SPONTANEOUS OBJECT RECOGNITION AND OBJECT LOCATION MEMORY IN RATS - THE EFFECTS OF LESIONS IN THE CINGULATE CORTICES, THE MEDIAL PREFRONTALCORTEX, THE CINGULUM BUNDLE AND THE FORNIX

The first experiment assessed the effects of neurotoxic lesions in eit her the anterior cingulate cortex (ACc) or the retrosplenial cortex (R Sc) on a test of object recognition. Neither lesion affected performan ce on this task, which takes advantage of the rat's normal preference to spend more time investigating novel rather than familiar stimuli. I n response to this negative result, a second experiment assessed the e ffects of much more extensive cingulate lesions (Cg) on both object re cognition and object location memory. The latter task also used a pref erence measure, but in this case it concerned preference for a novel l ocation. For comparison purposes this second study included groups of rats with lesions in closely allied regions: the fornix (Fx), the cing ulum bundle (CB) and the medial prefrontal cortex (Pfc). Comparisons w ith sham-operated control rats showed that none of the four groups (Cg , Fx, CB, Pfc) was impaired on the object recognition task, adding fur ther weight to the view that these structures are not necessary for as sessing stimulus familiarity. The Fx and Cg groups were, however, impa ired on the object location task, suggesting that these regions are ne cessary for remembering other attributes of a stimulus (spatial locati on).