Background: Disorders of language classically occur after left brain lesion
s, and disorders of spatial attention after right brain lesions. It is uncl
ear whether the hemispheric dissociation of functions is a fixed pattern of
brain organization. Objective: The authors determined whether lateralizati
on of language and lateralization of spatial attention also dissociate in p
eople 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 ran
dom basis from a sample of 326 healthy volunteers examined with functional
transcranial Doppler sonography, (fTCD) for language dominance. In these su
bjects, hemispheric lateralization of cerebral perfusion during a line bise
ction task was determined with fTCD. Results: The authors found a dissociat
ion between dominance for language and spatial attention in all but four su
bjects. In the latter subjects, there was a significant lateralization to t
he right hemisphere for both tasks. The four subjects showed normal intelle
ctual, linguistic, and spatial performance, with normal EEG and MRI scans o
f the brain. Conclusion: Even in the absence of brain pathology, the same h
emisphere can be dominant in control of both language and spatial attention
.