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M.L. Risner, E.V. Vukmanic, J. Bilotta; A Psychophysical Examination of Zebrafish Spectral Sensitivity . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4751.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The zebrafish (Danio rerio) has become an important animal model for the investigation of the genetic and physiological bases of visual processing of the vertebrate retina. However, zebrafish visual ability has received sparse behavioral analysis. The purpose of this study was to develop and implement an instrumental conditioning paradigm to obtain spectral sensitivity functions from adult zebrafish. Methods: Light–adapted adult zebrafish were trained within a three–chamber maze to swim into the chamber that contained a suprathreshold monochromatic stimulus; subjects received a food reward for a correct response. Training was complete when the subject reached a criterion of 80% correct responses on two consecutive sessions. Upon reaching the training criterion for a given stimulus wavelength, visual threshold was determined by varying the stimulus irradiance using an adaptive staircase procedure; two correct responses resulted in stimulus irradiance attenuation, and one incorrect response resulted in less attenuation. Initially, stimulus irradiance was attenuated by 0.9 log units until an incorrect or no response was produced; at this point, the irradiance was increased by 0.9 log units and then varied by 0.3 log units of attenuation for the remaining trials. Each staircase session consisted of 42 trials. Threshold values were obtained for wavelengths from 400 to 640 nm under a background irradiance of 5 µW/cm2, using the last 20 trials of the staircase session. Results: Light–adapted spectral sensitivity functions show peak sensitivity in the middle–wavelength region (500 nm) and a decrease in sensitivity to short– and long–wavelength stimuli. There was no evidence that the shape of the spectral sensitivity functions were altered by any color opponent mechanisms. Thus, under these light–adaptation conditions, spectral sensitivity functions appear to represent a luminance channel. Conclusions: Spectral sensitivity functions in the adult zebrafish can be obtained using an instrumental conditioning paradigm with an adaptive staircase method. The finding that the spectral sensitivity functions obtained with this method reflect a luminance channel is consistent with the results found in zebrafish ERG heterochromatic flicker photometry studies, adult goldfish psychophysics using a similar instrumental conditioning paradigm, and zebrafish spectral sensitivity functions using a reflexive optomotor response. However, the cone contributions to the spectral sensitivity functions across paradigms differ, suggesting that the exact nature of visual processing in the adult zebrafish varies across paradigms and tasks.
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