Comparison of brain structure and function between adolescents with Autism Spectrum Disorder and adolescents with Obsessive-Compulsive Disorder

Autism Spectrum Disorder (ASD) and Obsessive-Compulsive Disorder (OCD) are frequently comorbid and share deficits in executive function, highlighting a need to understand the shared and/or disorder-specific neurofunctional abnormalities underlying these behaviours. First, a comparative, multimodal meta-analysis between ASD and OCD was conducted on whole-brain voxel-based morphometry structural magnetic resonance imaging (MRI) studies and functional MRI studies of cognitive control. Second, functional MRI (fMRI) was used to scan adolescent boys with ASD or OCD, and control boys while they performed tasks measuring sustained attention and reward-based decision-making, including temporal discounting and gambling. Shared abnormalities were observed in the meta-analysis, where both clinical groups had reduced structure and function during cognitive control in medial prefrontal and anterior cingulate regions. During fMRI, shared abnormalities were also observed during executive function tasks of reward-based decision-making, where both clinical groups had reduced activation in ventromedial, inferior frontal and orbitofronto-striatal as well as temporo-parietal regions compared to controls. Disorder-specific abnormalities, on the other hand, were seen predominantly during tasks of non-emotional executive function. OCD patients had disorder-specific increases in striato-insular structure and function, whereas ASD individuals had increased structure but decreased function in dorsolateral prefrontal cortex during cognitive control. Temporo-parietal underactivation during sustained attention was uniquely associated with OCD compared to ASD and controls. These results present novel evidence that neurofunctional abnormalities, including temporo-parietal underactivation and striato-insular overactivation during non-emotional tasks of executive function may be mostly disorder-specific to OCD compared with ASD, whereas abnormalities during emotionally-driven tasks of reward-based decision-making are predominantly shared between ASD and OCD, particularly in ventromedial, inferior and orbitofronto-striatal regions. These studies provide preliminary indication that both shared and disorder-specific neurostructural and neurofunctional biomarkers underpin cognitive dysfunction in these disorders that may have implications for future diagnosis and treatment.