Reversal learning deficit in a spatial task but not in a cued one after telencephalic ablation in goldfish

The fish telencephalon seems to be involved in spatial learning and memory in a similar manner to the hippocampus of the land vertebrates. For instanc e, telencephalon ablated goldfish are impaired in the post-operative retent ion of a 'spatial constancy' task, which requires the use of mapping strate gies, but not in a directly cued task in which responses are based in a gui dance strategy. In this regard, previous experiments showed that intact gol dfish trained in the spatial constancy task presented considerable behavior al flexibility, as they showed fast reversal learning, that is, they requir ed less training compared with animals trained in the directly cued task an d made a lower number of errors to master the reversal than in acquisition. The purpose of the present work was to investigate if the goldfish telence phalon is involved in the faster reversal learning of the animals trained i n the spatial constancy task. Goldfish with bilateral telencephalic ablatio n, sham operated or intact, were trained in the spatial constancy task or i n the directly cued task. Telencephalic ablation selectively impaired rever sal learning in the animals trained in the spatial constancy procedure. Abl ated animals in this procedure reversed more slowly than control animals. B y contrast, telencephalic ablation did not produce any significant deficit during reversal in the animals trained in the directly cued task. These res ults provide additional evidence that the fish telencephalon, as the land v ertebrate hippocampus, plays a crucial role in the use of flexible spatial representations. (C) 2000 Elsevier Science B.V. All rights reserved.