The electrophysiology of selective target and distractor processing in visual search

The eyes provide more information than ever reaches awareness. Selection of relevant information for processing relies on a cognitive mechanism known as attention. In this thesis, two electrophysiological studies of visual attention are reported. Both studies focused on an electrical brain response called the N2pc that has been linked to attentional selection. The first study showed that when a salient nontarget and a less salient target are presented among distractors, the task-irrelevant nontarget elicits an N2pc. This demonstrates that attention can be captured by salient, task-irrelevant stimuli. The second study further investigated the electrophysiology of attentional selection by decomposing the N2pc into target-related and distractor-related sub-components. The same stimulus was found to elicit a contralateral ERP negativity when attended and a contralateral ERP positivity when ignored. These results suggest that attentional selection in visual search involves both distractor suppression and selective target processing and that the N2pc reflects both processes.