Dynamics of target and distractor processing in visual search: evidence from event-related brain potentials

When multiple objects are present in a visual scene, salient and behaviorally relevant objects are attentionally selected and receive enhanced processing at the expense of less salient or less relevant objects. Here we examined three lateralized components of the event-related potential (ERP) - the N2pc, Ptc, and SPCN - as indices of target and distractor processing in a visual search paradigm. Participants responded to the orientation of a target while ignoring an attentionally salient distractor and ERPs elicited by the target and the distractor were obtained. Results indicate that both the target and the distractor elicit an N2pc component which may index the initial attentional selection of both objects. In contrast, only the distractor elicited a significant Ptc, which may reflect the subsequent suppression of distracting or irrelevant information. Thus, the Ptc component appears to be similar to another ERP component - the Pd - which is also thought to reflect distractor suppression. Furthermore, only the target elicited an SPCN component which likely reflects the representation of the target in visual short term memory.