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Osamu Masuda, Keiji Uchikawa, Kenji Yokoi; Effects of retinal eccentricity on the temporal summation of double flashes. Journal of Vision 2003;3(12):63. doi: 10.1167/3.12.63.
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© ARVO (1962-2015); The Authors (2016-present)
It has been shown that chromatic contrast sensitivity deteriorates with retinal eccentricity, while recent studies suggest early visual mechanisms remain constant across eccentricity. We measured the temporal summation property of double flashes in the peripheral retina in order to investigate the early stage of color vision.
Two flashes of 10ms (in luminance conditions) or 20 ms (in chromaticity conditions) were presented with SOAs of 10 or 20 to 2000ms on a CRT monitor (100Hz). They were modulated from the mean level (50 cd/m2) in luminance with constant chromaticity (x=0.420, y=0.503) or in chromaticity along the line between red (x=0.625, y=0.346) and green (x=0.287, y=0.606) phosphors with constant luminance. The subject observed the stimuli at fovea or in the 30-deg temporal visual field. The stimulus was of 1deg in diameter at fovea or of 10deg in the periphery according to M-scaling (Ravamo & Virsu, 1979). The surround of the stimulus was a hemisphere dome (∼100cd/m2), illuminated by fluorescent lamps enough to maintain rods saturated. We measured the detection thresholds with two increment flashes or with an increment and a decrement flashes in luminance condition. In chromaticity condition, two red flashes or a red and a green flashes were used.
We derived the impulse response functions (IRFs) from the summation index obtained in the present results. It turned out that, in the luminance condition, IRF remained to be biphasic with the inhibitory phase, which had shorter time delay in 30-deg eccentricity. This result corresponds to the fact that CFFs in the periphery are higher than at fovea. In chromaticity condition, IRF in the periphery remains almost the same as at fovea, which suggests a possibility that the early mechanisms of color vision in the periphery resembles that at fovea.
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