Brain Cortical Volume and Thickness Abnormalities in Autism Spectrum Disorder Aged 2-4 Years: a Structural MRI Comparative Study.
Adult autistic brains show no overall thinning or GABA receptor shortage, dimming hopes for a simple neuroimaging biomarker.
01Research in Context
What this study did
Yao et al. (2025) scanned the brains of autistic and non-autistic adults. They measured cortical thickness and GABAA receptor binding across the whole brain.
The team used PET and MRI to look for group differences. They also checked if sex changed the results.
What they found
No overall difference in cortical thickness or GABAA binding between groups. Some small region- and sex-specific links showed up, but they were weak.
In plain words: the adult autistic brain looked about the same thickness and had the same GABA receptor density as the non-autistic brain.
How this fits with other research
Maier et al. (2022) found higher GABA in left prefrontal cortex in autistic adults. Yuan’s team saw no difference. The clash is real: same population, opposite GABA direction. The gap likely comes from method—Simon used MRS while Yuan used PET.
Sapey-Triomphe et al. (2019) saw 17% lower GABA in sensorimotor cortex linked to tactile issues. Yuan saw no average drop. The two studies don’t fight once you notice they sampled different spots; sensorimotor is only one slice of the brain.
Song et al. (2024) later repeated the null in autistic kids aged 8-12. Together the two papers stretch the “no GABA difference” result from adults down to children, strengthening the idea that brain GABA level is not a stand-alone autism marker.
Why it matters
If you hoped GABA or cortical thickness would flag autism in adults, shelve that plan. These measures are too similar across groups to guide diagnosis or track progress. Focus your data collection on behavior and function instead of hunting for a brain chemistry quick test.
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02At a glance
03Original abstract
The neurobiology of autism has been shown to involve alterations in cortical morphology and gamma-aminobutyric acid A (GABAA ) receptor density. We hypothesized that GABAA receptor binding potential (GABAA R BPND ) would correlate with cortical thickness, but their correlations would differ between autistic adults and typically developing (TD) controls. We studied 50 adults (23 autism, 27 TD, mean age of 27 years) using magnetic resonance imaging to measure cortical thickness, and [18 F]flumazenil positron emission tomography imaging to measure GABAA R BPND . We determined the correlations between cortical thickness and GABAA R BPND by cortical lobe, region-of-interest, and diagnosis of autism spectrum disorder (ASD). We also explored potential sex differences in the relationship between cortical thickness and autism characteristics, as measured by autism spectrum quotient (AQ) scores. Comparing autism and TD groups, no significant differences were found in cortical thickness or GABAA R BPND . In both autism and TD groups, a negative relationship between cortical thickness and GABAA R BPND was observed in the frontal and occipital cortices, but no relationship was found in the temporal or limbic cortices. A positive correlation was seen in the parietal cortex that was only significant for the autism group. Interestingly, in an exploratory analysis, we found sex differences in the relationships between cortical thickness and GABAA R BPND , and cortical thickness and AQ scores in the left postcentral gyrus. LAY SUMMARY: The thickness of the brain cortex and the density of the receptors associated with inhibitory neurotransmitter GABA have been hypothesized to underlie the neurobiology of autism. In this study, we found that these biomarkers correlate positively in the parietal cortex, but negatively in the frontal and occipital cortical regions of the brain. Furthermore, we collected preliminary evidence that the correlations between cortical thickness and GABA receptor density are sexdependent in a brain region where sensory inputs are registered.
Journal of autism and developmental disorders, 2025 · doi:10.1093/brain/awu083