Science Friday - What A Rodent Brain Shows Us About Love | If Colorado Was Flattened, How Big Would It Be?

Episode Date: July 29, 2024

What A Rodent Brain Shows Us About Love–And LossLove has the reputation of being a fairly unique human emotion. If we’re lucky, we can experience lots of love in our lives: with romantic partners, children, family, friends. But with love comes the possibility of another, less desirable emotion: heartbreak.Neuroscientists at the University of Colorado Boulder have found that these feelings seem to actually leave a mark on the brain, with dopamine and other feel-good chemicals flooding to the brain’s reward centers when lovers are reunited.The source for this data may be surprising: prairie voles, tiny rodents that are among the small percentage of mammals that form monogamous pair bonds. By studying their brains when the voles were united with their mates, researchers were able to pinpoint this dopamine flood that they suspect happens in humans’ own brains under the same conditions.When the voles were separated for four weeks—long enough for them to consider their pairing “over” and find new mates, the broken-up voles had much more muted dopamine response when reunited. Researchers say that could be good news for heartbroken humans because it shows the brain could have something of a “reset” mechanism that allows individuals to go on and form new bonds.Joining Ira to talk about this research is Dr. Zoe Donaldson, associate professor of behavioral neuroscience at the University of Colorado in Boulder.If You Rolled Colorado Out Into A Brownie, How Big Would It Be?The surface area of Colorado is 104,094 square miles, according to the US Geological Survey, making it the 8th largest state in the country.But the state, unlike our neighbors to the east, has a lot of extra geographical stuff — like mountains.One Coloradan who loves to spend time in those big hills wondered if our dear state wasn’t getting a bit short-changed. Denver-based photographer and editor Howard Paul also happens to love baked goods. So when he posed his question to Colorado Wonders, he couldn’t help but combine his two passions.Paul had a hunch that such a squishing would make Colorado the largest state in the lower 48. Bigger than Texas. Smaller than Alaska. (For whatever it’s worth, this numerically-challenged reporter thought that was an eminently reasonable guess.)The first bit of due diligence was to research if this quandary had been approached before. Well, what do you know, the headline of a March 2005 article from Ski Magazine reads “How big would Colorado be if you steamrolled all of the mountains?”Read the rest on sciencefriday.com.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.

What can small rodents tell us about the very human emotion of love? Romantic attachments make you feel good. And we know that these bonds also make bowls feel good. They find them highly rewarding and highly motivating. It's Monday, July 29th, and this is Science Friday. I'm SciFri producer Charles Bergquist. Prairie voles are one of the few mammals that form monogamous pear bonds. By studying these rodents, scientists have found that love leaves a mark on the brain,

A flood of dopamine and other feel-good chemicals that they think happen in our human brains, too. We'll talk about that story in just a bit. But first, a very important question. If you squished Colorado into an ooey-gooey brownie, how big would that brownie be? Here's Ira. Here to answer that very important question is Dan Boyce, reporter at Colorado Public Radio in Colorado Springs. Welcome to Science Friday.

Hello, Ira, great to be with you. Nice to have you, Dan. So where did this wild idea come from? I love it so much. We got the question from a listener, a Denver resident named Howard Paul. I spent a long time in the outdoors, and I think about brownies and German chocolate cake and so on. How large would Colorado be if I used a giant rolling pin and rolled it flat to one inch thick? That's really cool. Now, I would hypothesize that it would be somewhere, you know, not as big as the U.S. What did you think? I would take Howard's idea.

He was thinking that it's probably going to be bigger than Texas, but smaller than Alaska. Sounded like a great guest to me. You know, what do I know? Bigger than Texas, smaller than Alaska. I'll go for that. Great hypothesis. I would go with that. So how do you even begin to calculate how big Colorado would be as a brownie?

I'll be clear. First off, I did absolutely zero calculations for this. My first thought is I'm going to check to see if anybody else has ever. approach the question. And it turned out that there was this short article in this 2005 edition of Ski Magazine and they asked, how big would Colorado be if you steamrolled all the mountains? That sounds pretty close. And the conclusion of that article, it basically said that it would increase the state's footprint by 2,500 square miles, which should be a little bit bigger than Delaware. I thought that was a little anticlimactic, but I'm trying to justify this to myself.

I'm thinking, okay, that's not exactly what Howard's question was. It's not exactly the same thing. And so I went up to the U.S. Geological Survey. They have this office in Denver. And it was so humbling. They just put a team, a team of researchers on this. Oh, they didn't think it was a crazy idea. They wanted to know, huh?

They seemed genuinely curious about it. And they really nerded out over finding the answer. And Kim Mantey, she headed that team. She's the director of the USGS National Geospatial Technical Operations, center. So they're looking at this question, Ira, and they're saying the parameters that you set for answering something like this, that's what makes all the difference in the world. Like you got to put your mountains and your fields and your buildings and everything in there before you make your brownie. They actually debated that very question. Believe it or not,

this was one of the questions we asked ourselves, do you want bare ground or do you want trees and buildings as a part of this exercise? I will say they actually did decide not to do that. They're going to go just from the bare ground. But that's just one of the many parameters they had to consider. They're thinking, are we squishing Colorado? Are we going all the way down to sea level? Are we going to go to the core of the earth? They're debating that.

They decided to go, all right, we're going to go to Colorado's lowest elevation. And then one of the most important parameters they needed to figure out is they found out that that 2005 SkiM Magazine article, the methodology that that group of USGS researchers used was, they basically they stretched out the surface area. So picture that you have the top most layer of Colorado. It's like a giant scrunched up blanket. And the analyst, they took that giant scrunched up blanket and they just stretched it flat. So that's what they did in 2005.

But Howard's question, it was very different. You know, he's talking about rolling everything from the ground, but everything absolutely underneath the ground, all the dirt, all of the rock to this minuscule size of one. inch thick. And that's how we ended up with the answer. And Dan, I'm on the edge of my seat. How big is the Colorado Brownie? Let me get you some reference points here, Ira. So Colorado's surface area before our rolling pin squish, 104,000 square miles. Now let's get the final answer from USGS analyst Barry Miller. He's the one who crunched the final numbers. 4,4191,49,0.91 square miles. Wow. in 4.5 billion now. So to think of this another way, rolling out Colorado to one inch thick, leaves us with a surface area that is 22 times larger than the surface area of the planet Earth.

Here's how Howard Paul reacted to that. What? That is one big friggin brownie. We're going to have to bake it in sections. So what do you do with this information now? Bragging rights or give it to the local Chamber of Commerce, you know, the tourist board? You know, I think as far as bragging rights, sure, you know, whatever, if we want. It's important for us to re-contextualize and remember that we are comparing a squished Colorado to these unsquished reference points. And so how would Colorado compare to a squished Texas? That question, it still, you know, unfortunately remains unanswered. But Kim Anty, the woman who led the team at the U.S. Geological Survey,

she said her team is now really quite interested in performing the squish exercise for all 50 states. Well, Dan, you have provided this, I think, with one of the most unusual state of science reports ever. So thank you very much for taking to have to be with us today. Boy, it is my pleasure, Ira. You're welcome. Dan Boyd says a reporter at Colorado Public Radio. He's based in Colorado Springs. This is Science Friday. I'm Ira Plato.

Remember that famous song Love Potion Number Nine, that little bottle of elixir that smelled like turpentine looked like in the ink? Well, is there something in our bodies that turns on love like in the song? You know, love is a hard thing to study, and my next guest works to understand the neurobiology behind love, and she does so with some unusual subjects, Prairie Volz. Dr. Zoe Donaldson, Associate Professor of Behavioral Neuroscience at the University of Colorado in Boulder. Welcome to Science Friday. Thank you. I'm thrilled to be here. Can science really quantify what love is?

You know, I think scientists typically dodge this question by coming up with other terms, right? So we talk about pair bonding, which is kind of the scientific word for falling in love. And I think this is because when we talk about love, it's really this human emotion that we can talk about in literature, we encapsulate an art. And it's pretty hard to ask how those things, our literature, our art, et cetera, have an equivalent in other animals. Okay, so tell me why prairie voles are a good species to use for understanding these bonds. So prairie voles are these little tennis ball-sized rodents, and they live in the prairie states. So basically from Colorado, over to western Pennsylvania, from Canada, down to Oklahoma. And what makes them notable is that whether it's in the wild or in the laboratory, they will form these lifelong mating-based bonds. And this is incredibly

rare. So fewer than 10% of mammalian species are capable of this. We are definitely capable of this. And your more traditional laboratory rodents like mice and rats, they fall in this more traditional category of mate and leave. So okay, so tell me how this works. How do you study it? What do you look for in the body of the voles? So a good place to begin with this question is, how do you ask a bowl if they've formed a bond with their mating partner. Very, very difficult to do that. So we try to simplify things as much as possible. And the way we do this is in a way that's sort of equivalent to what I think of as dating, right?

So if you go to a bar with your partner, you're probably going to spend most of your time talking to them and not talking to someone that you don't know. And so we set up an equivalent scenario for the bulls where basically they can choose to go interact with their mating partner or they can go and choose to interact with some opposite sex bowl that they don't know. And what's really striking is that when they have formed these bonds, they just want to go over and they want to huddle with their partner. And we test this for three hours. And they do this for the vast majority of the test time. And it's quite adorable. And it looks totally different from a mouse or rat, where if it's a male and they've already mated with one of the

females, they actually don't even like that female anymore. And they want to spend most of their time with the female they've not yet mated with. You don't characterize this as a romantic attachment here, do you? I think that there are a lot of parallels between our romantic attachments and what we're studying in the vols, right? And so a really simple one is that your attachments, especially romantic attachments, make you feel good. And we know that these bonds also make vols feel good. They find them highly rewarding and highly motivating. Is it, though, a different kind of bond you would see in vols, for example, versus a bond between a parent and child? So we don't know the exact answer to this, but the short is that. there's a lot of overlap and there's some things that are different, right? So at the end of the day,

there are certain things that we share across all of our bonds. So one of the scientific terms that we use a lot is proximity seeking. And that just basically amounts to we like to be around that individual. And so this applies to pretty much all of our bonds, right? Like we like to be, if we're a toddler, we really like to be around our parents. If we have friends, we like to be around them. We like to be around our romantic partners. But there's also some differences. Obviously, there's behaviors we engage in with romantic partners that we don't engage in with parents and with friends. And so I think a big open question is, you know, what's shared in the brain, what's shared across these bonds? And then what enables these distinct differences in behavior that characterize different types of bonds that we form?

So neurologically, then, what is shared across the neurons? So we think that some of what is shared is probably the basic underlying structure, right? So all the behaviors that we share across these bonds, like the facts that we find them rewarding, we're motivating. We're motivating. to seek out these individuals, we want to be near them. That's probably a pretty common underlying architecture within the brain. Is there a certain neurotransmitter that you see more of? Yeah, so there's sort of a suite of neurotransmitters, but the most famous one is oxytocin. And so this is a small hormone. It's produced by your brain, but it actually does a whole bunch of different things. One of the things it's best known for is actually inducing labor. Wow. Yeah. So they give pitocin,

which is a synthetic version of oxytocin, which inducesan, which inducese. his labor. And that was one of the first things that was learned about oxytocin as a hormone was its function and reproduction. And then a few scientists thought, hey, you know what, rats do this weird thing where when they're a virgin and they've never given birth before, they don't like pups. But as soon as they've given birth, there's this switch in the brain where they just desperately want to take care of their pups. And there's this great series of experiments. We call them the pup raider experiments where they give a female rat who's just given birth, they give her a little lever and she can press the lever and they'll deliver a pup to her. And she'll just keep pressing this

lever until she has a mountain of pup so big that she couldn't possibly take care of all of them. No kidding. She's super motivated and it's this shift in behavior and that shift in behavior to wanting to take care of pups is mediated by oxytocin. Is this love potion number nine? Oxytocin? It's part of the love potion. I would say that the love potion is actually really complex, right? So in addition to oxytocin, you also have dopamine, you have another hormone called vasopressin. There's probably a role for serotonin. So it's a really complex mixture of things that's happening in the brain. Oxytocin is essential, but you can't just throw oxytocin at someone and have them fall in love with you. Wow, this is really interesting. I know you also studied

Prairie Vol breakup. Do they have broken hearts? They do. Yeah. So Prairieville broken hearts look a lot like human broken hearts. They show a lot of different types of behavioral, distress when they're separated from their partner. They show behaviors that are reminiscent of depression. And then one of the areas that my lab has been really actively working in is trying to figure out what is special about these breakups or even the loss of a partner compared to these other things like depression. And we think the key to this is actually yearning. So yearning is something you see only, you know, after a breakup or after the loss of a loved one. And it's something that differentiates those losses from, say, just general depression. So one of the things we see in

the Bulls is that they're actually a little bit more motivated to seek out their partner if they haven't seen them in a while. So this is the whole absence makes the heart grow fonder idea. Wow. Who would think that animals had the same kind of feelings that humans did? Is this surprising to you when you studied this? This is actually why I fell in love with the voles. Really? Yeah. This is what motivated me to become a social neuroscientist and to start studying attachment because as humans, if we think about the most important things in our lives, we usually start talking about having kids, getting married, you know, loss of a parent, or someone else who's incredibly important to us. And so I thought, you know, I want to study

these things that we find fundamentally important. And then I started thinking how we could do this. And it was clear that mice and rats have some real limitations since they don't form these bonds. And the more that we learn, the more I'm impressed by, you know, the conservation of how our brain works. It's just there, there's a, there is a blueprint for the brain. And so it's not totally surprising that these complex emotions that we feel as humans have some basic representation, even in other species. So you think there's like a correlation between what's going on with the vol's brain, what's going on in our brain? Yes, that's the premise to all of our research, because the idea is that what we discover in the voles may help guide us to develop

new therapies. And so there's a couple of directions this could go. One is that the vast majority of sort of neuropsychiatric disorders throughout the life course can affect our attachments. And this begins even early in life, it manifests in things like autism spectrum disorders. It also, if you think of things like schizophrenia and depression, you can have a reduction in your sort of attachments and how much social reward you feel. And later in life, you have things like neurodegenerative disorders, which have huge impacts on relationships and also people start displaying sort of inappropriate behaviors in relationships or even just social withdrawal. So why are we spending so much time studying rat brains about what's going on in our brains and not vol brains? So rats and mice are

excellent models for many, many things. And there's parallels with humans. If you want to understand how the brain makes your arm move or if you want to even understand just basic anxiety states or hunger or thirst, we share those with rats and mice. What we don't share with rats and mice is our really complex socio-emotional behaviors. All right. So what is there yet to be studied in the vol brains, comparing them to us that you would like to study? And I'll give you my blank check question. I give a lot of scientists. If you had all the money in the world and you could spend it on anything to learn more about what you want to know, what would you spend it on? What do you want to know? So I really want to know fundamentally how are these bonds encoded in the brain, but also how are they plastic at the same time?

So what unique features of our brain make it so that we can form these bonds, but we can also lose these bonds and we can adapt to that loss? And I want to fundamentally understand what is it about our neurons and their firing properties and the different inputs they get from hormones, et cetera, that enables this incredible complexity. And this complexity is something that defines us as humans. If anything, we take what voles can do and we just basically add steroids to it, right? Like we have terminology like frenemy. I doubt the voles have frenemies. But the complexity of the social behavior that we can study in vols compared to other models, I think really just gives us a lot to work with and a lot that can tell us something about the human condition.

Very interesting. One last question for you. So after this study, do you believe in life after love as? share would ask. Oh, absolutely. So the vast majority of us will lose someone in our lifetime. And for about half of us, we will lose a spouse. And so the idea that there isn't life after love is a pretty depressing idea. This is the plasticity that I mentioned. This is why I'm so fascinated with it, because we do have the ability to integrate these losses. It's not like we forget the people that we lost, but we have to sort of rework the memories that we have with them and what they mean to us. And so one of

my favorite sort of terminologies is actually from a clinician that I work with who says that those memories have to go from painful to bittersweet. Yeah. Wow. What a way to end our conversation. I have learned so much today. Thank you for this lesson on love, Dr. Donaldson. Thank you for having me. Dr. Zoe Donaldson, Associate Professor of Behavioral Neuroscience. That's at the University of Colorado in Boulder. That's all the time we have for now. A lot of folks helped make this show happen, including Beth Rami. Santiago Flores. Diana Plasker, Robin Kasmur.

And many more. Tomorrow, teeny tiny parasites are feasting on honeybee guts, and scientists are trying to stop them. But for now, I'm SciFri producer Charles Bergquist. Thanks for listening.