKee M. Denialism: what is it and how should scientists respond? The European Journal of Public Health (2009). 19:2-4.

[12] Kuhn J et al. Konzepte und Methoden der Klinischen Psychiatrie: Therapeutische Stimulationsverfahren für psychiatrische Erkrankungen [Deutsch] (2013). p24. Available here.

[13] “You are Hopeless if You Cannot Succeed Before 30” pressures the youth [Chinese]. People’s Daily Online (2012). Available here.

[14] Nitsche MA, Paulus W. Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. Journal of Physiology (2000). 527:633-9.

[15] Kadosh RC. Modulating and enhancing cognition using brain stimulation: Science and fiction. Journal of Cognitive Psychology (2015). 27:141-63.

[16] Poreisz C et al. Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients. Brain Research Bulletin (2007). 72:208-14.

[17] Sparing R, Mottaghy FM. Noninvasive brain stimulation with transcranial magnetic or direct current stimulation (TMS/tDCS)—From insights into human memory to therapy of its dysfunction. Methods (2008). 44:329–37.