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Pablo Alejandro Barrionuevo, Dingcai Cao; Rod-Cone Interactions in Mesopic Spatial Vision. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6239.
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© ARVO (1962-2015); The Authors (2016-present)
Rod-cone interactions have been largely studied in the temporal domain, however, how human spatial vision is affected by rod-cone interaction is poorly understood. In order to study rod-cone interactions in the spatial domain we determined the rod- and cone-mediated spatial contrast sensitivity functions (sCSFs) at a mesopic light level.
Stationary gratings were presented in a CRT-based four-primary system in which images from two CRTs were superimposed to produce four primaries at each pixel through a teleprompter mirror. The two CRTs were covered by different cut-off spectral filters in order to obtain primaries with different spectral distributions. Three kinds of stimuli (spatial average luminance 1 cd/m2) were generated using a silent substitution method: 1) an isolated rod grating that varied rod excitation while keeping L-, M- and S-cone excitations constant, 2) an isolated cone grating that varied L-, M- and S-cone excitations in phase while keeping rod excitation constant, and 3) a combined rod and cone grating that varied rod, L-, M- and S-cone excitations in phase. The spatial frequencies of the gratings were 0.25 cpd, 0.5 cpd, 1 cpd, 2 cpd, 4 cpd and 8 cpd. Contrast detection threshold contrast for each condition was obtained using a 2-Yes-1-No double-random staircase procedure.
The sCSFs for all three stimulus types had band-pass patterns with different band-pass indices and peak frequencies. Cone-mediated sensitivity was higher than rod-mediated sensitivity at low spatial frequencies but became similar at high spatial frequencies. The sensitivities with the combined stimulus were lower than rod- or cone- mediated sensitivities, particularly at high spatial frequencies.
Rod- and cone-mediated spatial functions can interfere with each other, leading to lower sensitivity with the combined stimulus at the same adaptation level. The differential rod- and cone-mediated sCSFs suggested different retinal circuitries may be involved in processing rod- and cone-inputs at mesopic light levels.
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