Revisiting places passed: sensitization of exploratory activity in rats with hippocampal lesions.

We examined the involvement of the hippocampus in short-term changes in exploratory behaviour in an open field (Experiment 1) and experimental contexts (Experiment 2). In Experiment 1, rats with excitotoxic lesions of the hippocampus were more likely to revisit recently visited zones within the open field than were control rats. Similarly, in Experiment 2 rats with hippocampal lesions showed greater exploration of a context that they had recently explored than a context that they had less recently explored. This short-term sensitization effect was not evident in control rats. These findings are consistent with the suggestion that the recent presentation of a stimulus has two opposing effects on behaviour, sensitization, and habituation, and that hippocampal lesions disrupt the short-term process responsible for habituation, but not that responsible for sensitization.