Corpus callosum morphometrics in young children with autism spectrum disorder.
In preschool autism, the corpus callosum is small for the size of the already-large brain, but later studies clash on whether this holds across ages and sexes.
01Research in Context
What this study did
Researchers scanned the brains of preschoolers aged 3–4.
Some kids had autism, some had general delay, and some were typical.
They measured the corpus callosum and the whole brain to see if the callosum was small even after heads got bigger.
What they found
Kids with autism had a callosum that looked too small for their already-large brains.
The gap was biggest for children labeled autistic disorder, smaller for PDD-NOS.
Children with general delay had the smallest callosum of all groups.
How this fits with other research
Zhang et al. (2023) saw the opposite: toddlers with autism had a larger callosum, especially girls.
The clash fades when you see Yun counted raw size, while Inbal counted size after correcting for big brains.
Noordenbos et al. (2012) followed kids for two years and found the small-callosum pattern sticks around, so the preschool gap is not a blip.
Cox et al. (2015) looked at hundreds of scans and found no callosum difference once head size was counted, leaving the field split.
Why it matters
You cannot eyeball a scan and guess social skill.
Yet knowing that many preschoolers with autism carry a small callosum, even inside a big brain, can help you explain why tasks that need both sides to talk—like complex play or rapid imitation—may lag.
Pair this info with your behavioral data, not in place of it.
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Join Free →When you read an MRI report that says 'large brain,' flip the page and check if the callosum size is noted—if it is small, plan extra practice for tasks that need both hands or quick social turn-taking.
02At a glance
03Original abstract
This study assessed midsagittal corpus callosum cross sectional areas in 3-4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD clinical subgroup analysis revealed greater proportional callosum reduction in the more severely affected autistic disorder (AD) than in pervasive developmental disorder-not otherwise specified (PDD-NOS) children. DD children had smaller absolute callosums than ASD and TD. Subregion analysis revealed widely distributed callosum differences between ASD and TD children. Results could reflect decreased inter-hemispheric connectivity or cerebral enlargement due to increase in tissues less represented in the corpus callosum in ASD.
Journal of autism and developmental disorders, 2006 · doi:10.1007/s10803-006-0121-2