PORTLAND, Ore. - Older women on hormone therapy are more sensitive to negative events, confirming speculation that age-related estrogen loss affects the brain's ability to process emotion, an Oregon Health & Science University study shows.
But that sensitivity to negative emotional events, such as viewing a photograph of a dead person, doesn't necessarily mean women taking estrogen remember those events any better.
In the study by researchers in the Cognition & Aging Laboratory at the OHSU School of Medicine's Department of Behavioral Neuroscience, hormone therapy in women appears to reverse the age-related loss of arousal to negative emotional events experienced by the elderly. It also points to specific changes in the brain's arousal system, in the regions that process emotion, and intensification of negative emotions.
The results were presented today at Neuroscience 2006, the Society for Neuroscience's 36th annual meeting at the Georgia World Congress Center in Atlanta.
Scientists have suspected a link between sex hormones and emotion. Strengthening this theory is the fact that brain regions tuned for processing emotion and storing emotional memory - the amygdala and hippocampus - also respond to sex hormones and contain hormone receptors. Thus, changes in "emotional enhancement" people experience as they age, including a reduction in the ability to remember negative events, may be modified by age-related loss of sex hormones or hormone therapy.
In the OHSU study, researchers compared the emotional responsiveness of 45 healthy older, post-menopausal women ages 65 to 85 who had used hormone therapy an average of more than 20 years, to that of 26 women not on hormone therapy. Their performance also was compared to that of young women ages 24 to 40, also on no hormone therapy.
The groups participated in two studies about emotion, including one in which they viewed scenes that had positive, neutral or negative emotional content A negative scene might contain a dead person, while a positive scene might contain puppies. The women then rated the scenes for valence, or the positive or negative nature of the scene, and arousal, or the intensity of the emotion. The women's memory for the scenes was then tested one to two weeks later.
While younger and older women, regardless of their hormone status, had similar valence ratings and similar patterns for memory, the groups differed in their ratings of arousal for the scenes. Women on hormone therapy rated negative scenes as more arousing than positive scenes, and just the opposite was found in the women without hormone therapy.
Similar results were found for responses to a story that contained negative content. Women on hormone therapy showed more arousal for the negative section of the story, and this increase in arousal carried over to the neutral ending.
The type of hormone therapy, such as estrogen alone or in combination with progesterone, did not affect results.
Despite increased arousal for negative scenes and events, hormone therapy did not impact memory. Heightened arousal did not translate into better memory for negative events as has been found in younger people. Therefore, in aging, the scientists suggest, the arousal system is modified and can't direct memory consolidation as it does in the young.
Heightened arousal to negative material among older women using hormone therapy is intriguing because the amygdala responds to emotional material and is also a site for estrogen activity, the researchers explained. One possible explanation for this is estrogen increases and sustains amygdala reactivity to negative emotional material in older women, but the brain system critical for storage of information, the hippocampus, does not respond to the increased signal from the amygdala.
Current studies are using neuroimaging methods, such as magnetic resonance imaging (MRI), to study brain activity in older men and women to investigate how hormone loss or hormone therapies change the brain's processing and memory for emotional events.
Jeri Janowsky, Ph.D., professor of behavioral neuroscience and neurology, OHSU School of Medicine, is director of the Cognition & Aging Laboratory. The study was funded by the National Institutes of Health.