Atypically rightward cerebral asymmetry in male adults with autism stratifies individuals with and without language delay.
Level 4 - case-series / case-control
Case-control neuroimaging study comparing adults with autism to matched neurotypical controls.
PubMed 26493275 · doi:10.1002/hbm.23023
What was done
The authors investigated structural brain asymmetry in 67 right-handed adult males with autism spectrum conditions (ASC) and 69 age- and IQ-matched neurotypical male controls. Voxel-based morphometry of grey matter volumes was used to evaluate group differences in asymmetry across cortical regions of interest. These structural findings were subsequently correlated with behavioral measures of language, motor, and visuospatial performance, as well as stratified by language onset history.
What was found
The abstract reports directional anatomical findings without reporting numerical values, effect sizes, or test statistics. Individuals with ASC demonstrated stronger rightward lateralization in the inferior parietal lobule and reduced leftward lateralization across auditory cortex regions (planum temporale, Heschl's gyrus, posterior supramarginal gyrus, and parietal operculum). This reduction in leftward auditory lateralization was more pronounced in individuals with ASC who had delayed language onset compared to those without delay, and correlated with greater childhood social reciprocity difficulties.
Why it matters
This work identifies structural asymmetry in language and auditory regions as a candidate neurophenotype in autism that distinguishes individuals based on developmental language delay history.
Limits
The study is restricted to adult right-handed males, precluding generalization to females, left-handed individuals, or pediatric cohorts. The cross-sectional design cannot establish developmental causality, and the abstract omits exact numerical effect sizes, volumetric measurements, and p-values.
Cited by
- contradicts Simon Baron-Cohen's autism research associates autism with hyper-development of the left cerebral hemisphere, explaining its higher prevalence in boys.