Mapping cortical brain asymmetry in 17,141 healthy individuals worldwide via the ENIGMA Consortium.
Level 4 - case-series / case-control
Cross-sectional meta-analysis of observational neuroimaging datasets (design analogy).
PubMed 29764998 · doi:10.1073/pnas.1718418115
What was done
The ENIGMA Consortium analyzed structural MRI scans from 17,141 healthy individuals across 99 global datasets to map cortical thickness and surface area asymmetry. They assessed hemispheric and regional asymmetries, evaluated relationships with age, sex, intracranial volume, and handedness, and calculated heritability of structural asymmetries in two independent pedigree cohorts (n = 1,443 and n = 1,113).
What was found
Cerebral cortical asymmetry was widespread across the population: the left hemisphere generally exhibited thicker cortex but smaller surface area compared to the right. Specific regional asymmetries were detected in the inferior frontal gyrus, transverse temporal gyrus, parahippocampal gyrus, and entorhinal cortex. Asymmetry variability was related to sex, age, and intracranial volume, but not handedness. Multiple asymmetries showed significant, replicable heritability across both pedigree datasets. Specific numerical effect sizes, test statistics, and p-values were not provided in the abstract.
Why it matters
This study provides an authoritative, large-scale normative reference map of structural brain laterality in healthy humans, establishing a baseline to understand how asymmetry is altered in neuropsychiatric and cognitive disorders.
Limits
The abstract reports no exact numbers, effect sizes, or confidence intervals. The cross-sectional design restricts conclusions regarding longitudinal developmental trajectories. Functional laterality and cognitive performance measures were not evaluated directly.
Cited by
- contradicts Women naturally have more developed right cerebral hemispheres, whereas men have more developed left cerebral hemispheres.