Delving Into Dad Brain with Dr. Darby Saxbe

Episode Transcript

Dr. Correa:
From the American Academy of Neurology, I'm Dr. Daniel Correa.

Dr. Peters:
And I am Dr. Katy Peters, and this is the Brain & Life podcast.
Here we are again. It's June. Oh wow. The year is just flying by, Daniel.

Dr. Correa:
Oh, gosh.

Dr. Peters:
I cannot believe it. Father's Day is just around the corner. And I hope that everyone is getting ready to celebrate their dads and everything fatherly. So happy fatherly day to you, Daniel, for being the best pet dad ever to all your pets. I think Cookie's got a special surprise for you. And by the way, have you heard any new dad jokes?

Dr. Correa:
Well, I also look forward to celebrating my own father, grandfather, and all the love and paternal support that we received. So I think wondering about dad jokes. Well, what do you call it when your brain cells throw a party?

Dr. Peters:
I don't know.

Dr. Correa:
A cerebral celebration. Or for those who like a lite bit of music, we always like music here on the podcast, what's a neuron's favorite type of music? Anything with good impulses. Or alongside the brain healthy discussions, to those who are going along with those healthy meals and thinking about, what do you call a brain on a diet?

Dr. Peters:
A light thinker.

Dr. Correa:
Ah, there you go.

Dr. Peters:
All right. Good, good. I think I got it. I got one. So I have one, it's not about brains at all, but it's sort of food associated because I'm getting hungry. What did the fried rice say to the shrimp?

Dr. Correa:
"We're so awful." I don't know.

Dr. Peters:
"Don't walk away from me."

Dr. Correa:
Oh, wow.

Dr. Peters:
Isn't that a bad? So bad.

Dr. Correa:
Yeah. These are bad ones.

Dr. Peters:
Yeah. I didn't want to type it everybody for Daniel into our notes so that he had to guess. He had to guess. But there are dad jokes or dad bods, and now there's even dad brains.
Let me tell you about dad brains. So Dr. Darby Saxbe is a renowned clinical psychologist and professor of psychology at the University of Southern California and she studies the neurobiological underpinnings of the transition to parenthood. She studied mothers, siblings, and also fathers. And she just came out with her studies delving into the neurobiology of how the brain changes after one becomes a father. She has a new book. It's entitled Dad Brain: The New Science of Fatherhood and How It Shapes Men's Lives. I had a really fun conversation with her and I learned a whole lot really about what happens during these important transition changes of societal relationships for both mothers and fathers, but particularly in this book it's about the experience of what happens with the dad's brain.
And so I hope all this nurse and of course all our dads enjoy the episode. And again, Happy Father's Day.

Dr. Correa:
Happy Father's Day.

Dr. Peters:
Hello, Brain & Life podcast audience. Hello, I'm your co-host, Dr. Katy Peters. And I'm really excited about our guest today. And I want to just say thank you to all the dads or fatherly people out there, but we're going to speak to Dr. Darby Saxbe. She is a clinical psychologist and professor of psychology at the University of Southern California, who is known for her research on the neurobiological underpinnings of the transition to parenthood. So this is going to be really fascinating because she has just authored a book called Dad Brain: The New Science of Fatherhood and How It Shapes Men's Lives. It's offered by Flatiron Books.
And welcome to the Brain & Life podcast, Dr. Saxbe.

Darby Saxbe:
So happy to be here. Thank you for having me.

Dr. Peters:
Thank you. And I just gave a short snippet introduction. Can you just tell us a little bit more about yourself and where you're joining us from?

Darby Saxbe:
Yes, absolutely. So I'm here in Los Angeles. And as you said, I'm a professor at the University of Southern California. I've been out in LA now for about 20 years. I went to graduate school at UCLA. And I have been studying fathers and families for my whole academic career, which is what inspired me to write this book.

Dr. Peters:
That is great. And you are a psychologist. Can you tell me a little bit more about your practice and about your research? Because it just sounds so fascinating.

Darby Saxbe:
Yes. So I actually, although I'm licensed as a clinical psychologist, I don't do any clinical practice. I direct our clinical training program here at USC, which means I help organize supervision for our graduate students.
Who are doing clinical psychology PhDs. But most of my job is research. So I run a lab called the NeuroEndocrinology of Social Ties Lab, and we have been studying the transition to parenthood since I started on the faculty over 15 years ago. So we run a study in which we bring couples who are expecting their first child into the lab. We draw their blood, we sample their saliva, we clip their hair. We put the fathers in the neuroimaging scanner and then we bring them back after the birth of their baby. Again, we scan the fathers, we look at their hormones through their biological samples yet again and we listen to them tell us about how that transition into parenthood is going.
So we've been doing that study for quite a long time. We're actually now running a seven-year follow-up and bringing the original families back into the lab now that the kids are school age. But that study is sort of the basis for some of the research findings on how men's brains change with parenthood that I talk about in the book.

Dr. Peters:
That is fascinating. And are you planning on going for the whole continuum to see when these relationships change, like when a child goes off to school or goes to college or gets a job? Or I think something for a fatherhood transition would also be when maybe somebody gets married, particularly when he has to give away his daughter in marriage. Are you planning on looking at those transitions?

Darby Saxbe:
Yeah. So the dream would be to keep following these families for another couple decades. It's just a question of whether we can keep convincing them to come back to the lab. So already with the seven-year follow-up, we're realizing that it's much harder to schedule parents of a seven-year-old than it is to schedule expectant parents who aren't juggling childcare or thinking about other siblings. So it's been a logistical challenge to get them back to the lab, but the goal would be to follow them into adolescence, into even their own children's adulthood.
And for the book, I talked to a father actually who said he felt like his relationship with his kids really kind of clicked into gear as they got older and he could do things like teach them how to drive, take them on trips, that those first few years of the sort of baby years can be actually a little challenging for men because they don't necessarily feel like they know what to do. And mom is often the primary parent if she has longer maternity leave than he has paternity leave. So that sort of older kid fatherhood experience is its own unique phenomenon that I think a lot of dads really enjoy.

Dr. Peters:
I think that's fascinating. And one of the things that I just learned a new term, it's called Maycember. And this is sort of, I guess, the rush of what happens during May with graduations and school ending and all the banquets and the transition. I'm sure it can be really hard to schedule those fathers once they are having to take kids to graduations and to T-ball and to soccer and everything.

Darby Saxbe:
Exactly. Yes. I have two very hardworking lab managers who do a lot of the scheduling of our families, and they are just doggedly pursuing some of the families who just have a million things going on. So we do try to get them all back, but inevitably, it's not possible to schedule everybody.

Dr. Peters:
And is there any difference between dad brains if they're girl dads versus boy dads?

Darby Saxbe:
Yeah, it's a good question. So in our study, we did not find any significant differences in the structures of any of the brain areas that we were looking at, but I did see some differences in testosterone patterns in fathers of boys versus fathers of girls. So the fathers of boys had higher testosterone prenatally and then more of a drop in testosterone after birth. So we haven't published on that yet. So this is hot off the presses, not even on the presses yet.

Dr. Peters:
Yay.

Darby Saxbe:
But at some point we're going to write this up for publication because we also saw some psychosocial differences in how fathers of boys versus fathers of girls appraised the parenting relationship.

Dr. Peters:
So tell us more about the book and what is the dad brain.

Darby Saxbe:
Yes, definitely. So the book actually was kind of inspired by my own relationship with my dad. So after my parents got divorced, we had joint custody. I was nine. My dad was kind of a single parent during the weeks that my brothers and I were staying at his house. And so I watched him go from kind of a prototypical checked out 1980s dad to totally hands-on primary parent who did all the cooking, all the cleaning, all the driving us to school, all the checking our homework and he really kind of transformed and rose to the occasion as a father. So I've always been fascinated by fatherhood and sort of how men are socialized to participate in parenting, how they show up differently as parents.
And then in my lab, as I said, because we've been scanning the men's brains over time, we've been able to see how brain structure and function change over that transition to parenthood. So what we found is that the brain does seem to change in first time fathers in ways that look similar in some ways, but also different in other ways from what's been observed in the maternal brain. So there's this sort of conserved parental brain that you see in both moms and dads, but there's some kind of distinct characteristics of that in fathers. And we've also found that the amount of time that dads are spending taking care of children is correlated with the degree of change that we can observe to their brains. So the father brain is kind of shaped by men's participation in care.

Dr. Peters:
That is very interesting. And what are the parts... Because I am a neurologist, we're all about localization. And for our listeners, what that means is like where in the brain does something map to. So we know that language is primarily on the left side of our brain and the front of our brain controls what we call executive functioning. What are sort of the anatomical underpinnings of a dad brain?

Darby Saxbe:
Yes. Yeah. So first of all, just the direction of change that we see is that there's actually a loss of brain volume, gray matter volume from prenatal to postpartum. And that is exactly what's been seen in many samples of mothers. And where we see the most volume loss is in what's called the cortical midline mentalizing network structures. So structures like the precuneus, the medial prefrontal cortex, that we know are sort of implicated in social cognition and thinking about oneself and thinking about other people's minds. And that's interesting because that loss of gray matter volume seems to not indicate a deficit, but rather a sort of refinement of functioning.
So when both moms and dads lose more gray matter volume in those regions, they actually then report better bonding with their kids and a smoother transition into parenthood. So it seems like what's happening is that the brain is actually rewiring to become more efficient in those areas where gray matter volume is lost.
And the other interesting piece is that in moms, you see gray matter volume decreases across the whole brain. And they're so striking that a machine learning algorithm can actually tell mothers apart from non-mothers based solely on the changes to their brains over time. But in the moms, you see changes to the cortex. And you also see subcortical changes like structures like the ventral striatum that's involved in reward processing or the amygdala that's involved in salience detection.
In fathers, you primarily see changes to the cortex, which is that outer layer of brain tissue that's kind of linked, as you know, with kind of higher order cognitive functioning. So the subcortex is considered to be, that's the limbic system that is kind of hormonally-modulated and involves many of our kind of emotional drives. Whereas the cortex is kind of where we do our thinking, our planning, our reasoning and our kind of more sophisticated somatomotor and visual system navigation.
I think that's interesting because fatherhood, in some ways, is unique from motherhood in that it is really socio-culturally variable. So dads who choose to invest in parenthood, and that might come from the demands of their local context or their cultural setting, those dads see more remodeling to the brain. So it's a little bit different from, I think, what you see in moms where there's that kind of flood of hormones that accompany pregnancy that helps to kind of jumpstart the mom brain. So the dad brain is more subtle, it takes more time to emerge, but it shows some of those same signature changes to gray matter volume.

Dr. Peters:
Thinking about gray matter volume loss, and in ways I like to think of it as like it's almost like pruning the system to make it more efficient, what do you think is signaling it? So you now have this human child, right? Is it hormonal? What is telling that neuronal tissue to, in a way, have less volume there? What is the signal? Do we know?

Darby Saxbe:
Yeah, I feel like that's a million-dollar question that we don't totally know the answer to, but we have some hunches. So one is that in moms it looks like changes in estrogen move in tandem with changes in gray matter volume. So there is a role that hormones are playing. And we know that fathers don't have the exactly the same hormones as moms, but we do see changes in testosterone levels in hormones like oxytocin and prolactin around that transition to parenthood.
I think the other thing that's happening is sort of experience dependent plasticity. So it's like the social cognition practice that one gets when taking care of an infant is helping to refine those neural structures. So we know that gray matter volume is also lost in early childhood. So as kids, young kids are learning, they're all over the place, their brains are taking in all kinds of information. And then when they get older and into school age, you actually start to see more pruning and reduction in gray matter volume as they learn because they're kind of developing these pathways and knowledge is kind of getting canalized in the sense that you need an efficient way to process information that you're encountering frequently. So the brain is kind of getting more specialized.
And that might be what's happening in parenthood too. The fact that we're seeing change in those mentalizing network structures kind of supports that hypothesis because if you think about what goes into caring for an infant who might be nonverbal, who can't clearly tell you what they need, you have to use a lot of empathy and a lot of social intelligence. So if you're getting a lot of practice kind of recruiting those structures, you might start to show neuroplasticity that's going to echo that.

Dr. Peters:
And when you look at sort of the baseline before, I guess I'd say the father process, is there variation in those gray matter areas before they have a child? And does that have implications on sort of the more social relationship? Because you're not just studying the brain, you're also studying how they're functioning as what are their feelings and what is sort of the psychology of it.

Darby Saxbe:
Yeah, it's a great question. It's kind of like, what is the baseline brain telling us about preparedness to parent? And we don't know a lot about that yet. We've done a few analyses in our lab to look at kind of starting brain volume and try to link it to some psychosocial characteristics. We haven't found a lot. I mean, our sample wasn't very big. I think we would need a much larger sample to really pick up on some of those subtle differences. But we do know that in research on childhood, adolescence, older adulthood, volume of specific structures can be linked to functioning. And I'm sure you know this literature better than I do, but things like hippocampal volume, which might be important for memory and late life. So figuring out exactly how brain structure is related to functioning I think is sort of the next piece of the puzzle that we need to kind of put into place.

Dr. Peters:
Yeah. I'm just reminded of one of our other guests, Dr. Joel Salinas, who talks about synesthesia and how... And he has empathy synesthesia. And I just sort of wondered, Dr. Salinas, if you're out there, we want to scan your brain and understand it a little more. I actually predict he'd be the kind of person who's probably had his brain scan. He's a wonderful, wonderful physician.

Darby Saxbe:
Always welcome to come to my lab.

Dr. Peters:
Always welcome to come. Because it is about sort of the empathy factor that is in there once presumably fatherhood happens. Now, not all of our listeners are going to be fathers. Some of them are just going to be more fatherly. Maybe they have like a pet or somebody that means a deep relationship to them. Do you see something sort of in fatherly practice with people that like, maybe it's a puppy, maybe it's a kitten, I'm the proud mother of four beautiful cats, so I just want to know for my own husband, cat dad.

Darby Saxbe:
Yes. Yeah. I think we all have that kind of innate drive to care for vulnerable creatures, right? It's like we're drawn to... And as you saw behind me, I have my cat here too. I have two cats and a dog. We're just drawn to these critters that we can take care of, whether that's human babies or puppies or kittens. And there is some research on this, it's called Kindchenschema, which is like the idea that sort of baby-like features are common across different animals and humans and even cartoon characters, like big eyes, big heads, small bodies. There's this sort of signature look that we've evolved to find attractive that elicits our care.
So in the book, I talk a little bit about just men showing up in various fatherly roles. We've seen changes in the numbers of men who are becoming teachers or social workers or clergy. Those numbers have dropped. I think that's unfortunate because men can make great contributions to mentorship, to be guides, to be leaders, to be protecting vulnerable kids or teens. And I think we want to be encouraging men, whether or not they're fathers, to be showing up in those kinds of roles because that's great for society.

Dr. Peters:
Agreed. I totally agree with you on this.

Darby Saxbe:
Yeah. I think we've sort of feminized certain professions or even certain personality characteristics. And the fact is as humans, we're flexible and we're designed to adapt to different situations. It's a myth to say only women are wired to care or men are primed to fight and not to take care of the young. You see across lots of different cultures, men absolutely participate in care and in child marrying whether they're fathers or not. And I think that's a role that's worth celebrating.

Dr. Peters:
I agree that it should definitely be celebrated. Now you are, again, a full-time researcher and now a big time author. What is your next area to focus in on your research into family relationships?

Darby Saxbe:
Yes. So now that we are doing the seven-year follow-up, we are very close to finishing that data collection. So the next goal is to really look at the kids' outcomes. And we're scanning, in this round of research, the kids' brains as well. So we have the dad brain scanned from prenatal, early postpartum, now seven years. We can look at longitudinal changes to men's brains and then we can also link that to how kids are looking. So we're giving kids something that's called the NIH toolbox. It's like an executive functioning battery and we're looking to see how the family is relating to each other. We're going to try to connect that with our brain measures from the early postpartum period to see how does prenatal stress and early postpartum stress kind of get under the skin in order to shape kids' development. So stay tuned. That'll be my next book in about seven years. It's going to be a while.

Dr. Peters:
Well, it's going to be... And it's a shared experience that they're having to both go through, I guess, MRI imaging that they're doing. And have you started scanning any of the children?

Darby Saxbe:
We have. And it's interesting that the kids are much more willing to go in the scanner if they see their dads do it. So we have the dads and kids come in together. And usually we'll have the dads go first because if a kid is a little bit nervous, he can see that his dad did fine. And so we've definitely learned on the fly about how to scan kids because as I'm sure you know, movement artifacts are a big problem when you have wiggly kids. So we've got all kinds of tokens and rewards that we give the kids if they can stay as still as possible so we can get some data.

Dr. Peters:
Yeah. Sometimes unfortunately we have to do sedation to get those scans, but I mean, I'd much rather do it for a cookie or a treat, I think, if you can do that. And it is true if they see their father doing it first, it's going to be hopefully an easier experience.
It actually brings up a memory of my own dad where we both had to get a vaccine. I can't remember the scenario or something, but he's like, "Well, I'll get the shot first." And so he got the shot, but he screamed. And so I was like, "Well, I don't want to get that shot." So it can go both ways. So hopefully, the dads will be good role models for the kids going into the scanner.
So Dr. Saxbe, one of the things that we do on this podcast is we really talk about brain health and what it means to us. Thinking about dad brain and your research, what is the most important thing that you do now for your own brain health?

Darby Saxbe:
Oh, that's such a great question. I feel like my brain health is probably not great because I've been so stressed out getting ready for my book to come out, but I really do try to exercise as consistently as I can, even if it's just walking the dog around the block. I try to get fresh air, I try to step away from my computer. And I'm kind of fanatical about sleep. I love to sleep. So my friends joke that if there's a party that starts after 9:00 PM, I will probably show up for 10 minutes and then make excuses and go home so I can go to bed.

Dr. Peters:
Well, that's good. I think sleep is very important. We've had done several podcasts just on sleep alone. And I agree with you. I guess it's sort of the new wellness trend, is to really find a way to sleep. And then the other question I want to ask, and we're trying to ask all of our guests this, is, what is the number one piece of advice you'd share with others about family relationships and the importance of psychology?

Darby Saxbe:
Great question. Yeah. I mean, I would say it matters to show up and to try to build quality relationships. So in the book I talk about some of the longitudinal research that's been done on men. One of the longest running studies of men's health, it's been going for over 80 years. The Harvard Grant Study recruited young men and the study followed them into late life. More than their fancy job titles, more than their incomes, it was really the quality of the men's relationships that seemed to shape their wellbeing. And that's kind of echoed by what we can see in the brain that isolation is correlated with worse brain health and social integration is frequently linked with better brain health. So I would say if you're busy and you have a lot going on and there's a choice between whether to get a little bit more work done or to do something that builds a relationship, it's important to remember that the relationship building is a health behavior too.

Dr. Peters:
I like that. That can also be another wellness, to have relationships and to try to avoid isolation as much as possible. And I think that's something we can definitely learn.
And again, Dr. Saxbe, this has been a wonderful conversation with you. I'm just so excited about your book. The full title is Dad Brain: The New Science of Fatherhood and How It Shapes Men's Lives. So again, Dr. Saxbe, thank you so much for this discussion.
I want all of our listeners to check it out. And I also want to say happy Father's Day to all the dads that are listening. And happy fatherly day too to all of the other maybe cat or dog dads.

Darby Saxbe:
Definitely. Thank you so much. This was such a pleasure.

Dr. Correa:
Thank you again for joining us today on the Brain & Life podcast. Follow and subscribe to this podcast so you don't miss our weekly episodes. You can also sign up to receive the Brain & Life Magazine for free at brainandlife.org.

Dr. Peters:
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Dr. Correa:
You can also find that information in our show notes. And you can follow Katy and me and the Brain & Life Magazine on many of your preferred social media channels. We're your hosts, Dr. Daniel Correa, connecting with you from New York City, and online, @neurodoctorcorrea.

Dr. Peters:
And Dr. Katy Peters joining you from Durham, North Carolina, and online, @katypetersmdphd.

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Most importantly, thank you and all of our community members that trust us with their health and everyone living with neurologic conditions.

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Delving Into Dad Brain with Dr. Darby Saxbe

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