Visual localization after rearrangement of retinotectal maps in fish

Abstract

In each lobe of the optic tectum, the primary visual centre of fishes, terminals of the optic nerve distribute themselves to form a precise visuotopic map of the visual field seen by the opposite eye^1,2. The tectum has an essential role in orienting a fish towards a food object before the fish seizes it^3,4. Moreover, experiments involving selective lesions or focal stimulation of tectum suggest that the detection and localization of an object in space depend on the visuotopic map, and that the fish's orienting response is directed by a ‘motor map’ in register with the visuotopic map^5–9. The relationship between the two maps has been studied here by taking advantage of the finding in goldfish that the removal of the caudal half of the tectum leads in tune to the formation of a compressed but functional visuotopic map^7,10,11. As behavioural orientation was found to be accurate despite compression, the putative motor map cannot be fixed anatomically in relation to the tectum.