RESPONSE LEARNING OF RATS IN A MORRIS WATER MAZE - INVOLVEMENT OF THEMEDIAL PREFRONTAL CORTEX

This study is concerned with the question whether the medial prefronta l cortex mediates spatial navigation requiring the expression of respo nse learning. It consists of two parts. In the first experiment it was investigated whether intact male Wistar rats can learn a spatial resp onse task in a Morris water maze, and, if so, how the learning of this task compares with the learning of a place task, in the same water ma ze. The data illustrate that rats can indeed learn the response task d emands, but also demonstrate that this task is more difficult to learn than the place task. This is evidenced by a slower and more capriciou s acquisition. Based on these findings a second experiment was conduct ed, in which sham-operated rats and rats with damage of the medial pre frontal cortex (mPFC) were compared for their acquisition in the respo nse task in the Morris water maze. The results showed that both escape latency and path length of the mPFC-damaged animals were significantl y higher than those of the sham-operated animals. A behavioral analysi s of the swimming paths demonstrated that the mPFC-damaged rats were m ore persistent in their use of a place strategy, while the sham-operat ed animals sooner switched to the more successful taxon-orientation st rategy. Taken together with previous findings these data support the h ypothesis of a functional dissociation of the mPFC with regard to its involvement in the expression of place and response learning.