Although the zebrafish has become an important model in visual
neuroscience, little has been done to examine the processing of its
higher visual centers. The purpose of this work was twofold. The first
purpose was to examine the physiology of the zebrafish retinotectal
system and its relationship to retinal physiology. Spectral sensitivity
functions were derived from visually evoked tectal responses and these
functions were compared to the functions of electroretinogram (ERG)
responses obtained using the same stimulus conditions. The second
purpose was to examine the recovery of visual functioning of the tectum
following optic nerve damage. The optic nerves of adult zebrafish were
damaged (crushed), and tectal visual processing was assessed following
damage. The results showed that the spectral sensitivity functions
based on the On-responses of the tectum and ERG were qualitatively
similar. The functions based on each response type received similar
cone contributions including both nonopponent and opponent
contributions. However, the spectral sensitivity functions based on the
Off-responses of the tectum and ERG differed. The results also showed
that the zebrafish visual system is capable of neural regeneration. By
90 days following an optic nerve crush, the spectral sensitivity
function based on the tectal On-response was similar to functions
obtained from normal zebrafish. Although the tectal Off-response did
recover, the spectral sensitivity based on the Off-response was not the
same as the function of normal zebrafish. These results support the
notion that different levels of the visual system process information
differently and that the zebrafish visual system, like those of other
lower vertebrates, is capable of functional regeneration.