When searching for an item with specific visual features, salient nontargets (distractors) sometimes capture attention. The repetition of search features, such as target and distractor colors, affects both successful search and effective distractor handling. Nevertheless, the specific consequences of trial-to-trial feature repetition and search context on behavior and EEG components are poorly understood. Here, we investigated how search feature repetition shapes the electrophysiological and behavioral correlates of target processing and distractor handling, testing theoretically-informed predictions of these signals with a mixed-effects model comparison approach. In two experiments, the colors of a singleton distractor and fixed-shape target either repeated or changed unpredictably across trials. A color singleton target and distractor appeared in Experiment 1, allowing efficient search among pop-out items, while targets in Experiment 2 were not uniquely colored, forcing participants to rely on slower shape-feature search. Capture by the color singleton distractor occurred only in pop-out search (Experiment 1), but repetition reduced distractor interference. This pattern was paralleled by the contralateral N2pc-PD complex: following a search color switch, the target-related N2pc was greatly delayed, and salient distractors elicited an N2pc followed by a reactive PD. This biphasic response was absent in Experiment 2, where color was of limited usefulness to search. Early and late contralateral positivities were not sensitive to search relevance or feature repetition, suggesting that the PD is unrelated to preparatory suppression. Attention- and capture-related lateralization components are not universally elicited by target or distractor features, but are driven specifically by expected features important to the search task.

In recent years, steady state visual evoked potentials (SSVEPs) became an increasingly valuable tool to investigate neural dynamics of competitive attentional interactions and brain computer interfaces. This is due to their good signal-to-noise ratio, allowing for single trial analysis and their ongoing oscillating nature that enables to analyze temporal dynamics of facilitation and suppression. Given the popularity of SSVEPs, it is surprising that only a few studies looked at the cortical sources of these responses. This is in particular the case when searching for studies that assessed the cortical sources of attentional SSVEP amplitude modulations. To address this issue, we used a typical spatial attention task and recorded neuromagnetic fields (MEG) while presenting frequency-tagged stimuli in the left and right visual field, respectively. Importantly, we controlled for attentional deployment in a baseline period before the shifting cue. Subjects either attended to a central fixation cross or to two peripheral stimuli simultaneously. Results clearly showed that signal sources and attention effects were restricted to early visual cortex: V1, V2, hMT+, precuneus, occipital-parietal and inferior-temporal cortex. When subjects attended to central fixation first, shifting attention to one of the peripheral stimuli resulted in a significant activation increase for the to-be-attended stimulus with no activation decrease for the to-be-ignored stimulus in hMT+ and inferio-temporal cortex, but significant SSVEF decreases from V1 to occipito-parietal cortex. When attention was first deployed to both rings, shifting attention away from one ring basically resulted in a significant activation decrease in all areas for the then to-be-ignored stimulus.