Knorr AG et al. (2018), I spy with my little eye: a simple behavioral a...

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Biol Open 2018 Oct 05;710:. doi: 10.1242/bio.035725.

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I spy with my little eye: a simple behavioral assay to test color sensitivity on digital displays.

Knorr AG , Gravot CM , Gordy C , Glasauer S , Straka H .

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Passive and interactive virtual reality (VR) environments are becoming increasingly popular in the field of behavioral neuroscience. While the technique was originally developed for human observers, corresponding applications have been adopted for the research of visual-driven behavior and neural circuits in animals. RGB color reproduction using red, green and blue primary color pixels is generally calibrated for humans, questioning if the distinct parameters are also readily transferable to other species. In particular, a visual image in the RGB color space has a clearly defined contrast pattern for humans, but this may not necessarily be the case for other mammals or even non-mammalian species, thereby impairing any interpretation of color-related behavioral or neuronal results. Here, we present a simple method to estimate the sensitivity of animals to the three primary colors of digital display devices based on the performance of object motion-driven visuo-motor reflexes and demonstrate differences in the color sensitivity between Xenopus laevis and Ambystoma mexicanum (Axolotl).This article has an associated First Person interview with the first author of the paper.

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	Fig. 1. Behavioral imaging of optokinetic responses in semi-intact amphibian preparations. (A) Images of semi-intact preparations of larval Xenopus: A1 modified from Ramlochansingh et al. (2014) and Axolotl (A2) at stage 53, with intact eyes, eye muscles and central visuo-motor circuits. (B) Schematics of infrared video recordings of the movements of both eyes with a CCD camera during horizontally oscillating vertical color (red, green, blue)-striped patterns projected onto a cylindrical screen (bottom). Scale bars: 1 mm.
	Fig. 2. Color-dependent optokinetic responses of Xenopus and Axolotl larvae. (A,C) Representative examples of horizontal positional oscillations of the left eye (colored traces) extracted from video sequences during constant velocity oscillations (0.2 Hz; ±10°/s; black trace) of a large-field red-black, green-black and blue-black striped pattern (intensity level 32) in a Xenopus (A) and an Axolotl larvae (C). (B,D) Averaged responses over a single cycle during visual motion stimulation with different color-striped patterns (color coded) at seven selected luminance levels (intensity levels 8, 16, 32, 64, 96, 128, 255) in Xenopus (B) and Axolotl (D) obtained from the responses of the recordings depicted in A and C.
	Fig. 3. Amplitude of optokinetic responses during motion stimulation with RGB colors. (A,B) Dependency of normalized eye movement amplitudes during large-field image motion on the intensity of the three primary colors (RGB, color coded) in Xenopus (A, n=12) and Axolotl larvae (B, n=9). Bold lines represent the average and the shaded areas the standard error of the mean. The relative intensities required for an optokinetic response at the threshold level of 0.8 are denoted with RTh, GTh and BTh separately for the three component colors and shown at higher magnification in the insets in A,B. (C) Exemplary red/green-striped image motion pattern (left) and corresponding intensity contrast images that a Xenopus tadpole (middle) and an Axolotl larvae (right) theoretically perceive according to the different color sensitivities depicted in A,B; schematic eye movements (bottom) elicited by horizontal oscillating motion of the colored pattern (double-headed arrows) indicating that the same red/green-striped image evokes different eye motion magnitudes in the two species.

References [+] :

Beck, Quantifying the ontogeny of optokinetic and vestibuloocular behaviors in zebrafish, medaka, and goldfish. 2004, Pubmed