Language Network Differences Among Verbally Fluent Autistic Adults
Authors:   , Kaminer Isabelle E. , Lee Nancy Raitano 
Published: February 2022

Autism Spectrum Disorder (ASD) is characterized by two symptom clusters: impairments in social interaction and communication as well as restrictive and repetitive behaviors and interests (RRB). Although all autistic individuals demonstrate some degree of impairment in social communication skills, non-social aspects of communication such as one's knowledge of word meanings and the grammatical rules of a language (i.e., structural language skills) vary widely. Verbally-fluent autistic adults often show similar, if not equal, task performance on structural language measures compared to typically developing individuals (Eigsti, et al., 2016). Their unique communication profile of relatively intact structural language skills but impaired social communication or pragmatic language skills offers the potential to broaden our understanding of social aspects of language that present persistent difficulties across the autism spectrum. The current study analyzed resting state functional MRI data, in conjunction with Autism Diagnostic Observation Schedule (ADOS-2) Social Communication scores, from 20 verbally-fluent autistic adults (VFAA) and 20 age and sex-matched typically developing control participants (TDCs). Data were originally collected at Indiana University but were obtained for the current study from the Autism Brain Imaging Data Exchange-II (ABIDE-II) repository. Prior to conducting primary analyses-which sought to examine differences between the VFAA and TDC groups in language network resting state functional connectivity-Neurosynth, an online meta-analytic tool that synthesizes published fMRI data, was used to identify regions of interest (ROIs) to be included in the study's language network. This was accomplished by searching Neurosynth using the term "language." Using ROIs derived from this search, within-group seed-to-voxel correlation analyses were completed to establish the language network in each group. This was followed by a between-groups seed-to-voxel analysis to determine regions of differential connectivity to the rest of the brain. A series of univariate regressions was run to establish the degree to which language network functional connectivity varies as a function of ADOS-2 Social Communication scores in the VFAA group. Separate seed-based connectivity analyses confirmed the presence of the language network in both groups. A between-groups seed-based connectivity analysis revealed one region of significant difference where language network connectivity to the rest of the brain (including those voxels within the network ROIs) was stronger in the VFAA group than the TDC group. This region was localized to the left angular gyrus extending medially into the temporoparietal junction (TPJ)/supramarginal gyrus (SMG). This region of difference largely overlaps with the left supramarginal gyrus ROI from the Neurosynth language network. A series of univariate regressions revealed robust associations between language to whole-brain connectivity and ADOS-2 social communication scores (sum of Communication and Social Interaction scores). Future research should seek to extend resting state language network studies across the spectrum of verbal abilities in autistic adults to provide a better picture of network differences underlying heterogeneity in structural language skills in autistic individuals. Lastly, longitudinal studies may provide insight into how functional connectivity differences in the adult brain emerge and change over the course of development. Such studies may provide insight into key developmental windows in which interventions may be most advantageous, and ultimately, contribute to larger efforts to support the growing population of autistic adults.