Abstract
The deployment of visual attention is associated with the N2pc EEG component, although it is not entirely clear what mechanism this component reflects. A computational model by Tan & Wyble (2015) suggests that this component reflects the transient process of engaging attention at the location of a stimulus in preparation for consolidating that information into memory (i.e. locking-on to a target's location). This conclusion stems from previous findings that the N2pc is only triggered by the first of two sequential targets at the same location, but is triggered by both targets when presented at different locations. We tested predictions from the Tan-Wyble model. First, we replicated the crucial finding that the N2pc is missing for a second target. Next, we tested a prediction that if there are distinct attention maps for different kinds of targets then there should be two N2pcs for sequential targets of different types. Two RSVP streams presented distractors (black letters) and two targets of different types (black digits and red letters) bilaterally. Presumably, separate attentional maps would each deploy attention to their respective target types, resulting in two N2pcs. However the results indicated only a single N2pc, which suggests a single attentional map. Next, we varied the latency between two targets to determine the point at which attention needed to be re-engaged following successful deployment. The second N2pc was clearly present for targets separated by 450ms but not 150ms, even on trials in which subjects reported both targets. This suggests that attention to a location needs to be re-engaged after several hundred milliseconds even though subjects know with certainty the target will be there. Finally, we extended the finding of a missing N2pc to three consecutive targets, suggesting that attentional engagement states can persist across a string of task-relevant items at a particular location.
Meeting abstract presented at VSS 2016