title: Main effect and interactions of brain regions and gender in the calculation of volumetric asymmetry indices in healthy human brains: ANCOVA analyses of in vivo 3T MRI data.
abstract: BACKGROUND
  Macroanatomical right-left hemispheric differences in the brain are termed asymmetries, although there is no clear information on the global influence of gender and brain-regions. The aim of this study was to evaluate the main effects and interactions of these variables on the measurement of volumetric asymmetry indices (VAIs).
  
  
  METHODS
  Forty-seven healthy young-adult volunteers (23 males, 24 females) agreed to undergo brain magnetic resonance imaging in a 3T scanner. Image post processing using voxel-based volumetry allowed the calculation of 54 VAIs from the frontal, temporal, parietal and occipital lobes, limbic system, basal ganglia, and cerebellum for each cerebral hemisphere. Multivariate ANCOVA analysis calculated the main effects and interactions on VAIs of gender and brain regions controlling the effect of age.
  
  
  RESULTS
  The only significant finding was the main effect of brain regions (F (6, 9373.605) 44.369, P < .001; partial η2 = .101, and power of 1.0), with no significant interaction between gender and brain regions (F (6, 50.517) .239, P = .964).
  
  
  CONCLUSIONS
  Volumetric asymmetries are present across all brain regions, with larger values found in the limbic system and parietal lobe. The absence of a significant influence of gender and age in the evaluation of the numerous measurements generated by multivariate analyses in this study should not discourage researchers to report and interpret similar results, as this topic still deserves further assessment.
authors.affiliation: MRI Unit, Medica Sur Clinic & Foundation, Mexico City, Mexico.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Roldan-Valadez
authors.forename: Camilo
authors.initials: C
authors.lastname: Rios
authors.forename: Marcela A
authors.initials: MA
authors.lastname: Suarez-May
authors.forename: Rafel
authors.initials: R
authors.lastname: Favila
authors.forename: Erika
authors.initials: E
authors.lastname: Aguilar-Castañeda
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D059906:Neuroimaging / Q000379:methods*; D055815:Young Adult
keywords: basal ganglia; cerebellum; cerebral cortex; cerebrum; limbic system; magnetic resonance imaging; multivariate analysis