Dissociations of cerebral cortex, subcortical and cerebral white matter volumes in autistic boys

Abstract

High-functioning autistic and normal school-age boys were compared using a whole-brain morphometric profile that includes both total brain volume and volumes of all major brain regions. We performed MRI-based morphometric analysis on the brains of 17 autistic and 15 control subjects, all male with normal intelligence, aged 7-11 years. Clinical neuroradiologists judged the brains of all subjects to be clinically normal. The entire brain was segmented into cerebrum, cerebellum, brainstem and ventricles. The cerebrum was subdivided into cerebral cortex, cerebral white matter, hippocampus-amygdala, caudate nucleus, globus pallidus plus putamen, and diencephalon (thalamus plus ventral diencephalon). Volumes were derived for each region and compared between groups both before and after adjustment for variation in total brain volume. Factor analysis was then used to group brain regions based on their intercorrelations. Volumes were significantly different between groups overall; and diencephalon, cerebral white matter, cerebellum and globus pallidus-putamen were significantly larger in the autistic group. Brain volumes were not significantly different overall after adjustment for total brain size, but this analysis approached significance and effect sizes and univariate comparisons remained notable for three regions, although not all in the same direction: cerebral white matter showed a trend towards being disproportionately larger in autistic boys, while cerebral cortex and hippocampus-amygdala showed trends toward being disproportionately smaller. Factor analysis of all brain region volumes yielded three factors, with central white matter grouping alone, and with cerebral cortex and hippocampus-amygdala grouping separately from other grey matter regions. This morphometric profile of the autistic brain suggests that there is an overall increase in brain volumes compared with controls. Additionally, results suggest that there may be differential effects driving white matter to be larger and cerebral cortex and hippocampus-amygdala to be relatively smaller in the autistic than in the typically developing brain. The cause of this apparent dissociation of cerebral cortical regions from subcortical regions and of cortical white from grey matter is unknown, and merits further investigation.

Modeling early cortical serotonergic deficits in autism

“…These findings are consistent with the increased cortical volumes described in children with autism. MRI studies have shown that the increased brain volumes in children with autism are to a large degree the result of increased white matter volumes [6,[56][57][58]. Using MRI-base morphometric analysis Herbert and colleagues [57] report disproportionately larger cerebral white matter volumes in boys with autism.…”

“…MRI studies have shown that the increased brain volumes in children with autism are to a large degree the result of increased white matter volumes [6,[56][57][58]. Using MRI-base morphometric analysis Herbert and colleagues [57] report disproportionately larger cerebral white matter volumes in boys with autism. They have gone on to localize the increased white matter volume to later or longer-myelinating regions of the radiate white matter compartment to all cerebral lobes (frontal, parietal, temporal and occipital) [58].…”

“…Initial MRI evaluation indicated that the increased brain volume in children with autism is the result of increased cerebral cortical gray matter and cerebral and cerebellar white matter [20,38]. However, more recent studies have demonstrated consistent increases in white matter volumes in children with autism [6,[56][57][58], which may be more pertinent to the key deficits in autism involving processing of complex social, sensory and language information.…”

Three-dimensional mapping of the lateral ventricles in autism

“…The overall excess in brain volume in patients with autism may result from abnormally high rates of growth for both gray and white matter in early childhood (Courchesne et al, 2001;Herbert et al, 2003;Hazlett et al, 2005Hazlett et al, , 2006. This early hypertrophy might be expected to influence the volume or shape of the lateral ventricles, but magnetic resonance imaging (MRI) studies of lateral ventricular anatomy in autism have yielded inconsistent results.…”

A Review on the Cognitive Neuroscience of Autism

“…Nine studies showed evidence of increased volume, while another nine studies had negative findings (see Figure 1). Of these nine, two approached a significant level of decreased volume (Rojas, Bawn, Benkers, Reite, & Rogers, 2002;Rojas et al, 2004), and another approached a significant level of increase (Herbert et al, 2003). Due to the small number of females diagnosed with autism, gender effects were measured in two studies only, with conflicting results.…”