Electrophysiological evidence for inhibition of return effect in exogenous orienting.

Although the inhibition of return (IOR) effect in exogenous orienting has been investigated extensively with the Posnerian cuing paradigm, there has been little evidence for the role of attentional processes in the IOR effect. The N2pc component was used as a marker of the deployment of spatial attention to isolate attentional processes in the IOR effect. Participants responded to task-relevant target displays that were preceded by cue displays in a non-predictive, exogenous cuing paradigm. A 1,000 ms of stimulus onset asynchrony (SOA) was designed to investigate the IOR effect. Behavioral results indicate that the SOA was sufficiently long to cause an IOR effect in the discrimination task. As for ERP patterns elicited by targets, the N2pc amplitudes were similar across cue types, but the N2pc latency was delayed when targets appeared at the cued location rather than at the uncued location. N2pc patterns demonstrated that the spatial attentional process is indeed an important mechanism underlying the IOR effect. The delayed N2pc for targets in the valid cue type suggested that IOR effect may reflect a delayed deployment of spatial attention to targets appearing at recently cued locations.