Abstract

This experiment was planned to find if the hippocampus exerts any influence upon the emotional reactivity of male rats. Thirty-five rats in which the hippocampus was almost totally removed through a small hole with a diameter 3 mm made in the neocortex at the boundary between the parietal and occipital lobes (hippocampal group), twenty-five rats with similar neocortical damage alone (opera ted control group), and twenty-three normal control rats(normal control group) were subjected to the experiment. In an attempt to evaluate gross changes in emotional reactivity with hippocampal ablated rats, a four point rating scale technique by Brady and Nauta(1953) was employed. Ratings were made for all animals on the following six behavior components: (1) resistance to capture in home cage, (2) resistance to handling, (3) squealing and vocalization reaction to capture and handling, (4) urination and defecation reaction to capture and handling, (5) Aggressive reaction to presentation o£ pencils in close proximity to the animal snout. (6) Aggressive reaction to proding with a forcep on the animal back. Two independent judges rated in the relatively standard situation. Ratings for all animals were performed four occasions, i.e., on the 3,4,5 and 6 week days after surgery. The results for emotional reactivity are shown in table (1), It is apparent that there appears a rather marked change in the emotional reactivity of the hippocampal animals as compared with both of the two control groups throughout the four successive postoperative tests. The table 1 shows that there is a gradual increase in the magnitude of emotional reactivity for all three groups over the consecutive postoperative weeks.