Learning What Is Irrelevant or Relevant: Expectations Facilitate Distractor Inhibition and Target Facilitation through Distinct Neural Mechanisms

Abstract

It is well known that attention can facilitate performance by top-down biasing processing of task-relevant information in advance. Recent findings from behavioral studies suggest that distractor inhibition is not under similar direct control but strongly dependent on expectations derived from previous experience. Yet, how expectations about distracting information influence distractor inhibition at the neural level remains unclear. The current study addressed this outstanding question in three experiments in which search displays with repeating distractor or target locations across trials allowed human observers (male and female) to learn which location to selectively suppress or boost. Behavioral findings demonstrated that both distractor and target location learning resulted in more efficient search, as indexed by faster response times. Crucially, distractor learning benefits were observed without target location foreknowledge, unaffected by the number of possible target locations, and could not be explained by priming alone. To determine how distractor location expectations facilitated performance, we applied a spatial encoding model to EEG data to reconstruct activity in neural populations tuned to distractor or target locations. Target location learning increased neural tuning to target locations in advance, indicative of preparatory biasing. This sensitivity increased after target presentation. By contrast, distractor expectations did not change preparatory spatial tuning. Instead, distractor expectations reduced distractor-specific processing, as reflected in the disappearance of the Pd event-related potential component, a neural marker of distractor inhibition, and decreased decoding accuracy. These findings suggest that the brain may no longer process expected distractors as distractors, once it has learned they can safely be ignored.

Inhibition in selective attention

“…Similarly, in search tasks, subjects are faster in responding to targets when a distractor is presented more often at one of the search locations, that is, when its location has become predictable. Crucially, this benefit of distractor predictability cannot be explained by more attention to the remaining possible target locations or mere priming . Of further note, observers are typically unaware of the unequal probability of distractor occurrences across display locations, indicating that this form of suppression relies on implicit learning mechanisms, that is, is not dependent on working memory .…”

“…Of further note, observers are typically unaware of the unequal probability of distractor occurrences across display locations, indicating that this form of suppression relies on implicit learning mechanisms, that is, is not dependent on working memory . In direct support of the notion that statistical distractor learning does not rely on working memory, Gao and Theeuwes recently showed that learning to suppress distracting information was not affected by the load of a concurrent working memory task.…”

“…In a recent study, we addressed the outstanding question as to whether and how distractor expectations may change the sensory representation of distracting information . Specifically, combining EEG and inverted encoding modeling, we investigated if distractor location learning, induced by keeping the distractor location stable over trials (i.e., four repetitions), was associated with changes in anticipatory spatial tuning to the distractor location.…”

“…Summary of results of our recent EEG study examining how distractor learning influences distractor processing. (A) Slopes of channel tuning functions (CTFs) tuned to the target location (top; green) and the distractor location (bottom; red), estimated based on total alpha power.…”

“…The Pd, a transient positivity contralateral to the distractor, is especially relevant as its amplitude inversely scales with behavioral measures of distractor interference . It is selectively elicited by distractors, and is independent from other lateralized components reflective of attentional selection, such as the N2pc and N1pc . Accordingly, the Pd has been proposed to reflect a mechanism that prevents or terminates the allocation of attention toward a salient distractor …”