ARI SHAPIRO, HOST:
The body transforms in remarkable ways during pregnancy, and so does the brain. A new study details the changes that occurred in one healthy 38-year-old woman's brain from three weeks before conception to two years after childbirth, and it presents a new dynamic picture of how pregnancy can reshape the brain. The results are out this week in the journal Nature Neuroscience, and Emily Jacobs of UC Santa Barbara is one of the authors. Welcome.
EMILY JACOBS: Thanks for having me.
SHAPIRO: Previous studies have looked at women's brains before and after pregnancy. Yours looked at the brain of one woman throughout that process. What did you find?
JACOBS: We've never witnessed the brain in the midst of this metamorphosis. So we used something called precision imaging. So this was one woman who was followed over the course of pregnancy, into the postpartum, and we observed these sweeping changes in gray-matter volume, cortical thickness, white-matter microstructure and ventricle volume, and we could see it all unfold week by week. It's almost like the maternal brain undergoes this choreographed change across gestation, and we're finally able to see the process in real time.
SHAPIRO: Any idea why?
JACOBS: Yeah, great question. We don't know from our study the million-dollar question, which is - why? What are the functional consequences? So we don't know how it's influencing behavior, but we can get some pretty intriguing hints from animal studies. So in rodents, this surge in estrogen and progesterone that happens during pregnancy programs brain circuits in the hypothalamus - this is a tiny structure nestled in the base of the brain. And this rewiring, at least in rodents, enhances mother sensitivity to smells and sounds from her newborn pups, and it triggers the onset of maternal behavior - so thinking things like nest building, licking and grooming.
But, you know, in humans it's a lot more complicated because we know that parental behavior occurs all the time in nongestational mothers, in adoptive parents and grandparents and fathers. So you have these people who don't experience gestation firsthand, and yet they're capable of displaying all of the nurturing behaviors needed to care for children. Why we're seeing this in mothers? Maybe it's just this fine-tuning and programming of these neural circuits to hone these behaviors, but it's not totally necessary, as we can see from these other groups.
SHAPIRO: Huh. You found pronounced decreases in gray-matter volume in this woman's brain. Is that a cause for concern?
JACOBS: (Laughter) Some people bristle - right? - when they hear that gray-matter volume decreases during pregnancy. It's like, ooh, that can't be a good thing.
SHAPIRO: Right.
JACOBS: But it probably isn't a bad thing. It's probably a really good thing because that change reflects the fine-tuning of neural circuits. It's not unlike the cortical thinning that happens to all humans during puberty, right? So in both cases, this is a highly adaptive process. It enables the brain to become more specialized. The analogy I like to think of is Michelangelo's David. So the artist starts off with this big block of marble, and the underlying beauty is revealed through the art of removal - right? - by carefully honing and fine-tuning the material. And with the brain, this process happens, we know, really early in development, happens again during puberty. And I think what we're seeing here for the first time is that pregnancy reflects this - yet another wave of cortical refinement.
SHAPIRO: I always thought sample size was an important part of scientific research. How much can you generalize from one brain about what millions of people might experience during and after pregnancy?
JACOBS: You know, neuroscience and psychology, for a long, long time, used this group averaging model, where we would take a group of people, we'd average their brain and we'd draw some conclusion. And that's fine. We learned a lot through that approach. But more recently, in the last five to 10 years, neuroscientists realized that there's a wealth of information in understanding how maybe just one brain changes dynamically over time. There's so much to be discovered by understanding how the brain is changing over this adaptive period of time. Now we have to do it in an expanded sample of women. We need greater diversity. We need greater numbers. And that's really what we're doing with this project.
SHAPIRO: That is Emily Jacobs, associate professor of psychological and brain sciences at UC Santa Barbara. Thank you.
JACOBS: Thanks so much. Transcript provided by NPR, Copyright NPR.
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