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Curvature coding in illusory contours.
Vision Res. 2009 Oct; 49(20):2518-30.VR

Abstract

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.

Authors+Show Affiliations

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada H3A 1A1. elena.gheorghiu@mcgill.caNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19682486

Citation

Gheorghiu, Elena, et al. "Curvature Coding in Illusory Contours." Vision Research, vol. 49, no. 20, 2009, pp. 2518-30.
Gheorghiu E, Kingdom FA, Sull M, et al. Curvature coding in illusory contours. Vision Res. 2009;49(20):2518-30.
Gheorghiu, E., Kingdom, F. A., Sull, M., & Wells, S. (2009). Curvature coding in illusory contours. Vision Research, 49(20), 2518-30. https://doi.org/10.1016/j.visres.2009.08.009
Gheorghiu E, et al. Curvature Coding in Illusory Contours. Vision Res. 2009;49(20):2518-30. PubMed PMID: 19682486.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Curvature coding in illusory contours. AU - Gheorghiu,Elena, AU - Kingdom,Frederick A A, AU - Sull,Manpreet, AU - Wells,Samantha, Y1 - 2009/08/12/ PY - 2009/03/27/received PY - 2009/06/17/revised PY - 2009/08/07/accepted PY - 2009/8/18/entrez PY - 2009/8/18/pubmed PY - 2009/12/16/medline SP - 2518 EP - 30 JF - Vision research JO - Vision Res. VL - 49 IS - 20 N2 - 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. SN - 1878-5646 UR - https://www.unboundmedicine.com/medline/citation/19682486/Curvature_coding_in_illusory_contours_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0042-6989(09)00370-8 DB - PRIME DP - Unbound Medicine ER -