We propose a novel approach to study the mechanisms underlying integration and segmentation in motion perception. This problem is central to motion processing, and it can also be used as a model for how the brain computes a global percept from many isolated local cues in other domains of vision. There has been previous research on this topic with stimuli such as plaids and random-dot displays, using brief-duration presentations. We will approach the problem in a novel way by focusing on the dynamics of perceptual alternations during long presentations of ambiguous motion displays. Such stimuli can evoke the perception of either motion integration long (""""""""coherency"""""""") or segmentation (""""""""transparency""""""""). At long presentations, perception alternates between coherency and transparency; it is bi-stable. Our Preliminary Results show that the dynamics approach provides more sensitive measures of the relative strength of segmentation versus integration than brief-presentation methods. Importantly, it allows to measure the strength of the two processes independently. We have already revealed a wealth of new information about the mechanisms of coherency and transparency and the interplay between them. Our approach offers more than just methodological advantages. It will provide an invaluable set of data for testing and further developing models for how the brain resolves the competition between motion coherency and segmentation. Furthermore, expanding the dynamics approach - at present restricted mostly to binocular rivalry - to another domain in vision will be an important step towards understanding general principles underlying competition and cooperation between different brain states. In the work proposed here, we have five specific aims: (I) to apply a new dynamic method we have developed, RTtransp, which provides a better measure of the relative strength of integration and segmentation, to test the effect of motion parameters over much wider ranges than had been possible so far. (II) to validate the dynamic method of Durations of Alternating Percepts (DAP) as a way of measuring the strength of two competing percepts independently; DAP has been extensively used in binocular rivalry but its validity in the motion domains needs further testing. (III) to use DAP to check how motion parameters that are known to affect the relative strength of motion segmentation and integration affect each of those processes independently. (IV) to use DAP to study the effect of static form cues for surface segmentation on the interplay between the segmentation and integration mechanisms in motion. (V) to use fMRI to relate our results to the physiological processes underlying motion integration/segmentation
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