Separate cue- and alpha-related mechanisms for distractor suppression.

Abstract

Research on selective attention has largely focused on the enhancement of behaviorally important information, with less focus on the suppression of distracting information. Enhancement and suppression can operate through a push-pull relationship attributable to competitive interactions among neural populations. There has been considerable debate, however, regarding (i) whether suppression can be voluntarily deployed, independent of enhancement, and (ii) whether the voluntary deployment of suppression is associated with neural processes that occur prior to distractor onset. Here, we investigated the interplay between pre- and post-distractor neural processes, while male and female human subjects performed a visual search task with a cue that indicated the location of an upcoming distractor. We utilized two established EEG markers of suppression: the distractor positivity (PD) and alpha power (∼8-15 Hz). The PD-a component of event-related potentials-has been linked with successful distractor suppression, and increased alpha power has been linked with attenuated sensory processing. Cueing the location of an upcoming distractor speeded responses and led to an earlier PD, consistent with earlier suppression due to the strategic use of a spatial cue. In comparison, higher pre-distractor alpha power contralateral to distractors led to a later PD, consistent with later suppression. Lower alpha power contralateral to distractors instead led to distractor-related attentional capture. Lateralization of alpha power was not linked to the spatial cue. This observation, combined with differences in the timing of successful suppression-as indexed by earlier and later PD components-demonstrates that cue-related, voluntary suppression can occur separate from alpha-related gating of sensory processing.Significance Statement Selective suppression of distracting information is important for survival. There are ongoing debates, however, regarding whether and how selective enhancement can be voluntarily deployed independent of selective enhancement. Here, we recorded EEG while subjects performed a visual search task with cues that indicated the location of upcoming distractors. Behavioral and electrophysiological results revealed that foreknowledge of a distractor's location speeded suppression (relative to non-cued trials), thereby facilitating target detection. The results further revealed that such cue-related suppression of a distractor can occur separate from alpha-related gating of sensory processing. That is, alpha-related suppression in the present task occurred independent of the spatially informative cue (i.e., on both cued and non-cued trials) and later than cue-related suppression (as indexed by later and earlier PD components).