Abstract
Converging theories and data suggest that atypical patterns of functional and structural connectivity are a hallmark neurobiological feature of autism. However, empirical studies of functional connectivity, or, the correlation of MRI signal between brain regions, have largely been conducted during task performance and/or focused on group differences within one network [e.g., the default mode network (DMN)]. This narrow focus on task-based connectivity and single network analyses precludes investigation of whole-brain intrinsic network organization in autism. To assess whole-brain network properties in adolescents with autism, we collected resting-state functional connectivity MRI (rs-fcMRI) data from neurotypical (NT) adolescents and adolescents with autism spectrum disorder (ASD). We used graph theory metrics on rs-fcMRI data with 34 regions of interest (i.e., nodes) that encompass four different functionally defined networks: cingulo-opercular, cerebellar, fronto-parietal, and DMN (Fair etal., 2009). Contrary to our hypotheses, network analyses revealed minimal differences between groups with one exception. Betweenness centrality, which indicates the degree to which a seed (or node) functions as a hub within and between networks, was greater for participants with autism for the right lateral parietal (RLatP) region of the DMN. Follow-up seed-based analyses demonstrated greater functional connectivity in ASD than NT groups between the RLatP seed and another region of the DMN, the anterior medial prefrontal cortex. Greater connectivity between these regions was related to lower ADOS (Autism Diagnostic Observation Schedule) scores (i.e., lower impairment) in autism. These findings do not support current theories of underconnectivity in autism, but, rather, underscore the need for future studies to systematically examine factors that can influence patterns of intrinsic connectivity such as autism severity, age, and head motion.
Highlights
Atypical patterns of functional and structural connectivity are proposed to be a hallmark neurobiological feature of autism (Belmonte et al, 2004; Just et al, 2004; Courchesne and Pierce, 2005; Cherkassky et al, 2006)
Betweenness centrality, which indicates the degree to which a seed functions as a hub within and between networks, was significantly different between groups and it was greater for participants with autism for the right lateral parietal (RLatP) seed of the default mode network (DMN) (t(26) = 3.52; p < 0.027 False discovery rate (FDR)-corrected) only
Because the anterior medial prefrontal cortex (aMPFC) was a region that showed significantly increased connectivity with RLatP in autism spectrum disorder (ASD) in whole-brain analyses, we examined whether the strength of connectivity between the RLatP seed and the aMPFC seed was correlated with Autism Diagnostic Observation Schedule (ADOS) scores, IQ, or age
Summary
Atypical patterns of functional and structural connectivity are proposed to be a hallmark neurobiological feature of autism (Belmonte et al, 2004; Just et al, 2004; Courchesne and Pierce, 2005; Cherkassky et al, 2006). Findings suggest developmentally increased white matter volume (Courchesne et al, 2001; Hazlett et al, 2006), radiate white matter bundles supporting interhemispheric and cortico-cortical connections (Herbert et al, 2004) and increased FA in infants and young children with autism (e.g., Ben Bashat et al, 2007; Wolff et al, 2012), whereas later in development (e.g., adolescents and adults), FA is decreased (e.g., Barnea-Goraly et al, 2004; Lee et al, 2007; Nair et al, 2013)
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