Lesions of the perirhinal cortex impair sensory preconditioning in rats.

The effects of lesions of the perirhinal cortex on the development of associations between two conditioned stimuli (CSs) were examined with a sensory preconditioning procedure. Rats were given either bilateral electrolytic lesions of the perirhinal cortex or control surgery. They were then given either paired or unpaired presentations of a light CS and a tone CS. All of the rats were then given eyeblink conditioning procedures that involved paired presentations of either the light or tone and a periorbital shock unconditioned stimulus (US). The rats were finally given a test session that consisted of unpaired presentations of the tone and light CSs. Sensory preconditioning was established in the control group, but not in the lesion group. The findings are consistent with the view that the perirhinal cortex is involved in forming associations between neutral stimuli (even in the absence of reinforcement).