Manipulo-spatial aspects of cerebral lateralization: clues to the origin of lateralization.

The right hemisphere advantage for split-brain patients on a variety of spatial tasks (block design, cube drawing, wire figures, and fragemented stimuli) is found to be highly dependent upon the involvement of manual activities in the perception of spatial relationships or the production of spatial responses. The cerebral localization of the neural substrate of manipulo-spatial functions suggests why the hemispheres differ along the manipulo-spatial dimension. These observations, in conjunction with other clinical data, are suggestive of the origins of cerebral lateralization.