Abstract
When two events occur in close temporal succession, processing of one can affect processing of the other. We discovered a novel electrophysiological component that may elucidate such inter-event interactions. Participants viewed two displays (S1 and S2) shown sequentially in different locations. S1 and S2 each consisted of a target and a distractor presented either on the horizontal or vertical meridian. A pronounced event-related potential positivity, lateralized to the location of the S1 target, was evoked by the onset of S2, which appeared 100-1400 ms after S1. We refer to this component as re-activation positivity (PR). To examine whether the PR indexes disengagement of attention from the S1-target location upon presentation of S2, an irrelevant fixation cross was inserted in the display sequence between S1 and S2. The critical finding was that the PR was elicited by both the fixation cross and by the subsequent S2, providing evidence against an attentional disengagement account. On an alternate hypothesis that the PR represents reactivation of a spatially-specific memory of the S1 target, we examined whether the PR would be modulated by the number of to-be-remembered items in S1. S1 was an 8-item search array containing either one or three digits on the same side of fixation, with all of the other items being irrelevant # symbols. S1 was followed 700 ms later by a task-irrelevant fixation cross and 1400 ms later by S2: a single centrally presented digit. The task was to report whether the S2 digit matched one of the digits presented in the S1 display. The magnitude of the PR elicited by both the fixation cross and S2 was larger when the S1 array contained three digits, compared with one digit. These results suggest that the PR component may index the spatially-specific reactivation of items held in memory.
Meeting abstract presented at VSS 2018