“Now, where did I put my keys?” If you’re always asking yourself that question, here’s a possible culprit: estrogen. As a new study conducted by neuroscientist Emily Jacobs ’04 shows, estrogen has a direct effect on cognition during a woman’s menstrual cycle, sharpening short-term (“working”) memory in some women—but having the opposite effect on others.
It all starts with dopamine, a chemical the brain uses to communicate. Dopamine is crucial to maintaining cognitive abilities like working memory, which is why drugs used to treat attention deficit disorders, like Ritalin, replicate its effects. But some people have naturally high levels of dopamine while others’ levels are low. Given these genetic differences, Jacobs and her team at the University of California, Berkeley, wanted to know what happens when women experience what Jacobs calls an “estrogen-induced dopamine boost” right before ovulation.
What they found is that women with low baseline levels of dopamine benefited from the extra dopamine at ovulation, excelling at tasks that tested their ability to keep information in their mind over a short delay, such as repeating a phone number thirty seconds later or repeating it backward. Women with high baseline levels, meanwhile, essentially overdosed on the extra dopamine, flunking the same working-memory tests.
The bottom line? Estrogen can help or hurt, but it all depends on the amount of dopamine you have in the first place. It’s a Goldilocks scenario: You don’t want too little or too much, you want just enough.
Jacobs says her study, which is in the publishing pipeline, has big implications for attention deficit hyperactivity disorder and hormone replacement therapy, since baseline dopamine levels aren’t currently taken into account either when Ritalin is prescribed for girls with ADHD or when estrogen is prescribed for menopausal women.
Jacobs plans to follow these threads as a postdoctoral fellow at Harvard and as a Robert Wood Johnson Foundation Health and Society Scholar. In the meantime, she says, “I’m just glad people are beginning to think about why these questions matter.”
Fall ’10 SAQ