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Anastasia Flevaris, Antigona Martinez, Steven Hillyard; Neural substrates of perceptual integration during bistable object perception. Invest. Ophthalmol. Vis. Sci. 2013;54(15):581.
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© ARVO (1962-2015); The Authors (2016-present)
Object perception depends not only on physical stimulus properties but also on endogenous, top-down factors that affect the observer’s perceptual state. In this study we equated physical properties to investigate the neural mechanisms of top-down contributions in object perception.
We recorded EEG and compared neural activity elicited by varying perceptions of the same physical image - a bistable moving image in which perception spontaneously alternates between dissociated fragments and a single, unified object.
A time-frequency analysis of EEG changes associated with the perceptual switch from object to fragment and vice versa revealed a greater decrease in alpha band (8-12Hz) power accompanying the switch to object-percept than to fragment-percept. Recordings of event-related potentials elicited by irrelevant probe flashes superimposed on the image revealed an enhanced positivity in the latency range of the P2 component (~184-212ms) when the probes were contained within the perceived unitary object. The topography of this positivity elicited by probes during object- relative to fragment-perception was distinct from the topography of the P2 elicited by probes during fragment perception, suggesting that neural processing of probes differed as a function of perceptual state. Two source localization algorithms estimated the neural generator of the difference positivity to lie in the lateral occipital cortex (LOC), a region associated with object perception.
These data suggest that objects attract attention and modulate the processing of individual elements occurring within their boundaries, perhaps reflecting the perceptual binding of the elements into a unified object. Importantly, these effects were observed when the perceived "object" in this case emerged as a function of the fluctuating perceptual state of the viewer.
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