Abstract
Cognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simultaneously searched for two possible targets presented among distractors, and selected one of them. In one condition, only one of the targets was available in each display, so that the choice was imposed, and reactive control would be required. In the other condition, both targets were present, giving observers free choice over target selection, and allowing for proactive control. Switch costs emerged only when targets were imposed and not when target selection was free. We found differential levels of activity in the frontoparietal control network depending on whether target switches were free or imposed. Furthermore, we observed core regions of the default mode network to be active during target repetitions, indicating reduced control on these trials. Free and imposed switches jointly activated parietal and posterior frontal cortices, while free switches additionally activated anterior frontal cortices. These findings highlight unique contributions of proactive and reactive control during visual search.
Highlights
During search for a visual object, a mental representation of the target object is maintained in visual working memory to guide attention toward potentially task-relevant regions (Desimone and Duncan, 1995; Olivers and Eimer, 2011)
A Bayes Factor analysis confirmed this pattern by showing that the model including both main effects and the interaction effect explains the data best (BF 1⁄4 7.8 Â 105) and was 12.2 times as likely as the best model including only the main effects
We asked observers to look for multiple targets and we manipulated whether both or only one of the two potential target colors were present in a search display
Summary
During search for a visual object, a mental representation of the target object is maintained in visual working memory to guide attention toward potentially task-relevant regions (Desimone and Duncan, 1995; Olivers and Eimer, 2011). In a gaze-contingent search paradigm, observers were instructed to always find one of two potential target colors They could either freely select the target to look for on a particular trial, as both targets would always be available in each search display, or the choice was imposed upon them, as only one of the two targets would be present on each trial. Forced target switches elicited post-trial power enhancement in the delta/theta band – a signal that has been associated with conflict detection (Cavanagh and Frank, 2014; Cohen, 2014; Duprez et al, 2018) We interpret these eye movement and EEG findings within an influential framework proposed by Braver (2012), which assumes a division of cognitive control into two modes: proactive and reactive control. In the present study we sought to uncover the brain areas underlying free and imposed multiple-target search
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