Reciprocal or independent hemispheric specializations: Evidence from cerebral dominance for fluency, faces, and bodies in right- and left-handers.
Emma Karlsson, Leah T. Johnstone, David P. Carey
Abstract
Objective: There are distinct cortical regions that respond preferentially to human faces and bodies.It is generally accepted that these face-and body-selective regions are lateralized with a preference for the right hemisphere, but unknown how frequently these biases occur or if they are lateralized in a complementary fashion to language processing.Methods: fMRI was used to examine face and body lateralization in two samples of righthanders (n's = 31 and 18) and left-handers (n's = 43 and 24) with 'typical', left hemisphere, language dominance to examine the frequency of these biases.Crucially, we also recruited individuals with 'atypical', right hemisphere, language dominance (n's = 17 and 10) to examine complementarity with language.Results: Language typical right-handers had consistent population-level and average rightsided biases for face-and body perception.Language typical left-handers had populationlevel biases for faces in sample 2, but not sample 1; and for bodies in sample 1 but not sample 2. Language typical left-handers were, on average, right-lateralized for faces in both samples, but right-lateralized for bodies in sample 1 only.Language atypicals did not have a populationlevel bias for body-or face perception, and were, on average, left-lateralized for faces in sample 1, but not in sample 2. Atypicals were not lateralized for body perception.Conclusions: These results add to the growing literature which suggests that many right hemisphere processes are not lateralized in a fully complementary fashion to language.Lefthanders seem to have more varied lateralization patterns even when language dominance is controlled for.