Abstract

This study was conducted to examine the effects of medial septal lesions on the spatial learning in rats. A standard Morris water maze task was used in both Experiment 1 and 2. In Experiment 3, a modified spatial working memory version of the Morris water maze task was used. In Experiment 1, colchicine or kainic acid(KA) lesions of the medial septal area were made in rats. Both colchicine and KA rats learned to find the hidden platform as quickly as sham-operated rats in the water maze, but KA rats spent somewhat less time in the training quadrant than did sham-operated rats in a probe trial. In Experiment 2, rats with pretraining infusion of lidocaine into medial septum showed impairment on acquision of the water maze, but they could retain place information as much as sham-operated rats in a probe trial. In Experiment 3, Animals were trained to swim directly to a visible platform in one of four quadrant and subsequently probed a hidden platform in the same location. Each day the platform was placed in a different quadrant. In the task, rats with colchicine-induced lesions to medial septum were significantly impaired relative to control animals. In summary, medial septal lesions did not consistently interfered with the acquisition of the standard Morris water maze task, but impaired the performance in a spatial working memory version of the water maze task. These results indicate that damage to the medial septum disrupts spatial working memory more than it disrupts cognitive mapping ability.