Despite decades of research, the brain basis of aberrant face processing in autism spectrum disorder (ASD) remains a topic of debate. The mid‐fusiform sulcus (MFS), a minor feature of the ventral occipitotemporal cortex, provides new directions for studying face processing. The MFS closely aligns with face‐selective cortical patches and other structural and functional divisions of the fusiform gyrus; however, it has received little attention in clinical populations. We collected structural MRI data from 54 individuals with ASD and 61 age‐and‐IQ‐matched controls ages 8 to 40 years. The MFS was identified on cortical surface reconstructions via 4 trained raters and classified into known surface patterns. Mean MFS gray matter volume (GMV), cortical surface area (SA), cortical thickness (CT), and standard deviation of CT (CT SD) were extracted. Effects of diagnosis, age, and hemisphere on MFS surface presentation and morphometry were assessed via multinomial logistic regression and mixed effects general linear modeling, respectively. The MFS was reliably identified in 97% of hemispheres examined. Macroanatomical patterns and age‐related decreases in MFS GMV and CT were similar between groups. CT SD was greater in the left hemisphere in ASD. Participants' ability to interpret emotions and mental states from facial features was significantly negatively correlated with MFS CT and CT SD. Overall, the MFS is a stable feature of the fusiform gyrus in ASD and CT related measures appear to be sensitive to diagnosis and behavior. These results can inform future investigations of face processing and structure–function relationships in populations with social deficits.
Lay Summary
A small structural feature of the brain related to seeing faces (the mid‐fusiform sulcus; MFS) appears similar in autism spectrum disorder (ASD) and neurotypical development; however, the thickness of this structure on the left side of the brain is more variable in ASD. People who are better at judging mental states from another person's eyes tend to have thinner and less variable MFS. This feature may teach us more about face processing and how brain structure influences function in ASD.
Background:Theory of Mind (ToM), the ability to attribute mental states to oneself and others, is frequently impaired in Autism Spectrum Disorder (ASD) and may result from altered activation of social brain regions. Conversely, Typically Developing (TD) individuals overextend ToM and show a strong tendency to anthropomorphize and interpret biological motion in the environment. Less is known about how the degree of anthropomorphism influences intentional attribution and engagement of the social brain in ASD.Objective:This fMRI study examines the extent of anthropomorphism, its role in social attribution, and the underlying neural responses in ASD and TD using a series of human stick figures and geometrical shapes.Methods:14 ASD and 14 TD adults watched videos of stick figures and triangles interacting in random or socially meaningful ways while in an fMRI scanner. In addition, they completed out-of-scanner measures of ToM skill and real-world social deficits. Whole brain statistical analysis was performed for regression and within and between group comparisons of all conditions using SPM12’s implementation of the general linear model.Results:ToM network regions were activated in response to social movement and human-like characters in ASD and TD. In addition, greater ToM ability was associated with increased TPJ and MPFC activity while watching stick figures; whereas more severe social symptoms were associated with reduced right TPJ activation in response to social movement.Conclusion:These results suggest that degree of anthropomorphism does not differentially affect social attribution in ASD and highlights the importance of TPJ in ToM and social attribution.
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