The N2pc component as an indicator of attentional selectivity

Event-related potentials (ERPs) were recorded during visual discrimination tasks in which stimulus arrays were presented that contained one lateral target and 3 (experiment 1) or one (experiments 2 and 3) non-targets. In experiments 1 and 2, targets differed from non-targets with respect to their form or their color. In experiment 3, word pairs were presented, with targets differing from non-targets with respect to their content. Subjects were required to respond to the identity of the target. In all experiments, an enhanced negativity was elicited at posterior electrodes contralateral to the location of the target. In the form discrimination tasks, this effect was present in the N1, N2, and P3 time intervals. In the color discrimination tasks, it was confined to the N2 time range. In the word discrimination task (experiment 3), this effect could only be observed over the left posterior hemisphere. It is argued that these lateralized negativities reflect the N2pc component that is assumed to indicate attentional filtering processes during visual search tasks. The present results extend this assumption by showing that this component is also elicited when targets are presented together with just one non-target item. It is argued that the N2pc may reflect the attentional selection of task-relevant stimuli.