Cholinergic Modulation of Hippocampal Activity during Episodic Memory Encoding in Postmenopausal Women: A Pilot Study

Abstract

Objective: The cholinergic system has been shown to modulate estrogen effects on cognitive performance in postmenopausal women. In an effort to further understand cholinergic contributions to cognition after menopause, this pilot study investigated the effects of two receptor-specific anticholinergic drugs on brain activation and episodic memory encoding in postmenopausal women not taking estrogen. Methods: Six healthy postmenopausal women took part in three drug challenges using the antimuscarinic drug scopolamine (2.5 microg/kg IV), the antinicotinic drug mecamylamine (20 mg PO), and placebo. During functional magnetic resonance imaging, participants performed a visual-verbal continuous recognition memory test that allowed for the separation of encoding and recognition processes. Results: Functional magnetic resonance imaging results showed greater hippocampal and frontal activation and less occipital activation during encoding relative to retrieval conditions. This pattern of activation was similar under both drug challenges. Conclusions: These results suggest that the changes in the cholinergic system may, in part, be responsible for menopause-related increases in brain activation.