What if your “thinking cap” wasn’t just something you figuratively put on when you had to think hard and focus on something? A new study shows that it’s possible to selectively manipulate our ability to learn by applying mild electric currents to the brain.
There’s a part of our brain that makes us go “oops!” when we make a mistake. Previous studies have shown that the medial-frontal cortex lets out a spike of negative voltage milliseconds after we make a mistake.
Robert Reinhart and Geoffrey Woodman from Vanderbilt University wanted to see if this particular activity influences learning -- since it seems to allow the brain to learn from our mistakes. “And that’s what we set out to test: What is the actual function of these brainwaves?” Reinhart says in a press release. “We wanted to reach into your brain and causally control your inner critic.”
They designed a series of experiments to test out a couple hypotheses. First, they wanted to show that it’s possible to control the brain’s electrophysiological response to mistakes. And second, they wanted to see if the effect could be enhanced or diminished just by changing the direction of electrical currents.
So, they used an elastic headband to secure two electrodes -- conducted by saline-soaked sponges -- to the cheek and the top of the head of volunteers. Then they applied the very mild “transcranial direct current stimulation,” which travels from the anodal (+) electrode through the skin, muscle, bones, and brain, and out through the corresponding cathodal (-) electrode. (This noninvasive method of stimulating the brain may, at most, cause a few seconds of tingling or itching at the beginning.)
The volunteers were treated three ways: with an anodal (current traveling from the crown of the head to the cheek), cathodal (cheek to crown), or a sham condition that replicated the tingling sensation without affecting the brain. After 20 minutes of stimulation, the subjects were given a learning task: using trial and error, figure out which buttons on a game controller goes with which colors displayed on a monitor. Occasionally there would be a signal to not respond (like a reverse “Simon Says”), and they had less than a second to respond correctly. All the while, the researchers were measuring their electrical brain activities. Ample chances to make mistakes means many opportunities for the medial-frontal cortex to fire.
When anodal (crown to cheek) current was applied, the spike was almost twice as large on average and significantly higher in 75 percent of the subjects. They made fewer errors, and learned from their mistakes more quickly than they did after the sham stimulus. The team saw opposite results when cathodal (cheek to crown) current was applied. The spike was significantly smaller; the volunteers made more errors and took longer to learn the task.
“So when we up-regulate that process, we can make you more cautious, less error-prone, more adaptable to new or changing situations -- which is pretty extraordinary,” Reinhart says. The duo also found that the effect lasted about five hours.
The work was published in the Journal of Neuroscience last week.
Image: John Russell/Vanderbilt University