Differential effects of hippocampal lesions on maze and passive avoidance learning in rats

Abstract

In a previous study it was shown that bilateral hippocampal lesions in rats have a deleterious effect on performance in a fourteen-choice multiple-T alley maze. Lashley had not observed such an effect with his maze III. We suspected that different types of mazes possibly do not have the same ability to differentiate animals with hippocampal lesions from normal ones. In the present study, the Hebb-Williams maze, which consists of a battery of twelve different maze patterns, was used. The over-all score in this test was found to differentiate clearly between rats with hippocampal lesions and normal animals. Furthermore, some maze patterns were found to differentiate the group with bilateral hippocampal lesions from normal animals better than other maze patterns. A test of passive avoidance was included in the experiments to provide an independent measure of “emotional” changes. None of the animals with hippocampal lesions deviated significantly from the normal rats on this test. On the other hand, a deficiency in passive avoidance behavior was produced in rats with bilateral lesions in the septal and insular areas. These observations confirm our previous findings that maze learning and passive avoidance learning are dependent on different brain structures.