THE EFFECTS OF HIPPOCAMPAL-LESIONS ON 2 NEOTIC CHOICE TASKS

We report two experiments in which rats with hippocampal lesions were tested in two neotic choice tasks that provided a clear distinction be tween novel and familiar alternatives. In the first experiment, rats w ith either dorsal or complete lesions were tested in an emergence task in which they were permitted to enter and explore a novel alley from a familiar nest box. Hippocampally lesioned animals did not differ fro m cortical lesioned controls on the latency to enter the novel alley, the duration of time spent in the alley, or the total number of rearin gs in the alley during the 1-h test. However, animals with complete hi ppocampal lesions were more active than the controls; they showed a pe rseverative tendency to return repeatedly to the familiar nest box. In the second experiment, rats with complete hippocampal lesions and cor tical lesioned controls were tested in a two-bottle taste neophobia ta sk with their familiar tap water and a novel saccharin solution. There were no differences between the groups in either the initial avoidanc e of the novel saccharin solution or the subsequent increase in saccha rin preference across repeated tests. In both experiments, hippocampal ly lesioned animals showed the same initial neophobic avoidance follow ed by the same exploratory habituation as did the controls. We discuss the similarity of the hippocampal perseveration to behavior found in other exploratory tasks and conclude that the hippocampus is not essen tial for neotic information processing.