Association Between Amygdala Activation in Response to Emotional Faces and Social Anxiety in ASD

Background:  Difficulty evaluating and interpreting facial expressions has been reported in autism spectrum disorders (ASD) and is thought to be associated with amygdala abnormality. However, previous fMRI studies of emotional face matching in ASD have reported reduced fusiform activation and increased activation of the precuneus, but no difference in amygdala activation.

Objectives:   fMRI was used to explore the neural basis of abnormal emotional face processing in ASD and to determine the effect of social anxiety on amygdala activation.

Methods:   During fMRI scanning, 29 individuals with ASD and 25 normal controls viewed Ekman faces depicting fear or anger.  Subjects were instructed to select which of two faces at the bottom of the screen portrayed the same emotion as the face at the top of the screen. The control condition consisted of a simple shape-matching task.  In addition, participants were administered the Social Avoidance and Distress Scale (SADS).   

Results: The ASD group reported significantly more social avoidance and distress on the SADS than the control group (p < 0001). For the comparison of emotional faces vs. shapes, controls evidenced significantly more left prefrontal activation than the ASD group and significantly less activation in the left precuneus, left cuneus, and bilateral lingual gyri. fMRI analyses were also conducted with the SADS total score entered as an independent variable. For the ASD group, greater social avoidance and distress was associated with increased activation in right amygdala and decreased activation in fusiform face area.

Conclusions: Overall, these findings support previous work indicating that individuals with ASD exhibit reduced prefrontal activation and increased activation in sensory cortices while performing cognitive tasks, in comparison with typically developing controls. The correlation between social anxiety and activation in the fusiform and amygdala suggests that level of social anxiety is critically related to functional abnormalities in these brain regions.