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Tanner DeLawyer, Rina Nakamura, Steven L Buck; Red-green balance differences between brown/yellow stimuli over a range of light levels. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
We previously observed differences in the relative amounts of red and green lights (RGbal) needed to balance observers’ perception of red vs. green in targets that appeared yellow compared to brown. We have also recently discovered differences in RGbal for brown stimuli viewed either monocularly or dichoptically. However, these differences were noted in selected conditions. We don’t know the generality of these findings across a range of target light levels beyond the selected conditions.
In this experiment we presented subjects with a 4°-diameter foveal target disk to one eye and a bright or dark contiguous surround annulus (2° width) to either the same eye (monocular conditions) or the opposite eye (dichoptic conditions). The region outside the annulus was bright or dark, the opposite of the annulus itself, continuing to the terminus of the screen. The target and annulus were perceptually contiguous under all conditions. Observers freely adjusted the RGbal (with luminance held constant) of the target to until it appeared neither reddish nor greenish. The target was presented at 11 different equally spaced light levels ranging from 1 to 32 cd/m2.
Results indicate that subjects set RGbal at greater L/L+M cone excitation for dichoptic than for monocular presentations. Additionally, subjects set RGbal at greater L/L+M cone excitation for bright compared to dark contiguous surrounds. There was no overall effect of light level on red/green, but there was an interaction with light level and bright/dark surrounds where subjects RGbal had greater L/L+M cone excitation as light level increased for bright surrounds, but went in the opposite direction for dark surrounds (less L/L+M as light level increases).
Importantly, (a) in the monocular conditions, the relation between RGbals with bright and dark surrounds was more complicated than previously shown, varying with light level and reversing direction at lower light levels, and (b) this pattern was not shown in dichoptic conditions, where relative RGbals for bright and dark surrounds were more consistent across light levels. The present study shows (a) further work is needed to assess the relation of RGbals on bright or dark surrounds under monocular conditions, and (b) the monocular/dichoptic difference adds new evidence supporting the action of multiple processes of brown induction
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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