Objectives: Using event-related functional MRI (fMRI) and a task that provided a behavioral measure of attention to briefly presented faces, we evaluated differences in brain function between adults with ASD and controls. We hypothesized that participants with ASD relative to controls would show greater amygdala activation to emotional faces.
Methods: During fMRI acquisition, a probe detection task was used to derive a measure of attention to faces. Participants (12 with ASD and 12 controls) viewed pairs of faces (angry/neutral, sad/neutral, happy/neutral, and neutral/neutral) for 500 msec. They then pressed a button to an asterisk that was either on the same or opposite side as the emotional face. ASD participants were recruited through the UM Autism and Communications Disorders Center. ASD was diagnosed with the ADOS and ADI-R.
Results: There were no group differences in the behavioral measure of attention. Relative to controls, participants with ASD showed greater right amygdala activation to sad faces (p<.05 small volume corrected) and trends in the same direction to other emotions. Moreover, amygdala activation to sad faces positively correlated with severity of social impairment. Finally, a connectivity (psychophysiological interaction) analysis showed that adults with ASD, relative to controls, had greater positive coupling between the right amygdala and visual processing structures (visual cortex and temporal lobe) and less positive coupling between the right amygdala and ventral prefrontal cortex.
Conclusions: When emotional faces are briefly presented and there are no group differences in attention, adults with ASD show greater amygdala activation than controls. Furthermore, ASD is associated with altered amygdala-cortical interactions.