FORGETTING IN RATS FOLLOWING MEDIAL SEPTUM OR MAMMILLARY BODY DAMAGE

This study examined the effects of medial septal (MS) and mammillary b ody (MB) radio-frequency lesions in an automated delayed-matching-to-s ample (DMTS) procedure using lever-position stimuli and rats. Memory p erformance pre- and postsurgery was assessed with a negative exponenti al decay function fitted to bias-free measures of recognition. Part 1 showed that MS, but not MB or sham-control surgery, impaired DMTS perf ormance. This impairment in the MS group was best characterized as an increase in the rate of forgetting. Part 2 examined the interaction be tween MS and MB lesion effects and proactive interference arising from responses made on the previous DMTS trial. The results indicated that proactive interference effects were similar for all groups. These res ults provide further support for the critical role of the MS region in memory function but indicate that damage to this brain region does no t disrupt memory function through a heightened sensitivity to proactiv e interference.