Inter- and intra-hemispheric connectivity and language in children with autism spectrum disorder.

Prior studies have demonstrated a role for the corpus callosum, the largest fiber bundle connecting the two hemispheres, in left lateralization of language and language abilities. Aberrant corpus callosum size and intra-hemispheric language connectivity via the arcuate fasciculus (AF), and reduced language lateralization have been found in autism spectrum disorder (ASD). The relationship, however, between inter- and intra-hemispheric connectivity of language regions has not been fully explored, particularly in ASD. Structural pathways were examined in 53 children with ASD and 49 typically developing children, 3-17 years. We examined inter- and intra-hemispheric pathways in relation to the neurocorrelates of language (i.e. connecting left and right inferior frontal gyrus and left and right posterior superior temporal gyrus and the AF) and language abilities. Inter-hemispheric pathway integrity was related to left and right AF in controls but showed a weaker relation with the right AF in ASD. However, there were no group differences in individual pathway integrity. In both groups, language was associated with left AF integrity. Further, differences in AF pathway integrity differed in the severely language impaired ASD subgroup. Our findings suggest possible decreased cohesiveness in the language network in ASD, with more studies needed examining the relation between various pathways, rather than just differences in individual pathways. Deficits in the integrity of the AF may be involved in prevention of typical development of language in ASD and should be further explored in individuals with ASD with severely impaired language.