Functional MRI reveals clues to social behavior

Hyperscanning allows multiple subjects in separate MR scanners to interact with one another

Researchers are increasingly relying on functional MRI to explore ties between abnormal neural development and chronic psychiatric illness. New research detailing the brain's activation during social interaction is adding to an understanding of psychiatric and developmental disorders that are social in nature.

For example, children with bipolar disorder routinely misinterpret neutral faces as hostile, based on the results of a study conducted at the National Institute of Mental Health (PNAS 2006;103:8900-8905). Evaluation with fMRI showed that the left amygdala, a fear hub, was the most active brain area of those with the disorder.

The more patients misinterpreted the faces as hostile, the more their amygdala flared. The results implicate deficient emotion-attention interactions in the pathophysiology of bipolar disorder in young patients and suggest that developmental psychobiology approaches to chronic mental illness have broad applicability.

"By finding a brain imaging trait that may be more selective than current clinical criteria, this line of research might help us refine our definition of pediatric bipolar disorder," said Dr. Thomas Insel, director of the NIMH.

In a separate study investigating the link between brain and behavior during a social exchange, scientists at Baylor College of Medicine developed an fMRI technique called hyperscanning (Science 2006;312;969-1069). Hyperscanning software uses the Internet to allow one scientist to control multiple scanners, even if they are located thousands of miles apart in different centers. The scientist running the experiment controls the nature and the timing of the sensory stimuli that are delivered to the subjects. The same researcher also controls the initiation and termination of scanning in each of the scanners and receives all of the data generated by the scanners.

The technique was used by the Baylor researchers to map where trust forms in the brain. The team evaluated responses between people in Texas and California who were hooked up to MR scanners. The neural mechanisms of trust were activated when one person gave an amount of money to the other and that person decided how much of that money to keep and how much to give back. The cingulate cortex, which is known to be involved in bonding and social interactions, generated a signal while the trust exchange was going on. That signal foretold what the person was going to do on the next play.

"It was an intentional signal. It said that this was their intention to either increase or decrease their trust," said P. Read Montague, Ph.D., a professor of neuroscience at Baylor and lead author of the study.

Researchers posit that this "social agency map" in the brain keeps track of who is responsible for an outcome during a social exchange between two interacting partners. The finding may provide insight into conditions such as schizophrenia, autism, and borderline personality disorder, where the capacity to model or trust others is broken or performing pathologically.