Intra-hemispheric intrinsic connectivity asymmetry and its relationships with handedness and language Lateralization.

M. Joliot, N. Tzourio-Mazoyer, B. Mazoyer
Neuropsychologia. 2016-12-01; 93: 437-447
DOI: 10.1016/j.neuropsychologia.2016.03.013

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1. Neuropsychologia. 2016 Dec;93(Pt B):437-447. doi:
10.1016/j.neuropsychologia.2016.03.013. Epub 2016 Mar 14.

Intra-hemispheric intrinsic connectivity asymmetry and its relationships with
handedness and language Lateralization.

Joliot M(1), Tzourio-Mazoyer N(2), Mazoyer B(2).

Author information:
(1)IMN, UMR 5293, GIN, CNRS, F-33000 Bordeaux, France; IMN, UMR 5293, GIN, Univ.
Bordeaux, F-33000 Bordeaux, France; IMN, UMR 5293, GIN, CEA, F-33000 Bordeaux,
France. Electronic address: .
(2)IMN, UMR 5293, GIN, CNRS, F-33000 Bordeaux, France; IMN, UMR 5293, GIN, Univ.
Bordeaux, F-33000 Bordeaux, France; IMN, UMR 5293, GIN, CEA, F-33000 Bordeaux,
France.

Asymmetry in intra-hemispheric intrinsic connectivity, and its association with
handedness and hemispheric dominance for language, were investigated in a sample
of 290 healthy volunteers enriched in left-handers (52.7%). From the
resting-state FMRI data of each participant, we derived an intra-hemispheric
intrinsic connectivity asymmetry (HICA) matrix as the difference between the left
and right intra-hemispheric matrices of intrinsic correlation computed for each
pair of the AICHA atlas ROIs. We defined a similarity measure between the HICA
matrices of two individuals as the correlation coefficient of their corresponding
elements, and computed for each individual an index of intra-hemispheric
intrinsic connectivity asymmetry as the average similarity measure of his HICA
matrix to those of the other subjects of the sample (HICAs). Gaussian-mixture
modeling of the age-corrected HICAs sample distribution revealed that two types
of HICA patterns were present, one (Typical_HICA) including 92.4% of the
participants while the other (Atypical_HICA) included only 7.6% of them, mostly
left-handers. In addition, we investigated the relationship between asymmetry in
intra-hemispheric intrinsic connectivity and language hemispheric dominance,
including a potential effect of handedness on this relationship, thanks to an
FMRI acquisition during language production from which an hemispheric functional
lateralization index for language (HFLI) and a type of hemispheric dominance for
language, namely leftward, ambilateral, or rightward, were derived for each
individual. There was a significant association between the types of language
hemispheric dominance and of intra-hemispheric intrinsic connectivity asymmetry,
occurrence of Atypical_HICAs individuals being very high in the group of
individuals rightward-lateralized for language (80%), reduced in the ambilateral
group (19%) and rare in individuals leftward-lateralized for language (less than
3%). Quantitatively, we found a significant positive linear relationship between
the HICAs and HFLI indices, with an effect of handedness on the intercept but not
on the slope of this relationship. These findings demonstrate that handedness and
hemispheric dominance for language are significantly but independently associated
with the asymmetry of intra-hemispheric intrinsic connectivity. These findings
suggest that asymmetry in intra-hemispheric connectivity is a variable phenotype
shaped in part by hemispheric lateralization for language, but possibly also
depending on other lateralized functions.

Copyright © 2016 Elsevier Ltd. All rights reserved.

DOI: 10.1016/j.neuropsychologia.2016.03.013
PMID: 26988116 [Indexed for MEDLINE]


Auteurs Bordeaux Neurocampus