Effects of limbic lesions, especially of olfactory bulbectomy on simple conditioned avoidance response in rats

Effects of olfactory bulbectomy, and lesions of the septum and dorsal hippocampus on emotionality as well as on the simple conditioned avoidance response in a two-way shuttle box were investigated in rats. The rats with bilateral olfactory bulbectomy (O. B. rats) showed hyperactivity and aggressive behavior, including mouse-killing behavior (muricide), and those with septal lesions exhibited hyperreactivity and hypoactivity, while the rats with hippocampal lesions became hypoactive without showing hyperreactivity. The O. B. and septal rats, on an average, showed a facilitation in acquisition of the conditioned avoidance response and a retardation in extinction. The muricidal group of O. B. rats, however, showed slower acquisition, while the nonmuricidal O. B. rats showed much faster acquisition and slower extinction than intact rats. Hippocampal lesions retarded acquisition.