Neurotoxic hippocampal lesions fail to impair reinstatement of an appetitively conditioned response.

Rats with ibotenate lesions of the hippocampus (HPC) and nonlesioned rats were trained with a Pavlovian appetitive conditioning procedure in which a visual conditioned stimulus (CS) was first paired with a food unconditioned stimulus (US) and then repeatedly presented in the absence of the food US. After extinction of the conditioned response (CR), half of the rats received presentations of the food US and half did not. On a final test of responding to the visual CS, rats that received the postextinction US presentations showed higher levels of conditioned responding than the rats that did not. This reinstatement of CRs was not affected by the HPC lesions, which nevertheless impaired performance on a water maze task known to be sensitive to HPC damage. These data are in contrast to those of A. Wilson, D. C. Brooks, and M. E. Bouton (1995), who found that lesions of the fornix abolished reinstatement of aversively conditioned behavior.