Detection of Negative Emotions in Autistics: Questioning the ‘Amygdala Hypothesis’

Abstract

Autism and Asperger’s Syndrome (AS) are neurodevelopmental conditions that are marked by social and communica- tion problems that involve difficulties with facial emotional processing, as well as restricted interests and behaviors. There have been conflicting reports in the literature regarding the perception of basic emotional expressions with some studies showing differences between the autistics and normal participants while others show no such differences. There have also been some reports of deficits in the processing of basic negative emotions in autism like fear, sad- ness and anger. These deficits shown by autistics are comparable to deficits shown by people with amygdala damage. These comparable deficits have led to the formulation of the ‘amygdala theory in autism’. However, a strong form of the amygdala hypothesis in autism still requires experimental evidence of distinctions between ‘subjective’ and ‘objective’ awareness of negative emotional stimuli. In some studies the activation in the amygdala is found when participants are subjectively unaware of the fearful faces but not when they are objectively unaware. Previous studies that have been conducted to investigate the facial emotion recognition deficits in autism in order to support the amygdala hy- pothesis have relied on the percentage correct values of the autistic subjects, which are known to be highly sensitive to response bias. Performance when evaluated according to standard signal detection methods provides a measure of sensitivity that is independent of a subject’s response bias. Only the latter methodology can provide a stringent test of the amygdala hypothesis.