The entorhinal cortex,but not the dorsal hippocampus,is necessary for single‐cue latent learning

Two experiments were conducted to examine the roles of the entorhinal cortex (EC), dorsal hippocampus (DH), and ventral hippocampus (VH) in a modified Latent Cue Preference (LCP) task. The modified LCP task utilized one visual cue in each compartment, compared to several multimodal cues used in a previous version. In the single‐cue LCP task, water‐replete rats drink water in one compartment of the LCP box on 1 day, and then have no water in a second compartment of the LCP box the following day (one training trial), for a total of three training trials. Rats are then water‐deprived prior to a preference test, in which they are allowed to move freely between the two compartments with the water removed. Latent learning is demonstrated when water‐deprived rats spend more time in the compartment that previously contained the water. Experiment 1 demonstrated that the single‐cue LCP task results in the same irrelevant‐incentive latent learning as the multicue LCP task. In addition, Experiment 1 replicated the finding that a compartment preference based on this latent learning requires a deprivation state during the preference test, while a compartment preference based on conditioning does not. Experiment 2 examined the effects of pretraining neurotoxin lesions of the EC, DH, and VH on this single‐cue LCP task. Results showed that lesions of the EC and VH disrupted the irrelevant‐incentive latent learning, while lesions of the DH did not. These results indicate that a latent learning task that involves one discrete compartment cue, rather than several compartmental cues, does not require the DH. Therefore, the EC appears to play a central role in single‐cue latent learning in the LCP task. © 2009 Wiley‐Liss, Inc.