Default Network Correlates of Obsessive Compulsive Symptoms in Autism Spectrum Disorders

Background: Autism Spectrum Disorders (ASD) are characterized by disturbances in social function and communication, and the presence of repetitive behaviors. In addition, ASD is associated with other co-ocurring symptoms, including obsessions and compulsions. These symptoms are reported in 37 - 95% of individuals with autism and have been observed to share some overlap with characteristic symptoms of obsessive-compulsive disorder (OCD). Given these observations, both ASD and OCD are hypothesized to share similar neurocognitive circuits that may underlie the presence of obsessions and compulsions in both disorders. The literature has suggested a possible role for default network dysfunction in ASD and OCD. Objectives: We hypothesized that an alteration of the interplay between structures of the default network may underlie obsessive and compulsive symptoms associated with ASD. We determined whether there are differences in default network connectivity between ASD individuals exhibiting high vs. low obsessive-compulsive symptoms. Methods: 25 ASD children (ages 10-18) and 25 controls matched for age, gender and IQ took part in this functional MRI (fMRI) study. The Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule were used to assist in the ASD diagnosis. None of the ASD children received a formal diagnosis of OCD. Obsessive and compulsive symptoms were evaluated by using the Obsessive–Compulsive Inventory-Revised (OCI-R). Categorization into ASD (high obsessive-compulsive symptoms) or ASD (low obsessive compulsive symptoms) groups was based on OCI-R scores: patients with scores <20 were categorized as having “low symptoms,” whereas patients with scores >20 were categorized as having “high” symptoms. During fMRI acquisition, participants were instructed to “let your mind wander freely” while looking at a fixation cross displayed in the middle of the screen for 10 minutes during fMRI acquisition. A seed region was placed in the PCC and functional connectivity was examined by obtaining the correlational activity between the posterior cingulate cortex (PCC) and other areas of the default network. Results: Initial efforts in our lab (including a sample of 12 adolescents with ASD and 12 controls) indicated that there are differences in default network functional connectivity between adolescent ASD individuals with high vs low obsessive-compulsive symptoms. Increased obsessive and compulsive symptom severity, as evidenced by higher OCI-R scores, was found to correlate with decreased functional connectivity between the bilateral parahippocampal gyrus, the bilateral angular gyrus, the superior frontal gyrus, and the PCC. Conclusions: Preliminary results show group differences in default network functional connectivity between adolescent ASD individuals with high vs low obsessive-compulsive symptoms. Upcoming analyses will yield additional information on the functional connections between default network structures thought to underlie obsessive and compulsive symptoms associated with ASD.