Second-order visual mechanisms and interhemispheric asymmetry V Babenko, P Ermakov |
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Department of Psychology, Southern Federal University, Russian Federation
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| It is a common view that the right hemisphere realizes global description of visual scenes. The first step of visual processing is local linear filtering which is bilaterally performed in a striate cortex. After that second-order visual mechanisms (SOVMs) spatially integrate the first-order filter outputs. The aim of our study is to reveal whether hemispheric asymmetry of visual processing arises at this level. To solve this problem we used mismatches between VEPs to nonmodulated and orientationally modulated checkerboard texture, composed of Gabor micropatterns. VEPs were recorded by 20 leads. 48 observers participated in the experiments. It was found that the mismatch has 3 waves. But in our opinion only the first wave which is generated between 170 to 250 ms represents SOVMs activity. Subsequent waves forming after 300 ms are apparently related with decision-making and preparation of behavioral response. We calculated localization of dipole source of this mismatch wave using one-dipole model. The dipole was located in the area 18 of the right hemisphere. Obtained results suggest that the right-side asymmetry during visual processing is formed as early as the initial stage of the spatial pooling of local orientation information. [Supported by RFH grant 12-06-00169] |
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