Reactivation of a previous target location: a new event-related potential component

Abstract

When two events occur in close temporal succession, processing of one can affect the 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 100-1100 ms after S1. We refer to this component as re-activation positivity (P_R). In follow-up experiments, we explored the processes that may be indexed by the P_R. To examine whether the P_R 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 P_R was elicited by both the fixation cross and by the subsequent S2, providing evidence against an attentional disengagement account. On the alternate hypothesis that the P_R represents reactivation of a spatially-specific memory of the S1 target, we examined whether the P_R would occur if attention were directed to the S1-target location, but that location did not contain an item to be remembered. On half the trials, a colour oddball within a circular array of otherwise homogeneously-coloured rings contained a line segment, the orientation of which was to be remembered. On the other half of the trials, the oddball ring was empty, hence there was nothing to remember, and no response was required. The S2 display consisted of a digit presented at fixation 700 ms after S1. The P_R was elicited by S2 on all trials, suggesting that maintenance of the S1-target in memory is also not essential for eliciting the P_R.

Meeting abstract presented at VSS 2017