Understanding neural activity behind behavior
By Graciela Gutierrez
A game is more than just child's play inside the lab of Dr. P. Read Montague, Jr., professor of neuroscience, and director of the Brown Human Neuroimaging Lab and the Computational Psychiatry Unit at Bayor College of Medicine. Each game contains the key to understanding the ways in which people behave and the neural activity with which they correlate.
To evaluate those diagnosed with disorders such as borderline personality, autism and even addiction, researchers use a trust game. It allows those taking part to exchange monetary units while their brain activity is being recorded using fMRI (functional magnetic resonance imaging). This information is then used to look at how people's brains react when interacting with each other.
In his latest study, which appeared in the journal Proceedings of the National Academy of Sciences, Montague and his colleagues looked at the neural actions behind a person's behavior when he or she is threatened.
How we behave
There are always unintended consequences when punishment is used to motivate certain actions, said Montague.
"Someone can make you show up to work on time by docking your pay when you are a few minutes late," he said. "You may show up on time but you are more likely to then act in a way to make yourself come out on top. In this case, that means a lack of cooperation."
For the study, the investor gives the investee a certain amount of units that will earn interest. A request for a return of a portion of interest earned follows. Usually, you would expect that the interest would be split evenly between the two players.
However, the investor makes three decisions before giving the investee any monetary units. He or she decides the amount of money to invest, the amount of money to request back and whether or not to impose a threat, meaning taking a set amount from the investee, regardless of how that person responded.
As expected, the investee was less likely to cooperate when threatened.
"The difference is greater when the investment is larger," said Montague. "Once you get to the point where splitting the amount becomes unfair, cooperation begins to drop."
Brain's reaction
Activity in the brain reflected the person's actions. Several brain regions were significantly more active when a non-threat exchange took place and less active when a threat was involved.
One area in particular, the ventral prefrontal cortex that is responsible for evaluating uncertain situations, was a good indication of a person's decision when faced with a threat.
"By looking at that area and how the brain was functioning, we were able to predict how the investee would react," said Montague.
Step toward understanding
One implication of these findings is that the study gave the researchers a better understanding of how the trust game can be used to understand social interactions.
One aspect of the game that is now in use is to focus not only on the person with the developmental or behavioral disorder, but also at the healthy person playing along with them.
"A person with an addiction or mental illness isn't the only one affected. Their families or friends are thrust into this social situation where the dynamic is altered," Montague said. "By looking at the healthy person's brain activity, we can see whom they are interacting with – someone with autism or even someone from a different culture."
The game could also be used to understand the genetics of mental illness and disorders.
"Instead of looking for genes associated with neural function, we look for genes associated with behavioral function that co-vary with neural function, and we use those to say what is different genetically."
Others who took part in the current study include, Drs. Jian Li, department of psychology, New York University; Erte Xiao, department of social and decision sciences, Carnegie Mellon University; and Daniel Houser, interdisciplinary center for economic science, George Mason University.
The research was supported by grants from the Kane Family Foundation, the National Institute of Neurological Disorders and Stroke and the National Institute on Drug Abuse.
Montague holds the Brown Foundation Chair of Human Behavioral Neuroscience.
