Science Friday - MRIs Show How The Brain Changes During Pregnancy

Episode Date: October 23, 2024

Pregnancy is a hugely transformative experience, both in how it can change someone’s day-to-day life, and how it affects the body. There’s a key part of the body that’s been under-researched in relation to pregnancy: the brain.Those who have been pregnant often talk about “pregnancy brain,” the experience of brain fog or forgetfulness during and after pregnancy. There’s also the specter of postpartum depression, a condition that affects about 1 in 7 women post-birthing. There’s still a dearth of information about what causes these cognitive, psychological, and emotional experiences.In a recent study, scientists took MRI scans of participants before, during, and after pregnancy, and spotted distinctive changes in the brain’s gray and white matter. While these anatomical changes are noticeable, the researchers are still trying to determine what they actually mean for behavior. Joining guest host Kathleen Davis to talk about this study is Dr. Liz Chrastil, associate professor of neurobiology and behavior at the University of California Irvine.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Being pregnant can change your brain matter. So what does that mean for cognitive function? You know, we've had millions of years of evolution, and this is probably adaptive in some way, but we don't necessarily know what way that is adaptive. It's Wednesday, October 23rd, and you're listening to Science Friday. I'm SciFright producer Dee Petersmith. Pregnancy is a hugely transformative experience, but there's a big part of those bodily changes that is historically understudied, and that's what happens in the brain.

There's new research that shows distinctive changes in both gray matter and white matter in the brain over the course of pregnancy, but there's still lots of questions that remain to be answered. Here's Cyphrise Kathleen Davis with more. Here with me to explain these changes and what they might mean is my guest. Dr. Liz Krastel, Associate Professor of Neurobiology and Behavior at the University of California Irvine. Welcome to Science Friday. Thanks for having me, Kathleen. So this research, it's my understanding, is very near and dear to your heart because it wasn't just any pregnant brain that was being studied. It was yours, right? Right. I was studying my own brain. So I was working with Emily Jacobs, my collaborator, and her student, Laura Pritchard, who had just finished a menstrual cycle study, and we were working on menopause in other ways. But then I was planning a pregnancy. And so he said, hey, we got to do this. So that's how it sort of started.

We went from there, and it was really exciting to be your own, own participant in your own study. And it sounds like this is a really understudied part of pregnancy research, right? Studying the actual brain? Exactly. We had almost no information about the human brain and what happens during pregnancy. There have been a few studies looking before and after, you know, testing people before they got pregnant and then what their brains look like after pregnancy. but we were really missing the during. And so we had really almost no idea what was going to happen to the human brain while

pregnancy was ongoing. And so what were you really hoping to pinpoint here? We're hoping to look at understanding more about what was happening. Again, during pregnancy, we were looking at a couple of key features. So we were looking at brain structures, mainly focusing on the structure of the brain and how it might change. So we're looking at volume, like sizes and like the strain. of the connections and the quality of the brain connections. So we're looking at gray matter,

which is the cell bodies of the neurons. And we're looking at volume of gray matter in certain areas like the hippocampus, which is important for learning and memory. And it's important for when people have something like brain fog that might be part of it. So we're looking there. We're looking at cortical thickness, which again is sort of volume across the brain. And then we're looking at white matter, which are the axons of the neurons, which are the connections between neurons. And those are sort of these big fiber tracks that go across the brain. And we're looking at the health of those connectivity and sort of how well the connections are. And so we think of white matter as like a road and you want your road to be well paved. So we were looking at the quality of those connections there. And so as kind of the central test subject in this project, what sort of test did you actually run yourself through to find out the answers to these things? So we did MRI scanning. And so the scan.

did several structural scans looking at those volumes that I was talking about, a diffusion imaging, which looks at the white matter. We have a couple other ones that we did as well. But it was about, you know, a half hour scan, 45 minutes each time. And just went in there and did a blood draw as well so that we could also connect it with sex hormones. What is it like to be at the center of a study that you're actually doing research on? Was that a little bit of like a not, not, no pun, intended. Was that a little bit of like a cognitive challenge for you? It was okay. You know, it was exciting, I think, more than anything, because again, we were just forging new territory. And so it was sort of like we knew we needed a neuroscientist to do this study almost because knowing what it

takes to do these MRI scans. Of course, I've done tons of MRI scans in the past just because that's what we might meet research is about. And so sort of being able to know what it takes to do this and what it might be involved with was part of it. And so it was just more exciting than anything. And we never really looked at the data until it was done. And so that was another thing that was helpful, I think, because I didn't see my brain changing in real time at any time. So, you know, we never wanted to, you know, affect anything with the study while it was going on. And so we didn't look at it until well after. So I just kind of was going in and, you know, hoping everything was fine, but essentially, but not, not looking at how things were changing.

Right. I would imagine if you're actually looking at scans in real time and seeing, oh, wow, things are really changing in there. That might be a little disorienting. Right, right, exactly. And we had expected for sure some changes. And again, looking at the pre and post studies, we had expected some decreases in gray matter volume. So it wouldn't be totally surprising, but we still didn't want to like do it in the time. So tell me exactly what you found. So we found overall this decrease in. in gray matter volume and cortical thickness across the board of about 4%, which is not that big, but that's a sizable amount when you're thinking about your brain. And there was some variability, so some actually increased a little bit. Some went down by as much as like 13%. But overall, the average was about 4% brain reduction in volume from before and after.

And that was pretty much a linear trend. So it kind of just kept going down. We did also some postpartum scans, so several scans after pregnancy, and then about six months. on a year and two years out. And so that gray matter volume rebounded a little bit, but it mostly stayed the same. And then it kind of kept the same level for the two years out. Then we also found in the white matter,

this really interesting non-linear relationship. So what we found was an increase in the white matter, connectivity, integrity, that peaked around the second to third trimester. And then it went back to baseline by the time the baby was born. And so that had this sort of interesting peak. and then return of sort of integrity that we wouldn't have seen if we had just done a before and after design. So if we had just done before and after, we would have completely missed that part.

And so this was a really new and interesting finding that we were able to discover. In general, what do we know about gray matter, white matter, and what they actually do in the brain, like what their purpose is? Yeah. So, you know, gray matter are the cell bodies. And so, you know, we think that a redone, in gray matter might be worse. So when you think about it, you're like, oh, your brain drinks. That doesn't sound so great. But, you know, there's a lot of things that are going on there.

So there are pruning. And it could be the amount of dendritic spines, which are the connections between sort of each neuron at the synapse. And so that's one possibility in terms of the reduction. And that might not be a bad thing. So in adolescence, there's a similar reduction in volume during the adolescence in puberty time. And so it's not necessarily a problem.

We also see this during childhood that there can be changes in connectivity and pruning and things like that. So reductions in volume are not necessarily a bad thing. But we don't necessarily know, again, what the actual cellular mechanisms are for this reduction and volume. And likewise, we don't necessarily know what the cellular mechanisms are for the increase in white matter integrity. We need some more animal studies to do that. But what we can say is, again, that we do see this. the quality of the connection, so the white matter is, again, like this sort of like tube that runs across your brain, connecting broad areas or straw. Sometimes you think about that. So we're looking at the diffusion

of water in the white matter. And so it looks like the diffusion is happening, or less diffusion, in the sense that it's going more like it's going through a straw, which is what you want. You want it to be more like it's going through the straw and sort of better road paving again for your white matter. So, you know, these are how your neurons are connecting to each other and how their volume is happening. And so, again, what we need to know now that we have some of this information is to go into either in vitro studies or animal studies and to understand more about what are those particular dynamics happening on the cellular level. So we're looking at a scale that's a little harder for us to see at this point. I know that you study behavior. At this point, is there anything we can glean about?

how these differences in gray matter and white matter might actually change our behavior in pregnancy? That's the big question that we want to find out. So we know a little bit about behavior. So we know from animals that if you give animals who vaguely have never had any pups, if you give them some of these hormones, that they will now have some changes in their maternal behavior and grooming behavior and caregiving behavior and things like that. So we know that there are some certainly aspects of this. We know from another study, from that Susanna Caramona study that looked at before and after in humans that some of the relationship with the volume reduction that they saw was related to some social interactions, recognizing your infants and a little bit of

maternal care. So we think that there's some relationship, but we still don't really know what it means. And so that's the big question that we want to move forward with is understanding does it mean anything for care? Does it mean anything for things like brain fog or thinking or anything like that? So I didn't actually experience any brain fog when I was pregnant. So as far as I remember, so I didn't really have that experience, but a lot of people do. And so we want to know more about what's going to likely happen in terms of these changes in the brain and are they going to be affecting people's behavior. Yeah, I want to ask you about brain fog because I've heard this term pregnancy brain referred to a lot by people in my life over the years. And, you know, this idea

that there is brain fog and maybe forgetfulness that happens during and after pregnancy, we even got a message from listener Chris and Traverse City who said that they could feel their IQ drop when they were pregnant. I think there's maybe a little bit of a joke in there. But could this idea of pregnancy brain be connected to these changes? And like, what do we need to study to know if that's the truth? Right. So it's certainly possible. And so that's, again, what we need to find out. And so there's a lot of things that can contribute to a pregnancy brain, this feeling, right? So what we don't know exactly is where it's stemming from. So, you know, you're not sleeping as much or sleeping as well, certainly during pregnancy,

but of course, well, after pregnancy, right? You're stressed out, you're worried, lots of things like that. You're starting to like take care of another, you know, human being. You have to demand all those other things. Right. So there's a lot of things that can be going on both during and after pregnancy that we can attribute this to. And so it's hard to know exactly if it's specific to the brain structure, if it's more about sleep, if it's more about stress or other things. And so that's what we need to find out more with. So one thing that we're really interested in looking at next is some of these behaviors and thinking about both cognition in terms of pregnancy brain and thinking. We're also really interested in thinking about

postpartum depression and peripartum depression. So a lot of people, again, experience these depressive symptoms, and we want to know if the structure is important for that. And so is it anything that's happening during pregnancy? Is that predictive of postpartum depression? Is it after pregnancy? Is it something else? And so understanding more about that is going to be really informative. There's lots of other things that might be important, too, things like preeclampsia,

which is really more like high blood pressure, but that's a vascular issue that's going to affect your brain, and there might be signatures of preeclampsia in the brain, and that might also have long-term health implications. And so that's something, again, that can be really important as we move forward. So I think there's a lot of open questions here. And this research, I think, really opens more questions than it answers. And so we're excited about it. It makes me wonder if these changes in the brain during pregnancy is one of those things that developed in evolution and it has some sort of importance, but we just might not know what it is yet.

Exactly. And so that's sort of my take on it is that, you know, we've had millions of years of evolution. and this is probably adaptive in some way, but we don't necessarily know what way that is adaptive, right? So it's almost certainly going to be helpful, but is it a trade-off with other things, right? So because your body's changing with all these other systems that are going on, and there's certain energy requirements, right? So is it going to be a trade-off with other things? Or is it enhancing, right? Again, likely to be in maternal care or other things, but maybe not. And so figuring out where it's adaptive and then where it's maladaptive, right?

So when it goes wrong and someone gets postpartum depression or something else, where is that happening? And how can we detect that and sort of figure out ways to detect that? So to me, it's a little staggering that this type of research hasn't been done before, considering how many pregnancies happen all the time. When you got pregnant, were you like, okay, if no one else is going to do this work, I'm just going to do it on myself, on my own terms. Yeah, pretty much. Exactly.

So we kind of knew that you needed a neuroscience. to do this. And so, you know, I've done MRI scans many times in my life just because that's what we do. And so, you know, being able to know what it takes to do this and to set this up and to make it happen was kind of needed. And yeah, it really is just shocking. I mean, the paper, again, it opens more questions than it answers. And so it's just the fact that we ask this question is why we're getting so much response because people want to know and no one's bothered to find out. And so that's where I think there's a lot of open things to talk about. And it's really, again, shocking, it's 2024.

And we know so little about what goes on during pregnancy and generally in the female brain and other things. So like, again, thinking about menopause. That's another area that we're really interested in. And again, very little is known about that. I think there's a little bit more there. But, you know, historically women's brain health has been understudied. And so that's something that really needs to have a change in understanding. an approach to think about that. Did actually having this pregnancy experience bring up other questions

that you want to know the answer to, you know, being pregnant while working on this study? I mean, are there other things that came up that maybe you weren't expecting to? Yeah, well, I think for sure. You know, certainly I didn't necessarily know what to expect. What would sorts of things would happen. And so, yeah, so I wasn't sure whether I would have any sort of brain fog symptoms, and I didn't, but I could have. And that might have had certain implications, just trying to understand more about, you know, comfort levels and things like that, trying to understand more about, yeah, just sort of planning and all the stress and things like that. We're definitely something that I would like to be able to do more. And then sort of support systems, I think, as well afterwards. I think that's a big important question that should be studied more, and we didn't get a chance to look at that.

So we've talked a lot about the unknowns that still exist around this topic. But now that we have this first round of information, we have this map, right? I mean, what would you really love to learn next? We'd really love to learn how this relates to your brain function. And so, again, this was all structure. And so understanding more about the functioning of your brain would be a really important question. And then how that relates more to behavior. So again, and behavior very broadly. So again, memory, attention, depression, all those sorts of things. I think they're all open. Well, that is all the time that we have for now. I would love to thank my guest, Dr. Liz Krastel, Associate Professor of Neurobiology and Behavior at the University of California, Irvine. Thanks so much for joining us. Thanks for having me, Kathleen. And one more thing before we head to the break. We need you for just a couple of minutes. Yes. you. We're surveying listeners to our radio show and our podcast, the folks who attend live or virtual events. Those of you who follow us on social media, who are dedicated to our book club,

we want to hear from all of you, no matter how you enjoy Science Friday. So go to sciencefriiday.com slash survey. This is your chance to help write the next chapter of Science Friday, so we want to hear from as many of you as possible. Once again, that's Science Friday. dot com slash survey. And thanks. And that's all the time we have for now. A lot of folks help make the show happen, including Jordan Smudjick, Charles Burgquist, George Harper, John Dancosky.

Next time, we'll talk about death in the animal kingdom and how different creatures conceive of mortality. But for now, I'm SciFry producer Dee Peter Schmidt. We'll catch you then.