Elsevier

Biological Psychiatry

Volume 59, Issue 1, 1 January 2006, Pages 1-6
Biological Psychiatry

Original article
Cortical Gray and White Brain Tissue Volume in Adolescents and Adults with Autism

https://doi.org/10.1016/j.biopsych.2005.06.015Get rights and content

Background

A number of studies have found brain enlargement in autism, but there is disagreement as to whether this enlargement is limited to early development or continues into adulthood. In this study, cortical gray and white tissue volumes were examined in a sample of adolescents and adults with autism who had demonstrated total brain enlargement in a previous magnetic resonance imaging (MRI) study.

Methods

An automated tissue segmentation program was applied to structural MRI scans to obtain volumes of gray, white, and cerebrospinal fluid (CSF) tissue on a sample of adolescent and adult males ages 13-29 with autism (n = 23) and controls (n = 15). Regional differences for brain lobes and brain hemispheres were also examined.

Results

Significant enlargement in gray matter volume was found for the individuals with autism, with a disproportionate increase in left-sided gray matter volume. Lobe volume enlargements were detected for frontal and temporal, but not parietal or occipital lobes, in the subjects with autism. Age and nonverbal IQ effects on tissue volume were also observed.

Conclusions

These findings give evidence for left-lateralized gray tissue enlargement in adolescents and adults with autism, and demonstrate a regional pattern of cortical lobe volumes underlying this effect.

Section snippets

Sample

Subjects for this study were a subset of a previously described sample of autistic and control subjects where brain enlargement on MRI was observed in the autistic individuals (Piven et al 1996). This sample provided an ideal opportunity to explore regional patterns of gray and white matter tissue volumes in a sample of autistic individuals with increased average total brain volume. The study was reviewed and approved by the University of Iowa Institutional Review Board. Written informed

Results

Consistent with results reported in the original sample (Piven et al 1996), total cerebral volume was significantly increased in the subset of autistic individuals versus controls included in this analysis (F1,34 = 5.16, p = .03). Mean total cerebral volume (SD) for the subjects with autism was 1222.8 cm3 (25.6) versus 1123.7 cm3 (32.5) for controls.

Table 2 presents the overall results of the repeated measures mixed model analyses showing significant tissue by hemisphere effects in cases versus

Discussion

In this study we examined gray and white tissue volumes by hemisphere and cortical lobe, in a group of autistic individuals known to have brain enlargement on MRI. Results revealed an increase in left-sided, cortical, gray tissue volume with no significant increase in white tissue volume. Subjects with autism had significant enlargement of gray tissue in the frontal and temporal, but not parietal or occipital lobes.

Our finding of increased gray tissue volume suggests the presence of an aberrant

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