Trust game in laboratory advances knowledge of brain signatures

"This may be the first time a physical signature for a personality disorder has been identified," said Dr. P. Read Montague, professor of neuroscience at Baylor College of Medicine and director of the BCM Brown Foundation Human Neuroimaging Laboratory. "For the first time, to my knowledge, we have a specific brain association for people with a personality disorder," said Dr. Stuart Yudofsky, chair of the Menninger Department of Psychiatry & Behavioral Sciences at BCM.

The scan casts a new light on the neurobiology of borderline personality disorder, said Dr. Brooks King-Casas, the studys lead author. He said the finding could be used as a future diagnostic tool or even a way to determine the effectiveness of a treatment.

"It's important that this biological signature has been identified," said Dr. King-Casas. The scientific finding provides further evidence that severe mental illness is "not just a matter of bad attitudes or a lack of will."

The finding may help eliminate the stigma associated with such disorders.

People with borderline personality disorder suffer from an inability to understand the actions of others. They frequently have unstable relationships, fly into rages inappropriately or become depressed and cannot trust the actions and motives of other people.

"We have great strength in the area of personality disorders through our relationship with The Menninger Clinic," said Dr. Yudofsky. Study co-author Peter Fonagy, PhD, director of Menninger's Child & Family Program, is a pioneer in treating borderline personality disorder using mentalizing, by which we manage such feelings as frustration, anger, sadness, anxiety, shame and guilt without resorting to automatic fight-or-flight responses or ways of coping that are ultimately self-destructive. Mentalizing appears to be a key human capacity.

Others who took part in this work include Carla Sharp, PhD, director of research at Menninger's Adolescent Treatment Program, and Laura Lomax and Terry Lohrenz of BCM. Funding for this work came from the Child & Family Program at The Menninger Clinic, the National Institute of Mental Health, the National Institute of Neurological Disorders and Stroke and the National Institute on Drug Abuse.

In the study, people with borderline personality disorder played a "trust" game with healthy people of the same age and social and educational status.

In the game, one player called an investor sends $20 to the other called a trustee. The investment is tripled, and the trustee splits the profits with the investor. The trustee decides how much to send back, thus determining whether the investor recoups a profit or not. Profit requires cooperation between trustee and investor.

Both investor and trustee play the game while their brains are scanned by fMRI devices through use of software called hyperscanning. The fMRI shows areas of blood flow in parts of the brain during the interaction between two people.

In this study, activity in an area of the brain called the anterior insula, known to respond when "norms" are violated, showed up on the scans. In the healthy people, the anterior insula showed activity that responded in direct proportion to the amount of money sent and the money received. However, in people with borderline personality disorder, that part of the brain responded only to sending the money-not to the money received.