Elsevier

Biological Psychiatry

Volume 66, Issue 10, 15 November 2009, Pages 935-941
Biological Psychiatry

Archival Report
A Meta-Analysis of the Corpus Callosum in Autism

https://doi.org/10.1016/j.biopsych.2009.07.022Get rights and content

Background

Previous magnetic resonance imaging (MRI) studies have reported reductions in corpus callosum (CC) total area and CC regions in individuals with autism. However, studies have differed concerning the magnitude and/or region contributing to CC reductions. The present study determined the significance and magnitude of reductions in CC total and regional area measures in autism.

Method

PubMed and PsycINFO databases were searched to identify MRI studies examining corpus callosum area in autism. Ten studies contributed data from 253 patients with autism (mean age = 14.58, SD = 6.00) and 250 healthy control subjects (mean age = 14.47, SD = 5.31). Of these 10 studies, 8 reported area measurements for corpus callosum regions (anterior, mid/body, and posterior), and 6 reported area for Witelson subdivisions. Meta-analytic procedures were used to quantify differences in total and region CC area measurements.

Results

Total CC area was reduced in autism and the magnitude of the reduction was medium (weighted mean d = .48, 95% confidence interval [CI] = .30–.66). All regions showed reductions in size with the magnitude of the effect decreasing caudally (anterior d = .49, mid/body d = .43, posterior d = .37). Witelson subdivision 3 (rostral body) showed the largest effect, indicating greatest reduction in the region containing premotor/supplementary motor neurons.

Conclusions

Corpus callosum reductions are present in autism and support the aberrant connectivity hypothesis. Future diffusion tensor imaging studies examining specific fiber tracts connecting the hemispheres are needed to identify the cortical regions most affected by CC reductions.

Section snippets

Search Strategy and Exclusion Criteria

PubMed/MEDLINE and PsycINFO were searched for studies from January 1970 to June 2008 using the terms “autism or PDD or pervasive developmental disorder” and “corpus callosum.” A specific search for Asperger's disorder was also done but no published studies were identified. Additional studies were identified by reviewing the references of each article found. Studies were included if they reported measurement for the total corpus callosum area in patients with autism and healthy control subjects.

Results

Ten studies met inclusion criteria with each study providing one effect size (Table 1). Of these 10 studies, two studies only provided total CC area (33, 34) and two studies only provided data for broad regions but not Witelson subdivisions (24, 27). One study included only enough information to evaluate W1 through W4 and W7 (32). Another study only included enough information to evaluate W4 through W7 (23).

Table 1 presents demographics and study characteristics. Studies contributed 503 total

Discussion

Findings from the present investigation provide strong support to previous studies suggesting involvement of CC in the pathophysiology of autism. The present meta-analytic results indicate that total CC area is smaller in autism, consistent with studies implicating the CC in emotional and social functioning (47) and higher cognitive processes such as decoding nonliteral meaning, affective prosody, and understanding humor (48, 49). The CC provides integrated interhemispheric communication

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