Description
Autism spectrum disorder (ASD) is an increasingly prevalent neurodevelopmental disorder characterized by repetitive behaviors and impaired social communication and interaction. There has been a growing consensus that behavioral and brain abnormalities can only be explained at the level of interconnected networks. Evidence indicates atypical long distance connectivity in ASD and a few recent studies have found atypical local connectivity as well. However, aside from theoretical speculations about reduced increased local and reduced long-distance connectivity, there is little empirical evidence on how abnormal local connectivity relates to long distance connectivity. A specific question is whether local overconnectivity may indicate relatively isolated processing or overly integrative processing. Archival functional MRI resting state data were available for 42 children and adolescents with ASD (7-18 y/o) and 43 typically developing (TD) participants matched for age, motion, and non-verbal IQ. These data underwent a standard fMRI preprocessing pipeline including motion, slice-time, and field map correction, spatial smoothing and bandpass filtering, and removal of nuisance regressors (6 rigid-body motion parameters, white matter, ventricles). Regional homogeneity (ReHo) was used to examine local connectivity, and clusters of between-group differences were used as seeds in subsequent whole brain functional connectivity analyses. In the ASD group, local overconnectivity in posterior regions was mostly associated with underconnectivity in distal regions, suggesting a link between local over- and long-distance underconnectivity specifically for visual regions and reduced cooperation with frontal lobe in ASD. Locally overconnected left fusiform gyri was underconnected with other visual cortices, including primary visual cortex. Cingulate and medial frontal regions showed extensive underconnectivity throughout medial cerebral cortex in the ASD group on both ReHo and whole brain analyses. Overall, the findings suggest that hypothesis of generally increased local and reduced distal connectivity in ASD requires modification, as it applies solely to some striate and extrastriate visual cortices, which are locally overconnected, but underconnected with some distal frontal regions.
