ABSTRACT
Abstract The unfolding of behavioral features associated with autism spectrum disorder (ASD) occurs in the latter part of the rst and in the second years of life. This dramatic shift in symptom presentation suggests underlying neuroanatomical and functional brain changes that either precede or cooccur with the emergence of aberrant behavioral features. In this chapter we will review recent literature on the neurodevelopment of ASD, particularly focusing on longitudinal studies since brain development is nonlinear during this time period. Key results to date include ndings indicating that sometime before two years of age the brain undergoes a period of overgrowth. Infant-sibling research studies have identied abnormal development of white matter ber tracts, corpus callosum size, and extra-axial uid as early as six months of age. These ndings indicate that it may be possible to use brain features in the rst year of life to predict ASD, providing a means to identify infants for very early intervention studies with the hope of improving long-term outcomes.
