| Discrimination of changes in the slopes of the amplitude spectra of natural images: band-limited contrast and psychometric functions. | |
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MedLine Citation:
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PMID: 9509160 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Thresholds were measured for discriminating changes in the slopes of the amplitude spectra of stimuli derived from photographs of natural scenes and from random-luminance patterns. The variety and magnitudes of the thresholds could be explained by a model based on the discrimination of the changes in band-limited local contrast. Different spatial scales of local contrast (or different spatial-frequency bands of about 1 octave) were implicated for different reference spectral slopes; the model implicated a lower frequency-band for stimuli with shallower amplitude spectra. The implications of the model were tested experimentally by using stimuli in which the spectra were changed within restricted spatial-frequency bands. When the amplitude spectra of the test and reference stimuli differed only within the implicated frequency bands, thresholds were affected little. However, when the test and reference spectra differed at all frequencies except those in the implicated bands, thresholds were elevated markedly. The forms of the psychometric functions for the discrimination task were entirely compatible with the hypothesis that the task relies upon the ability to discriminate changes of contrast. The Weibull functions fitted to the data had slope parameters (beta) in the range 1 to 3, compatible with discrimination of low (but suprathreshold) contrasts. |
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Authors:
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D J Tolhurst; Y Tadmor |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Perception Volume: 26 ISSN: 0301-0066 ISO Abbreviation: Perception Publication Date: 1997 |
Date Detail:
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Created Date: 1998-04-02 Completed Date: 1998-04-02 Revised Date: 2009-09-29 |
Medline Journal Info:
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Nlm Unique ID: 0372307 Medline TA: Perception Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 1011-25 Citation Subset: IM |
Affiliation:
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Department of Physiology, University of Cambridge, UK. djt12@cam.ac.uk; yt102@cam.ac.uk |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Contrast Sensitivity
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physiology* Humans Models, Biological* Pattern Recognition, Visual / physiology Photic Stimulation Psychometrics Sensory Thresholds / physiology* |
| Grant Support | |
ID/Acronym/Agency:
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//Wellcome Trust |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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