Hemispheric specialization for language: Brain volume matters
Brain Research. 2006-01-01; 1068(1): 184-193
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1. Brain Res. 2006 Jan 12;1068(1):184-93. Epub 2005 Dec 27.
Hemispheric specialization for language: Brain volume matters.
Josse G(1), Hervé PY, Crivello F, Mazoyer B, Tzourio-Mazoyer N.
(1)Groupe d’Imagerie Neurofonctionnelle, UMR 6194, CNRS, CEA, Université de
Caen/Paris V, France.
Increasing brain volume may impose constraints, through longer information
transfer delays, on the distributed networks supporting language. Here, we
assessed the relative effects of brain volume and other putative predictors of
the functional variability of perisylvian language areas, as probed with PET,
during both a language comprehension and a language production task. In the case
of language comprehension (story listening), a linear combination of planum
temporale surface, brain volume and handedness could explain almost 60% of the
functional asymmetry observed in the perisylvian area. Without brain volume, the
goodness of fit was significantly decreased (39%, P < 0.05), and furthermore, the
effect of handedness was not detected anymore. This was due to the fact that in
our sample, left-handers (n = 12) had a significantly larger brain volume as
compared to right-handers (n = 8, P = 0.03). As for language production (verb
generation), brain volume and the planum temporale also played a role. However,
in this case, the main predictor of functional variability was handedness, where
a greater degree of right-handedness was associated with larger activation of
left inferior frontal regions. Depending on the language component of interest,
these results support different (yet compatible) theories on hemispheric
specialization. Left specialization for comprehension could be attributed to the
constraints of processing speech stimuli, while a gestural origin of language is
mostly supported by the relation we observed between left specialization for
production and right-handedness.
PMID: 16380101 [Indexed for MEDLINE]