| Curvature coding in illusory contours. | |
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MedLine Citation:
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PMID: 19682486 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We have employed the shape frequency and shape-amplitude after-effects (SFAE and SAAE) to investigate: (i) whether the shapes of illusory and real curves are processed by the same or different mechanisms, and (ii) the carrier-tuning properties of illusory curvature mechanisms. The SFAE and SAAE are the phenomena in which adaptation to a sinusoidal-shaped contour results in a shift in, respectively, the perceived shape-frequency and perceived shape-amplitude of a test contour in a direction away from that of the adapting stimulus. Both after-effects are believed to be mediated by mechanisms sensitive to curvature (Gheorghiu & Kingdom, 2007a, 2009; see also Hancock & Peirce, 2008). We observed both shape after-effects in sinusoidally-shaped illusory contours defined by phase-shifted line-grating carriers. We tested whether illusory and real contours were mediated by the same or different mechanisms by comparing same adaptor-and-test with different adaptor-and-test combinations of real and illusory contours. Real contour adaptors produced after-effects in illusory contour tests that were as great as, or even greater than those produced by illusory contour adaptors. However, illusory contour adaptors produced much weaker after-effects in real contour tests than did real contour adaptors. This asymmetry suggests that illusory contour curves are encoded by a sub-set of mechanisms sensitive to real contour curves. We also examined the carrier-tuning properties of illusory-contour curvature processing using adaptor and test illusory contours that differed in the luminance contrast-polarity, luminance scale and orientation of the carriers. We found no selectivity to any of these dimensions for either even-symmetric or odd-symmetric line-gratings carriers, even though selectivity to these dimensions was found for real contours. |
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Authors:
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Elena Gheorghiu; Frederick A A Kingdom; Manpreet Sull; Samantha Wells |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2009-08-12 |
Journal Detail:
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Title: Vision research Volume: 49 ISSN: 1878-5646 ISO Abbreviation: Vision Res. Publication Date: 2009 Oct |
Date Detail:
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Created Date: 2009-10-05 Completed Date: 2009-12-14 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0417402 Medline TA: Vision Res Country: England |
Other Details:
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Languages: eng Pagination: 2518-30 Citation Subset: IM |
Affiliation:
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McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada H3A 1A1. elena.gheorghiu@mcgill.ca |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Contrast Sensitivity
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physiology Figural Aftereffect / physiology Form Perception / physiology* Humans Optical Illusions / physiology* Orientation Pattern Recognition, Visual / physiology Photic Stimulation / methods Psychophysics |
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