This blog is the fourth in a series of guest posts on technology and the brain to celebrate Scientific American Mind’s 10-year anniversary. The magazine’s special November/December issue similarly highlights the interface between code and thought in profiling a future, more digital YOU.
Imagine a medical device that is so simple to build and cheap to acquire that anyone with an Internet connection and a local Radio Shack can use it tweak their brains–to become smarter, more focused, calmer, or happier. Such a device nominally exists. Transcranial direct current stimulation (tDCS) involves sending low-current electricity into the brain via carefully placed electrodes attached to the scalp. Our best current guess is that the electricity puts neurons in a state that leads them to fire (send out signals) more readily after receiving input from other neurons. The result is a temporary change in the brain that could, in theory, be helpful to those who want to learn faster, to improve their mood, or to modify their mental functioning in any way.
A growing number of scientific studies is beginning to detail the ways in which tDCS can increase focus, improve mood and sharpen memory. For example, in a 2014 Journal of Neuroscience article, neuroscientists Robert Reinhart and Geoffrey Woodman from Vanderbilt University demonstrated that tDCS applied over medial frontal cortex caused individuals to learn a simple reaction time task more quickly and to correct themselves more readily after making an error. Further, reversing the polarity of stimulation reversed the effects, making people worse at correcting themselves than when they received sham stimulation, which mimics the sensation of electrical current without delivering electricity. These results were replicated across four experiments, and were observed in two types of tasks. In short, the authors found that changing activation in regions of the brain associated with cognitive control improved people’s cognitive control, supporting the idea that the medial frontal cortex really does govern this function, and that such control can be modified. This work is complementary to techniques such as functional magnetic resonance imaging (MRI) that allow scientists to look for associations between brain regions and cognitive processes, but cannot show that activity in those regions truly underlies memory, attention or language.
Thus, tDCS is an exciting technique that holds promise in increasing our understanding of how the brain works, and in improving brain function in specific and targeted ways. One possible future, imagined by Marom Biksem and Peter Toshev in Scientific American Mind, suggests that instead of pill bottles, tDCS devices could line the walls of your local pharmacy. In our research lab, we are currently investigating the potential role of tDCS in improving creativity. By applying tDCS over regions of prefrontal cortex that are involved in analogical reasoning, we hope to improve people’s ability to think divergently to solve problems. These experiments are in the early stages, but may help us to gain knowledge about how the brain does creative thinking and how we might be able to improve such processes.
Meanwhile, these devices have moved outside the laboratory into people’s homes. A quick Internet search reveals pre-made devices available for less than a hundred dollars from retailers like The Brain Stimulator, but overwhelmingly, many people are choosing to fuse, solder, and wire their own creations. In amateur tDCS, well-meaning individuals without prior electronics experience build brain stimulation devices from batteries, cable, and absorbent sponge with great effort and pride. Much of the enthusiasm for homemade tDCS devices is likely due to the small, but mounting scientific literature supporting their utility. People understandably might want to improve cognitive function by way of a machine that promises great results and few side effects. Still other people might be motivated by a chance to engage in citizen science, to contribute to public knowledge through the free medium of YouTube.
The rise of citizen scientists willing to give themselves a buzz in the name of both self-improvement and public knowledge is an interesting and slightly worrying phenomenon. Burns from overly-juiced electrodes and little-understood electronics kits abound; because electrode placement at home is both crude and not much more than educated guesswork, people may inadvertently stimulate unintended brain regions and networks with unforeseeable consequences. Much is also unknown about the longer-term effects of zapping your brain with electricity; widespread mainstream scientific use of these devices is still new enough that we don’t yet know how chronic stimulation will affect the brain over the time scale of years. As a result, experts such as psychologist Roi Cohen Kadosh and neuroethicist Julian Savulescu of Oxford University, writing in the journal Current Biology in 2012, do not recommend widespread use of the technology, particularly not in children, as almost no work has been done to establish the safety and efficacy of tDCS in this group as of yet.
Since the amateur community has already bypassed such academic concerns, the question is not whether people should build and use their own tDCS machines, but rather whether these machines can truly offer any benefit. Currently, anecdotal claims that homegrown tDCS devices have produced cognitive or other benefits are difficult to evaluate for a number of reasons. First, amateur researchers cannot reasonably compare the treatment to a control condition–that is, to a situation comparable to the treatment in other important aspects but without its key ingredient. To test tDCS, scientists compare it to sham stimulation: subjects feel a slight tingling at the scalp but receive no electrical current. Ideally neither the scientist nor the participant know whether the stimulation is real or fake, reducing both the expectations of the participant (which can influence the outcome) and the scientist’s unconscious bias in favor of his or her hypothesis. In particular, confirmation bias, the tendency to search for evidence that confirms our hypotheses, can be extremely powerful. Such a bias occurs in daily life, as when we “see” more evidence for nasty behavior from someone we have already labeled a jerk. Similarly, if I strap a tDCS device to my head and I pick a particular montage (electrode arrangement) that is expected to improve my attention, chances are I’m going to see improvement in my attention–whether or not the treatment is actually effective. Serving as both the experimenter and the participant violates the aim of impartiality in collecting our data.
In addition, precise placement of electrodes is difficult in amateur setups. For example, if one is aiming to improve memory retrieval, stimulating the left inferior prefrontal cortex (LPFC) would be a good place to start. But what of the LPFC’s role in language production? And how can we be sure that we are targeting the specific sub-region of the LPFC that guides memory retrieval? Most home enthusiasts do not have access to an EEG cap, which makes accurate positioning relatively automatic. Some scientific labs also use MRI scans of individual participants to further specify exactly where underneath the skull a particular fold of the cortex may lie. Instead, homemade devices include electrodes that individually fasten to the head using tape or stickers. One strategy for placement involves following, as closely as possible, a universal brain map called the international 10/20 system, which points to positions for electrodes with respect to the lobe of the brain beneath it. Using this method, people can place electrodes by taking measurements of various landmarks across their own scalps, and interpolating distances relative to where a standard EEG cap would have an electrode. This is clearly not a foolproof system. In addition, a one-size-fits-all map for electrode placements may, in fact, fit none, as every person’s brain has a somewhat unique structure. As a result, it is difficult for the layperson to be certain about which region of the brain he or she is actually stimulating.
Even if electrodes were perfectly placed on the head in a given experiment, that positioning still does not guarantee increased excitability of the exact neurons governing a particular brain function. Although in some cases psychologists have been able to identify regions that seem to govern particular functions such as attention, motivation or memory, increasingly, neuroimaging studies have revealed the interconnectedness of different brain regions and the corresponding extent to which certain functions cannot be localized to discrete brain regions. For this reason, the effects of using tDCS to target specific brain regions are not fully understood. Contrary to popular belief, we simply cannot be sure that stimulating brain region X will affect cognitive process Y but not Z, because the neuroscience does not support that level of specificity. In some cases, such a strategy is effective, but we cannot count on it. Proceeding without a broad and deep understanding of the literature regarding the cognitive processes supported by a certain brain region makes for some dangerous guesswork; this fact strongly separates home enthusiasts from scientists who have made careers out of gaining an intimate familiarity with how the brain works. This fact determines how we can be confident that, say, the work of Reinhart and Woodman might produce sound new knowledge about brain functioning, whereas amateur tDCS administration is much more likely to muddy the epistemic waters.
Despite these caveats, the fact that people are willing to self-experiment in the name of science is a good thing. With better education and understanding of the supporting science, there might be a place for citizen brain stimulators to contribute to science. One great strength of the Internet is in crowdsourcing; imagine tens of thousands of knowledgeable and vetted amateurs taking to their garages to mass-replicate findings published in scientific journals and demonstrating that, in fact, a standard tDCS protocol applied over medial frontal cortex does produce measureable and lasting improvements in cognitive control. Perhaps we are on the threshold of a revolution in rapid replication of the cumbersome and expensive traditional scientific study.
>>Next in the series: “Simply Shining a Light Can Reveal the Brain’s Structure”