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

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

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?”