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Retinal mediators of uniform color appearance

Date

2019

Authors

Douda, Nathaniel D., author
Volbrecht, Vicki, advisor
Nerger, Janice, committee member
Dik, Bryan, committee member
Draper, Bruce, committee member

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Journal ISSN

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Abstract

The landscape of retinal cell distribution changes drastically from the central retina (0˚ retinal eccentricity) out to the peripheral retina, with changes occurring both in the photoreceptor mosaic (i.e., ratios, densitiy, size, and distribution of both rod and cone photoreceptors) and physical structures within the eye (i.e. optic disc/blind-spot and macular pigment). With all of these changes to the retinal mosaic, it is no surprise that observers report differences in hue appearance between the same physical stimuli presented to different locations on the retina; however, when large stimuli simultaneously cover those same regions of the fovea and peripheral retina, observers report similar color appearance. The present study investigated how information from the fovea and peripheral retina are combined to produce a uniform perceptual experience. In the first experiment, observers were presented full-field (1°, 23°, 35°) or annular (17° inner diameter/23° outer diameter, 5° inner diameter/35° outer diameter) monochromatic stimuli, ranging from 420 to 660 nm in 20 nm steps for 500 ms at 1.3 log tds. After 30 minutes of dark adaptation, four observers described their hue perceptions using the "4 + 1" hue-naming procedure, in which observers described the stimulus by assigning percentages to one or two of the four elemental hue terms (blue, green, yellow, and red) with the condition that the percentage(s) totaled 100%. Additionally, observers also described how saturated the stimulus appeared on a scale from 0 to 100%. The hue-naming data were similar between the annular and full-field stimuli, suggesting that the peripheral retina holds more weight in determining the hue of large fields. A second experiment was conducted to investigate whether one specific region of the peripheral retina had more influence over the hue of the annulus and large fields. Stimuli of 3° were centered at 10˚ eccentricity in the temporal, nasal, inferior, and superior retinas, and hue values from those locations (as well as the mean of all four locations) were compared to hue naming data from the 23˚ annulus. Results showed, in general, that observers varied in which retinal region the 3˚ field was most similar to in hue appearance of the 23˚ annulus, but that the mean of all four retinal locations was a good approximation of the 23˚ annulus. A final experiment was conducted to investigate the impact of minimizing rod input (bleach conditions) relative to conditions with maximized rod input (dark-adaptation conditions). While the bleaching field influenced hue perception, the overall trend showed that the hue appearance of the annular stimuli most closely aligned with the hue appearance of the full-field stimuli. The findings of the present study are discussed with respect to factors such as rod photoreceptors, chromatic system suppression of rods, spatial integration, cone photoreceptor wiring and ganglion cell inputs, gain mechanisms, macular pigment, and cortical perceptual filling-in/out.

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Subject

hue naming
vision
visual perception
psychophysics
color perception
visual neuroscience

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