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Language and spatial attention can lateralize to the same hemisphere in healthy humans
1Department of Neurology, University of Münster, Germany. floeel@uni-muenster.de
Background:
Disorders of language classically occur after left brain lesions, and disorders of spatial attention after right brain lesions. It is unclear whether the hemispheric dissociation of functions is a fixed pattern of brain organization.
Objective:
The authors determined whether lateralization of language and lateralization of spatial attention also dissociate in people with atypical (i.e., right hemispheric) language dominance.
Methods:
The authors selected 10 subjects with typical, i.e., left hemispheric, and 10 with atypical, i.e., right hemispheric, language representation on a random basis from a sample of 326 healthy volunteers examined with functional transcranial Doppler sonography (fTCD) for language dominance. In these subjects, hemispheric lateralization of cerebral perfusion during a line bisection task was determined with fTCD.
Results:
The authors found a dissociation between dominance for language and spatial attention in all but four subjects. In the latter subjects, there was a significant lateralization to the right hemisphere for both tasks. The four subjects showed normal intellectual, linguistic, and spatial performance, with normal EEG and MRI scans of the brain.
Conclusion:
Even in the absence of brain pathology, the same hemisphere can be dominant in control of both language and spatial attention.