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Lora T. Likova, Christopher W. Tyler; Spatiotemporal relationships in a dynamic scene: Position interruption and transient synchronization in stereomotion induction. Journal of Vision 2002;2(10):83. doi: 10.1167/2.10.83.
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© ARVO (1962-2015); The Authors (2016-present)
The visual mechanisms for detecting spatiotemporal relationships between objects in a dynamic scene are not well understood. Recently, we have established purely stereoscopic motion induction (Likova & Tyler, 2001, Perception). Surprisingly, in addition to the stereomotion in the surround, a lateral target shift was required in order for stereomotion induction to occur. In this study, we explore this puzzling result by using a target interruption paradigm. The stimuli were dynamic two-frame autostereograms consisting of a target and a surround; both horizontal lines of discs. Instead of shifting laterally, target presentation was interrupted in synchrony with either the onset or the offset of the surround disparity transitions, for durations from 25 msec to 575 msec of the 600 msec surround dwell times. All interruption conditions longer than 25 msec elicited stereomotion induction. Thus, the percept of induced depth motion does not depend on position change of the stimulus (distal or proximal). On the other hand, no significant stereomotion induction occurred for gaps of 0 and 25 msec, and full induction was obtained only for gap durations from ∼100 – 400 msec. It is therefore clear, first, that temporal interruption of the target is the critical feature for stereomotion induction, rather than retinal displacement or activation of the lateral motion system. It seems that the release from a continuous disparity (or a continuous depth position signal) could derive either from parvo interruption or magno inhibition of the signal. The lack of position information frees the interpretative perceptual system to use heuristic assumptions appropriate within a particular context. Second, our results indicate the importance of synchronization between the corresponding transient target and surround signals. A model of the target/surround interactions will be considered in the context of dynamic organization principles operating in stereomotion perception (and misperception).
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