2. Septal activation impaired the retrieval of a previously stored hippocampal place cell representation regardless of age. When the environment was changed, medial septal activation impaired the encoding process in young, but facilitated the encoding of the new information in aged rats.

3. Effect of aging on hippocampal place cells

4. Medial septum and theta rhythm

5. Inactivation of the MS decreases hippocampal theta and spatial task performance. Intraseptal cholinergic drugs increase hippocampal theta power and can promote memory performance in scopolamine- treated or aged memory-impaired rats but not in young rats.

6. So… The present study examined whether increased MS activation (by intraseptal carbachol, a cholinergic agonist) would promote remapping, indicating the encoding or establishment of a new representation of the environment within the hippocampus.

8. YOUNG AGED CONTROLCARBACHOL

9. YOUNG AGED CONTROLCARBACHOL