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Tomoya Nakamura, Ikuya Murakami; Microgenesis of orientation appearance during common-onset masking. Journal of Vision 2021;21(9):1838. doi: https://doi.org/10.1167/jov.21.9.1838.
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A target is rendered less visible by a sparse mask with common onset and delayed offset relative to the target. Studies of this common-onset masking (COM) usually measure visibility by determining target discriminability. However, our conscious experience contains suprathreshold appearance as well as visibility. In VSS 2020, we reported that COM alters appearance by reducing orientation repulsion that normally occurs when a vertical target is surrounded by tilted inducers. Here, we examined the time course of this reduction by limiting the temporal position of inducers. Observers were asked to indicate whether a vertical target, a Gabor patch, presented for 33 ms appeared tilted clockwise or counter-clockwise. The inducer was composed of eight equally-spaced Gabor patches along a virtual circle concentrically surrounding the target. The inducer duration was fixed at 67 ms, and the target-inducer SOA was varied. As a mask, we presented five dots placed at each vertex of a virtual inverted pentagon (having no vertical orientations) concentrically surrounding the target. In the simultaneous-offset condition, the mask appeared and disappeared together with the target. In the delayed-offset condition, the target and mask appeared together but the mask remained 300 ms after the target disappeared. In the no-mask condition, the mask was not presented at all. The repulsion occurred not only when the inducer was simultaneous with the target but also for earlier and later inducers. Nevertheless, the mitigation of repulsion caused by COM occurred only for later inducers. In addition, orientation discriminability was not deteriorated regardless of the mask offset conditions. It is suggested that COM broadly terminates temporal evolution of internal representations, influencing diverse phenomena beyond the well-known visibility reduction, such as the contextual modulation of the suprathreshold appearance of orientation. Some updating process to alter object representations from the target to the mask might trigger this termination.
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