| The contrast dependence of the cortical fMRI deficit in amblyopia; a selective loss at higher contrasts. | |
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MedLine Citation:
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PMID: 20063352 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Although there is general agreement that the fMRI cortical response is reduced in humans with amblyopia, the deficit is subtle and has little correlation with threshold-based psychophysics. From a purely contrast sensitivity perspective, one would expect fMRI responses to be selectively reduced for stimuli of low contrasts. However, to date, all fMRI stimuli used in studies of amblyopia have been of high contrast. Furthermore, if the deficit is selective for low contrasts, one would expect it to reflect a selective M-cell loss, because M-cells have much higher contrast gain than P-cells and make a larger contribution to the threshold detection of stimuli of low spatial and medium temporal frequencies. To test these two predictions, we compared % BOLD response between the eyes of normals and amblyopes for low- and high-contrast stimuli using a phase-encoded design. The results suggest that the fMRI deficit in amblyopia depends upon stimulus contrast and that it is greater at high contrasts. This is consistent with a selective P-cell contrast deficit at a precortical or early cortical site. |
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Authors:
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Robert F Hess; Xingfeng Li; Guangming Lu; Benjamin Thompson; Bruce C Hansen |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Human brain mapping Volume: 31 ISSN: 1097-0193 ISO Abbreviation: Hum Brain Mapp Publication Date: 2010 Aug |
Date Detail:
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Created Date: 2010-07-26 Completed Date: 2010-11-12 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9419065 Medline TA: Hum Brain Mapp Country: United States |
Other Details:
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Languages: eng Pagination: 1233-48 Citation Subset: IM |
Copyright Information:
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2010 Wiley-Liss, Inc. |
Affiliation:
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Department of Ophthalmology, McGill University, Montreal, Quebec, Canada. robert.hess@mcgill.ca |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adolescent Adult Amblyopia / complications, pathology* Brain Mapping Cerebral Cortex / blood supply*, physiopathology* Computer Simulation Contrast Sensitivity / physiology* Dominance, Ocular / physiology Female Humans Image Processing, Computer-Assisted / methods Magnetic Resonance Imaging* / methods Male Models, Neurological Oxygen / blood Perceptual Disorders / etiology, pathology* Photic Stimulation / methods Psychophysics Reaction Time / physiology Young Adult |
| Grant Support | |
ID/Acronym/Agency:
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MOP53346//Canadian Institutes of Health Research |
| Chemical | |
Reg. No./Substance:
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7782-44-7/Oxygen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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