Differential effects of medial septal lesions on spatial-memory tasks

Radiofrequency (RF) or quisqualate (QUIS) lesions of the septal area were made in rats, and acquisition of the radial-arm maze and the Morris water maze was assessed. Both RF and QUIS rats learned to find the hidden platform as quickly as sham-lesioned rats in the Morris water maze, whereas RF rats were markedly impaired and QUIS rats were mildly impaired on the radial-arm maze. A spatial-discrimination version of the Morris water maze, however, revealed a deficit in RF but not QUIS rats. Interestingly, the performance of RF rats on this task was not altered by a dose of scopolamine, a muscarinic antagonist, that disrupted the performance of sham-lesioned animals. Since the relative sensitivity of these spatial tasks to disruption by septal lesions was not clearly related to spatial-mapping requirements, impaired cognitive mapping does not completely account for septal-lesion effects on memory tasks.