MEDIAL SEPTAL-LESIONS IN RATS PRODUCE PERMANENT DEFICITS FOR STRATEGYSELECTION IN A SPATIAL MEMORY TASK

Rats with medial septal (MS) lesions have been shown to consistently u se a stereotypic response strategy rather than a nonstereotypic spatia l learning strategy when solving a radial maze task. The present study examined the long-term effects of MS lesions on spatial memory perfor mance to determine whether MS lesions permanently impair rats from usi ng a nonstereotypic strategy. Male rats, initially trained on a radial maze, were given either MS or sham surgeries and were subsequently re tested on the maze. Consistent with previous studies, all rats with MS lesions used a stereotypic strategy during the postoperative retest. However, when placed through a series of retraining phases that requir ed the rat to use a nonstereotypic strategy to solve the task, none of the MS rats could solve the task. These results indicate that lesions of the medial septum produce permanent spatial memory deficits that c annot be restored through extensive behavioral training.