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Cortical Folding Differences in Autism Spectrum Disorder (ASD) and Attention-Deficit/ Hyperactivity Disorder (ADHD) Relative to Typically Developing Peers (TD): Data from the Pond Network
The limited number of studies that have investigated cortical folding in ASD and ADHD present contradictory results. To the best of our knowledge, no study has investigated cortical folding across individuals with ASD and ADHD and typically developing controls (TD), and little is known about the relation of this measure to clinical symptoms.
Objectives: We examined cortical folding in children and adolescents with ASD and ADHD relative to TD, and the relation between cortical folding and social, attention, behavioural and adaptive functioning difficulties across disorders.
Methods: T1-weighted MRI, cognitive and behavioural data of children and adolescents with ASD, ADHD and TD, between 6.1-15.9 years of age, were obtained from the Province of Ontario Neurodevelopmental Disorders (POND) Network dataset, an Ontario Brain Institute-funded multi-site study. FreeSurfer software was used to obtain whole-brain 3-D measures of cortical folding using local Gyrification Index (lGI), a surface-based measure providing vertex-wise quantification of cortical folding. General linear model (GLM) analyses was conducted, on the module QDEC (Query, Design, Estimate, Contrast) on FreeSurfer to examine lGI differences between groups.
Results: 42 ASD (mean age: 12.11, SD: 2.76), 17 ADHD (mean age: 11.97, SD: 2.43) and 76 TD (mean age: 12.79, SD: 3.11) participants with IQ>70 were included in this preliminary study, which revealed significantly reduced cortical folding in individuals with NDDs relative to controls in a left hemisphere cluster located in the superior parietal lobe (p<0.0001). No significant difference in cortical folding was found on comparison of ASD versus ADHD groups. Decrease in cortical folding was associated with better adaptive functioning, less hyperactive/impulsive & inattention impairments, but more repetitive behaviours across all children with NDDs. No significant relation was found between cortical folding and social communication deficits. All results were corrected for multiple comparisons using Monte-Carlo simulations.
Conclusions: Findings of cortical folding differences in individuals with ASD and ADHD relative to TD point to an early marker of altered development in these conditions that predates clinical onset and may drive other brain alternations. Findings of no significant differences between ASD and ADHD suggests further similarities between these two NDDs.