ACQUISITION AND RETENTION OF NEGATIVE PATTERNING IN HIPPOCAMPAL-LESIONED RATS

In this series of experiments, we examined whether animals with aspira tion lesions of the hippocampus could retain a negative patterning tas k learned preoperatively (Experiment 1) or acquire a negative patterni ng task postoperatively (Experiment 2). In a negative patterning task, each of two single cues is followed by an unconditioned stimulus (A+, B+), while the two cues presented together are not followed by the un conditioned stimulus (AB-). Rats were exposed to a novel context and a llowed to drink a saccharin solution for 15 min on AB- trials. On A+ t rials, the rats were exposed to saccharin alone, and on BS trials, the rats were exposed to the novel context with a water bottle and were g iven an injection of LiC1 in both cases. The rats showed aversions to the context and saccharin alone but consumed large amounts of the sacc harin when the two cues were presented together. While hippocampal-les ioned rats showed some deficits on retention tests, they showed good a cquisition of the negative patterning task.