Gaussian Mixture Modeling of Hemispheric Lateralization for Language in a Large Sample of Healthy Individuals Balanced for Handedness

Bernard Mazoyer, Laure Zago, Gaël Jobard, Fabrice Crivello, Marc Joliot, Guy Perchey, Emmanuel Mellet, Laurent Petit, Nathalie Tzourio-Mazoyer
PLoS ONE. 2014-06-30; 9(6): e101165
DOI: 10.1371/journal.pone.0101165

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1. PLoS One. 2014 Jun 30;9(6):e101165. doi: 10.1371/journal.pone.0101165.
eCollection 2014.

Gaussian mixture modeling of hemispheric lateralization for language in a large
sample of healthy individuals balanced for handedness.

Mazoyer B(1), Zago L(1), Jobard G(1), Crivello F(1), Joliot M(1), Perchey G(1),
Mellet E(1), Petit L(1), Tzourio-Mazoyer N(1).

Author information:
(1)Groupe d’Imagerie Neurofonctionnelle, Centre National de la Recherche
Scientifique, Commissariat à l’Energie Atomique, et Université de Bordeaux,
Bordeaux, France.

Hemispheric lateralization for language production and its relationships with
manual preference and manual preference strength were studied in a sample of 297
subjects, including 153 left-handers (LH). A hemispheric functional
lateralization index (HFLI) for language was derived from fMRI acquired during a
covert sentence generation task as compared with a covert word list recitation.
The multimodal HFLI distribution was optimally modeled using a mixture of 3 and 4
Gaussian functions in right-handers (RH) and LH, respectively. Gaussian function
parameters helped to define 3 types of language hemispheric lateralization,
namely “Typical” (left hemisphere dominance with clear positive HFLI values, 88%
of RH, 78% of LH), “Ambilateral” (no dominant hemisphere with HFLI values close
to 0, 12% of RH, 15% of LH) and “Strongly-atypical” (right-hemisphere dominance
with clear negative HFLI values, 7% of LH). Concordance between dominant
hemispheres for hand and for language did not exceed chance level, and most of
the association between handedness and language lateralization was explained by
the fact that all Strongly-atypical individuals were left-handed. Similarly, most
of the relationship between language lateralization and manual preference
strength was explained by the fact that Strongly-atypical individuals exhibited a
strong preference for their left hand. These results indicate that concordance of
hemispheric dominance for hand and for language occurs barely above the chance
level, except in a group of rare individuals (less than 1% in the general
population) who exhibit strong right hemisphere dominance for both language and
their preferred hand. They call for a revisit of models hypothesizing common
determinants for handedness and for language dominance.

DOI: 10.1371/journal.pone.0101165
PMCID: PMC4076312
PMID: 24977417 [Indexed for MEDLINE]

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