| Spatial-scale contribution to the detection of mirror symmetry in fractal noise. | |
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MedLine Citation:
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PMID: 10474892 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We investigated how the detection of mirror symmetry depends on the distribution of contrast energy across spatial scales. Stimuli consisted of vertically symmetric noise patterns with fractal power spectra defined by 1/f beta slopes (-2 < or = beta < or = 5). While overall rms contrast remained fixed at 25%, symmetry-detection thresholds were obtained by corrupting the signal with variable amounts of noise with identical spectral characteristics. A first experiment measured thresholds as a function of spectral slope, and performance was found to be substantially facilitated in images with power spectra that characterize natural scenes (1.2 < or = beta < or = 3.2). In a second experiment, symmetry was removed from randomly chosen octave bands and replaced by noise with the same spectral profile. Results revealed that only in images with 1/f2 spectra does performance decrease by constant amounts across all frequency bands. Together, the results imply that symmetry mechanisms extract equal amounts of information from constant-octave frequency bands but lack the ability to whiten stimuli whose spectral slopes differ from those of natural scenes. Results are qualitatively well predicted by a multichannel model that (1) relies on spatial filters with equal-volume point-spread functions and constant-octave frequency bandwidths and (2) restricts the computation of symmetry to spatial regions whose dimensions are proportional to the filters' spatial scale. These findings are also consistent with the notion that mechanisms that mediate the perception of form exploit the ability of early vision to reduce second-order redundancy in natural scenes. |
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Authors:
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S J Rainville; F A Kingdom |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of the Optical Society of America. A, Optics, image science, and vision Volume: 16 ISSN: 1084-7529 ISO Abbreviation: J Opt Soc Am A Opt Image Sci Vis Publication Date: 1999 Sep |
Date Detail:
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Created Date: 1999-09-23 Completed Date: 1999-09-23 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 9800943 Medline TA: J Opt Soc Am A Opt Image Sci Vis Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 2112-23 Citation Subset: IM |
Affiliation:
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McGill Vision Research Unit, Montréal, Québec, Canada. stephane@jiffy.vision.mcgill.ca |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Artifacts* Differential Threshold Fractals* Humans Male Models, Biological Pattern Recognition, Visual / physiology* Photic Stimulation Random Allocation |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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