Using event-related potentials (ERPs), the present study examined the electrophysiological and attentional asymmetries between the upper vis- ual field (UVF) and the lower visual field (LVF) while subjects were performing a target detecting task. The early ERP components showed a smaller P1 and a larger N1 in LVF than in UVF over the oc- cipito-parietal areas, while the late components (N2 and P3) showed no difference between the two visual fields. In addition, the attention enhancement on the P1 component was greater in UVF than in LVF. These findings suggest that the function of the UVF and LVF differ in terms of both early visual informa- tion processing and attentional modulation.
