Decreased central corpus callosum volume is associated with repetitive behaviours and motor difficulties in autistic children

Along with the core characteristics of the condition, autistic individuals commonly experience motor coordination difficulties, potentially related to a reduced cortical connectivity. Being the largest human commissure, the corpus callosum (CC) plays an essential role in interhemispheric connectivity and has been often involved among autistic atypicalities. This study aimed to investigate the volumes of corpus callosum subregions in a group of drug-naive, autistic children and to explore its possible associations with both core features and motor coordination skills. Thirty-five autistic children (2.5-12 years) were compared with a group of 35 closely IQ-matched, non-autistic peers. CC was identified and segmented into five subregions using Freesurfer. Callosal volumes were compared between the two groups and correlated with parental ratings of core autistic features as assessed by the Social Responsiveness Scale and with motor features as assessed by the Developmental Coordination Disorder Questionnaire. Associations between CC volume and Autism Diagnostic Observation Schedule scores were also explored in autistic participants. Autistic children showed a reduced volume of the central segment of the CC, in the context of a comparable CC total volume. This reduction appeared to be correlated with symptoms of restricted and repetitive behaviours in autistic children, and to parental ratings of autistic mannerisms and motor skills across participants. These findings expand the current knowledge about the neural mechanisms underlying autism, suggesting that the reduced connectivity through the CC might have implications for both core and motor features of autistic individuals. Lay SummaryDifferences in brain development have been widely outlined in autism. Exploring brain scans of 35 autistic and non-autistic children aged 2.5-12 years and closely matched for cognitive functioning, we found that the central part of the corpus callosum was smaller for the autistic group. This reduction was associated with the level of restricted and repetitive behaviours in autistic children, and to parental ratings of autistic mannerisms and motor coordination skills across participants. This work offers new empirical evidence that interhemispheric connectivity is atypical in autism and that the corpus callosum can be involved in the manifestation of both core and motor characteristics of autistic children.