The Effect of Handedness on Visual P300 Responses and Visual Scanning Pathways

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AbstractIt is thought that hemispheric asymmetry is reflected to behavioral asymmetries. The most prominent behavioral asymmetry is hand preference. This study consisted of two groups (14 each) with different handedness. Event-Related Potentials (ERPs) to a visual oddball task were recorded from 19 sites, and another session with a “change detection paradigm” was applied, where the visual scanning pathways were recorded. Although the comparison of P300 grand averages of 19 sites showed no significant difference between the groups, the comparison of the central sites (Fz, Cz, Pz) showed significant differences of both, amplitude and latency, (p<0.05; p<0.04) respectively, where larger amplitudes and longer latencies were found in the right handed group. Both groups have showed larger P300 amplitudes of right hemispheric responses (p<0.01) in inter-hemispheric comparison. The results of “change detection paradigm” have shown no significant difference between the groups. The cognitive processing of visual information was found to be more dominant at the right hemisphere in both groups, and stronger at central sites in right handed subjects than their left handed counter partners. The study included both, right- and left handed subjects, which makes it more specific than the previous studies in the field. The present findings were related with the results of studies which examine the thickness of the skull, the size of corpus callosal area and the functional specialization of hemispheres.