| Orientation discrimination for objects defined by relative motion and objects defined by luminance contrast. | |
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MedLine Citation:
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PMID: 2635467 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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A bar-shaped area within a pattern of random dots was demarcated by moving the dots within the bar at a velocity equal and opposite to the velocity of dots outside the bar. Orientation discrimination for this motion-defined dotted bar was compared with orientation discrimination for a contrast-defined dotted bar that was created by switching off all dots outside the bar. Orientation discrimination was approximately as acute (approx. 0.5 deg) for a motion-defined bar as for a contrast-defined dotted bar, provided that dot contrast and speed were both high. Furthermore, this 0.5 deg discrimination compares with the most acute values reported for sharp-edged lines and sinewave gratings. For the motion-defined bar discrimination fell off rapidly when dot contrast was reduced, but remained acute for the contrast-defined bar for a further reduction of 0.6 log units. Thus, there was a 4:1 range of contrasts over which discrimination had collapsed for the motion-defined bar but remained acute for the contrast-defined bar. For the motion-defined bar discrimination also fell off rapidly at low dot speeds, but was almost unaffected by speed for the contrast-defined bar. These findings bear on the question whether orientation of motion-defined and contrast-defined bars are analyzed by the same or by different neural mechanisms, and pose a challenge for current theories of orientation discrimination. |
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Authors:
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D Regan |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Vision research Volume: 29 ISSN: 0042-6989 ISO Abbreviation: Vision Res. Publication Date: 1989 |
Date Detail:
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Created Date: 1990-06-14 Completed Date: 1990-06-14 Revised Date: 2006-11-15 |
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: 1389-400 Citation Subset: IM; S |
Affiliation:
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Department of Psychology BSB, York University, Ontario, Canada. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Contrast Sensitivity / physiology* Humans Light* Male Middle Aged Motion Perception / physiology* Orientation / physiology* Space Perception / physiology Visual Pathways |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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