[Shift of visual laterality difference by loading of auditory discrimination tasks (author's transl)].

To investigate the functional relationship between the right and the left cerebral hemispheres in normal man, the effects of verbal and nonverbal auditory loads on the visual laterality difference in recognizing line orientation and Japanese letters were examined. The left visual field superiority in recognizing line orientation increased with nonverbal load, and disappeared with verbal load. On the other hand, the right visual field superiority in recognizing letters increased with verbal load, and disappeared with nonverbal load. The results were interpreted as indicating that when verbal or nonverbal auditory load was presented to both hemispheres through both ears, shift of functional dominance occurred between the two hemispheres which were connected by corpus callosum.