Mediodorsal thalamus lesions in rats impair radial-arm maze performance in a cued environment

Abstract

In a previous experiment (Stokes & Best, 1988), we showed that rats lesioned in the mediodorsal nucleus of the thalamus performed poorly on a radial maze placed in a visually deprived environment. The present experiment was designed to assess performance of similarly lesioned rats on the radial maze when extramaze cues were plentiful. Sixteen rats were trained on the radial maze; 7 then received electrolytic lesion of the mediodorsal thalamic nucleus. Despite excellent preoperative acquisition of the task, postoperative performance was severely impaired in all animals given lesions. These animals made more errors, and made errors earlier in the session, than did control animals. Furthermore, animals with lesions developed stereotyped patterns of responding on the maze, as had animals in the previous study. Thus, we replicated our previous findings with respect to the effects of lesions of the mediodorsal nucleus, and extended their generality to a more usual, visually enriched testing environment. Our results indicate that the impairment in maze performance subsequent to mediodorsal thalamus lesion is nonspecific, affecting memory secondarily. © 1990, Psychonomic Society, Inc.. All rights reserved.