| Coherence and the judgment of spatial displacements in retinitis pigmentosa. | |
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MedLine Citation:
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PMID: 10343808 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We used a motion coherence paradigm to test the hypothesis that patients with retinitis pigmentosa (RP) have difficulty discriminating the direction of spatial displacements because of a random loss of motion-sensitive units owing to cone photoreceptor dropout. Minimum (Dmin) and maximum (Dmax) displacement thresholds of patients with typical RP or Usher syndrome were compared with those of age-similar, visually normal subjects. Two-frame random dot cinematograms were used, in which a group of target dots, which comprised 40-100% of the dot array in steps of 20%, were displaced in one of four directions, whereas the non-target dots were randomly repositioned between frames. Reducing the dot coherence in this way increased Dmin and reduced Dmax for both the RP patients and control subjects. Furthermore, the displacement thresholds of the RP patients were displaced laterally from normal along a log coherence axis, consistent with the hypothesis that the patients had a reduced effective (intrinsic) coherence. However, the displacement thresholds of control subjects, when measured at a reduced coherence, did not mimic those of RP patients at full coherence when both groups were tested with a range of dot contrasts and dot areas. These apparently discrepant findings can be reconciled if it is assumed that the patients' effective coherence varies with stimulus visibility. |
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Authors:
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K R Alexander; D J Derlacki; G A Fishman |
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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, P.H.S. |
Journal Detail:
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Title: Vision research Volume: 39 ISSN: 0042-6989 ISO Abbreviation: Vision Res. Publication Date: 1999 Jun |
Date Detail:
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Created Date: 1999-06-14 Completed Date: 1999-06-14 Revised Date: 2007-11-14 |
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: 2267-74 Citation Subset: IM |
Affiliation:
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Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine 60612, USA. kennalex@uic.edu |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Contrast Sensitivity Female Humans Male Motion Perception / physiology* Pattern Recognition, Visual / physiology Retinitis Pigmentosa / physiopathology* Sensory Thresholds / physiology Space Perception / physiology* Visual Acuity |
| Grant Support | |
ID/Acronym/Agency:
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EY01792/EY/NEI NIH HHS; EY08301/EY/NEI NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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