Behavioral spectral sensitivity of the zebrafish (Danio rerio)

While the zebrafish (Danio rerio) continues to become an important animal model for the investigation of the genetic and physiological bases of visual processing of the vertebrate retina, its visual behavior, particularly regarding color processing, has received little attention. The purpose of this study was to obtain behavioral spectral sensitivity functions from adult zebrafish using an appetitive instrumental conditioning procedure. A three-chamber maze was implemented to train light-adapted adult zebrafish to swim into the chamber that contained a suprathreshold monochromatic stimulus for a food reward. Visual threshold was determined by varying the stimulus irradiance using a 'two-down one-up' staircase procedure. Threshold values were obtained for wavelengths from 340 to 640 nm. Spectral sensitivity functions obtained show contributions from two nonopponent cone mechanisms (UV and S) and two opponent mechanisms (M-S and L-M). These cone mechanisms are qualitatively similar to those obtained via physiological measures from the On-responses of the zebrafish retina and optic tectum. However, the functions are not quantitatively similar suggesting that further visual processing takes place beyond the processing of the retinal circuitry and processing of the initial stages of the optic tectum. These results demonstrate that the zebrafish is an excellent model to examine and compare the relationship between physiological and behavioral color processing.