Strategic control over extent and timing of distractor-based response activation.

In choice reaction time (RT) tasks, performance is often influenced by the presence of nominally irrelevant stimuli, referred to as distractors. Recent research provided evidence that distractor processing can be adjusted to the utility of the distractors: Distractors predictive of the upcoming target/response were more attended to and also elicited stronger motor responses. In an event-related potential (ERP) study, we investigated whether not only the extent of distractor processing (as suggested by these previous results), but also the timing of distractor-based response activation is subject to strategic control. In a temporal flanker task, in which a distractor stimulus preceded the target, we manipulated distractor utility (i.e., by varying the proportion of congruent distractor-target combinations, 75% vs. 25%) as well as the stimulus onset asynchrony (SOA) between distractors and targets (350 ms vs. 1,000 ms) in different blocks of trials. The distractor-locked lateralized readiness potential (LRP) was overall larger in blocks with a high proportion of congruent trials indicating stronger distractor-based response activation when distractor utility was high. Of importance, the LRPs occurred overall later when the SOA was long. This suggests that distractor-based response activation can be postponed and thus adjusted to the temporal factors of the context. Modulations of early visual potentials (P1 and N1) indicate that this postponement of motor activation is related to both sensory-perceptual downgrading of distractor stimuli and reduced activation of task-relevant stimulus-response transformation processes at the time of distractor perception. (PsycINFO Database Record