Hemispheric asymmetry in processing visual half-field pattern-reversal stimuli assessed by reaction time and evoked potentials.

Reversing checkerboard patterns, like those used to elicit clinical visual evoked potentials (VEPs), were adapted to the study of cerebral lateralization of visual processing in a divided visual field experiment. Seventeen right-handed subjects (9 male, 8 female) provided left- and right-handed responses to pattern-reversal stimuli presented in left, right and both visual half-fields in pseudorandom order. Simple unwarned RTs were shorter for left- compared with right-field stimuli under left-hand response conditions. Parietal VEPs obtained from 9 of the subjects showed larger amplitudes for left compared with right field stimuli at the right hemisphere. The results were consistent with an efficiency model of cerebral dominance incorporating both interhemispheric transfer time and a reduced efficiency for left hemisphere processing of our patterned visual stimuli.