Salient distractors open the door of perception: alpha desynchronization marks sensory gating in a working memory task

Focusing attention on relevant information while ignoring distracting stimuli is essential to the efficacy of working memory. Alpha- and theta-band oscillations have been linked to the inhibition of anticipated and attentionally avoidable distractors. However, the neurophysiological background of the rejection of task-irrelevant stimuli appearing in the focus of attention is not fully understood. We aimed to examine whether theta and alpha-band oscillations serve as an indicator of successful distractor rejection. Twenty-four students were enrolled in the study. 64-channel EEG was recorded during a modified Sternberg working memory task where weak and strong (salient) distractors were presented during the retention period. Event-related spectral perturbation in the alpha frequency band was significantly modulated by the saliency of the distracting stimuli, while theta oscillation was modulated by the need for cognitive control. Moreover, stronger alpha desynchronization to strong relative to weak distracting stimuli significantly increased the probability of mistakenly identifying the presented distractor as a member of the memory sequence. Therefore, our results suggest that alpha activity reflects the vulnerability of attention to distracting salient stimuli.

Statistical learning of frequent distractor locations in visual search: A role for post-selective distractor rejection processes?

People can learn to ignore salient distractors that occur frequently at particular locations. This distractor-location probability-cueing effect has been attributed to learnt suppression of the likely distractor locations at a pre-selective stage of attentional-priority computations. An alternative, post-selective account would be that distractors are as likely to capture attention at frequent as at rare locations, but attention can be disengaged faster from distractors at frequent locations. Eye-movement studies confirm that learnt suppression, evidenced by a reduced rate of oculomotor capture by distractors at frequent locations, is a major factor, whereas the evidence is mixed with regard to a role of rapid disengagement (pro: Wang et al., 2019; contra: Di Caro et al., 2019). However, methodological choices in these studies limited conclusions as to the contribution of a post-capture effect. Using an adjusted design, here we positively establish the rapid-disengagement effect and demonstrate further processes contributing to probability cueing beyond the oculomotor capture and disengagement dynamics. Moreover, we examine statistical-learning effects not only for distractors defined in a different visual dimension to the search target (comparable with previous work), but also for distractors defined within the same dimension, which are known to cause particularly strong attentional capture. Of theoretical importance, we corroborate our previous finding of responses being slowed (on distractor-absent trials) to targets at frequent distractor locations only in the same-, but not the different-, dimension condition. Consistent with a pre-selective origin, this target-location effect already impacted the latency of the very first saccade.