Reentrant Processing as Indexed by the N2pc

Abstract

A component of brain activity called the N2pc is associated with attending to a stimulus positioned laterally in a visual search display, however, the N2pc also seems to reflect processing associated with the complexity of visual search tasks. The brain activity of 96 undergraduates was recorded while they completed a complex visual search task featuring a ‘yes/no’ keyboard response and an oddball target vs. a simpler visual search task featuring a ‘go/no-go’ keyboard response and a single-colour target. The result of equally large N2pcs between the complex and simple tasks suggested that extra cognitive processing steps for the complex task are not reflected by the N2pc. However, these tasks may have been more equal in complexity than intended, since they both involved a single step of directing attention to the target. In experiment 2, 38 undergraduates completed more complex, two-step visual search tasks that required further analysis of the target, whether to report the colour of an oddball or to report the presence of a specific-colour oddball. These two-step tasks yielded larger N2pcs than experiment 1. This suggests that the N2pc reflects processing associated with visual search task complexity in terms of the number of steps taken to visually analyze a target. This finding is compatible with a reentrant processing view, whereby the N2pc reflects additional loops of reentrant cognitive processing required for more complex, two-step tasks.