Autism and the social brain: the first year puzzle

The atypical features of social perception and cognition observed in individuals diagnosed with autism have been explained in two different ways. First, domain-specific accounts are based on the assumption that these end-state symptoms result from specific impairments within component structures of the ‘social brain network’. Second, domain-general accounts hypothesize that rather than being localized, atypical brain structure and function is widespread, or that the apparent social brain differences are the consequence of adaptations to an earlier occurring widespread changes in brain function. Critical evidence for resolving this basic issue comes from prospective longitudinal studies of infants at-risk for later diagnosis. We highlight selected studies from the newly emerging literature on infants at familial risk for autism to shed light on this issue. Despite multiple reports of possible alterations in brain function in the first year of life, overt behavioral signs do not emerge until the second year. Our review reveals only mixed support, within this very early period, for localized deficits in social brain network systems, and instead favors the view that atypical development involving perceptual, attentional, motor, and social systems precede the emerging autism phenotype