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Clayton Hickey, Matthew Weaver, Hanna Kadel, Wieske van Zoest; How do we ignore salient distractors?. Journal of Vision 2017;17(10):205. doi: 10.1167/17.10.205.
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© ARVO (1962-2015); The Authors (2016-present)
Our visual environment is too rich for us to deal with at once, so we sample from it by making eye movements. Optimally, we should suppress stimuli that are strategically unimportant so as to ensure that useful objects are fixated first. But there is little actual evidence that distractor suppression plays a role in oculomotor control. Here, we use concurrent recording of EEG and eye-tracking first to determine if distractor suppression fosters efficient eye-movement behaviour. Participants searched for targets presented alongside salient distractors, and we subsequently sorted trials as a function of which stimulus was first fixated. Results show that target-directed saccades are associated not only with enhanced attentional processing of the target, as reflected in the N2pc, but also stronger suppression of the distractor, as indexed in the distractor positivity (Pd). In a subsequent experiment, we build from this finding to investigate the impact of proactive distractor cues. These tell people about the characteristics of non-targets they should ignore before search begins. We find that people are better able to ignore cued distractors, as reflected in saccadic accuracy and reaction time. But, surprisingly, this is associated with a reduction in the distractor-elicited Pd. This suggests that distractor cues do not act by potentiating online attentional suppression, but rather by reducing cortical sensitivity to distractor features before the stimuli appear. We investigate this hypothesis in further time-frequency analyses of EEG data preceding target- and distractor-directed saccades, identifying correlates of oculomotor control in the phase synchronization of parietal alpha and occipital beta. Our results demonstrate the key role of distractor suppression in oculomotor control, pointing at two ways such suppression can be instantiated in the brain.
Meeting abstract presented at VSS 2017
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