[The social deficit in autism: focus on joint attention]

Autism is best thought of as a spectrum disorder with the dimensional components of social cognition, communication and flexibility varying between individuals meeting the criteria of autism. The core clinical feature that defines autism is a disturbance in social interaction which is not absolute and differs depending on a child's cognitive level, developmental stage, and the type of social structure in which they are observed. Social skills are under strong genetic influence with a continuous distribution of social interaction deficits in the general population with arbitrary cutoffs defining who is and is not affected with an autism spectrum disorder; this is the result of a complex interplay between numerous biological and environmental factors. Joint attention refers to the capacity of individuals to coordinate attention with a social partner in relation to some object or event and a disturbance in this early skill and in particular impairment in the ability to initiate joint attention, is a central symptom of autism.

There are data to suggest that dorso-medial frontal cortex and anterior cingulate contribute to the development of an infant's ability to maintain representations of self, a social partner and an interesting object. The ability to engage frequently in social orienting behaviors and ultimately in numerous episodes of social attention coordination, or joint attention, may be a critical experience during a particular developmental window that serves to organize social neurodevelopment. A neurodevelopmental model explaining how these early deficits in social cognition may lead to autism is reviewed.