The amygdala, autism and anxiety.

Brothers has proposed that the amygdala is an important component of the neural network that underlies social cognition. And Bauman and Kemper observed signs of neuropathology in the amygdala of the post-mortem autistic brain. These findings, in addition to recent functional neuroimaging data, have led Baron-Cohen and colleagues to propose that dysfunction of the amygdala may be responsible, in part, for the impairment of social functioning that is a hallmark feature of autism. Recent data from studies in our laboratory on the effects of amygdala lesions in the macaque monkey are at variance with a fundamental role for the amygdala in social behaviour. If the amygdala is not essential for normal social behaviour, as seems to be the case in both non-human primates and selected patients with bilateral amygdala damage, then it is unlikely to be the substrate for the abnormal social behaviour of autism. However, damage to the amygdala does have an effect on a monkey's response to normally fear-inducing stimuli, such as snakes, and removes a natural reluctance to engage novel conspecifics in social interactions. These findings lead to the conclusion that an important role for the amygdala is in the detection of threats and mobilizing an appropriate behavioural response, part of which is fear. If the amygdala is pathological in subjects with autism, it may contribute to their abnormal fears and increased anxiety rather than their abnormal social behaviour.