It's a familiar feeling: the cautious impulse to hit the brakes when the highway begins to curve, or the urge to watch your step when stepping off an escalator. Now, researchers say they've identified the region of the brain that prompts us to be extra careful in tricky situations.
The anterior cingulate cortex (ACC)-–an area located near the top of the brain's frontal lobes-– has long been known to help detect mistakes in action--such as hauling the wrong suitcase off an airport carousel. Now, using a combination of computational modeling and brain imaging studies, cognitive neuroscientists Joshua Brown and Todd Braver at Washington University in Saint Louis, Missouri, have shown that the ACC can also predict-–based on past experience-- how likely the person is to goof up on a given task.
For the study, published today in Science, the researchers showed participants a computer screen with a horizontal line that developed an arrowhead after a few seconds. As soon as this happened, participants had to press a right or a left button corresponding to the direction of the arrow. On some trials, a more prominent second arrow appeared soon after the first, positioned right above the first arrow and pointing in the opposite direction. If that happened, participants had to change gears and press the other button. The longer the delay between the first and the second arrow, the more committed the participants became to pressing the first button and the harder it was for them to change their response mid stream.
Easier trials displayed arrows of a particular color, while those with a greater chance of error used a different color. Functional MRI of the participants' brain activity showed that the ACC became more active when the color associated with the higher error rate was presented--an effect that grew stronger over hundreds of trials.
"The ACC seems to learn from experience when the chances of making a mistake might be high," says Brown. He speculates that the ACC communicates this alert to other parts of the brain, leading to an adjustment of behavior such as slowing down on the highway.
It's "a clever and innovative study," says Matthew Botvinick, a psychologist at the University of Pennsylvania in Philadelphia. "The challenge now is to come up with a comprehensive account of ACC function."
Joshua Brown's homepage