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Aaron Clarke, Stéphane Rainville; Psychophysical evidence for object segregation through endogenous asynchrony. Journal of Vision 2009;9(8):928. doi: https://doi.org/10.1167/9.8.928.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction:Decomposing the retinal image into its constituent objects involves grouping the neural outputs responding to common objects and segregating these from the outputs responding to separate objects. Prior research has suggested that perceptual groups are represented cortically through synchronous oscillatory firing. Modeling studies have further suggested that separate perceptual groups be represented by asynchronously firing neural populations. We provide evidence corroborating this hypothesis, showing both that elements lying on a common object are endogenously synchronized and that elements lying on separate objects are endogenously desynchronized.
Methods:We adopted a similar paradigm to that of Cheadle et al., (2008) where subjects judged the synchrony of two flickering Gabors embedded in a static background pattern. We constructed the background patterns around the Gabors such that it placed them either a) on a common object, b) on separate objects, or c) on no objects. We found that the static background pattern significantly affected subjects' ability to judge the target Gabors' synchrony. Comparing synchrony judgments within and between background patterns allowed us to estimate the endogenous neural coherence imposed on the neural populations responding to the patterns.
Results:We replicated Cheadle et al.'s finding that Gabors on a common object are endogenously synchronized relative to Gabors in the no object pattern. We extended this result by showing that Gabors on separate objects are actively desynchronized relative to both the no object condition and to the one object condition.
Conclusions:More than just synchronizing neural responses to common objects, our evidence implies that there is also an active desynchronization process that segregates responses stemming from separate objects. This finding suggests a mechanism by which objects are segregated from each other - different objects are tagged with different phase labels that are actively repelled from one another.
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