The Mid-Fusiform Sulcus in Autism Spectrum Disorder: Establishing a Novel Anatomical Landmark Related to Face Processing.
Autistic people show bumpier, thicker mid-fusiform folds that track weaker face skills, echoing past activity studies but offering no direct therapy lever.
01Research in Context
What this study did
Researchers scanned brains of people with autism. They measured the thickness of a tiny fold called the mid-fusiform sulcus. This fold sits in the face-processing patch on the left side of the brain.
The team also gave face-naming tests. They wanted to see if thicker or bumpier folds went hand-in-hand with worse face skills.
What they found
Autistic brains showed more jagged thickness in that fold. Thicker, more variable folds linked to lower face scores. The result fits a long line of "face area" differences in autism.
How this fits with other research
O'Connor et al. (2008) first showed weaker activity in this same patch. The new study adds a reason: the fold itself is less uniform.
Kuang et al. (2025) pooled 25 fMRI studies and found low activity in the left inferior frontal gyrus during emotion tasks. Together, the two papers paint a picture of both weak signals and uneven structure.
Lacroix et al. (2024) used EEG and saw poor tuning to fearful faces. Their timing data and the MRI thickness data look different on the surface. Yet both point to the fusiform region working poorly in autism, so the studies support rather than clash.
Why it matters
You cannot fix a sulcus with a prompt, but you can plan smarter lessons. Expect face-name programs to take longer. Add extra cues like hair color or voice pitch. Track progress with objects as well; Arkush et al. (2013) showed autistic learners lean on general memory, not face memory.
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02At a glance
03Original abstract
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.
Autism research : official journal of the International Society for Autism Research, 2021 · doi:10.1002/aur.2425