Pregnant pause in memory
 Parking lots can be confusing at the best of times, but when you're pregnant
they can be hell. Especially large lots, or garages with many levels. Dr. Liisa
Galea knows from personal experience that finding a parked car can be a
challenge during the last weeks of pregnancy. "It was 4:45 p.m. and I had
to pick up my son at 5 p.m., and I was in tears in the parking garage because I
couldn't remember where I had parked my car," she recalls.
And she'd like to know why. The NSERC-funded psychologist is studying how
estrogen levels affect learning and memory. Dr. Galea says that while many
quirky behaviours get attributed to fluctuating hormone levels, few women
associate changes in their ability to think with their menstrual cycle.
"There's a lot of evidence that the ability to orient position is
related to
hormones. These spatial abilities decline during the third trimester of
pregnancy and then bounce back later on."
We need two kinds of memory to guide us back to our parked car at the end of
the day. We use reference memory - our long-term, stable memory that doesn't
change from day-to-day - to remind us that we always park in Lot B. Then we rely
on working memory, which incorporates new information, to help us recall our
exact day-to-day position in the lot.
Working memory is facilitated by low levels of estrogen, particularly
estradiol. This would make it easier for a woman to locate a car at certain
times of the month, for example, during menstruation. However, during
menopause, when estradiol is absent or extremely low, working memory
declines.
Working memory also suffers if estradiol levels are very high, as they are
during ovulation or the last trimester of pregnancy. That's when it gets
harder to pinpoint the exact spot where the car was left.
Many women notice changes in their memory after menopause. "You see a
decline in any kind of memory with aging," Dr. Galea says. "Not only
does
working memory get fuzzier, but verbal memory - remembering a list of words,
like a shopping list that you've left at home on the fridge - tends to be
affected and improved with hormone replacement therapy."
Of course, hormone replacement therapy is controversial. One year ago, the
U.S. National Institutes of Health stopped its combination estrogen-progesterone
hormone replacement therapy trials because it was
found to have more risks than benefits. "The estrogen-alone trial has not
been stopped," Dr. Galea says. "But the trial is studying Premarin,
which is
conjugated estrogens. I think we should be looking at estradiol," she
argues, "which is the estrogen that drops rapidly after menopause."
Males are not left entirely out of the equation, because testosterone is
converted to estradiol in the brain. And men have just as many estrogen
receptors in the brain as women.
But exactly how estradiol exerts its effect on the brain is still a mystery.
Does estradiol affect behaviour through its action on gene regulation, or
through neurotransmitters such as dopamine? Why do estrogens seem to protect
against the detrimental effects of stress caused by the release of the cortisone
hormone?
Dr. Galea's experiments with rats and meadow voles aim to tease apart these
questions and reveal the underlying mechanism that makes it more difficult to
remember a relatively "simple" thing such as where you parked your
car.
More information
Contact Dr. Galea at lgalea@psych.ubc.ca
Article from NSERC
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