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Alexandra List, Aleksandra Sherman, Anastasia V. Flevaris, Marcia Grabowecky, Satoru Suzuki; Neural signatures of local and global biases induced by automatic versus controlled attention. Journal of Vision 2010;10(7):92. doi: 10.1167/10.7.92.
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© ARVO (1962-2015); The Authors (2016-present)
Two mechanisms have been identified for orienting to local versus global visual information. One mechanism directs attention to a hierarchical level via the persistence of attention to the most recently attended level, i.e., an automatic priming effect. A second mechanism is via voluntary effort, i.e., a controlled shift of attention. Both mechanisms, whether automatic or controlled, bias individuals to attend to either local or global information. In the current experiment, we tested whether these behavioral biases rely on similar neural dynamics. Participants viewed hierarchical stimuli and identified one of two target letters while EEG was recorded from 64 scalp electrodes. In one session, participants identified targets presented equiprobably at either the local or global level. We expected priming to the most recently attended level and confirmed this behaviorally. In a second session, 100%-predictive local or global cues preceded each hierarchical stimulus. We expected participants to shift attention to the cued hierarchical level and also confirmed this behaviorally. Distinct EEG activity patterns emerged depending on whether a bias was generated automatically or from a cue. Specifically, we compared induced oscillatory EEG activity in the ∼2-second blank interval following identification of a local or global target (i.e., during a primed state) or following a local or global cue (i.e., during a controlled state). Globally-primed states showed enhanced gamma (high frequencies: 30-50 Hz) oscillations over the right hemisphere compared to locally-primed states, and locally-primed states showed enhanced bilateral posterior alpha and beta (low frequencies: 6-30 Hz) oscillations compared to globally-primed states. In contrast, globally-cued states showed enhanced posterior alpha frequency oscillations compared to locally-cued states. These results reveal that behavioral biases for directing attention to local or global hierarchical levels rely on distinct neural oscillatory states, depending on whether the bias is driven by automatic or controlled attention.
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