The effects of nucleus basalis magnocellularis lesions in long-evans hooded rats on two learning set formation tasks, delayed matching-to-sample learning, and open-field activity

Rats with quisqualic acid lesions of the nucleus basalis magnocellularis (n BM) and control rats were compared in discrimination reversal learning set (DRLS) and olfactory discrimination learning set (ODLS) tasks, a delayed ma tching-to-sample task (DMTS). and open-field activity. Evidence of learning set formation was seen in control rats but not in nBM-lesioned rats in bot h the DRLS and ODLS tasks. Better-than-chance performances were seen for bo th groups in DMTS, indicating no impairment after nBM lesions. There were n o group differences in open-field activity. These findings suggest that the nBM is important for higher cognitive processing such as "learning to lear n" and thus is important for a complex form of reference memory. In additio n, perseverational, working memory, and attentional deficits could not expl ain learning set impairment after nBM lesions.