I spy with my little eye: A simple behavioral assay to test color perception in animal virtual reality setups

摘要

Virtual reality has become an increasingly popular and powerful tool to study behavior and perception in humans and a?? more recently a?? also in animals. Driven by the advances in computer animation technology, virtual realities (VR) can now closely mimic natural scenes. However, little is known about how animals (whose photoreceptors differ from those of humans) perceive colors that are presented on RGB digital screens. In this study, we present a simple behavioral assay to test color perception in an animal VR setup and demonstrate results from experiments employing semi-intact preparations of Xenopus laevis tadpoles at mid-larval stages. The optokinetic reflex (OKR) is a visual motion driven gaze-stabilizing motor reaction and appropriately elicited by an internal representation of the visual surround's movement. Online eye tracking permits a measurement of the OKR in response to different visual scenes in a VR setup. Optokinetic stimuli were presented at a constant velocity (?±10?°/s, 0.2 Hz) using black/color striped patterns in any of the three component colors (red, green and blue). By varying the intensity of the colored stripes, we obtained response amplitude curves for each color. The intensities required to obtain an optokinetic response above a specific threshold level were determined by the relative sensitivity to an individual RGB color and was used to estimate the relative spectral sensitivity of Xenopus tadpoles. Systematic employment of this technique demonstrated that the relative sensitivity (cR,G,B) to the component colors of the display were cR = 0.275 ?± 0.032 for red, cG = 0.585 ?± 0.028 for green and cB = 0.140 ?± 0.017 for blue in Xenopus laevis tadpoles. This relatively simple method can thus be extended to other species using other suitable visuomotor transformations as behavioral readout to validate color presentation in virtual reality setups used for animal experiments.