Abstract
We have previously demonstrated that two attentional control sets (ACSs), each defined by a separate color, can be maintained over distinct locations in space, as observed in reaction times (RTs) to target stimuli. The current study used event-related potentials (ERP) to examine the neural responses to both cues and targets in order to determine the timing and specificity of attentional capture in this paradigm. Participants were instructed to maintain central fixation while responding to targets of only one color per location (e.g., blue target at left placeholder, green target at right placeholder). Prior to target onset, each placeholder was highlighted with a cue that matched the ACS for that side (“good” cue), a cue that matched the ACS for the opposite side (“bad” cue), or an achromatic cue (“neutral” cue). Behavioural results confirmed that target RTs are fastest for trials with good cues, relative both to trials with bad cues and to trials with neutral cues. This behavioural effect was reflected in the ERPs time-locked to target onset; specifically, the P3 component, a neural marker of attentional selection and consolidation, peaked at earlier latencies for targets following good cues. We also examined the ERPs time-locked to cue onset, specifically the N2pc component that reflects the current locus of attention. In our paradigm, a greater N2pc amplitude would indicate that attention has shifted in response to the cue. We found the greatest N2pc amplitudes for good cues relative to neutral cues, with a smaller although still discernible degree of capture for bad cues. Together these results suggest that late attentional selection is responsible for speeded target processing, and that ACSs do not operate as an early, all-or-nothing filter of bottom-up capture.
Support from the Natural Sciences and Engineering Research Council of Canada and an Early Researcher Award to S. F. from the Ontario Ministry of Research and Innovation.