Research Topics
| PSYCHOPHYSICAL STUDIES OF COLOR DEFECTIVE VISIONSummaryPrincipal Investigator: JOEL M POKORNY Affiliation: University of Chicago Country: USA Abstract: This application is directed toward the study of visual mechanisms in observers with normal vision, observers with congenital color vision defects, and observers with acquired visual defects secondary to various disease states. The studies are designed to reveal the biological processes that limit human visual performance. The proposed research is organized into 6 projects: Project 1 concerns the mechanisms limiting the human observer's sensitivity at low light levels. Project 2 looks at the function of the two major processing streams between eye and brain, and how the parvocellular (PC) and magnocellular (MC) pathways are involved in achromatic discriminations. Measures will be taken for a variety of spatial tasks in normal observers, and PC and MC function will be measured in color defective observers and in patients with ophthalmic disease. Project 3 involves delineating the postreceptoral pathways for rod signals and rod-cone interactions. The proposed experiments examine the role of the rod system in daylight vision. Project 4 addresses the function of a newly discovered retinal ganglion cell type with the properties of an S-cone off cell. Experiments are designed to assess psychophysically the function of this new cell type. Project 5 describes continuing collaborative neurobiological studies of retinal function that allow the opportunity to compare retinal and psychophysical responses to the similar or identical light stimuli. Project 6 involves the development and evaluation of new clinical tests of visual function that may improve the functional diagnosis of congenital color vision defects and help differentiate patients with eye disease. The goal is to translate difficult and time-consuming psychophysical experiments into rapid and easily performed clinical tests. In addition to empirical studies, models of normal and abnormal vision will continue to be developed. The theoretical approach is based on the question: to what extent can established biological or physical phenomena explain the data of color vision? This approach is one which allows us to examine the plausibility of various hypotheses that are not subject to direct experimental evaluation. Funding Period: 1977-04-01 - 2008-03-31 more information: NIH RePORT Top Publications
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Publications
Audiophile hardware in vision science; the soundcard as a digital to analog converterMarco J H Puts
Department of Ophthalmology and Visual Science, Visual Science Laboratories, The University of Chicago, Chicago, IL, USA
J Neurosci Methods 142:77-81. 2005..Using soundcards on other platforms would not be a problem, as long as there exists a low level library that would enable the wave table to be filled...
Chromatic discrimination in the presence of incremental and decremental rod pedestalsDingcai Cao
Visual Science Laboratories, Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA
Vis Neurosci 25:399-404. 2008..The results indicated that the rod and cone signals combined differently in determining chromatic discrimination for different post-receptoral pathways...- S-cone discrimination for stimuli with spatial and temporal chromatic contrastDingcai Cao
Visual Science Laboratories, Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA
Vis Neurosci 25:349-54. 2008..The data are interpreted in terms of a model consistent with primate koniocellular pathway physiology. The paradigms provide an approach for studying the effects of spatial and temporal contrast on discrimination in natural scenes... 
Rod contributions to color perception: linear with rod contrastDingcai Cao
Department of Ophthalmology and Visual Science, University of Chicago, 940 East 57th Street, Chicago, IL 60637, USA
Vision Res 48:2586-92. 2008..This linear relationship could be described by a model based on primate ganglion cell responses with the assumption that rod signals were conveyed via rod-cone gap junctions at mesopic light levels...- Sequential processing in vision: The interaction of sensitivity regulation and temporal dynamicsVivianne C Smith
The University of Chicago, Opthalmology and Visual Science, 940 East 57th Street, Chicago, IL 60637, USA
Vision Res 48:2649-56. 2008..Psychophysical data reflect the sensitivity regulation of the retinal ganglion cell pathways but show a decline in temporal resolution that is most pronounced for the post-retinal processing of Parvocellular signals... - Rod-cone interactions and the temporal impulse response of the cone pathwayAndrew J Zele
School of Optometry and The Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Brisbane, QLD 4059, Australia
Vision Res 48:2593-8. 2008..Rod-cone interactions are a fundamental operation in visual temporal processing under mesopic light levels, acting to decrease the temporal bandwidth of the visual system... - Chromatic adaptation in red-green cone-opponent retinal ganglion cells of the macaqueBarry B Lee
State University of New York, State College of Optometry, 33 W42nd Street, New York, NY, USA
Vision Res 48:2625-32. 2008..The changes in maintained activity following a step change in chromaticity took tens of seconds to return toward a baseline level, but changes in cone weighting appeared much faster... - Anisometropic amblyopia: spatial contrast sensitivity deficits in inferred magnocellular and parvocellular visionAndrew J Zele
Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois, USA
Invest Ophthalmol Vis Sci 48:3622-31. 2007..To measure achromatic spatial contrast sensitivity in patients with anisometropic amblyopia under conditions favoring inferred parvocellular (PC) or magnocellular (MC) pathway mediation... - Linking impulse response functions to reaction time: rod and cone reaction time data and a computational modelDingcai Cao
Department of Ophthalmology and Visual Science, The University of Chicago, 940 East 57th Street, Chicago, IL 60637, USA
Vision Res 47:1060-74. 2007..This is the first model to provide a neural basis for the variation in reaction time with retinal illuminance, stimulus contrast, stimulus polarity, and receptor class modulated... - Human and macaque pupil responses driven by melanopsin-containing retinal ganglion cellsPaul D R Gamlin
Department of Vision Sciences, University of Alabama at Birmingham, AL 35294, USA
Vision Res 47:946-54. 2007.... - Threshold units: a correct metric for reaction time?Andrew J Zele
Visual Science Laboratories, Department of Ophthalmology and Visual Science, The University of Chicago, 940 East 57th Street, Chicago, IL 60637, USA
Vision Res 47:608-11. 2007..To compare reaction time (RT) to rod incremental and decremental stimuli expressed in physical contrast units or psychophysical threshold units... - Achromatic parvocellular contrast gain in normal and color defective observers: Implications for the evolution of color visionMargaret Lutze
Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA
Vis Neurosci 23:611-6. 2006.... - Dark-adapted rod suppression of cone flicker detection: Evaluation of receptoral and postreceptoral interactionsDingcai Cao
Department of Ophthalmology and Visual Science, University of Chicago, Chicago, Illinois 60637, USA
Vis Neurosci 23:531-7. 2006..We conclude that rod-cone interactions in flicker detection occurred strongly in the magnocellular pathway... - The color of night: Surface color perception under dim illuminationsJoel Pokorny
Department of Ophthalmology and Visual Science, University of Chicago, Chicago, Illinois 60637, USA
Vis Neurosci 23:525-30. 2006..At the three lowest light levels there were distinct color appearances mediated exclusively by rods. We speculate that at these light levels the visual system estimates probable colors based on prior natural experience... - Spatial and temporal chromatic contrast: Effects on chromatic discrimination for stimuli varying in L- and M-cone excitationAndrew J Zele
Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA
Vis Neurosci 23:495-501. 2006..For all test chromaticities, discrimination was best in the absence of chromatic contrast. Chromatic contrast discrimination is determined by either the spatial or temporal contrast component of the signal... - Matching rod percepts with cone stimuliDingcai Cao
Department of Health Studies, University of Chicago, IL 60637, USA
Vision Res 45:2119-28. 2005..The data are consistent with a hypothesis of perceptual normalization of scotopic vision to the chromatic appearance of objects under photopic conditions... - Associating color appearance with the cone chromaticity spaceDingcai Cao
Department of Health Studies, The University of Chicago, 5841 South Maryland Avenue, MC 2007, Chicago, IL 60637, USA
Vision Res 45:1929-34. 2005..This makes it possible to plot the cone chromaticities associated with the eight color names used by Boynton and Olsen's observers to describe the non-dark appearing colors... - The color of night: surface color categorization by color defective observers under dim illuminationsJoel Pokorny
Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois, USA
Vis Neurosci 25:475-80. 2008..We reasoned that the reduction in color gamut that a dichromat experiences at photopic light levels leads to a limited association of rod color perception with objects differing in scotopic reflectance...