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David F Nichols, Howard S Hock, Annemie Ploeger, Gregor Schöner; Linking levels in motion pattern formation through dynamical coupling: evidence from psychophysics and simulations. Journal of Vision 2003;3(9):278. doi: 10.1167/3.9.278.
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© ARVO (1962-2015); The Authors (2016-present)
Motion pattern formation is studied for the motion quartet, a bistable apparent motion stimulus for which either a horizontal or vertical motion pattern is perceived. Because there is more detector activation for shorter motion paths (Gilroy & Hock, 2000), the horizontal pattern is favored when the aspect ratio of the quartet (vertical/horizontal distance) is relatively large, and the vertical pattern is favored when the aspect ratio is relatively small. The dynamical basis of pattern formation is indicated by the occurrence of hysteresis when the aspect ratio is gradually increased and gradually decreased (Hock, Kelso & Schöner, 1993). In the current study, changes in motion detector activation were introduced during the course of hysteresis “runs” by perturbing the luminance contrast of the motion quartet. This perturbation affects the dynamics of local motion detectors; for the same reduction in contrast, motion sometimes is perceived and other times nonmotion is perceived (Hock, Kogan & Espinoza, 1997). It was found that perturbations of luminance contrast affect the pattern-level hysteresis obtained by varying the aspect ratio of the motion quartet, and further, that the reduction in hysteresis due to a downward perturbation depends on the local-level dynamics (i.e., whether or not there is a switch from motion to nonmotion as a result of the perturbation). This evidence for the coupling of local- and pattern-level dynamics is simulated with non-linear dynamical equations representing the activation of directionally selective motion detectors in Area V1 (where inhibitory interactions are with detectors activated by motion-independent stimulus information) and Area MT (where inhibitory interactions are with motion detectors having different directional selectivity).
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