Effects of selctive lesions of the nucleus basalis magnocellularis on working memory in rats.

Abstract

The nucleus basalis magnocellularis (NBM) of the rat brain is analogous to the nucleus basalis of Meynert found in humans. Alzheimer's disease patients have working memory impairments, which may be attributable to damage to the basal nucleus of Meynert. Excitotoxins such as quisqualic and ibotenic acid have been previously used to make lesions of the NBM in research animals. NBM lesions made with ibotenic or quisqualic acid are known to impair working memory. However, in addition to damaging the cholinergic neurons of the NBM, the lesions made by these excitotoxins also destroy cells of other nearby structures, and it is unclear whether the impairments found are due to damage to the NBM or to surrounding non-cholinergic structures. With the recent advent ofthe highly selective immunotoxin 192 IgG-saporin, it may be possible to determine if lesions involving only the cortically projecting NBM cholinergic neurons impair working memory. The current experiment tests the hypothesis that selective lesions of cholinergic neurons of the NBM impair working memory. To test this hypothesis, a delayed non-matching-to-position-task was used as a test for working memory. Results of this experiment provide novel evidence of the involvement of the cholinergic neurons of the NBM in working memory and will contribute to our understanding of the cognitive impairments seen in Alzheimer's disease.