Slower acquisition of positively reinforced behavior following medial, but not dorsolateral, septal lesions in rats.

: This study was conducted to examine effects of medial and dorsolateral septal lesions on acquisition by using a modified autoshaping procedure. The results showed that following medial septal lesions, lever-pressing responses had long latencies and were fewer than following either dorsolateral septal lesions or control operations. However, during later sessions, the rats with medial septal lesions started to press. The long response latencies and low response rates shown initially by rats with medial septal lesions may have been due to delayed classical conditioning. Following medial septal lesions, the acetylcholinesterase activities of the different subdivisions of the hippocampus correlated positively with the number of lever-press responses emitted during Session 1. The group with dorsolateral septal lesions acquired the task just as fast as the control group and showed higher response rates than the other two groups during the final sessions. The latter result may be ascribed to generally increased locomotor activity.