Categorical Dimensions of Social Impairment and Disrupted Functional Connectivity in Autism Spectrum Disorders: When Does Continuous Become Discrete?

There is increasing interest in conceptualizing psychiatric impairments from a dimensional rather than categorical perspective, with hope that a new approach will expedite treatment of recalcitrant symptoms that cross diagnostic boundaries and compromise adaptive functioning. The companion paper by Elton et al. ( ) used a technologically advanced neuroinformatics approach to illustrate that neither a fully dimensional nor fully categorical approach may be adequate. These authors interrogated a developmental disconnection hypothesis of autism spectrum disorder (ASD) ( ) through analysis of a large repository of resting-state functional magnetic resonance imaging (fMRI) data, made available through the Autism Brain Imaging Data Exchange ( ). Hierarchical linear regression analyses examined disruption in four resting-state networks (dorsal attention, default mode, salience, and executive control) from three perspectives; 1) categorical, contrast of ASD participants with typically developing children; 2) dimensional, an association between functional connectivity and scores on the Social Responsiveness Scale ( ) across all participants; and 3) hybrid, test of group differences in the association between the Social Responsiveness Scale and functional connectivity. Although both categorical and dimensional approaches revealed perturbation of resting-state networks, perhaps most interestingly, the hybrid analysis revealed that the strength of these associations between Social Responsiveness Scale and functional connectivity differed between participants with ASD and typically developing children, with discrete areas within each network showing either increased or decreased association strength, depending on group membership. Although some regions showed distinct categorical and dimensional effects, other regions were overlapping, suggesting that the impact of network connectivity on one’s social responsiveness may depend partially on whether these networks underwent typical development or were neurodevelopmentally compromised.