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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