4.4 Article

A Surface-based Analysis of Language Lateralization and Cortical Asymmetry

Journal

JOURNAL OF COGNITIVE NEUROSCIENCE
Volume 25, Issue 9, Pages 1477-1492

Publisher

MIT PRESS
DOI: 10.1162/jocn_a_00405

Keywords

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Funding

  1. National Institutes of Health [R01NS052585-03]
  2. National Institute on Aging [5R01AG029411, 5R01AG022381-08]
  3. National Institute of Neurological Disorders and Stroke [1R01NS069696-01A1]
  4. National Center for Research Resources [P41-RR14075, R01 RR16594-01A1]
  5. National Center for Research Resources (NCRR BIRN Morphometric Project) [BIRN002]
  6. National Center for Research Resources (Functional Imaging Biomedical Informatics Research Network [FBIRN]) [U24 RR021382]
  7. National Institute for Biomedical Imaging and Bioengineering [R01 EB001550, R01 EB006758, 1K25 EB013649-01]
  8. Government of Flanders

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Among brain functions, language is one of the most lateralized. Cortical language areas are also some of the most asymmetrical in the brain. An open question is whether the asymmetry in function is linked to the asymmetry in anatomy. To address this question, we measured anatomical asymmetry in 34 participants shown with fMRI to have language dominance of the left hemisphere (LLD) and 21 participants shown to have atypical right hemisphere dominance (RLD). All participants were healthy and left-handed, and most (80%) were female. Gray matter (GM) volume asymmetry was measured using an automated surface-based technique in both ROIs and exploratory analyses. In the ROI analysis, a significant difference between LLD and RLD was found in the insula. No differences were found in planum temporale (PT), pars opercularis (POp), pars triangularis (PTr), or Heschl's gyrus (HG). The PT, POp, insula, and HG were all significantly left lateralized in both LLD and RLD participants. Both the positive and negative ROI findings replicate a previous study using manually labeled ROIs in a different cohort [Keller, S. S., Roberts, N., Garcia-Finana, M., Mohammadi, S., Ringelstein, E. B., Knecht, S., et al. Can the language-dominant hemisphere be predicted by brain anatomy? Journal of Cognitive Neuroscience, 23, 2013-2029, 2011]. The exploratory analysis was accomplished using a new surface-based registration that aligns cortical folding patterns across both subject and hemisphere. A small but significant cluster was found in the superior temporal gyrus that overlapped with the PT. A cluster was also found in the ventral occipitotemporal cortex corresponding to the visual word recognition area. The surface-based analysis also makes it possible to disentangle the effects of GM volume, thickness, and surface area while removing the effects of curvature. For both the ROI and exploratory analyses, the difference between LLD and RLD volume laterality was most strongly driven by differences in surface area and not cortical thickness. Overall, there were surprisingly few differences in GM volume asymmetry between LLD and RLD indicating that gross morphometric asymmetry is only subtly related to functional language laterality.

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