Abstract
Abstract: :
Purpose: Research has shown that the cone contributions to the zebrafish electroretinogram (ERG) components vary with age. The purpose of this study was to compare the visual processing of larvae and adult zebrafish optic tectum by deriving spectral sensitivity based on the ON- and OFF-components of the visually evoked tectal response. Methods: Adult and larvae (6-8 days postfertilization) zebrafish (Danio rerio) were light-adapted to a broadband background light while visually evoked tectal responses to stimuli of various wavelengths (320 to 640 nm) and irradiances were obtained. Spectral sensitivity functions were derived from irradiance versus response amplitude functions from tectal responses to stimulus onset (ON-component) and stimulus termination (OFF-component); stimulus duration was 250 ms. Results: In adults, the spectral sensitivity functions obtained from the ON- and OFF-components differed from one another. The ON-component received cone contributions from the UV-, M- and L-cones, with an inhibitory S-cone contribution. The OFF-component received cone contributions from the S-, M- and L-cones, with no indication of any UV-cone input. In addition, larvae zebrafish spectral sensitivity functions were somewhat similar to the adult zebrafish spectral sensitivity functions, particularly for ultraviolet and short-wavelength stimuli, but were less sensitive to middle- and long-wavelength stimuli. Conclusion: The cone contributions to the ON- and OFF-components of the optic tectum of the zebrafish are different from one another. The specific cone inputs to the tectal response components differ from those found in the ON- and OFF-components of the zebrafish ERG response, suggesting that the two levels of the visual system process information differently. Also, there appears to be a developmental trend in the cone contributions to the zebrafish optic tectum that is consistent with the results from ERG zebrafish data.
Keywords: 593 superior colliculus/optic tectum • 394 electrophysiology: non-clinical • 347 chromatic mechanisms