Structural and functional underconnectivity as a negative predictor for language in autism

Abstract

The development of language, social interaction, and communicative skills are remarkably different in the child with autism spectrum disorder (ASD). Atypical brain connectivity has frequently been reported in this patient population. However, the interplay between their brain connectivity and language performance remains largely understudied. Using diffusion tensor imaging tractography and resting-state fMRI, the authors explored the structural and functional connectivity of the language network and its relation to the language profile in a group of healthy control subjects (N = 25) and a group of children with ASD (N = 17). The authors hypothesized that in children with ASD, a neural connectivity deficit of the language network can be related to the observed abnormal language function. They found an absence of the right-hemispheric arcuate fascicle (AF) in 28% (7/25) of the healthy control children and in 59% (10/17) of the children with ASD. In contrast to healthy control children, the absence of the right-hemispheric AF in children with autism was related to a lower language performance as indicated by a lower verbal IQ, lower scores on the Peabody Picture Vocabulary Test, and lower language scores on the Dutch version of the Clinical Evaluation of Language Fundamentals (CELF-4NL). In addition, through iterative fMRI data analyses, the language impairment of children with ASD could be linked to a marked loss of intrahemispheric functional connectivity between inferior frontal and superior temporal regions, known as the cortical language network. Both structural and functional underconnectivity patterns coincide and are related to an abnormal language function in children with ASD.

Connectivity in Autism

“…The Verly group 54 focused on the language network (superior longitudinal fasciculus) in adolescents and found no difference between groups in their DTI study, but did report a significant leftward asymmetry in fractional anisotropy and apparent diffusion coefficient. The presence or absence of bilateral arcuate fasciculus had a significant effect on performance on a language test and on intra-hemispheric functional connectivity between cortical language centers (the inferior frontal gyrus and the superior temporal gyrus) in the ASD group.…”

“…20,22,29,33,39,40,47,49,50,55 Posterior cingulate cortex (PCC) was reported in eight studies to have reduced, 21,29–31,40,41,47,50 and in three reports to have increased, long-range connectivity to other ROIs. 30,41,43 The precuneus, 29,33,41,43,47,50 anterior cingulate cortex (ACC), 21,22,33,43,50 superior temporal gyrus, 34,39,43,50,54 posterior superior temporal sulcus, 20,49,53 anterior insula, 20,37,49 and parietal lobule 35,50,53,55 each had four to five reports of reduced, with either one or two reports of increased, long-range connectivities. Verly and colleagues 54 reported a widespread reduction in inter-hemispheric connectivity among the ROIs studied, with the exception of the arcuate fasciculus part of the superior longitudinal fasciculus).…”

“…30,41,43 The precuneus, 29,33,41,43,47,50 anterior cingulate cortex (ACC), 21,22,33,43,50 superior temporal gyrus, 34,39,43,50,54 posterior superior temporal sulcus, 20,49,53 anterior insula, 20,37,49 and parietal lobule 35,50,53,55 each had four to five reports of reduced, with either one or two reports of increased, long-range connectivities. Verly and colleagues 54 reported a widespread reduction in inter-hemispheric connectivity among the ROIs studied, with the exception of the arcuate fasciculus part of the superior longitudinal fasciculus). In their research-based study, the DiMartino group, reported an increased degree of centrality (i.e., number of direct connections) for posterior parahippocampal gyrus and amygdala, and decreased degree of centrality for precuneus, 23 and in their article based on the ABIDE data set, the same group reported a decreased degree of centrality and regional homogeneity for striatum 48 (Supplemental Table B).…”

“…Exceptions include reports by the Ameis, 74 Billeci, 76 Nagae, 75 Nair, 55 Sivaswamy, 63 and Verly 54 groups. The Billeci group 76 has reported increased fractional anisotropy and mean diffusivity in multiple regions, including the corpus callosum, whereas the Sivaswamy group 63 has reported increased fractional anisotropy and mean diffusivity in the cerebellar peduncle area.…”

“…40,50,54,55 Rudie and colleagues 40 found that the presence of the MET risk allele resulted in reduced connectivity from the PCC to medial PFC and reduced fractional anisotropy in the splenium of the corpus callosum (the fiber pathway originating from PCC/precuneus), irrespective of the study group. The presence of the MET risk allele in the ASD group, however, resulted in more severely compromised brain circuitry and greater impairment in social behaviors.…”