Language and spatial attention can lateralize to the same hemispdhere in healthy humans

Flöel A., Knecht S., Lohmann H., Deppe M., Sommer J., Dräger B., Ringelstein E., Henningsen H.

Abstract

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.