ABSTRACT
The pioneers of ASD defined it as an affect disorder already manifested in infancy. Nevertheless, the idea that ASD is caused by some kind of cognitive deficit dominated for more than a century. Now it is well documented that ASD is associated with abnormalities in the brainstem which cause deficits in the ability for prospective movement coordination and affect attunement. The first specific signs of ASD appear from 6 months but become more apparent towards the end of the first year. Based on the heritability of the disorder, a flourishing line of research examines infant siblings of children with ASD. Data reveal that infants later diagnosed with ASD show impairments in imitation, imitation recognition, initiation and response to joint attention, functional play, symbolic play, and coordination of expressive modalities, as well as intersubjective synchrony. In ASD, deficits in prelinguistic communication skills predict serious problems in early language development. An early marker of the disorder is the uneven comprehension-production profile, which reveals fundamental deficits in social understanding.
