Decreased homotopic interhemispheric functional connectivity in children with autism spectrum disorder.
Mirror-side brain links are weaker in 5- to 10-year-olds with autism and track symptom severity.
01Research in Context
What this study did
Yao et al. (2021) scanned kids aged 5-10 with autism and typical kids while they rested. They looked at how well matching areas in the left and right brain talk to each other.
They used resting-state fMRI to measure homotopic interhemispheric functional connectivity. Then they compared the two groups and checked if weaker links matched worse autism symptoms.
What they found
Children with autism already showed weaker mirror-side brain links in key networks. The weaker the links, the stronger the social and repetitive symptoms.
The pattern was clear by early elementary school. This makes the measure a possible early biomarker.
How this fits with other research
de Leeuw et al. (2024) extends the story. They found the hippocampus also loses its front-back specialization in autism across ages 3-25. Together, the papers show both left-right and front-back circuits are off track.
Ma et al. (2022) charted cortico-striatal links over a wider age span. They show the gap keeps growing after age 10. Shuxia's snapshot at 5-10 is the starting line of that long race.
Stevens et al. (2018) seems to disagree. During a motor task, kids with autism showed more long-range connectivity, not less. The clash disappears when you see one scan was at rest, the other during action. Different states, different networks, different directions.
Why it matters
You now have a concrete brain measure that is already different by kindergarten. If you work with young kids with autism, you can tell families that weaker mirror-brain links line up with social difficulty. While you can't scan every child, you can use the finding to explain why early, intensive social teaching is key. Target skills that need both sides of the brain working together, such as turn-taking or imitation games.
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02At a glance
03Original abstract
While several functional and structural changes occur in large-scale brain networks in autism spectrum disorder (ASD), reduced interhemispheric resting-state functional connectivity (rsFC) between homotopic regions may be of particular importance as a biomarker. ASD is an early-onset developmental disorder and neural alterations are often age-dependent. Although there is some evidence for homotopic interhemispheric rsFC alterations in language processing regions in ASD children, wider analyses using large data sets have not been performed. The present study, therefore, conducted a voxel-based homotopic interhemispheric rsFC analysis in 146 ASD and 175 typically developing children under-age 10 and examined associations with symptom severity in the autism brain imaging data exchange data sets. Given the role of corpus callosum (CC) in interhemispheric connectivity and reported CC volume changes in ASD we additionally examined whether there were parallel volumetric changes. Results demonstrated decreased homotopic rsFC in ASD children in the posterior cingulate cortex (PCC) and precuneus of the default mode network, the precentral gyrus of the mirror neuron system, and the caudate of the reward system. Homotopic rsFC of the PCC was associated with symptom severity. Furthermore, although no significant CC volume changes were found in ASD children, there was a significant negative correlation between the anterior CC volumes and homotopic rsFC strengths in the caudate. The present study shows that a reduced pattern of homotopic interhemispheric rsFC in ASD adults/adolescents is already present in children of 5-10 years old and further supports their potential use as a general ASD biomarker. LAY SUMMARY: Homotopic interhemispheric functional connectivity plays an important role in synchronizing activity between the two hemispheres and is altered in adults and adolescents with autism spectrum disorder (ASD). In the present study focused on children with ASD, we have observed a similar pattern of decreased homotopic connectivity, suggesting that alterations in homotopic interhemispheric connectivity may occur early in ASD and be a useful general biomarker across ages.
Autism research : official journal of the International Society for Autism Research, 2021 · doi:10.1002/aur.2523