YOUR BRAIN ON TECHNOLOGY
In April 2012, Mark-Andre Duc sat in a hospital in the southern Swiss city of Sion, controlling the movements of a foot-tall robot at Switzerland’s Federal Institute of Technology, about sixty miles away. Alone, the feat is far from newsworthy—on average, the Earth is about 150 million miles from Mars and human controllers manage to drive the rover Curiosity. But Mark-Andre Duc was different from NASA rover pilots in one important way: he’s paralyzed. Unable to move his fingers or legs, Mark-Andre Duc drove the robot with his mind. Wearing a cap of electrodes, he imagined lifting a left finger to turn the robot left and imagined moving a right finger to turn the robot right. A computer linked to his “thinking cap” decoded his brain’s slight electrical signals and relayed the commands to the remote robot.
Then a month later, a woman who preferred to remain anonymous and so was known as “S3” sat in a chair facing a robotic arm. Attached to the surface of the motor cortex of S3’s brain was a bean-sized implant with ninety-six thin electrodes that read the patterns of her brain activation. Though paralyzed fifteen years earlier, S3 controlled the robotic arm with her thoughts, using it to lift a cup of hot coffee to her lips and take a sip.
Just as Mark-Andre Duc and S3 used their brains to control technology, you can use technology to control your brain. For example, the American Psychological Association recommends the use of electroconvulsive therapy to treat severe depression. A practice known as deep brain stimulation inserts electrodes that act like pacemakers to control the tremors of Parkinson’s disease, the fixations of obsessive-compulsive disorder, the pain of a phantom limb, or even to improve spatial memory—helping subjects learn to accurately navigate virtual mazes.
If you’re going to run 800 milliamps and a couple hundred watts through your brain as in electroshock therapy, or insert metal wires deep beneath your skull as in deep brain stimulation, best leave it to trained professionals, preferably with steady hands and multiple PhDs.
But there’s a third modern form of firing electricity into your brain that you can do yourself this afternoon! Powered by a nine-volt battery, transcranial direct current stimulation, or tDCS, is relatively safe, and in addition to the obvious recreational value of running current through your gray matter, an explosion in recent research shows that this little bit of electricity can go a long way toward boosting a number of brain functions.
That’s because your neurons generally sit around waiting for electricity to reach a critical threshold, at which point—pop!—they fire, propagating current along their lengths. Transcranial direct current stimulation increases the baseline electricity that neurons feel, and so it takes less additional electricity to make neurons in the area fire. If neurons were little guns, adding the gentle electric current of tDCS would be like changing out a twenty-pound spring for a hair trigger.
Speaking of guns and triggers, some of the best evidence for the usefulness of tDCS comes from tests by the US Defense Advanced Research Projects Agency (DARPA), which studied the use of tDCS to train snipers. Training took place in a virtual environment called DARWARS and used videogames to train recruits in things like the rules of engagement, cross-cultural communication, and how to blast the heck out of a never-ending swarm of virtual attackers. DARPA being DARPA, it apparently seemed too mundane to simply present recruits with an onslaught of bloodthirsty ambushers when they could do the same thing to recruits while firing electricity through their brains!
Electricity has to make a circuit and so recruits wore a moistened anode (which shoots electrons) on their right temple and a cathode (which sucks electrons) on their left upper arm. The exact version of DARWARS played by electrified recruits had them survey a scene for danger—“a shadow cast by a rooftop sniper, or an improvised explosive device behind a rubbish bin,” writes Douglas Fox in the journal Nature. Recruits had to recognize the threat and neutralize it before it neutralized them. And with electricity coursing through their brains, they did it more than twice as well as non-electric (acoustic?) recruits. In threat recognition, speed, and marksmanship, tDCS made recruits better. Do a quick Google search for tDCS, and you’ll see more than a dozen studies showing similar gains in learning or performance.
Because tDCS runs current from a “plus” wire to a “minus” wire, not only can you boost the function of a brain region, you can simultaneously lower it in another. For example, the right anterior temporal lobe is implicated in sudden insight, but is undermined by the naysaying left anterior temporal lobe. Researchers hooked up tDCS to amp the right and blunt the left and saw a resultant rise in aha thinking. And for the common pairing of schizophrenia and depression, tDCS can increase mood in the left dorsolateral prefrontal cortex while decreasing activity (and thus hallucinations) in the temporal cortex.
So what is this tDCS wundermachine? You’re probably picturing a pricey MRI tube full of whirring fans and blinking lights—and, in fact, a well-known cousin of tDCS, transcranial magnetic stimulation, lives up to that expectation, costing about $50,000 for a rig. But speaking at a neurotechnology conference, Harvard’s Eric Wasserman said, “Half the people in this room could build [a tDCS machine] with parts from RadioShack.” The device is simple: a nine-volt battery is connected with wires to large, flat sponges that are moistened and then applied to the head.
Oh, and maybe you’re wondering if it’s safe. Believe it or not, before attaching electrified sponges to human heads, researchers have wondered the same thing. The Department of Neurophysiology at Georg-August University in Germany zaps as many patients with tDCS as anyone, to treat conditions including migraines, tinnitus, and post-stroke complications, as well as healthy subjects for the purpose of science. And they asked 102 of these patients about their side effects. As expected, 70.6 percent of them felt mild tingling during tDCS and 35.3 percent reported feeling mildly fatigued afterward. A few reported headache (11.8 percent), nausea (2.9 percent), and insomnia (0.98 percent), but this was within the expected range of people who might have felt these complications even without tDCS. A study at the City College of New York found that the most harmful side effect was rare instances of skin irritation at the site of the electrodes, and used animal models to explore the upper limits of tDCS current. Let’s just say it’s unwise to exceed 149.2 amps per square millimeter of brain surface. However, even if you could suck all the amps instantaneously from a nine-volt battery in one great shock (which you can’t), you wouldn’t hit this threshold. Just keep it to a single nine-volt and to twenty minutes per pop and you should be good to go—you know, in an at-your-own risk, only-if-you-dare kind of way.
Seriously: use at your own risk. While results to date seem to indicate that tDCS is safe, you are messing with your brain here. And because this is a new field, studies on the effects of long-term or repeated use are still lacking. I’m not telling you that it’s a good idea to try this. Still think that turning your brain into a DIY electric guinea pig sounds fun? If so, the following exercise describes the results of successful tDCS studies and how to approximate them at home.
DIY TDCS
This diagram shows how to construct the basic tDCS machine, although many variations exist (or you can order one for about $350 from the company Mind Alive). Now the question is where to stick the sponges. Pick your desired result from the list of studies below, and then apply the anode sponge as shown in the numbered diagram that follows, and place the cathode sponge on your upper arm.
1. At MIT, tDCS of the primary motor cortex helped subjects learn a fine motor skills task.
2. At Harvard, tDCS of the dorsolateral prefrontal cortex increased subjects’ performance on a working-memory task.
3. A tDCS study at the University of Zurich found that stimulation of the right prefrontal cortex made subjects more forgiving.
4. Researchers in Boston and São Paulo, Brazil, collaborated on a study that found tDCS on the left dorsolateral prefrontal cortex increases executive function, making subjects less impulsive and less risk-seeking.
5. DARPA’s tDCS marksmanship training, explained earlier.
6. University of Sydney study mentioned earlier, which increased insight by tDCS of the anterior temporal lobe.
7. Many studies show benefits of tDCS of motor regions affected by stroke (e.g., Nair et al, 2008; Hummel et al, 2006; Hesse et al, 2007). Search online for images of “motor cortex map” and apply anode to affected area.
8. The NIH Behavioral Neurology Unit found increased verbal fluency after tDCS of the left prefrontal cortex.
9. A number of studies use tDCS to treat depression, most commonly anodal stimulation of the left dorsolateral prefrontal cortex.
10. A Harvard clinical trial of cathodal tDCS of epileptic brain areas led to 64.3 percent reduction in epileptic discharges. Apply cathode to affected area.
11. A Harvard study found increased memory for musical pitch with tDCS of the left supramarginal gyrus.
Click here to download this exercise.
Click here for answers.