New Review Examines the Theory of Hypoactive vs. Hyperactive Amygdala
A tendency to avoid eye contact is often an early indicator of autism in young children. Difficulties with eye contact frequently continue through the lifespan, creating challenges for social interactions for people on the spectrum. A new review published in the Journal of Autism and Developmental Disorders examines conflicting evidence of two contradictory theories on why individuals with autism avoid eye contact. One theory suggests that reduced eye contact is a direct result of a hypoactive (under-active) amygdala, which reduces the importance of the eyes in social and communication development. The other hypothesis suggests the exact opposite. Instead, this theory believes that an hyperactive (over-active) amygdala causes an unpleasant arousal or over stimulation, which leads to eye contact avoidance. After analyzing eleven studies on the topic, the paper’s authors provide evidence against the hypoactive amygdala theory, since none of the reviewed studies observed reduced amygdala activity in participants with autism compared to neurotypical controls. Conversely, eight out of the eleven studies supported the hyperactive amygdala hypothesis. Specifically, two studies showed that amygdala activity is positively related with visual attention to the eye region in individuals on the spectrum, but not with neurotypical controls. Three other studies discovered amygdala activity and/or activity in the subcortical threat detection was increased in people with autism but not in controls when gaze was directed to the eye region of fearful or grotesque faces. Evidence taken from the remaining studies demonstrates that the amygdala activity precedes subsequent gaze away from the eye region of facial stimuli for those on the spectrum, which indicates that eye avoidance is a strategy utilized to manage amygdala-mediated over-arousal. The authors suggest that eye avoidance is likely to reduce opportunities for social interaction among children with autism, which most likely will cause negative developmental effects for the social brain.
