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Anna Grubert, Martin Eimer; Concurrent attentional template activation during preparation for multiple-colour search. Journal of Vision 2019;19(10):233. doi: https://doi.org/10.1167/19.10.233.
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Visual search is guided by attentional templates for target-defining features. Using a new rapid serial probe presentation (RSPP) paradigm and N2pc components as electrophysiological markers of attentional capture, we recently showed that templates for a specific target colour are transiently activated during the preparation for individual search episodes (Grubert & Eimer, 2018). Here, we used similar RSPP procedures to assess the preparatory activation of multiple target templates in two-colour search tasks. Circular search displays (presented every 1600 ms) contained a colour-defined target among five differently coloured distractors. Brief circular probe displays that included a target-colour singleton among grey items were flashed in rapid succession (every 200 ms) throughout each block, at a different eccentricity than the search displays. N2pcs were measured to each successive target-colour probe in the interval between two search displays. Probe N2pc amplitudes increased during the preparation period and were largest for probes directly preceding the next search display, reflecting transient template activation. This temporal pattern was observed not only when all search targets had a single constant colour but also when targets were defined by one of two equiprobable colours (two-colour search), demonstrating the concurrent activation of two colour templates. To assess whether such multiple template activation states can be adjusted strategically, we ran two additional two-colour search tasks where one target colour was more frequent (80%/20%), and where target colours alternated between search displays so that the upcoming target colour was fully predictable (ABAB). Probe N2pcs revealed identical template activation for both colours in the 80%/20% task, and an activation of the target colour template that was irrelevant for the next search display in the ABAB task. These results demonstrate that while multiple preparatory target templates can be activated simultaneously, there are remarkable limitations in the top-down strategic control of these template activation states.
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