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Sean Green, William C. Schmidt; Independent modulation of illusory line motion by onset and offset transients. Journal of Vision 2006;6(13):46. doi: 10.1167/6.13.46.
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Illusory Line Motion (ILM, Hikosaka, Miyauchi & Shimojo, 1993) was used to investigate the influence of a priming object's appearance (onset) or disappearance (offset) on perception of nearby objects. ILM is motion within an abruptly appearing or disappearing (probe) line near a (priming) object. Forward-ILM occurs when the primer precedes the probe's appearance, and the probe appears to expand away from the primer. Reverse-ILM (von Grunau & Faubert, 1994) occurs when the primer remains while the probe disappears, and the probe seems to shrink toward the primer. Gradient accounts attribute these illusions respectively to spatial gradients that facilitate (Hikosaka, et al., 1993) and temporally extend signal transmission (Schmidt & Klein, 1997) near the primer.
Experiment 1 manipulated the timing of primer appearance or disappearance to assess its effect on ILM within an appearing or disappearing line. Primer onset time influenced ILM within an appearing line but not a disappearing one, while primer offset time influenced ILM within a disappearing line but not an appearing one. This suggests that the representations underlying Forward and Reverse-ILM exert distinct, transient-specific effects.
Experiment 2 investigated ILM within a probe transient that could be interpreted as either an offset or onset. Primer onset and offset timing simultaneously influenced ILM, consistent with the concurrent presence of independent gradients of facilitation and temporal extension. That Forward and Reverse ILM were sensitive to modulation by a single primer transient (onset or offset) that selectively affected perception of a like probe transient suggests that transient-specific representations mediate these effects.
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