Dorsal and ventral hippocampal lesions and behavior

The behavior of rats with either dorsal or ventral hippocampal lesions was compared to that of a control group in a series of tests. Dorsal hippocampal lesions made rats hyperactive in novel situations, did not affect rates of habituation, facilitated acquisition of a conditioned emotional response (CER), and retarded acquisition of a one-way active avoidance response. Ventral hippocampal lesions made rats hyperactive in novel situations, affected the rate of habituation of exploratory responses, retarded extinction of the CER, and tended to facilitate acquisition of the one-way active avoidance response. These results demonstrate that the dorsal and ventral hippocampus are functionally distinct. When applied to an examination of previous data, this differentiation may help to clarify present confusion about hippocampal function. Possible functions of the dorsal and ventral areas are discussed.