SELECTIVE HIPPOCAMPAL-LESIONS ABOLISH THE CONTEXTUAL SPECIFICITY OF LATENT INHIBITION AND CONDITIONING

The contextual specificity of the conditioned response (CR) and latent inhibition (LI) was examined in rats with select e hippocampal lesions. Acquisition of the CR to a novel conditioned novel conditioned stimulus (CS) was equally rapid in control and hippocampal rats (Experiments 1 and 2), and CS preexposure disrupted acquisition, (i.e., produced LI) to an equal extent in both groups (Experiment 2). In control subjects, however, the CR established in one context transferred incompletely to a second context (Experiment 1), and LI was attenuated when CS preexposure and conditioning occurred in different contexts (Experiment 3). This context specificity of the CR and LI was not apparent in hippocampal rats-the CR and LI transferred readily from one context to another. In addition, hippocampal rats were impaired in a spatial learning task (Experiment 2) but were unimpaired in learning a Pavlovian contextual discrimination (Experiment 3). These results suggest that a common contextual retrieval process underlies the contextual dependence of the CR and of LI and that this process is mediated by the hippocampus.