Rearrangements of the retinotectal projection in Rana pipiens after unilateral caudal half‐tectum ablation

Abstract

When the caudal half-tectum is ablated aid the optic nerve is cut in adult Rana pipiens, recordings from optic nerve terminals show that the entire visual field comes to be represented in retinotopic ordcr on the reinairring rostral half-tecturn (compression). In contrast, if the caudal half-tectum is ablated but the optic nerve is left intact, no compression of the retinotectal projection results. Instead, the terminals displaced from the ablatcd tissue form apermanently disorganized projection to the rostral half-tectum superimposed on the unaltered representation of those parts of the retinawhich normally project there. The receptive field locations of tectal ncurons in both groups of animals show that the altered retinotectal projections make functional synapses. This conclusion is further supported by hehavioral data. which show that the accuracy of prey-catching movements is altered in both groups of frogs. The anomalous retinotectal maps can be interpreted by menas of amodel which includes polarity cues derived from the tectum and ordering cues derived from repelling interactions among fiber terminals.