Perirhinal cortex ablation in rats selectively impairs object identification in a simultaneous visual comparison task

In Experiment 1, rats discriminated among computer-generated visual display s (scenes) comprising 3 different shapes (objects). One constant scene (unr ewarded) appeared on every trial together with a trial-unique variable scen e (rewarded). Four types of variable scene were intermingled: (a) unfamilia r objects in different positions from the constant; (b) unfamiliar objects in same positions as the constant; (c) same objects as the constant in diff erent positions; (d) same objects and positions, recombined. Aspiration les ions of perirhinal cortex impaired performance with type (b) only. Experime nt 2 tested spatial delayed nonmatching-to-sample. The perirhinal group wer e impaired nonsignificantly, and less than fornix-transected rats in an ear lier study. Rats' perirhinal cortex, like monkeys', subserves object identi fication in the absence of memory requirement but does not contribute subst antially to hippocampal system spatial memory function.