Abstract
Event-related potentials (ERPs) were recorded while subjects received patterned stimuli that were presented briefly in random order to upper and lower visual fields at intervals of 430-540ms. In attention conditions, subjects were instructed to maintain eye fixation to a central point, and attend to one visual field in order to detect occasional targets, stimuli with slightly different pattern. Passive control, no task conditions were also administered to check the influence of fixation shifts on ERPs. In consistent with the previous studies of pattern visual-evoked potentials (VEPs), the early ERP deflections over parietal and occipital areas revealed a striking reversal of polarity between upper and lower field stimulation : P120-180 to upper stimuli and N140-190 to lower stimuli. Selective spatial attention was manifested in the P120-180 and N140-180 waves as an amplitude enhancement. The fixation shifts in the control conditions produced a different pattern of ERP changes. These findings suggest attention effects on the pattern-specific VEP component, C2.
