Exploratory behavior as a function of hippocampal damage, stimulus complexity, and stimulus novelty in the hooded rat

Exploration by hooded rats of two stimuli differing in complexity was investigated as a function of lesion location, preexposure complexity, and preexposure time over three successive 10-min periods. Results indicated the preexposure complexity altered the total number of exploratory responses of both lesioned and normal animals as a function of test stimulus complexity. Significant habituation rate differences were found between normal and operated animals, with similar effects occurring between cortical control and hippocampally damaged animals with one stimulus. There were no significant behavioral differences between animals receiving dorsal or ventral hippocampal lesions for the paradigm employed. Approaches to an area illuminated as the stimulus area, but containing no stimuli, revealed apparent light-dependent response decrements in the hippocampally lesioned animals. These results suggest that hippocampally lesioned animals and, in some instances, cortically lesioned animals, cannot rapidly shift certain modes of response even though the necessary information has been acquired and can be evidenced when different response constraints are imposed.