Laterality Effect on Visual Orientation Processing: An Event-Related Potential Study

Although previous studies have demonstrated visual spatial frequency processing in human, how orientation discrimination alter visual spatial frequency processing in temporal mechanism has not yet been elucidated completely. To investigate this, we design to performing a classical perceptual tasks of grating orientation discrimination. Participants were told to identify the orientation of the stimulus and pressed relevant button as quickly and accurately as possible. We assessed the diversity by measuring the magnitude of reaction times (RT) and event-related potential (ERP) results, which showed that the subject's response was strongly depended on spatial frequency (p < 0.05). The evoked brain activity during orientation discrimination was significant hemispheric asymmetry, the amplitude of middle stage (270–410 ms) for right hemisphere was larger than that for left hemisphere. In addition, the laterality effect was depended on spatial frequency, significant difference was found between low and high spatial frequency (p < 0.05). These results provide unique insight about how the brain processes visual orientation information and provide some basic data for human hemispheric asymmetry.