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Abstract
This study sought to replicate CitationHerbert et al. (2003a), which found increased overall white matter (WM) volume in subjects with autism, even after controlling for head size differences. To avoid the possibility that greater WM volume in autism is merely an epiphenomena of macrocephaly overrepresentation associated with the disorder, the current study included control subjects with benign macrocephaly. The control group also included subjects with a reading disability to insure cognitive heterogeneity. WM volume in autism was significantly larger, even when controlling for brain volume, rate of macrocephaly, and other demographic variables. Autism and controls differed little on whole-brain WM voxel-based morphometry (VBM) analyses suggesting that the overall increase in WM volume was non-localized. Autism subjects exhibited a differential pattern of IQ relationships with brain volumetry findings from controls. Current theories of brain overgrowth and their importance in the development of autism are discussed in the context of these findings.
Notes
Supported in part by the National Institutes of Child Health and Human Development 5 U19 HD035476-07 and NIMH 1RO1 MH080826 and the NICHD Collaborative Programs of Excellence in Autism (CPEA) and the Ira Fulton Foundation.
*2 Sample t-Test comparing Combined Autism versus Combined Control Groups.
†Two Typically Developing patients unclassified as to whether macrocephalic or normocephalic.
*p values refer to univariate general linear model (GLM) test of total brain and regional volume differences, adjusting for age.
† Overall F-test of group differences was obtained using multivariate general linear model (GLM) for correlated data, controlling for age [F(9,73) = 1.7600, p = 0.0909]
*p values refer to univariate general linear model (GLM) test of total brain and regional volume differences, adjusting for age.
‡Overall F-test of group differences was obtained using multivariate general linear model (GLM) for correlated data, controlling for age [F(8,74) = 1.8957, p = 0.0733].
**p = 0.02.
