"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.
The finding sprigs from a study during which 55 people with borderline personality disorder played a "trust" game with 55 normal people of the same age and social and educational status.
In the game, one player called an investor sends 20 dollars 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.
While the people played the game, their brains were scanned with the help of functional MRI devices and software called hyperscanning.
The scans a revealed a brain malfunction associated with the disorder, a serious but common mental illness that affects a person's perceptions of the world and other people.
During the 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 normal 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
King-Casas says that the scan provides fresh insights into the neurobiology of borderline personality disorder, which may someday be used as a diagnostic tool or even a way to determine the effectiveness of a treatment.
"It's new and different because it's not a lesion (or injury to the brain) but it is a difference in perceiving information that comes from an interaction." That is the area where people with borderline personality disorder have the most problem," said Dr. Stuart Yudofsky, chair of the Menninger Department of Psychiatry and Behavioral Sciences at BCM.
A research article on this study appears in the current issue of the journal Science.