Functional dissociation of the hippocampus and prefrontal cortex in learning and memory

In Experiment 1, rats with lesions to the prefrontal cortex were tested on a variable-interval delayed alternation problem, and their performance was compared with that of rats with hippocampal lesions in a previous study (Winocur, 1985). In Experiments 2 and 3, groups of prefrontal, hippocampal, and operated control rats were administered a test of conditional discrimination learning. Prefrontal rats were impaired in learning both tasks, but their performance was not affected by temporal manipulations that challenged episodic memory. In contrast, rats with hippocampal lesions were not impaired in basic learning, but their performance on both tasks deteriorated at relatively long delays. The results confirmed the importance of the hippocampus in long-term recall of specific events and implicated the prefrontal cortex in nonepisodic learning and memory functions.