Impaired place navigation in place and matching-to-place swimming pool tasks follows both retrosplenial cortex lesions and cingulum bundle lesions in rats.

Abstract

The retrosplenial (RS) cortex (area 29) and the adjacent cingulum bundle (CG) are components of neural circuits that include the hippocampus. Given the evidence suggesting that the hippocampus plays a central role in spatial navigation, several lines of investigation have examined the possible contributions of these structures to spatial navigation. The combined and/or separate contributions of these structures have been difficult to establish because their close proximity usually results in combined injury after lesions and because there have been conflicting results related to lesion type and the strain of rat subjects. The purpose of the present study was to compare the effects of selective CG damage with selective RS damage in Long-Evans rats, a domestic rat strain that displays superior spatial skills, and by using spatial behavior assessment procedures that are sensitive to CG damage. Rats with cytotoxic N-methyl-D-aspartate (NMDA) RS lesions or surgical CG transection were tested on two spatial tasks in the Morris water task; a place learning task, sensitive to nonspatial and spatial behavior, and a matching-to-place task, sensitive to spatial behavior. Both the RS and CG groups were impaired on most measures relative to the control group on both the place task and the matching-to-place task. The results are discussed in relation to the anatomical organization of CG and RG projections to the hippocampus and with respect to their possible separate/conjoint contributions to spatial behavior.