Neural responses to viewing human faces in autism spectrum disorder: A quantitative meta-analysis of two decades of research.

The human face communicates a wealth of socially relevant information such as person identity, emotion, and intention. A consistent behavioral finding in autism spectrum disorder (ASD) is reduced attention to or difficulty drawing meaning from faces. However, neuroimaging research into the neural correlates of face processing differences in ASD has returned mixed results. While many studies find hypo-activation or hypo-connectivity of core and extended face network regions, others show hyper-activation, equal activation, or even activation shifted to object-selective fusiform gyrus (FG) regions in ASD during face processing. This study consolidates two decades of literature to reveal common and consistent patterns of brain activation when viewing human faces in ASD. It also addresses whether face processing in ASD is routinely shifted to object-centric regions of the FG. To do so, we conducted an extensive search of the neuroimaging literature according to PRISMA guidelines. Peak activation coordinates from a final set of 23 studies, yielding a sample of 713 participants (338 ASD), were included for quantitative meta-analysis using Activation Likelihood Estimation (ALE). ASD within-group results across studies revealed a single activation cluster in the left FG, which presented laterally to the mid-fusiform sulcus (MFS). Typically developing groups displayed common activations across core and extended face network regions. Exploratory analysis of between group findings from the literature did not yield significant results. Overall, our results suggest that individuals with ASD consistently activate at least one typical face network region, the left FG, when processing faces and this activation is not routinely shifted to object-centric areas of the FG.

The Mid-Fusiform Sulcus in Autism Spectrum Disorder: Establishing a Novel Anatomical Landmark Related to Face Processing.

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.