ABSTRACT
Visual event-related potentials (ERPs) were recorded during an oddball paradigm (OBP) and a simple reaction paradigm (SRP) to investigate the effect of stimulus-onset asynchrony (SOA) on ERPs under constant and random conditions in nine healthy individuals. NA was obtained by subtracting ERPs for SRP from those to the frequent nontarget of OBP. N2 was obtained by subtracting ERPs to the frequent nontarget from those to the rare target of OBP. N1, P2, and P3 latencies during OBP were shorter, and N1 amplitude of OBP, P1, and P2 amplitude of SRP, and NA amplitude were larger under constant conditions than under random conditions. We suggest that visual information processing is faster and more effective under constant conditions than under random conditions. NA potential related to the pattern recognition processing was significantly interfered with under random conditions, whereas N2 potential related to the stimulus classification was less influenced by the rhythm. The visual selective processing activity was influenced by the SOA with the positive shift of the waveform "20% rare target of OBP-100% target of SRP" under random conditions.
