Facilitation and inhibition in selective attention: Two sides of the same coin?

Abstract

A long-standing question in attention research has been if and how attention can suppress distracting information. Previous studies addressing this question often used paradigms in which the task-relevant location was known beforehand, so that observers could simply pay more attention to the relevant location to prevent distraction. This renders it unclear whether enhancement and suppression always co-occur, as two sides of the same coin, or whether they subserve independent mechanisms. We conducted two behavioural and one EEG experiment to examine whether observers can selectively suppress irrelevant locations and the underlying neural mechanisms. Search displays with repeating target or distractor locations across trials allowed observers to learn which location to selectively attend or suppress. Both learned attention and suppression resulted in more efficient search as indexed by faster response times. Crucially, suppression was observed without target-location foreknowledge, unaffected by the number of possible target locations, and could not be explained by priming. To determine how distractor-location foreknowledge facilitated performance, we applied a spatial encoding model to EEG data to reconstruct activity in neural populations tuned to the relevant or irrelevant location. Target-location foreknowledge increased neural tuning to the relevant location prior to stimulus presentation, indicative of enhanced attention. This sensitivity increased after target presentation. By contrast, distractor repetition only changed neural tuning to the distractor location immediately preceding visual stimulation, and subsequently reduced distractor processing, as reflected in a flattening of the tuning curve and the disappearance of the Pd ERP component. These findings suggest independent facilitatory and inhibitory attentional mechanisms. Meeting abstract presented at VSS 2018