Impaired vision for binocular tasks after unilateral optic nerve regeneration in the frog Litoria moorei

Abstract

Behavioural responses to objects in the binocular field were examined in frogs with one regenerate and one intact optic nerve. Data were compared to those for normal controls and for frogs with vision via one intact optic nerve. During prey acquisition, frogs with regenerated optic nerves underestimated the distance to the prey on their first strike; as a consequence, the regenerate series made several attempts to achieve a successful prey capture. By contrast, normal frogs and those using only one eye struck accurately at the prey and usually captured it on the first attempt. However, frogs using only one eye struck from a closer distance than either the regenerate or normal series. Frogs with regenerated optic nerves also made more errors than either of the other series when leaping through a set of closely spaced horizontally aligned rods. Our results show that prey capture and the negotiation of horizontally aligned rods is impaired in animals using one regenerated and one intact optic nerve as compared to both normal frogs and those using only one eye. We suggest that the poor visual performance for frogs with one regenerated and one intact optic nerve for tasks presented in the binocular field is related to the integration of a degraded and a normal image within the visual centres.