UBC Reports | Vol. 49 | No. 12 | Dec. 4, 2003

What to Expect -- or Make That Forget -- When You’re Expecting

Psychology research explores link between hormones and memory

By Erica Smishek

Expectant mothers not-so-affectionately call it “baby brain” -- that memory loss that strikes during pregnancy, especially in the third trimester, and leaves them wondering where they’ve put their keys or parked their car.

It’s no laughing matter and it’s not their imagination. But it could be their hormones.

Liisa Galea, an associate professor of psychology at UBC, is studying how estrogen levels affect learning and memory. She says while people blame fluctuating hormone levels for all kinds of strange behaviours and emotions, few women make the connection between their menstrual cycle and their ability to think.

“Evidence shows that the ability to orient position in the environment is related to hormones,” Galea explains. “These spatial abilities decline during the third trimester of pregnancy and bounce back later on.”

She knows of what she speaks. Pointing out her office window to the parking lot across UBC’s West Mall, Galea recounts her own inability to find her car on numerous occasions during her last weeks of pregnancy.

“I was supposed to pick up my son at 5 p.m. and had 15 minutes to get there,” she says. “I was in tears in the parking garage because I couldn’t remember where I left my car.”

People need two kinds of memory to find their cars at day’s end. Reference memory -- long-term stable memory that does not change from day-to-day -- reminds us that we always park in Lot One. Working memory -- which assimilates new information that changes frequently -- allows us to recall the specific spot in the lot.

Galea explains that medium levels of estrogen, particularly estradiol, assist with spatial working memory. Estradiol levels are optimum during menstruation, for example, so a woman would find it easier to locate her car during that particular time of the month.

Levels are absent or extremely low during menopause, however, and are very high during ovulation or the last trimester of pregnancy. These times are associated with poorer spatial ability, hence spatial working memory declines and finding that car gets more difficult.

Women aren’t alone in the battle. Men have just as many estrogen receptors in the brain as women and testosterone is converted to estradiol in the male brain.

Galea’s research with rats and meadow voles, funded through the Natural Sciences and Engineering Research Council of Canada, explores how estradiol affects learning and memory and the brain. Does it affect the architecture of the brain and change of the shape of brain cells? Does it regulate the birth of new neurons in adulthood? And why do estrogens (women produce three different forms -- estrone, estradiol and estriol) seem to protect against the detrimental effects of stress caused by the release of the corticosteroid hormones?

“Having kids is a life-changing experience,” she says. “It’s not until you experience it that you see some of the questions that arise. When I got pregnant, I realized that there wasn’t a lot of work being done in this area.”

While there have been anecdotal reports of memory problems from women in pregnancy and menopause, studies from the scientific community have been limited. Some have attributed weakened memory to iron-deficiency during pregnancy, others to high levels of oxytocin, a natural hormone produced in women during pregnancy and while nursing.

In the late 1990s, British researchers scanned the brains of 10 moms-to-be during their last trimesters and again a few months after their babies were born, and announced that brain cell volume decreases during pregnancy, only to plump up again sometime after delivery.

“It was a big splash in the media at the time,” Galea says. “But the problem was that researchers never did baseline measurements. Their results just lead to more questions. Could it really mean that maybe the brain grew? Does it mean that childbirth makes the brain more efficient? Or is it just that we have more to do once we’re mothers and have to become better managers?”