ERP indices of reflexive attention effects on visual search

How does involuntary attentional capture affect visual processing and reorienting during search? Reflexive attention facilitates responses and enhances visual processing during target discrimination in simple cueing studies. Although voluntary cues also cause behavioral and neural enhancement of target processing, Kiss et al. (2009) found no effect on target selection during search following voluntary attentional shifts, nor any differences in the event-related potential (ERP) thought to index selection during search, the N2pc. Another ERP component, the invalid ipsilateral negativity (IIN; Hopfinger & Mangun, 2001), has been proposed as an index of disengagement and reorienting following involuntary attentional capture. The present ERP study aimed to dissociate mechanisms of spatial reorienting from distractor suppression, and determine how reflexive attention affects discrimination during pop-out search. A non-predictive peripheral cue was rapidly followed by a pop-out search to compare differences in target processing when attention was either captured to the target’s location in advance (cued targets), or had to be reoriented from an erroneous location to the target (uncued and neutral targets). ERP indices of early visual processing (e.g. P1 component) showed a significant enhancement for cued relative to uncued-location targets and neutral targets. Cued-location targets produced the largest N2pc, suggesting that the amplitude of this component is related to the amount of attentional resources employed during selection rather than the act of shifting the focus of spatial attention. A significant IIN was found at a longer latency than in previous cueing paradigms, occurring after the N2pc, and in the condition in which the N2pc was smallest. These results indicate that: (1) reflexive attention enhances early sensory processing during visual search, (2) the N2pc is an effective marker of the location of attention, not an index of shifting spatial attention, and (3) the IIN is a potential index of reorienting following involuntary capture. Meeting abstract presented at VSS 2013