Obessions, Compulsions? Anterior Cingulate Reacts to Costly Mistakes, April 15, 2006
It happens to all of us, no matter how hard we try. Whether it's deleting a computer file and realizing a split-second later that we can't get it back, or dropping a bag of groceries, or realizing that our gas tank is nearly empty on a lonely stretch of highway, we all make mistakes that aren't just annoying, but potentially costly.
Now, a team of University of Michigan researchers has looked inside the human brain and captured the instant when someone makes a costly mistake. What they've found is interesting by itself, but may also help scientists understand mental health problems such as obsessive-compulsive disorder, or OCD.
In general, the U-M scientists found that a particular part of the brain called the rostral anterior cingulate cortex, or rACC, becomes much more active when a person realizes he or she has made an error that carries consequences - for instance, losing money.
By contrast, the same area of the brain doesn't show the same level of activity when the mistake doesn't carry a penalty, or even when a correct action carries a reward. The rACC is thought to be involved with emotional responses, and scientists had suspected it might also be involved in response to costly errors. But this is the first brain-imaging study to test that idea.
Interestingly, the U-M team had previously shown that the rACC area became much more active in response to a no-penalty error in the brains of a small group of OCD patients, compared to people without the condition. OCD is often characterized by an untoward anxiety or fear about errors or failures in certain aspects of everyday life, with repetitive patterns of behavior to ward off or prevent such events.
The new research, published in the Journal of Neuroscience, involved 12 healthy adults who had their brains scanned using a powerful functional MRI (fMRI) imaging machine, while they were asked to respond to a series of 360 visual-based tests.
Some of the tests carried a monetary reward between 25 cents and $2, while others carried penalties of the same size. Still others carried no reward or penalty. The participants were told they had a $10 "credit" to begin, and that they would receive real cash depending on their balance at the end.
The participants had to correctly, and within a deadline of a few hundred milliseconds, press a button corresponding to one of two alphabetic letter pairs. They were instructed to determine which letter was the odd one out in a series of other letters. Some of the letter sequences were more confusing than others. They received immediate feedback telling them if they were wrong or too late in responding.
"In general, the response to a mistake that cost them money was greater than the response to other mistakes, and the involvement of the rACC suggests the importance of emotions in decision and performance-monitoring processes," says Stephan Taylor, M.D., an associate professor in the Department of Psychiatry at the U-M Medical School and lead author of the new paper. "It's very interesting to us that the same part of the brain that responded in our OCD study on regular, no-cost errors also responded in healthy individuals when we made the error count more."
The new research confirms previous U-M studies using a different brain-activity monitoring technique and led by senior author William Gehring, Ph.D., Arthur F. Thurnau Professor of Psychology in the U-M College of Literature, Science, and the Arts and director of the U-M Human Brain Electrophysiology Laboratory.
For more than a decade, Gehring has used a measuring tool known as the event-related potential or ERP to study brain responses to various situations, assessing changes in electrical activity through sensors arranged on a mesh cap that is placed on the head. The method is similar to techniques used to study the brains of people with epilepsy or sleep problems, but the electrical signal from the brain is processed in a different way. In prior studies, Gehring and his colleagues observed a distinct brain electrical response to errors, dubbing it ERN for "error-related negativity."
Using ERP, Gehring and his colleagues localized the brain's response to errors to the vicinity of the rACC, a larger region of the brain known as the medial frontal cortex. Working with Joe Himle, Ph.D., and Laura Nisenson, Ph.D., from the U-M Anxiety Disorders Program in the Department of Psychiatry, he performed a study in OCD patients that showed heightened response to errors in the same area.
Now, the fMRI technique has allowed the researchers to localize this response even more precisely. The fMRI scanner uses magnetic fields to create images based on blood flow, and can detect tiny changes in the rate of blood flow in and out of various areas of the brain. The more blood flowing to a specific area, the more active the cells in that area are - and therefore, the more processing that is going on in those brain cells.
"We hypothesized that the brain response to errors was involved in an emotional reaction to making an error," says Gehring. "Our new fMRI result not only confirms this, but it also allows us to pinpoint the area in the brain that shows the exaggerated error response."
Taylor, who treats patients with psychiatric disorders, says the next step is to study patients using the same test as was used in healthy participants. The researchers also hope to study the impact of cognitive behavioral therapy, a form of "talk therapy", on OCD patients' response to errors. They are currently recruiting participants for that study.
"It appears to us so far that OCD patients may have a hyperactive response to making errors, with increased worry and concern about having done something wrong," he says. "We hope that this kind of research will help us get a handle on this condition and see which normal brain circuits have gone awry in people with OCD." The new finding does not have immediate implications for the treatment of OCD, Taylor cautions, but further research could help lead to more tailored treatment designed for each patient. The research team hopes to study people with depression as well.