Visual function in goldfish with unilateral and bilateral tectal ablation.

Following complete bilateral tectal ablation, the ability to detect light recovers in about three weeks. The non-tectal retinal connections which may mediate detection are about one log unit less sensitive than the retinotectal connections. At moderate illumination levels, tectumless fish do not react visually to objects. Tectumless fish integrate luminous flux over a very wide area (at least 25 degrees diameter) while the critical diameter for the normal in this experiment is smaller. Subcortical structures may mediate the interocular transfer of a brightness discrimination. The ipsilateral retinotectal projection following unilateral tectal removal is functional, with normal sensitivity to detection of light.