This investigation will focus on two areas: 1) early communication impairments as predictors of autism spectrum disorder (ASD) and later developmental delays, and 2) the relationship between communication and evidence of CNS function (sleep, EEG) and structure (MRI DTI and volumetrics) in young children at risk for ASD. The objective is to delineate early communicative impairments that predict ASD vs. other developmental delays and to examine how these impairments correlate with brain abnormalities in both structure and function.