Mechanisms underlying the left visual-field advantage in the dual stream RSVP task: evidence from N2pc, P3, and distractor-evoked VEPs.

When two letter streams containing two targets (T1 and T2) are presented left and right, T2 is better identified in the left hemifield. This study on 16 healthy participants used evidence from ERPs to decide whether this advantage is due to better processing in the right hemisphere or to overload of the left one. N2pc and P3 components evoked by T1 and T2 were measured, as well as the VEPs evoked by the stream of distractor stimuli. Already at the onset of the stream, these VEPs peaked earlier at the right than at the left hemisphere. N2pc was evoked earlier and P3 amplitudes were larger with left than with right T2. Previously reported side differences in T1-evoked N2pc were no longer obtained after correcting for constant hemispheric differences. The faster VEP latencies at the right hemisphere from the very beginning of the stimulus series may reflect an advantage in structuring fast sequences, which may cause the left visual-field advantage.