Postoperative environmental enrichment attenuates fimbria-fornix lesion-induced impairments in Morris maze performance.

Male Wistar rats were given a bilateral or a unilateral transection of the fimbria-fornix; subsequently they were kept in standard laboratory housing conditions or in enriched environments for 6 weeks, after which they were tested in the Morris maze. In the acquisition phase of the experiment rats with a bilateral lesion of the fimbria-fornix were markedly impaired in their ability to locate the hidden platform, while rats with unilateral lesions displayed no such impairment. However, rats with a bilateral lesion displayed a less severe deficit when they had been housed postoperatively in the enriched environment. In the retention phase of the experiment rats with a bilateral lesion swam markedly less time in the platform zone only when they had been housed in standard conditions. They also spent more time in the edge zone than the other groups. Rats with a bilateral lesion that were housed enriched did not swim more in the edge zone. Despite their good performance during acquisition they did not display a clear preference for the platform zone. Thus, it was speculated that enriched rats with a bilateral lesion had learned to leave the side of the pool to search for the platform and with the aid of this different strategy improved their performance.