In April the Defense Advanced Research Projects Agency (DARPA) announced contracts for a program to develop practical methods to help someone learn more quickly. In the ensuing press coverage, the endeavor drew immediate comparisons to The Matrix—in which Neo, Keanu Reeves’s character, has his brain reprogrammed so that he instantly masters kung fu.
DARPA is known for setting ambitious goals for its technology development programs. But it is not requiring contractors for the $60-million, four-year effort to find a way to let a special-forces soldier upload neural codes to instantaneously execute a flawless wushu butterfly kick.
The agency did award contracts, though, to find some means of zapping nerves in the peripheral nervous system outside the brain to speed the rate at which a foreign language can be learned by as much as 30 percent, a still not too shabby goal.
Sending an electric current into the vagus nerve in the neck from a surgically implanted device is already approved for treating epilepsy and depression. The DARPA program, in tacit acknowledgment of the fact that mandatory surgery might be unacceptable for students contemplating an accelerated Mandarin class, wants to develop a noninvasive device to stimulate a peripheral nerve, perhaps in the ear. The goal is not just to hasten the learning of foreign languages but also to facilitate pattern-recognition tasks, such as combing through surveillance imagery.
Learning, of course, has nothing to do with laying down bits on a formatted magnetic disk. Sensory inputs to the eyes or ears set off a cascade of events that relays signals to various regions of the vast neural substrate of the brain’s some 86 billion neurons.
The first part of DARPA’s Targeted Neuroplasticity Training (TNT) program will consist of basic research. It will try to confirm that coursing an electric current through a peripheral nerve outside the central nervous system will eventually enable someone to perform a task such as distinguishing more rapidly whether the word ma in Mandarin has several meanings, such as mother (mā) or horse (mǎ), depending on the tonal inflections.
DARPA decided learning enhancement was worth pursuing because of published research that has shown that peripheral nerve stimulation can result in the production of signaling chemicals—neuromodulators such as norepinephrine—that aid in the rewiring that takes place during learning—“synaptic plasticity” to invoke the techie term of art.
I asked Doug Weber, who heads the TNT program at DARPA, about the difference between using a nerve-zapping device and taking modafinil, Ritalin or any other pharmaceutical compound that purportedly exhibits cognitive-enhancing properties. “The thing you can’t do easily with a pill that you can do very easily with neurostimulation is control timing and dosing,” Weber says. Swallowing the pill might ratchet up levels of acetylcholine, norepinephrine or other signaling molecules after they go through your system, but ingestion cannot be paired to the precise moment that a ma tone sounds.
Besides a cultural nod to The Matrix, TNT also evokes the current tech fad for neurohacking—downing a pill or donning headgear to improve cognition. If the online do-it-yourself crowd is to be believed, zapping the brain to help language learning has already gotten off to a desultory start. Try searching for the keywords “tDCS” and “language learning.” Then look for results such as a Reddit post entitled “Accelerating Foreign Language Learning with TDS.” Also, don’t miss “Did tDCS Give Me Dyslexia?”
Purchased or do-it-yourself, tDCS (transcranial direct-current stimulation) is the fad du jour for neurohackers. It channels a small electric current into the brain through two electrodes placed on the scalp. Many of the posts about tDCS are devoted more to the proper electrode placement on the scalp than the subtle differences of of mā versus mǎ.
Skepticism also pervades the published literature. A study published online on May 16 in Psychological Science showed little benefit from adding tDCS to a cognitive-training program for older adults. Weber says the TNT program intentionally avoided tDCS:
You’re applying this very small current to the scalp, and if you look at it from the standpoint of the path of least resistance, it means that most of it is going to be shunted through the scalp, and so your skin is going to absorb most of the charge. Very little, if any, will get through the skull because the skull is thick, and it’s a high-impedance barrier. And whatever current does trickle through the skull, which again is very little, will again be shunted through by the CSF [cerebrospinal fluid] and other fluid that sits between the neurons of the brain and the skull. So just from a pure physics standpoint, it’s magical to me that there’s any effect, whereas with peripheral nerves, we know exactly what the direct effects of stimulation are.
Even so, the researchers must still figure out what happens during the remapping of the neural connections that occur when we learn something—no small task. Detecting when signaling molecule levels increase—a sign that nerve stimulation may be having the desired effect—must be done by examining changes in pupil size and other indirect measures.
The closer one looks at what happens during the learning process, the more humility is in store. In May, I posted an interview with Falk Huettig of the Max Planck Institute for Psycholinguistics, a researcher who had just published a study about the enormous changes that occur in the brain when an illiterate adult learns to read. In addition to the questions Scientific American published online, I asked Huettig whether he thought a simple pulsing of electric current through a peripheral nerve would suffice to speed learning. “The hypothesis that vagal and trigeminal nerve stimulation allows people to learn foreign languages faster is certainly interesting but very much a long shot,” he told me.
Weber says the decision was made by DARPA to focus on a few areas, such as learning foreign languages, because peripheral nerve stimulation is thought to be a good candidate for enhancing the ability to discriminate sounds—again, the má versus mà challenge. He readily acknowledges that much is still unknown. It might be necessary, for instance, to take steps to ensure that the memory of a new skill is not quickly forgotten, perhaps by enhancing sleep in some way. But DARPA’s ambitions could still yield payoffs, Weber notes: “Any partial success in this program will have a high impact if we learn something new about how the brain adapts, acquires and refines cognitive skills.”