Reduced neural habituation in the amygdala and social impairments in autism spectrum disorders

Objective: Amygdala dysfunction has been proposed as a critical component in social impairment in autism spectrum disorders. This study was designed to investigate whether abnormal habituation characterizes amygdala dysfunction in autism spectrum disorders and whether the rate of amygdala habituation is related to social impairment. Method: Using functional MRI, the authors measured change over time in activation of the amygdala and fusiform gyrus to neutral facial stimuli in adults with autism spectrum disorders and healthy comparison adults. Results: The comparison group evidenced significantly greater amygdala habituation bilaterally than the autism spectrum group. There were no group differences in overall fusiform habituation. For the autism spectrum group, lower levels of habituation of the amygdala to the face stimuli were associated with more severe social impairment. Conclusions: These resul ts suggest amygdala hyperarousal in autism spectrum disorders in response to socially relevant stimuli. Further, sustained amygdala arousal may contribute to the social deficits observed in autism spectrum disorders.