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Description
Autism spectrum disorder (ASD) is a neurodevelopmental disorder. The inherent heterogeneity of autism presents great challenges for researchers, but evidence across neuroimaging modalities is now converging, implicating aberrant connectivity patterns involving numerous functional networks. At the same time, there is minimal agreement as to the exact patterns of aberrant connectivity in ASD, with numerous competing theories. Given the complexities and inconsistencies of the ASD literature, data-driven techniques can provide unbiased approaches to uncovering connectivity patterns. In the current study, we used graph theory to examine differences in connectivity patterns between the ASD and typical development (TD) groups using resting state functional magnetic resonance imaging (fMRI) data, which reflect fluctuations in oxygen levels in the brain as an indirect measure of neuronal activity. For the analysis, we first used graph theory to examine functional connectivity at the regional level in a large sample of low-motion resting-state fMRI scans. We then tested how within-network connectivity differed between the two groups, as well as how it changed with age in the two groups. In the second portion of the study, we used independent component analysis to define functional resting-state networks in the brain and then graph theory to examine how the networks interact. Once again, we tested for group differences in connectivity and age-related changes. Findings suggest decreased density of connectivity in the ASD group compared to the TD group, both at the regional and network levels. Within-network connectivity was significantly reduced in the ASD group for somatosensory & motor, auditory, cingulo-opercular task control, subcortical, and default mode networks. Furthermore, numerous networks in ASD showed differing age-related trajectories. Both groups exhibited a decrease in regional connectivity with age. The TD group showed the expected increase in network connectivity with age, but this trend was not present in the ASD group. These findings support the theory of reduced network integration with age in ASD.
