Spatial influences on motor and language function.

In subjects with parietal lobe lesions, performance on motor and language tasks differed as a function of the side of space to which subjects directed their attention or acted. Subjects with left parietal lesions performed better when attention was directed to stimuli in left hemispace (that is, the left side of their environment), and those with right parietal lesions showed a similar effect when attending to stimuli in right hemispace. Hemispace effects were not observed in subjects with lesions located elsewhere in the cerebral hemispheres, or in subjects with subcortical lesions. These data are consistent with the view that not only motor but also cognitive operations such as language, which do not appear to have any intrinsic spatial organization, are maintained in registration with spatial systems, and that this attention-requiring linkage confers a processing advantage.