A review of: Christopher J. Keary, Nancy J. Minshew, Rahul Bansal, Dhruman Goradia, Serguei Fedorov, Matcheri S. Keshavan, Antonio Y. Hardan (2009). Corpus Callosum Volume and Neurocognition in Autism Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-009-0689-4

Just last week I had the opportunity to hear Dr. Richard Davidson, one of the fathers of the field of affective neuroscience, give a lecture in which he discussed brain volume differences in children with autism. The last pre-publication article of Journal of Autism and Developmental Disorders was very timely, as it also examines brain volume differences in austim, specifically in the Corpus Callosum. The CC is a structure that serves as a connection bridge between the two brain hemispheres. Since it contains a vast number of connecting pathways, anomalies within the Corpus Callosum have been associated with disorders that are hypothesized to be related to impaired connectivity between key brain areas. While a number of studies have shown that people with autism tend to have reduced CC volume, the authors of the current study wanted to expand this research by examining whether such reduced volume is also associated with the type of cognitive difficulties found in autism.

The authors examined 32 individuals with autism (29 males, 2 females, mean age 19.8 with a range of 8 to 45 years) who had been diagnosed via ADOS/ADI, and 32 typically developing individuals who were matched for gender, age, IQ, and socio economic status. None of the participants had history of infections genetic or metabolic disorders, birth asphyxia, head injuries, or seizures. The participants completed a series of neurocognitive tests as well as a MRI scan of their brain.

The results indicate that, when compared to typically developing individuals, participants with autism had smaller Corpus Callosum. This reduction in volume was limited to specific areas including the Rostrum, Genu, Anterior Body. Furthermore, as expected based on previous findings, the individual with autism had much lower scores on executive functioning (cognitive) tests when compared to typically developing participants.

The major finding however is that among typically developing participants within group variation in Corpus Callosum volume was not associated with variation in performance on the neurocognitive tests. That is, the size of the Corpus Callosum did not predict how well these participants would perform on the cognitive tests. However, among individual with autism, the size of the Corpus Callosum was associated with performance on this test, in that those with smaller Corpus Callosum tended to have more impaired performance than those with larger CC volumes.

This study provides additional evidence of Corpus Callosum atrophy in individuals with autism and the possible role of such anomaly in neurocognitive functioning, especially executive functioning tasks.

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8 Responses to Autism, Cognition, and the Corpos Callosum

  1. Nestor

    Thanks for the translation. Any idea what causes or leads to the Corpus Callosum atrophy?

  2. HI Harold, there are many lines of research on this, as anomalies in the cc are associated with many neurodevelopmental disorders. A good term to search is for “agenesis of the corpus callosum”. You will see many websites discussing possible factors that contribute to anomalies in the CC development.

    Although agenesis is an extreme form of malformation, that research may help understand what contributes to the reduced volume seen in autism. Nestor.

  3. Susan says:

    I’m wondering if glial cells can still be a causal factor.

  4. Hi Susan. Yes, most researchers agree that the causes of autism are likely numerous. The finding on the corpos callosum differences does not negate the possibility that many other factors (including anomalies in glial cell pruning) trigger or affect the development of autism. Nestor.

  5. Lindsay says:

    Hi Nestor,

    These volumetric studies are interesting, and give me a lot to think about in terms of how autistic brains develop.

    I've read quite a few of them, and they all seem to have sample sizes in the 15-30 people range. While this is enough to suggest a pattern, it's also so small as to leave me with doubt as to whether the observed phenomenon is typical of autism in general or represents just one of many subtypes. (Autism is already a heterogeneous enough category as to make this a decent possibility!)

    Are you aware of any neuroanatomical studies of autism with larger (say, n > 100) sample sizes?

  6. RAJ says:

    Smaller corpus collosum size and low scores on executive functioning tasks are also observed in a host of neurodevolopmental and neuropsychiatric conditions including schizophrenia, OCD, fetal alcohol syndrome, TICS, even in children with a history of emotional stress and abuse.


    I wish autism researchers would go beyond using a normal population control group. Autism is associated with an early, long-lasting disruption in brain development without any specific abnormalities that are not found in other neurodevelopmental and neuropsychiatric conditions that are associated with ‘social impairments’.

    Perhap ‘Autism Spectrum Disorders’ should be given a more meaningful label like ‘Neurodevelopmental Disorder Spectrum’.

  7. Nancy says:

    Does autism cause the shrinking the corpus callosum? Or does the shrunken corpus callosum cause autism?

    In other words, does this study point to causation, or simply to correlation?

    We know that when parts of the brain are well used, they grow larger (e.g., the left hand area for violin players). When they are not well used, they are left undeveloped.

    It is not surprising that areas in autistic brains are underdeveloped, just as there are (undoubtedly) parts that are overdeveloped. But it would be an unwarranted leap of logic to assume that the size causes the autism, and not the other way around.

  8. Sorry for the delay in responding.

    @Lindsay, Sorry I am not aware of any study with very large samples (n=100). fMRI and similar studies are so costly and difficult to conduct that unfortunately they usually include very small samples.

    @RAJ. I think we have discussed your concerns regarding the lack of specificity of most of autism research. “Specificity” is important when the researcher is interested in examining factors that are UNIQUE to autism. However, that is not the objective of most autism or medical research (nor should it be). When examining causal factors of any condition, there is no reason to believe that causal factors (e.g., malnutrition, obesity, smoking, etc) cause only ONE condition. Just as conditions are caused by multiple factors, those same factors also affect (or cause) multiple conditions. The fact that reduced corpos callosum volume is observed in many other disorders does not invalidate the possibility that corpos callosum atrophy may play a role in the development of autism.

    @Nacy. You are correct. These findings are correlational in nature. They only state that participants with autism displayed reduced volumes when compared to typically developing individuals. We can not conclude, based on this study alone, that reduced corpos callosum causes autism. However, for scientists that are examining such causal theory, these results are “consistent” with the theory.

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