Autism Traits in the Typical Population Are Related to Regional Changes in Brain Structure

Background: Autism spectrum disorder (ASD) is characterized by impaired social interaction and communication, and repetitive behaviors.  However, these traits are highly variable across individuals with ASD.  Some have argued that ASD forms a continuum, which extends into the general population.  Recent work has shown that the extent to which typically developed (TD) adults display autistic traits, as measured using the autism-spectrum quotient (AQ) (Baron-Cohen et al., 2006), predicts performance on behavioral tasks that are impaired in ASD (e.g. social cognition and communication).  However, only two studies have examined the structural brain correlates of the AQ in TD, and no study has investigated the correlation between brain structure and the AQ in both TD and ASD.

Objectives: The objective of the present study was to investigate whether differences in autistic traits, as measured with the AQ, are related to regional brain structure in a similar way in both TD and ASD adults.

Methods: Participants included 26 adults with ASD (mean age= 28.9, SD= 6.8, mean IQ = 109.73, SD= 13.6) and 26 typically developing adults (mean age = 25.2, SD= 4.4, mean IQ = 115.96, SD= 11.6).  All participants completed the AQ.  T1-weighted structural MR images were obtained for all participants on a 3T MRI scanner.  Detailed gray matter measures were performed using cortical thickness analyses via the CIVET pipeline.  We then performed correlations between the total AQ score and the cortical thickness results to test for possible interactions across the ASD and TD groups.

Results: As expected, the ASD group scored higher than the TD group on the AQ overall.  Preliminary analyses revealed an inverse relationship between total AQ score and cortical thickness in inferior frontal and precentral gyrus in both ASD and TD. However, only the TD group (and not ASD) showed a positive correlation between total AQ score and cortical thickness in parahippocampal gyrus.

Conclusions: These preliminary results are consistent with previous findings of atypical brain structure and function in frontal cortex that was related to atypical social cognition in ASD.  We provide evidence that autistic traits are reflected in specific brain structures across TD and ASD in a partially overlapping way.