Perceptual differences and perceptive fields in binocular and monocular color vision
Date
2016
Authors
Opper, Jamie K., author
Volbrecht, Vicki, advisor
Davalos, Deana, advisor
Anderson, Chuck, committee member
DeLosh, Ed, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
This study investigated perceptual differences in stimuli viewed with one eye (monocular) or two eyes (binocular) in the central (fovea) and peripheral retina (10° retinal eccentricity). In particular, this study focused on changes in color perception for monochromatic stimuli (450 nm to 670 nm, in 20 nm steps) varying in size (1°, 1.7°, 2.25°, 2.7°, 3.7°). A hue-scaling procedure was utilized to ascertain hue perception. With this procedure, three binocular normal and one strabismic amblyope assigned percentages to each of the four elemental hues (i. e., blue, yellow, red, and green) as well as saturation. Only one to two hue terms were allowed to describe a single stimulus, and the percentages had to sum to 100. Members of opponent-color pairs (red/green and yellow/blue) could not be used simultaneously to describe the same stimulus. Hue-scaling results from normal observers showed that, in general, smaller stimuli (1°, 1.7°, 2.25°) in the peripheral retina resulted in weaker hue perception than a 1° stimulus presented to the fovea, although this reduction was less noticeable for the binocular peripheral conditions than for the monocular peripheral conditions, and more noticeable for the monocular nasal retinal condition than the monocular temporal retinal condition. Differences between peripheral and foveal hue perception abated as stimulus size increased. Additionally, the range of wavelengths where blue (yellow) was perceived was narrower (wider) in the periphery relative to the fovea for all stimulus sizes. No differences were observed between monocular and binocular foveal hue or saturation perception, where only one stimulus size was used (1°). Peripherally-presented binocular stimuli fell upon the nasal retina of one eye and the temporal retina of the other, and peripheral binocular hue and saturation perceptions for smaller stimuli were more similar to that of the monocular temporal retina, regardless of whether the stimulus fell on the temporal retina of the left or right eye. Since hue-scaling data were obtained for several stimulus sizes in the peripheral retina it was possible to derive the size of perceptive fields, which are perceptual analogues of receptive fields and indicate the stimulus size at which hue perception stabilizes; i.e., the size at which amount of perceived hue ceases to increase with further increase in stimulus size. Perceptive fields measured in the monocular nasal retina were larger than those measured in the monocular temporal retina for all elemental hues. Overall, monocular perceptive fields were larger than the binocular perceptive fields. Possible physiological reasons for the findings include suppression of chromatic signals by rod photoreceptors, differences in cone photoreceptor distribution and relative ratios of cone types over the surface of the retina, and changes in the nature of the connections of the cone photoreceptors to their associated ganglion cells with increasing retinal eccentricity. The amblyopic observer was found to have abnormal hue and saturation perception relative to the normal observers, particularly for stimuli perceived as red and green, which may be due to abnormalities in the parvocellular pathway, the neural pathway presumed to mediate the perception of red and green.