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Kathrin Ohla, Thomas Gruber, Velitchko Manahilov, Matthias M. Müller; Motion-induced attentional capture enhances induced gamma-band activity. Journal of Vision 2007;7(9):453. doi: https://doi.org/10.1167/7.9.453.
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© ARVO (1962-2015); The Authors (2016-present)
Different visual features are known to be processed in separate parts of the brain. It is still unclear by which mechanisms these features are combined into an integrated percept. Several results point to an important role of gamma-band oscillations (20–100 Hz) in binding separate features of objects in the correct combinations. However, attention might also facilitate the perception of coherent objects. It was suggested that coherent percepts are more likely to catch attention than incoherent ones. Only recently, it was proposed that grouping and attention rely on a common implementation process: synchronized activity in the gamma-band range. Thus, we investigated whether or not a figure popout, which attracts focal attention, is linked to increased cortical activity in the gamma band. If induced gamma band responses (iGBRs) represent feature binding, enhanced iGBRs should be observed whenever a coherent figure is presented. Furthermore, this effect should be more pronounced when the figure is induced by motion due to enhanced figure saliency. We conducted three experiments in which participants discriminated figures from non-figures under different conditions of figure saliency and popout. We investigated the role of figure properties by means of motion coherency of random dots in experiment 1. In experiment 2, stimuli were arrays of oriented Gabor patches which could either form a salient geometric figure or no coherent figure. In experiment 3, a sudden change from one array of Gabor patches to another induced apparent motion, but only when a figure was present. We found elevated iGBRs in response to figures accompanied by apparent motion in experiments 1 and 3, which may point to stronger attentional recruitment. No effects between figures and non-figures were found for patterns with immediate onset in Experiment 2 which suggests that low level feature binding is not sufficient to study the oscillatory activity of cortical networks.
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