Kim M. Dalton of the University of Wisconsin-Madison and her colleagues studied 27 autistic teenagers who looked at pictures of faces (see image) while a magnetic resonance imaging (MRI) machine scanned their brains. The researchers also tracked the subjects' eye movements as they studied the images. "This is the very first published study that assesses how individuals with autism look at faces while simultaneously monitoring which of their brain areas are active," Dalton says. When the image included a direct gaze from a nonthreatening face, brain activity in the amygdala--a brain region associated with negative feelings--was much higher for autistic children than it was in members of the control group. "Imagine walking through the world and interpreting every face that looks at you as a threat, even the face of your own mother," remarks study co-author Richard Davidson, also at UW-Madison.
The results also indicate that a brain area associated with face perception, known as the fusiform region, is fundamentally normal in autistic children; it does exhibit decreased activity, however. Davidson notes that this could result because the over-aroused amygdala makes an autistic child want to look away from faces. In addition, he comments that it was surprising that "when subjects with autism averted their gaze away from the eye region of a face, they showed reduced activity in the amygdala, suggesting that the gaze aversion is serving a functional purpose." The findings are published today in the journal Nature Neuroscience.