The effect of the response-shock postponement interval on free operant avoidance by septal lesioned and normal rats

Fourteen female hooded Long-Evans rats (7 septal-lesioned and 7 normal) were trained under a free-operant avoidance schedule. After extensive training during which the response-shock (R-S) postponement interval was 20 sec, the subjects were tested under a 10 sec, a 6 sec, and an additional 20 sec R-S interval. The measurement of avoidance proficiency indicated that septal-lesioned subjects were more effective than normals in avoiding shock during all R-S intervals examined. This result was related to the hypothesis that the lever apparatus is unfavourable to animals who freeze in response to shock by lever holding. Septal-lesioned subjects appear less inclined to adopt the species-specific defensive act of freezing and in addition, appear to have difficulty in maintaining a rearing posture which would be more proficient in avoiding shock.