To determine whether regenerating neural pathways can support visual
behavior, adult goldfish (Carassius auratus) were injected
intraocularly with ouabain and tested for the presence of reflexive visual
behaviors (dorsal light reflex and optokinetic nystagmus) and the ability
to respond to visual stimuli in a classical conditioning paradigm. All
visual behaviors were absent or greatly diminished until 8 to 10 weeks,
when retinal layering had returned. At 10 weeks post-ouabain, reflexive
behaviors to supra-threshold stimuli were near normal; however the ability
to detect supra-threshold stimuli in the conditioning paradigm did not
recover until 13 weeks. Absolute dark-adapted threshold and light-adapted
spectral sensitivity measured at 13 to 17 weeks were abnormal:
Dark-adapted threshold was elevated by 1.5 log units and light-adapted
spectral sensitivity was markedly narrower than normal. No responses to
50% contrast sinusoidal gratings could be obtained through ouabain-treated
eyes using the classical conditioning technique, even though responses
through the untreated eye remained. Results demonstrate that: (a) visually
mediated behaviors return in goldfish with ouabain-treated retinas; (b)
the time course of recovery of reflexive responses in luminance and
spatial domains parallels return of ERG function and of tectal activity;
and (c) visual function that is mediated by regenerating retina appears
not to be as sensitive as vision via normally developed retinal
pathways.