Scientists last week reported an exciting innovation for autism research in a study that scanned the brains of people with autism during social interactions. The study, funded in part by Autism Speaks, revealed a reduced brain signal in people with autism that might be related to their sense of self. The study appeared as the cover article in the high-profile journal Neuron, and heralds a new tool for understanding why individuals with autism have difficulty in social interactions.
"It's the first time anyone's actually engaged kids with autism in a social exchange as they're being scanned," said first author Pearl Chiu, Ph.D., of the Computational Psychiatry Unit (CPU) at Baylor College of Medicine. While scanning people with autism using functional magnetic resonance imaging (fMRI) is commonplace, this study goes further by monitoring their brain activity while they interact with another person. In fact, both people's brains were scanned simultaneously, using a method called "hyperscanning" which was pioneered by the senior author of the study and director of the CPU, P. Read Montague, Ph.D. Hyperscanning allows scientists to "eavesdrop on both brains at once," said Dr. Montague, providing essential data for understanding the neural underpinnings of social exchange.
To study social interactions in the confined space of a fMRI scanner where it is crucial for the head to remain still, subjects in separate scanners played an interactive trust game while watching screens and using toggle buttons to relay their responses to each other, in a setup reminiscent of online video gaming. This trust game involves exchanges of money between two players, and has been used to characterize and quantify reciprocal interactions between people. "It's designed to probe social exchange, social interaction, reciprocity, and sensing and responding to social signals," said Dr. Montague.
The new study found that adolescent boys with high-functioning autism could understand and play the game successfully, performing similarly to age- and IQ-matched controls. Even though their game playing was normal, however, their brain activity was not. Scanning during the task revealed unusually quiet activity in a portion of the cingulate cortex, a part of the brain thought to mediate social cognition. This occurred just after the autistic individual decided on the amount of money to give to his partner in the other scanner. In contrast, control subjects displayed high activity in the same situation. This particular brain activity was termed a "self response" because it occurred whenever a person made a decision of their own, but not when presented with the decision of their partner.
The discrepancy between normal game playing and abnormal brain signals points to key differences in how the subjects with autism processed the social interaction. "It's almost as though they can mimic what needs to occur in a social interaction, but the deeper attribution of that interaction to themselves is absent," said Dr. Chiu, who also pointed out that each subject had been in intensive behavioral therapy to learn appropriate social behaviors. The diminished "self responses" in the individuals with autism resembled the decreased responses observed in control subjects when they play a computer that does not reciprocate as a human would, said Dr. Montague.
The researchers speculate that the decreased self responses reflect an impaired sense of self in autism, which could lead to difficulties in navigating social situations. For example, making good guesses about another person's intent is a key skill during a social interaction, and this ability likely draws from awareness of one's own intentions. Consistent with this idea, the strength of the "self responses" in the individuals with autism correlated with their symptom severity: those with the most reduced “self response” activity had the most severe symptoms in the social and communication domains.
The brain circuitry that mediates social behavior is still a mystery, which is why Dr. Montague's technique is so important. The innovative combination of game playing and hyperscanning can effectively probe the social difficulties that are some of the most defining features of autism. Now that social interactions can be imaged inside the lab, these powerful techniques—with a willing cadre of volunteers with autism—can begin to examine the brain mechanisms of social exchange, leading to a better understanding of why people with autism struggle in social situations. The more we understand why individuals with autism have difficulty in social interaction, the better we will be able to design interventions that can help overcome this difficulty.
–Michele Solis, Ph.D.