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Yutaka Sakaguchi; Contrast dependency of orientation filling-in. Journal of Vision 2002;2(7):198. doi: 10.1167/2.7.198.
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© ARVO (1962-2015); The Authors (2016-present)
[Purpose and Background] The author examined the time required for perceptual filling-in when the target and surround were differently-oriented gratings. The previous study (Vision Research, 41, 2065–77) revealed that the time significantly varied dependent on the relation between their orientations. The present study asked how the relation between their contrasts affected the time for filling-in. [Method] Participants observed a color monitor binocularly from 50 cm distance with their head fixed by a chin rest. They should fixate at the center cross throughout a trial. A Gabor patch (diameter: 1.4 deg, eccentricity: 7 deg) was presented on a circular surround region (diameter: 12 deg) filled with a sinusoidal grating. Their spatial frequency and average luminance were 2.5 cpd and 30 cd/m2, respectively, and their orientations were fixed. Participants were told to respond immediately after the target (i.e., Gabor patch) disappeared. In Exp. 1, the target contrast was altered from 0 to 100% with the surround contrast fixed to 10, 25 or 50%, while in Exp. 2, the surround contrast was manipulated with the target contrast fixed. [Result] In Exp. 1, reaction time (RT) was significantly prolonged as the target contrast became higher, while its magnitude was diminished with a higher contrast of surround. In more detail, RT remained almost constant when the target contrast was lower than the surround contrast, but increased for higher target contrasts. In Exp. 2, the surround contrast showed a similar but much weaker effect. It should be noted that higher surround contrasts did not facilitate the filling-in. [Conclusion] The time for orientation filling-in depended on the target and surround contrasts. Target/surround contrast ratio seems a key to explain this dependency, but it alone cannot explain the whole phenomenon. Some non-linear interaction is required to understand its underlying mechanism.
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