The role of the optic tectum in various visually mediated behaviors of goldfish

Abstract

Five visually mediated behaviors were assessed following ablation of one or both lobes of the optic tectum in goldfish. Three of the behaviors disappeared following tectal ablations; optomotor response (swimming with the stripes in a rotating striped drum), food pellet localization and shadow-induced deceleration of respiration. Two of the behaviors persisted following tectal ablation: optokinetic nystagmus (movement of the eyes with the stripes in a rotating striped drum) and dorsal light reflex (tilting of the vertical axis toward the brighter of two laterally placed lights). The unexpected result that lesioned fish tracked the stripes with their eyes, but did not swim after them as normal fish did, suggest that the tectum serves a pre-motor function in addition to its sensory role. In addition, the results demonstrate that selected behaviors can be used to establish whether functional tectal or non-tectal connections are made by regenerating goldfish optic nerves.