RATS OBJECT-IN-PLACE ENCODING AND THE EFFECT OF FORNIX TRANSECTION

We, studied the perception of simple computer-generated scenes by norm al and fornix-transected Dark Agouti rats. In Experiment 1, the rats w ere rewarded for approaching trial-unique variable scenes differing fr om a constant scene that was the same across trials (constant-negative paradigm). The groups performed equivalently when scenes differed onl y in their objects or only in the occupied positions; however, when tw o scenes shared an object-place combination, the normal rats were more likely to see them as similar than were the fornix-transected rats. I n Experiment 2, the rats learned to discriminate pairs of scenes. Agai n, there was no lesion effect when scenes differed by a single cue, ob ject or position, but when the two scenes comprised the same objects i nterchanged in position, fornix-transected rats learned relatively eas ily. Fornix transection reduces rats' sensitivity to object-place comb inations within scenes, consistent with D. Gaffan's account of scene m emory as an animal analogue of episodic memory deficits in amnesia.