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Benay Başkurt, Aaron Clarke; Electrophysiological Footprints of Grouping by Synchrony. Journal of Vision 2018;18(10):1058. doi: 10.1167/18.10.1058.
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The role played by neural synchrony in representing perceptual grouping relationships is still a mystery. While early studies demonstrated that synchrony seems to play a role in perceptual grouping (Engel, Konig, Kreiter, & Singer, 1991; Gray, König, Engel, & Singer, 1989), others questioned synchrony's role, suggesting that it may be epiphenomenal (Shalden & Movshon, 1999). The debate continues today with studies like Samonds, Zhou, Bernard and Bonds (2006) showing that synchrony arises along neural representations of object contours, while Roelfsema, Lamme and Spekreijse (2004) suggests that synchrony is not used in perceptual grouping. Here, find evidence in favour of the synchrony hypothesis for perceptual grouping using EEG with human observers. We presented to pairs of flickering Gabors (one synchronous and the other with varying levels of asynchrony) and asked observers to indicate which pair was more synchronous in a paradigm similar to that used by Cheadle et al. (2008). Critically we embedded the flickering Gabors in a background of static Gabors that either made the flickering Gabors appear to be parts of the same contour, or parts of separate contours. One pattern was presented to the left visual hemifield and the other to the right hemifield, thereby allowing us to separate out the phase-locked activity in the EEG recordings representing the two patterns. An examination of the Fourier transform of the activity evoked by each pattern revealed that the one-object pattern was represented with a smaller phase difference between flickering elements than for the two-object pattern, thereby providing support for the grouping by synchrony and segmentation by asynchrony hypothesis.
Meeting abstract presented at VSS 2018
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