Applying mild electrical currents to your head could take away pain, help memory and improve attention — and the US military is very interested. Emma Young reports.
In the summer of 2010, Ryan Clark twisted his ankle during a gym class. It was painful, but inconvenient more than anything. He was put on crutches for a week and his ankle healed. Then, six weeks later, the pain returned — only this time, it was a lot worse. Ryan ended up in a wheelchair, unable to bear the agony of walking. Drugs and rehab helped and after six weeks or so he recovered. Then he injured himself again, and a third time, each minor accident triggering pain that became horrendous. "They were just normal injuries for a nine-year-old," says Ryan's father, Vince, "but for him it was huge. As well as the pain, he got tremors. His muscles locked up. He'd go into full body spasms, and just curl up on the floor."
Ryan was eventually diagnosed with complex regional pain syndrome, a disorder that affects one in a million children his age. Vince Clark, who directs the Psychology Clinical Neuroscience Center at the University of New Mexico in Albuquerque, threw himself into understanding the syndrome and finding ways to help Ryan. Traditional painkillers had provided no relief, so Clark wondered about what he'd been researching in his lab. It's called transcranial direct-current stimulation (tDCS) and it involves applying mild electrical currents to the head.
TDCS belongs to a group of techniques known as 'non-invasive brain stimulation' because they don't involve surgery. It is still experimental, but even in 2010, it was showing promise not only for alleviating pain, but for boosting the brain, improving memory and attention in healthy people. The US Department of Defence (DoD) wondered whether it might benefit military personnel. By the time Ryan became sick, Clark had led DoD-funded studies that explored this question, and produced remarkably good results.
The Royal College of Surgeons, London, January 1803. An audience watches in anticipation as the maverick Italian scientist Giovanni Aldini strides into the room. Someone else is on display before them: George Forster, a convicted murderer, who was earlier hanged at Newgate Prison. Using a primitive battery and connecting rods, Aldini applies an electrical current to the corpse. To the spectators' amazement, it grimaces and jerks. In response to rectal stimulation, one of its fists seems to punch the air.
Aldini was fascinated by the effects of electricity on both the body and the mind, Clark tells me. After claiming to have cured a 27-year-old depressed farmer using electrical stimulation, Aldini tried it on patients with 'melancholy madness' at the Sant'Orsola Hospital in Bologna. He had only limited success, in part because the patients were terrified of his apparatus.
Aldini's experiments with electricity were the beginning of a long and storied episode in the history of psychiatry. Electroconvulsive shock therapy, which requires currents strong enough to trigger seizures, was introduced in the late 1930s. But with the rise of effective new drug treatments as well as public criticism in books like Ken Kesey'sOne Flew Over the Cuckoo's Nest, electrical therapies fell out of favour. "At some point, our culture became worried about electricity and its effects," says Clark. "It was something scary. There was a general anxiety about it, and people weren't willing to look at it in a rational, calm way."
Clark is animated as he recounts the rise and fall, and subsequent rise, of electrical stimulation of the brain. While the use of electricity on people became frowned upon, neuroscientists still studied the effects on animals — "A lot of my professors in grad school had played with the effects of electricity in living tissue," Clark says. In the 1960s, scientists found that tDCS, which involves currents up to a thousand times less powerful than those used in electroconvulsive shock therapy, could affect brain-cell 'excitability' and help with severe depression. But drugs still seemed more promising as psychiatric treatments, so tDCS was abandoned.
Then in the 1980s, electroshock therapy enjoyed a resurgence. It became clear that it could treat some patients with severe depression for whom the drugs did nothing. Around the same time, interest was growing in something called transcranial magnetic stimulation (TMS). A patient undergoing TMS sits very still while a wand held above the skull generates a magnetic field that penetrates their brain. This can relieve depression and also help in rehabilitation after a stroke or head injury.
In 2000, Michael Nitsche and Walter Paulus at the University of Göttingen, Germany, reported that tDCS could alter a person's response to magnetic stimulation. While TMS forces brain cells to fire, tDCS "primes the pump", as Michael Weisend, a former colleague of Clark, describes it, making it more likely that a brain cell will fire in response to a stimulus.
Neuroscientists' interest in tDCS was reignited by the Göttingen studies. But what really got people talking were the serendipitous findings that tDCS could change the brain functioning not only of patients but also of healthy people, who had been included in the trials only for comparison. This work was hugely influential, Clark says. Researchers began to investigate the potential of tDCS to boost healthy brains. Results showing that it could enhance learning and memory were some of the first to come in. Other teams looked at using tDCS to treat pain. Like many of his colleagues, Clark found it fascinating.
After a postdoctoral role at the National Institute of Mental Health, working in part on TMS, Clark had moved to Albuquerque in a joint appointment with the University of New Mexico and the Mind Research Network (MRN), a non-profit neuroscience research institute. His work focused on brain imaging and schizophrenia. By 2006, he was promoted to Scientific Director at the MRN. Clark was keen to work on tDCS but also needed to get the MRN out of financial difficulties. The institute had over-spent badly. "We were in a financial black hole," he says. "We needed a lot of money fast."
Around this time, the Defence Advanced Research Projects Agency (DARPA), the part of the DoD responsible for developing new technologies for military use, put out a call for proposals for research in an area they dubbed "Accelerated Learning". A general call like this attracts ideas from scientists from across the nation, each hoping that DoD dollars will flood their way. Clark and the MRN got the go-ahead. "We put a proposal together to use tDCS. And it was funded. And a lot of money came in quickly. A lot of people's jobs were saved."
It's clear that to Clark, the preservation of jobs by this influx of cash — which ultimately totalled $US6 million — helped to justify the use of military funds. He talks positively about the way DARPA does business. "I do really like their philosophy. They want to promote research that is very cutting-edge and very risky; a 90 per cent failure rate in their portfolio is ok, because the 10 per cent that works will change the world. We got lucky to be in that 10 per cent."
Brian Coffman smiles reassuringly as he leads me into a small room. He's had tDCS done plenty of times, he says, and he's administered it to around 300 people so far. Some report itching, heat and tingling, but nothing serious. Rarely, someone develops a headache.
Coffman, a PhD student who works with Clark, uses adhesive tape to attach the non-stimulating cathode electrode to my left upper arm and the anode, which delivers the current, to the side of my head, up between my ear and my eye. This positioning is designed to maximise the current that is drawn through the target region of my brain. The electrodes are inside sponges that have been soaked in conductive salt water, so a little of the saline drips down my face. They're connected by wires to a 9 volt battery. When Coffman switches on the battery, I feel a tiny spark on my arm. Static discharge, he explains, and apologises.tDCS and me
As Coffman turns the current up to 2 milliamps, the maximum level used in most tDCS studies, I feel a scratchy sensation on my arm, but that's it. Coffman checks that I'm comfortable, then I'm put to work on a computer-based task. The software is called DARWARS, and it was designed to help familiarise US Army recruits with the types of environments they might encounter in the Middle East. Clark and his team modified it, adding hidden targets to half the 1,200 still scenes. Fairly crude computer-generated images flash up briefly, showing derelict apartment blocks, desert roads, or streets filled with grocers' stands. I have to press buttons on a keyboard to indicate whether there's a threat in the scene or not. Occasionally, it's pretty obvious. Mostly, it isn't. A training period helps the user learn what can be dangerous and what is likely to be benign. When I miss an enemy fighter who's partially concealed, one of my virtual colleagues drops to the dust and I'm verbally admonished: "Soldier, you missed a threat. You just lost a member of your platoon."
I didn't feel that the stimulation helped me, though Coffman tells me later that my performance did improve afterwards. This means nothing scientifically — but I can at least attest that while I didn't feel any mentally sharper during or after the tDCS, I didn't experience any negative effects, either.
The MRN team used this software in part of their DARPA-funded research. First, they imaged volunteers' brains to see which regions were active as they learned to spot threats. Then they applied 2 milliamps of direct current for 30 minutes to that crucial region — the inferior frontal cortex. They found that stimulation halved the time it took volunteers to learn. This was a huge surprise, says Clark. "Most tDCS studies don't achieve a huge effect. A lot are borderline."
This is one of the criticisms that has been levelled at tDCS: the results aren't always that good. Clark is convinced this is because a lot of the studies haven't involved imaging the brain first, to pinpoint the regions that really need stimulation. "A lot rely on common knowledge about how the brain is meant to be organised. I've learned in 33 years of looking at the brain that we still have a lot to learn," he says. Michael Weisend, who collaborated on the study, agrees — he calls the imaging work "the secret sauce".
Despite the impressive results, feedback from colleagues was mixed. And by then, Clark was feeling uncomfortable about several things, not least his benefactors.
"It's big. Oh yeah, it's big," agrees Estella Holmes, an Air Force public affairs representative, who has just driven me in through the gates of the Wright-Patterson Air Force Base in a minivan. Wright-Patt, as it seems to be referred to by anyone who knows the place, is near Dayton, Ohio, and is the largest of all the US Air Force bases, employing some 26,000 people. It is rich in aviation history. In and around this area, Wilbur and Orville Wright conducted pioneering experiments into flight. What they helped to start continues here, at the Air Force Research Laboratory (AFRL).
The AFRL includes the 711th Human Performance Wing, whose mission is to "advance human performance in air, space and cyberspace". Wright-Patt is so vast, not even Holmes is quite sure where we're going. We have to ask a passing airman for help. He's dressed in fatigues, even though it's a Monday. On Mondays, Holmes has informed me, it's protocol to wear the blue uniform, unless a grimy task is scheduled. When we get inside, though, everyone seems to be in fatigues. A group of airmen — the term is used for both men and women — are holding an informal meeting at a café in the atrium, while others are walking to their various tasks. Previous Air Force Surgeons General survey the scene from oil paintings hung along one long wall. The atmosphere is quietly busy.
When a young man approaches us, incongruous not only because he's in civilian clothing (a grunge-cool three-piece suit) but because of his long, wavy hair and goatee beard, I'm momentarily thrown. "When I first met Andy, he looked like he could be active military, while I had a ponytail down to my belt," Weisend tells me later. "I like to think I got him on the long-hair path and I'm proud of that!"
Andy McKinley is Weisend's research partner and the military's principal in-house tDCS researcher, leading a lab at the Human Performance Wing. His father was a biomedical engineer in the AFRL. "I guess I followed in his footsteps," McKinley says. "I also liked the fact that my research could lead to the development of technologies that could continue to give us a strategic military advantage and improve national security." He joined two years after finishing his bachelor's degree and started out investigating the effects of high G-forces on pilots' cognitive performance. After a PhD in biomedical engineering, minoring in neuroscience, he began work on non-invasive (not involving surgery) brain stimulation. "We began noticing a lot of the medical literature suggesting that cognitive functioning could be enhanced," he says. "And particularly in control groups, which were normal, healthy participants. We began thinking: if it could help with those healthy participants, it could potentially be an intervention tool we could use here in the military to help advance cognitive function."
McKinley has anywhere from six to ten people working on this with him (the number fluctuates according to whether he has summer students or not). And as far as he is aware, his is the only team within the US military, or any other military, investigating non-invasive brain stimulation. Other countries are certainly interested — the UK's Defence Science and Research Laboratory, part of the Ministry of Defence, is paying for research at the University of Bangor, Wales, on whether tDCS can enhance learning by observation, for example, and for PhD students at the University of Nottingham to conduct studies on enhancing cognition and performance, in part using tDCS.
As a technology, tDCS is unusual in that its effects on healthy people were discovered by accident. So McKinley's research has two prongs. The first is to better understand the basic neuroscience. The second is to develop practical applications.
The day I visit, a tDCS trial is underway in one of McKinley's small labs. An airman sits at a monitor, wired up with electrodes, his jacket slung over the back of his chair. Plane-shaped icons keep entering his airspace. He has to decide whether each incoming plane is a friend or a foe. If it's a foe, he must send a warning. If it flies off, fine. If it doesn't, he must bring it down. The lab is silent, apart from the bleeps as he hits the buttons, and the smash as a software missile destroys an uncooperative plane.
The task obviously involves decision making, but it also has a physical 'motor' component: you must press the buttons in the correct sequence, and you must do this quickly, to get a good score. After a while, this kind of task becomes pretty automatic. "If you imagine learning to ride a bike or a manual vehicle, your process is very conscious at first because you're thinking about all the steps. But as you do it more often, it becomes more and more unconscious," McKinley says. "We wanted to see if we could accelerate that transition with tDCS."
Brain imaging suggested that the best way to do this would be to stimulate the motor cortex while the volunteer was doing the task. But McKinley and his team added a twist: after the stimulation, they use tDCS in reverse to inhibit the volunteers' prefrontal cortex, which is involved in conscious thinking. The day after the stimulation, the volunteers are brought back for re-testing. "The results we're getting are fantastic," McKinley says. People getting a hit of both mid-test and inhibitory stimulation did 250 per cent better in their retests, far outperforming those who had received neither. Used in this way, it seems that tDCS can turbo-boost the time it takes for someone to go from being a novice at a task to being an expert.
In theory, this two-step process might be used to speed all kinds of training, in everything from the piloting of a plane to marksmanship. But for now, image analysis is high on McKinley's list. This is painstaking work that requires a lot of attention. Image analysts spend their whole working day studying surveillance footage for anything of interest.
In other studies, McKinley's team have also used tDCS to supercharge attention, which could help the image analysts too. Volunteers were asked to engage in a rudimentary simulation of air traffic monitoring. Performance at this type of task usually declines over time. "It's a pretty linear decrement," McKinley says. But when they stimulated the dorsolateral prefrontal cortex of volunteers' brains, an area they had found to be crucial for attention, they found absolutely no reduction in performance for the entire 40-minute duration of the test. "That had never been shown before," he says enthusiastically. "We've never been able to find anything else that creates that kind of preservation of performance."
TDCS is not the only brain stimulation tool that he finds interesting. As well as ongoing work into magnetic stimulation, other teams are looking at ultrasound and even laser light, as well as different forms of electrical stimulation, using alternating current, for example. McKinley is about to start looking at ultrasound too, and he's interested in how alternating current can influence brainwaves. But while he says he's agnostic about what type of stimulation might turn out to be best for cognitive enhancement, tDCS has some advantages. For a start, unlike ultrasound or magnetism, electricity is a natural part of brain-cell communication, and it's cheap and portable. He thinks tDCS is the best bet for a wearable brain-stimulating device.
Ultimately, McKinley envisages a wireless cap incorporating electroencephalography (EEG) sensors as well as tDCS electrodes. This two-in-one cap would monitor brain activity and deliver targeted stimulation when necessary — boosting the wearer's attention if it seems to be flagging, for example. The basic technology is already available. And McKinley and Weisend are working to improve and refine it. With help from materials specialists at the AFRL, they have developed EEG-based electrodes that use gel, rather than a wet sponge, and which they say are more comfortable to wear. They also now favour an array of five mini-electrodes within each cathode and anode, to spread the current and reduce the risk of any damage to the skin.
Along with improvements in learning and attention in normal situations, McKinley has found that tDCS can combat the kinds of decline in mental performance normally seen with sleep deprivation. Other researchers have found that, depending on where the current is applied, tDCS can make someone more logical, boost their mathematical ability, improve their physical strength and speed, and even affect their ability to make plans, propensity to take risks and capacity to deceive — the production of lies can be improved or impaired by tDCS, it seems. While much of this work is preliminary, all of these effects may potentially be exploited by any military organisation — though McKinley is at pains to point out that 'soldier mind control' is not what he's about. The biggest barriers to rolling out a tDCS cap for routine use by US military personnel — or anybody else, for that matter — are related not so much to the technology or even the effects it can engender, but to unanswered questions about the fundamental technique.
"Let's talk about skulls!"
I'm sitting with Mike Weisend in Max & Erma's, an all-American restaurant about a five-minute drive from his new office at the Wright State Research Institute, which itself is only about ten minutes from the Wright-Patterson Air Force Base. Also at the table are Larry Janning and David McDaniel from Defence Research Associates, a local company that creates technologies "to support the Warfighter".
In the car on the way over, Weisend told me about his early, gruesome attempts to get a better idea of what happens to electricity when it's applied to the skull. "First, I allied with a company that does acoustic damage research on cadaver heads. The idea was we'd get the heads afterwards. It was an incredibly messy, unpleasant business. I couldn't handle it." But this kind of data is high on his and McKinley's wish list.
No one yet knows what duration of electrical stimulation or what number of stimulations has the biggest impact on performance, or what level of current is optimal. Nor does anyone know whether stimulation might produce permanent change — which might render the two-in-one cap unnecessary, McKinley says, but which may or may not be desirable, depending on the application. There are hints from various studies that even a single session of tDCS might have long-lasting effects. No one knows how long the impacts on attention persisted after the 40-minute cut-off in the air traffic control study, he says.
Another thing nobody knows for sure is where the electricity actually goes when it's applied to various parts of the skull. Certainly, it's a pretty broad, imprecise type of stimulation — a "shotgun" approach, rather than a "scalpel", as Weisend describes it. But while there are models that indicate where neuroscientists think the electricity goes in the brain, and so exactly which parts it's affecting, this isn't good enough, says McKinley. You can't put electrodes throughout a living person's head to find out. "So what we want," McKinley tells me, "is a phantom skull."
Today, Weisend wants to talk to Janning and McDaniel about building this phantom — a model of a human head. The idea is to use a real skull, but with a gelatinous, conductive, brain-mimicking goo inside.
At first, no one's quite sure how to fit the skull with sensors in a way that might produce realistic results, particularly as Weisend wants it to be useful for research with a range of stimulation techniques. Over black-bean burgers and soup, there's talk about multiplex receivers and problems with pulsing signals. Then McDaniel comes up with the idea of inserting a folded fan-type circuit board into the hole at the base of the skull, then opening it up once it's inside. Weisend jumps on the idea. He holds his fists together, the phalanges of his knuckles in contact. "This is like the brain," he says. "You've got fibres running like my fingers." A fan shape would be a decent mimic for the fibres, he decides. "I like this idea. I like it a whole lot!"
Both McKinley and Weisend are interested in the basic neuroscience of precisely what tDCS does to the brain, as well as the technology — and the question of safety. This is clearly a big concern when you're talking about zapping the brain with electricity, even if the current is very small. The positive tDCS findings, and the relative cheapness of the kit, has made do-it-yourself tDCS a popular topic for discussion on the internet. You can buy what you need for under $US200, and, judging by the online forums, plenty of people are. But Weisend has some major concerns about this. For a start, the electrodes themselves.
"See this?" He rolls up his right sleeve to reveal a small scar on his inner forearm. "I test all the electrode designs myself before we do it on regular subjects," he says. "I don't like to do anything to other people I don't do to myself." After trying out one particular new electrode, a research assistant wiped his arm and a plug of skin the size of a dime came out. "It was the consistency of phlegm," Weisend says. "I could see the muscle underneath." The problem was the shape: the electrode was a square, and the current had concentrated at the corners. This was one of many, mostly less unpleasant, results that helped lead McKinley and him to develop the current-spreading five-electrode array.
Nicely packaged consumer tDCS kits, aimed at the public rather than scientists, are already on sale. But Weisend and McKinley — and every other tDCS researcher I've talked to — think it's too early for commercial devices. In fact, they all seem worried. If something goes wrong and someone gets hurt, perhaps by an imperfect electrode design or using the kit for 'too long' — a duration that has yet to be defined — not only will that be regrettable for the individual but tDCS as a concept will be stigmatised, McKinley says.
So far, there seem to be no harmful effects of tDCS, at least, not at the levels or durations of stimulation that are routinely used. Weisend believes there's no such thing as a free lunch, and admits there could be side-effects to tDCS that no one knows about yet. Others are more optimistic. Felipe Fregni, Director of the Laboratory of Neuromodulation at the Spaulding Rehabilitation Hospital in Boston, Massachusetts, says there's no reason to think even long-term use will cause problems, provided that it's at the low levels and durations that are typically used in the lab studies. "Being a clinician, one thing we are taught at medical school is that treatments that work well have huge side-effects. Then you see something with literally no side-effects, and you think, are we missing something, or not? TDCS is only enhancing what your system is doing. I feel confident that it is pretty safe, based on the mechanisms."
The absence of side-effects — which most drugs can't boast — is one of the reasons tDCS is so exciting as a clinical tool, says Vince Clark. In many cases, a drug will be more appropriate. But tDCS can relieve pain without making an addict of the user. It can affect the brain without also damaging the liver. As there seem to be no side-effects, tDCS is at least as safe as many drugs that are currently approved for use on kids. Eleven per cent of children in the USA have been diagnosed with attention deficit hyperactivity disorder, and many are on stimulants such as Ritalin. No one knows for sure that there are no very long-term effects of using tDCS — but the same may be said for Ritalin, Clark says.
While tDCS is not approved by the US Food and Drug Administration for any medical use, anecdotal reports lead Clark to believe that its 'off-label' use (when doctors recommend something which they think can help their patient but which isn't officially recognised as a treatment) is growing, particularly for chronic pain and depression. Hospitals are starting to use the technique clinically. In Boston, Fregni and his colleague León Morales-Quezada recently began to use tDCS during rehab on young patients with brain injuries. With one boy, a three-year-old who had suffered severe brain damage after a near-drowning in a swimming pool, they got "fantastic" results, Morales-Quezada says. After the treatment, the boy had much better control over his movements, and he was able to speak.
There's another 'risk': that the device won't help everyone, and people will say tDCS doesn't work. In fact, people do not respond equally to stimulation, and no one yet knows exactly why. This is just one of the areas that needs more research — which requires money.
To Clark, his studies aren't fundamentally about helping to teach a soldier how to spot a threat and deal with it — which, in the real world, might involve identifying and killing an enemy — but about investigating how the brain detects threats. "A lot of people who've reviewed my work will say that it's good work — but does it have to be about the military? That makes them unhappy. A lot of intellectuals are made uncomfortable by war. Which I am."
There's something else, which clearly bothers him still. In 2003, Joseph Wilson, a former US diplomat, published a piece in the New York Times arguing that President George W Bush had misled the public about claims of Iraqi purchasing of uranium in Africa, part of the wider furore over the decision to go to war in Iraq. A week later, his wife, Valerie Plame Wilson — a friend of Clark — was outed as a CIA agent. This was retribution, her husband claimed, for his article. "I'd known Valerie for ten years before this, not knowing she was a CIA agent," Clark says. "She was a wonderful patriot, and I was really unhappy that because people were angry at her husband, she lost her career and her ability to do that work… So here were my friends, going through this. And here was I, being pressured to use this technology for weapons development."
Weapons development? Around the time of the DARPA grant, the focus of the Mind Research Network had begun to shift more and more towards developing tools the military could use, Clark says. "I'm not allowed to say what was discussed, but I can mention some possibilities," he says. "A device that makes enemy troops unconscious, or makes them too confused or upset to fight, might make a weapon. Weapons that alter thoughts or beliefs, or directly affect decision-making or 'reward' pathways in their brain to alter their behaviour, or that keep someone conscious while they are being tortured, might be achieved." He'd also heard talk of using tDCS to help improve sniper training, which he didn't approve of. "I had my principles and goals, and they had theirs, and they were in direct conflict."
In 2009, an error was found in bonus payments to the research assistants on the DARPA project. Clark says that it wasn't that serious, but against the background of his disputes with colleagues over the direction of the institute, it became a big problem. Soon after, he lost his position as principal investigator on the DARPA work.
After enthusiastic handshakes and promises of further discussions with the men from Defence Research Associates, Weisend yawns, and apologises. He's been in Ohio for only six weeks. It's been a busy period of settling in, getting to know new colleagues and meeting potential collaborators. Also, he and his wife finally got a TV last night, he adds. He couldn't resist staying up to watch old Star Trek episodes. Back inside his office, we sit down and talk about tDCS, his current projects, the Mind Research Network, Vince Clark, the Department of Defence, and the "colour of money".
Weisend's cousin David was in the US Special Operations Forces. His sister, Joan, was a career corpsman in the US Navy. She completed numerous tours around the world, including to Iraq and Africa. A shipboard fire on one of her tours resulted in multiple operations on her wrist, neck and shoulder. Between 1997 and 2004, Weisend also worked at the New Mexico Veterans Affairs Hospital, running a magnetoencephalography (MEG) centre, which performed highly detailed scans of patients' brains. He remembers one patient in particular, a woman who'd received a head injury after falling from a moving vehicle during the first Gulf War. As a result, she had epilepsy. MEG scanning of her brain allowed the medical team to perform surgery that stopped the seizures, with the least possible damage to healthy tissue. "I personally saw the health effects [of military action] on soldiers at the hospital, and my sister, and my cousin," he says. "Anything I can do to help those guys and gals, I'll do."
When Clark lost his position, Weisend was asked to take the lead, and it was he who developed and supervised the second phase of the research. DoD funding forms a big part of his lab income at the Wright State Research Institute, says Weisend — it's for "exciting, fun" projects he can't talk about. He's well aware that not everyone is comfortable about military-related grants. "There are people, particularly in university departments, that get worried about the 'colour of money' — Defence money, rather than NIH [National Institutes of Health] money for pure science," he says. His opinion is that you never know how basic research is going to be used, and if it is used for harm, it's the agency doing the harm that should be open to blame, rather than the researcher who did the original science.
What about the tDCS research on sniper training that Clark had heard about? That belongs to the category of research that has appeared "in the popular press" but not "in the lab", Weisend says, though adding that he isn't opposed to it, in theory. "The bottom line is that Vince and I see the world differently, with respect to the DARPA work and the directions it took," he says. "If Vince had conversations about weaponising our results, I was not privy to those conversations. Could the results be weaponised? Undoubtedly. But then again, so could a ballpoint pen. We have always focused on performance enhancement as measured by reducing errors and uncertainty. We never did any experiments on weapons at MRN."
For a long time, it was difficult to get military volunteers for the DARPA-funded studies, Weisend tells me. Unlike civilians, they couldn't be paid for taking part. Then he hit on the idea of ordering a special coin. He passes one over to me. It's weighty and impressive, the size of a medal. On one side is a raised relief of the exterior of a human brain, on the other the full-colour emblems of both the 711th Human Performance Wing and the Air Force Research Laboratory, with "The Mind Research Network" printed underneath.
Coins like these are really popular within the military, Weisend says. He shows me his collection. There's one from a friend at the Pentagon, another from his cousin, from his time with the 20th Special Operations Squadron of the Air Force, the Green Hornets. "We couldn't figure out how to get military people in the door," he says, "then we came up with these. And they came out of the woodwork to get them."
While the MRN-led studies involved a mix of military and student volunteers, Andy McKinley recruits his volunteers from the Wright-Patterson Air Force Base. At the moment, tDCS is still experimental, McKinley stresses. It is not yet a routine part of US military training. But some researchers are worried.
Bernhard Sehm, a cognitive neurologist at the Max-Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, has a list of concerns about tDCS and the military. For a start, he says he's far from convinced that lab results would transfer to real-world scenarios, with complex demands — such as combat. Also, "some researchers have argued that the enhancement of one specific ability might result in a deterioration of another," he says. "To use non-invasive brain stimulation in soldiers poses a risk both to the person receiving and to other persons who might be harmed by his actions." Sehm is also worried about soldiers' autonomy. "In general, people in the military cannot really decide voluntarily whether to accept a 'treatment' or not," he says.
As the DoD continues its funding of tDCS research, some researchers in the field have decided to take a firm stand against military-related money. Chris Chambers, a psychologist at Cardiff University, in Wales, conducts research into magnetic brain stimulation. When he was approached by representatives from QinetiQ, a British defence technology firm, who told him that funding might be available for joint collaborations, he says he rejected their overtures, on a point of principle.
This isn't necessarily an easy decision. Pharmaceutical companies aren't interested in paying for the research, because not only is tDCS not a drug but in some cases it could be in direct competition with a drug, and may even have big advantages. "It doesn't circulate through the body, so it won't affect other organs that most drugs can damage," Clark says. "It's not addictive. If there's any problem, you can turn it off in seconds. It's also cheap." These benefits, unfortunately, restrict researchers' options to public funding bodies (who haven't exactly thrown money at tDCS), private defence-related companies, or the military.
In the past, DoD funding has produced innovations that have had a huge impact on civilian life — think of the Global Positioning System of satellites or even noise-cancelling headphones. Andy McKinley hopes a safe, effective form of tDCS will join that list. While the DoD doesn't have enough in-house specialists to do the research, it does have cash.
Clark still acts as a research supervisor at the MRN, but works mostly at the university. He is currently gathering "whatever little pieces of money I can find" to pursue medical-related research: to investigate whether tDCS can cut drinking in alcoholics, reduce hallucinations in people with schizophrenia, and calm impulsive behaviour associated with fetal alcohol spectrum disorder. While this research is relatively cheap, funding is still a problem. Given the recent rapid rise in tDCS research published in academic journals, Clark hopes the NIH will soon start taking tDCS research seriously, and pay for large-scale, controlled studies.
Among the promising leads are further findings that tDCS also seems to work well with types of pain that don't respond well to conventional painkillers, like chronic pain, and pain from damaged nerves. In these cases, the target is usually the motor cortex, and the idea is to reduce pain signals. Which brings me back to Ryan, one of the biggest motivations for Clark's research. Did Clark eventually try it on his son? When Ryan first got sick, "none of the doctors here had heard of tDCS," he tells me, "and without medical help, I decided I wasn't going to do it". He also came across a low-tech approach: an 'orthotic', similar to the mouthguards people used to stop night-time teethgrinding. To Clark's surprise, this relieves Ryan's pain and eases his movement. But Clark says he'd be happy for Ryan to try tDCS. If the mouthguard stopped working and he could find a clinician who would work with the technique, "I don't think it would be any problem".
Clark raves about its potential to aid sick people, like his son, and healthy people alike. But he says he's clear now about his position on what funds to accept and what research to do. "I want to see tDCS used to help," he says, "not to harm."
This article first appeared on Mosaic and is republished here under Creative Commons licence. Mosaic is dedicated to exploring the science of life. Each week, it publishes a feature on an aspect of biology or medicine that affects our lives, our health or our society; it tells stories with real depth about the ideas, trends and people that drive contemporary life sciences. Mosaic is published by the Wellcome Trust, a global charitable foundation that seeks to drive extraordinary improvements in human and animal health. It covers subjects that fit with the Trust's mission and vision, but isn't limited to the research the Trust funds.