Effects of lateral and medial septal lesions on exploratory behavior in the albino rat

Abstract

The effects of selective medial and lateral septal lesions on exploratory behavior were studied in the rat. Three types of open-field test and two tests of object exploration were used. In the firts experiments, medial but not lateral septal lesions abolished exploration of an open-field accessible from the home-cage. No effects of either of the lesions were found in a standard open-field (Experiment 2). In the third experiment, rats with medial septal lesions were less active and showed a preference for the smaller compartments of the testing apparatus. These results suggest that a change in exploratory behavior following medial septal lesions may be primarily due to their effect on emotionality (increased fear). Two tests of object exploration (Experiments 4 and 5) showed that both types of selective septal lesions enhanced approaches to the novel object placed in the home-cage, but they did not affect object exploration and object preference in other conditions (Experiment 5). The same experiments revealed an increased level of activity (rearing and ambulation) in the rats with lateral septal lesions. It is concluded that the effect of medial septal lesions on exploration is due to increased fear of novel places (but not objects). Lateral septal lesions, on the other hand, increase activity in the rats but there is no evidence that this activity represents enhanced exploration.