Reported in the online edition of the journal Social Neuroscience, the study implicates abnormalities in the brain's inter-regional communication system, which connects the gray matter's computing centers.
"The communication between the frontal and posterior areas of the social brain network is impaired in autism, making it difficult to understand the intentions of others," said study's senior author Marcel Just, the D.O. Hebb Professor of Psychology at Carnegie Mellon.
This is the first time that a study has measured the synchronization between the brain areas that make up the Theory of Mind (ToM) network, which is responsible for processing the intentions and thoughts of others, and has provided such concrete evidence of faulty social network connections.
For measuring the ToM network's effectiveness, the researchers asked 12 high-functioning autistic adults and 12 control participants to view animations of interacting geometric figures, and then asked them to select the word from several choices that best described the interaction.
A large triangle, for instance, would nudge a small triangle to move outside its enclosure, and the correct word choice would be "persuading".
The researchers observed that he control subjects were consistently better at inferring the intention from the action than their autistic counterparts.
Functional magnetic resonance imaging (fMRI) was used to measure activation levels in all of the cortical areas that compose the ToM network, while the subjects were performing the task.
To determine the synchronization levels in the network, activation levels in several frontal and posterior brain regions were examined simultaneously.
The researchers found that the synchronization was reliably lower in the group with autism.
They also observed that the autistic participants' brains showed much lower activation levels than their counterparts in the frontal regions.
The measures of brain activity in autism, such as the activation level in the posterior part of the ToM network, were correlated with how well each autism participant performed in the Happe's Strange Story Test - a pencil-and-paper assessment of an individual's understanding of non-literal statements, such as figures of speech.
"This study offers compelling evidence that a lack of synchronization in the Theory of Mind network is largely responsible for social challenges in autism. That evidence can provide the foundation for therapies that are more useful than current approaches," said Just, director of Carnegie Mellon's Center for Cognitive Brain Imaging.
According to the research team, the new findings go to suggest that it just might be possible to tailor autism therapies to the brain communication deficit on a case-by-case basis.
Measuring the connectivity before and after an intervention also could be used to determine effectiveness, they say.