Differential fear conditioning in Asperger's syndrome: implications for an amygdala theory of autism.

Since the first descriptions of individuals with autism spectrum disorders (ASD), abnormalities in socio-emotional behaviours have been described as amongst the most characteristic clinical features of this condition. Current evidence in this area suggests that individuals with ASD experience difficulties in the perception and expression of emotions within the social domain. The causes for these emotional difficulties are, however, still poorly understood. At the developmental level, it is unclear whether emotional disturbances constitute a primary feature of the clinical presentation of ASD or whether they are secondary to abnormalities in other areas of cognition. At the neurobiological level, it is still debated to what extent abnormalities of the limbic system, in particular the amygdala, may be responsible for the emotional disturbances characterising ASD. Here we show that a group of individuals with Asperger's syndrome exhibit a pattern of abnormality in differentially acquiring fear, which suggests that their fear responses are atypically modulated by conditioned and non-conditioned stimuli. On the basis of these results and the existing literature we suggest that ASD may be characterised by atypicalities in the integration of physiological and cognitive aspects of emotional experiences which we argue arise because of poor connectivity between the amygdala and functionally associated cortical areas.