Direct current applied to the scalp polarizes underlying brain tissue, creating either a positive or a negative charge near the electrode. In vitro studies have shown that a weak current can substantially change the firing rate of neurons–with an increase or decrease in firing rate that depends on the orientation of the electric field. Evidence suggests that increases in firing enhance local brain function and decreases do the opposite.
Zapping brains is not new. In the 1960s, low-level direct current was used to treat mental disorders, but investigators became more interested in chemical treatments until recently, when neuroscientists and clinicians began looking for targeted brain boosters with fewer side effects than pills. Wassermann thinks that one day we will be able to buy a tiny device that can be inserted into a hat or attached to a headband and turned on when we need a brain boost.
My Brain, Altered
I feel a slight uptick, like a medium hit of caffeine; it gently lifts the fog of my fatigue, though I don’t feel any smarter. I settle down to take some tests of cognition and emotion. Most telling is a gambling game that presents four virtual decks of facedown cards on a computer screen; when I click on them, cards turn over, and I either win money or lose it, depending on the card. A ticker measures my winnings at the top of the screen. At first the cards seem random, but then patterns develop: I need to figure out which stacks will yield more gains than losses, and vice versa. After a few minutes, my initial mild boost dissipates. I lose at the gambling game, though not by much. The next morning I return after a good night’s sleep. Taking the gambling test sans stimulation, I win a modest amount of virtual cash.
Later that second day I participate in a third experiment. Instead of running a negative current through the electrodes attached to my forehead, as he did the first time, Koenigs applies a positive current. The effect on my frontal lobe causes a noticeable sense of relaxation and a drop-off in motivation as I play the gambling game. Oddly enough, I win big anyway. I also experience a strange sensation when I begin speaking to the researchers: I’m starting sentences and then losing my motivation to finish them. Koenigs says this is exactly what his experiment is trying to show: that performance is affected differently by different currents. I suspect my results have more to do with yesterday’s exhaustion versus today’s well-restedness, but the electricity has noticeably messed with my mind.
The day after that, I’m in New York City in the office of Steven Lamm, a physician who advocates the prescription of Provigil for patients with sleep disorders, persistent fatigue, or jet lag. “I would like to prescribe it more than I do,” he says, “but because it has only been approved for severe sleep disorders, insurance doesn’t cover the cost of the drug for many of my patients.” Lamm has used Provigil himself when he is jet-lagged or short on sleep and needs to be sharp. “It is unhealthy to not get enough sleep,” he tells me, “but sometimes it can’t be helped.” Lamm checks my blood pressure and takes a history, tells me about the drug, and scribbles out a prescription for five 200-milligram tabs.