32093
The Default Mode Network in Autism Spectrum Disorders and Attention Deficit Hyperactivity Disorder
Autism Spectrum Disorders (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) are neurodevelopmental disorders with overlapping phenotypic symptomatology and shared genetic makeup. Previous studies have investigated ASD and ADHD using resting state functional magnetic resonance imaging (rfMRI). One particular functional network of interest is the Default Mode Network (DMN) as it has been implicated in several mental disorders. ASD studies have reported mixed trends of increased and decreased functional connectivity (FC) in the DMN, whereas ADHD studies have reported increased FC.
Objectives:
Previous studies have investigated DMN alterations in ASD and ADHD separately, considering these two disorders as unique clinical conditions. Current research has done little work to address NIH’s recent Research Domain Criteria (RDoC) that mental disorders may lie on a continuum. To better understand shared characteristics between ASD and ADHD, this study analyzed the DMN FC in both ASD and ADHD children. ADHD-Combined (ADHD-C) and ADHD-Inattentive (ADHD-I) subtypes were also investigated.
Methods:
Archival datasets from Autism Brain Imaging Data Exchange (ABIDE)-I and ADHD-200 datasets were used, with 33 ADHD, 35 ASD, and 32 typically developing (TD) males (ages = 7–17 years) used in the study. The Data Processing Assistant for RfMRI Advanced Edition (DPARSF-A, Version 4.3_171210) as well as comparisons between global signal regression (GSR) versus no GSR were used. 11 regions of interest (ROIs) from the Dosenbach-160 (DOS-160) atlas related to executive functioning (EF) and attentional network regions were investigated due to deficits in EF and attentional networks noted in existing ASD and ADHD literature. Effects of demographic covariates and motion (age, IQ, group, meanFD) on average FC and individual ROI pairs were also studied using general linear models (GLMs).
Results:
FC correlations were compared across the ASD, ADHD, and TD groups with three comparisons: ADHD-TD, ASD-TD, and ADHD-ASD. Average and individual DMN connectivity across the 11 ROIs were also calculated. Increased positive correlations were seen post GSR in ADHD-TD comparisons, with positive correlations between the inferior temporal cortex (inf-temp) and the anterior cingulate cortex (ACC) (p<0.05). Positive correlations between the mPFC and vlPFC were also present after applying GSR ( p < 0.05). Finally, ASD-TD t-test results showed decreased negative correlations after applying GSR, with only one negative correlation between the ACC and occipital DMN regions. After plotting correlational trends pre and post GSR, ADHD-C subtype and ASD groups presented similar patterns of average DMN FC, whereas ADHD-C and ADHD-I subtypes showed opposing trends of average DMN FC. Individual FC between the 11 DMN ROI pairs showed that negative correlations increased for ADHD-ASD between ROIs, such as vlPFC and sup-front(p<0.05) in the GLM with age, VIQ, and group after running GSR.
Conclusions:
These results confirmed our RDoC based hypothesis that ASD and ADHD share similar negative correlational patterns in DMN related ROIs. This lays the framework for investigating additional overlapping brain-behavior deficits in executive functioning and attentional network regions in the DMN. However, additional brain-behavioral analysis, as well as a larger sample size comparing ASD, ADHD, and TD groups is warranted.