“Science must begin with myths, and with the criticism of the myths,” reads the very first sentence of Susana Carmona’s new book A Mother’s Brain. The line is borrowed from Conjectures and Refutations, a foundational work in the philosophy of science published in 1963 by Karl Popper. Carmona picks up the gauntlet. She begins with the tenacious myth that mothers’ brains turn to mush the moment a baby begins to grow in their wombs, a cognitive fog that stretches into their final years. Then she spends the rest of the book complicating and reframing it.
For nearly two decades, Carmona, a neuroscientist, has been studying how motherhood remodels the female brain. In 2017, following publication of a landmark study in Nature Neuroscience, she established the Neuromaternal lab at the Instituto de Investigación Biomédica del Hospital Gregorio Marañón in Madrid.
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Motherhood, she has found, remaps the cortex, enhances plasticity, and triggers changes that not only cement the mother-baby bond and profoundly alter a mother’s sense of self, but can improve her well-being. A mother herself, Carmona weaves some of her own experiences into the narrative of her new book, giving her findings a first-person immediacy.
I spoke with Carmona recently about how motherhood is like adolescence, whether non-gestational mothers can experience some of the cognitive benefits of motherhood, and how little we understand about perinatal depression.
Does motherhood hurt a woman’s memory?
So far, our research suggests that memory deficits are restricted to the third trimester and the first years postpartum, but that over the long-term, there are improvements to cognitive function. We also learn a lot from the process of mothering: cognitive flexibility, tolerance for frustration, negotiation, working as a team, all skills that are very relevant not only for our personal life, but our professional life. A friend once told me she sees being a parent as doing a masters in humanity, because you see how everyone functions from scratch, what motivates them, what frustrates them, and how to deal with them.
Why do the myths about mommy brain persist?
Part of that comes because a high percentage of women report that their memory is not as it used to be. The problem is when you take that anecdote and turn it into a slogan, but you don’t get into the potential mechanism behind it. Until very recently, it was just something that we kept on repeating: “You have mommy brain.”
What our research group is trying to do is to evaluate that from a scientific perspective and understand the biological mechanisms, because gestation is metabolically demanding, and breastfeeding, too. A lack of sleep makes things worse. It doesn’t matter if you’re a mother or not. If you do not sleep, you’re going to have certain challenges cognitively speaking.
We also know that baby stimuli, especially within the postpartum period, really kidnaps the attention resources of the mother. Hearing your baby cry is not just another relevant auditory stimuli. It resonates throughout your whole body. It can make your breasts let down milk. That’s how powerful this physical resonance is.
But actually, when you look at the recent data, what they have found in middle-aged women, is that motherhood, either through biological mechanisms or more environmental ones, protects against brain aging. They have run these studies with the UK Biobank dataset, comparing mothers versus non-mothers. It doesn’t follow the same women over time, which would be the ideal design. It’s just mothers versus non-mothers. But they found fewer signs of brain aging in women who were mothers decades earlier. What we don’t know is whether there were differences at baseline.
You write about this concept “matrescence,” a word I had never heard before. What does that word mean, and where does it come from?
That word was coined for the first time by the medical anthropologist Dana Raphael in the 1970s. She used this term to refer to the fact of becoming a mother. But it never caught on. Later, Aurélie Athan, who’s a psychologist and psychiatrist, recovered this term and started talking about it from the psychological perspective and the psychiatric perspective.
What does it mean? It’s just a neologism that mixes motherhood with adolescence in order to highlight the parallelisms that take place between these two neuroendocrine transitions. During both periods, there is a redefinition of the self. There are also these hormonal fluctuations that not only change the body, but also change the brain. I think that the magic of this word is that it kind of overrides the narrative of momnesia.
The danger of giving priority to this term of momnesia is that when you believe something, you end up giving in to it. I know many women who just stop doing a master’s degree or other career aspirations because they believe that once you become a mother, you’re no longer going to have the same cognitive resources. You just have to take care of your kids because it’s the only thing you can do.
If you keep on believing this narrative of your brain without understanding the causes, it’s kind of dangerous. That’s what I like matrescence, because it highlights these other processes. In the end, we are the words we speak.
You write that we need to do more research on what gets better for mothers cognitively. What kind of studies would you design to try to answer that question?
Something that people keep on repeating, and I think it’s wonderful, is that parents are the second fastest learners, after their own children. I want to test that. We can make inferences by looking at the degree of neuroplasticity in the parental brain, but maybe what we should do is a longitudinal study and see whether they actually learn faster than other adults their age. I would love to know also whether their learning is only related to stimuli that have been linked to the baby somehow. For instance, do they learn a language more rapidly only when they are teaching that language to the baby? I think that could be an interesting question to explore. But I have many other questions more closely related to my field of research that I think are important to investigate first.
What questions are those?
The first publication about the brain changes in mothers was published almost a decade ago. But in scientific terms, that’s like yesterday morning. We found these profound changes, like nothing I’ve ever seen before, and I’ve seen many, many brain scans. Now, I want to know, for instance, how these brain changes relate to all the physiological changes that take place in the body of a woman. We have textbooks describing the cardiovascular changes, the immune changes, the metabolic changes. And now we have added the brain into the equation.
How do we mix all that together? How are these changes related? How are the immune changes affecting the brain changes? How do they communicate? And of course, one of our north stars is to try to use this data to prevent and predict perinatal mental health disorders.
So we have started to build the house with the roof: That’s a popular phrase in Spanish. We are trying to diagnose peripartum depression without understanding the profound changes that happen in neurotypical women during pregnancy. We need to better characterize these trajectories, not only in anatomy, but also in functional connectivity and cerebral blood flow, for instance. Once we know what normal looks like, we can try to identify potential deviations that might help us to predict and prevent perinatal mental health disorders. Those are my main questions right now, but I have many others.
What are the existing explanations for perinatal and postpartum depression today?
There are different mechanisms. It’s a multifactorial disease, like many other psychiatric disorders. We know there are imbalances in certain hormonal metabolites. We also know that birth experience plays an important role. We know that certain brain changes have been linked to these conditions. And on the other side of the spectrum, we know that social isolation, parental leave policies that are too short, economic stress, PTSD, or abuse during infancy are also linked to it. We’re trying to collect all this data. For some women, brain data and biological factors might play a bigger role, whereas for others, environmental aspects might play a more relevant role.
Is there any evolutionary explanation?
None of them really convince me. For instance, in rodents, when the mother perceives that conditions are poor—like temperature is bad or resources are lacking—they enter into a mood where they don’t take care of the babies or even attack them. You can imagine an evolutionary explanation for this, but I don’t really feel comfortable with it.
How many of the changes in the brain and the body of the mother are tied to biological processes versus environmental ones? If you’re an adoptive mother or a stepmother, or you have a surrogate carry your babies because you cannot, do any of those processes still occur?
I’m so happy you asked that question because I don’t want this research to be misunderstood. We have studies in which we compare the brains of women before and after they become gestational mothers. We also include non-gestational mothers in these studies, for example, when you have same-sex couples, to control for the biological effects and distinguish them from the environmental ones. We also include fathers. We use different control groups in order to disentangle the percentage of variance that exists in each group. And what I can tell you is that the data show very clearly that the brain changes that occur in gestational mothers are way more pronounced than in non-gestational mothers or in fathers, because the whole body changes.
Our breasts produce milk, our cardiovascular system pumps 50 percent more blood. We have dramatic hormonal changes in the brain. We have found that these changes facilitate or accelerate the onset of maternal caregiving, but they do not determine it and they are neither necessary nor sufficient.
What we have found is that there are also subtle changes in non-gestational mothers and fathers. They take place a little bit later and the magnitude is different. We don’t need a brain scan to make the claim that fathers and adoptive mothers and grandparents are fantastic caregivers.
So you can get into the caregiving effect, you can behave maternally through other routes. It doesn’t necessarily have to go through the gestational hormones. Just interacting with the baby, staying with the baby, caregivers learn to take care of the baby. And I love this sentence: We care because we love, but we also love because we care. It’s bi-directional. So in terms of brain changes, they are way more pronounced in gestational mothers. How these brain changes translate directly to caregiving, that’s an open question.
I was wondering if you could talk a little bit about how microchimerism works, this idea that some DNA from a baby can remain in many of the mother’s organs long after birth. You point out in the book that there are a lot of unanswered questions, such as whether mothers have the DNA of miscarried babies in their tissue or whether it happens to all mothers.
Most of these studies come from animal models, but in humans, what they have found is that women who had baby boys may carry XY cells in the brain. There are a lot of questions. For me, it sounded like science fiction. I performed a study on mice, and what I can tell you so far is that it’s not very common. It’s not that you find these baby cells in every single mother, but they exist, and sometimes it happens. It’s possible that it tends to happen when there has been certain danger to the mother, and these cells that are left behind are there because they migrated in order to help repair tissue damage, for instance, from a C-section.
Another thing that is important is that they usually talk about cells containing the DNA of the baby, but it might be that just exosomes or little vesicles with the DNA of the baby inside stay behind. It’s not something that I’ve been doing much research on but I have many questions: How do they cross the blood-brain barrier to get into the brain tissue? Are these holdovers stem cells that keep on regenerating? But what the literature is showing is that cells with the DNA of the baby migrate into the mother in a widespread way, not only on the brain, but also the liver, the breast tissue, the C-section tissue.
There are many pieces that I’m still trying to connect. But I know that a number of researchers now are trying to study whether this process contributes something positive for the mother or triggers autoimmune disorders, which are more common in women.
A mother’s brain is very activated by her child, as you note, and she can find it almost difficult to resist attending to the child’s crying. What is it about the specific mother-child bond that allows her to respond in this instinctive way to her own baby?
There are some studies that say that from the very beginning, a mother can recognize the smell of her baby, but these findings are kind of controversial. Some studies replicate the effect, but others do not. But mothers do learn to identify their own baby’s cries. And it’s not a normal learning process. It’s a learning process in which the stimuli is so relevant that you’re highly motivated to learn about it, because it’s very distressing. It’s not normal auditory stimuli. It’s something that resonates in your body.
That doesn’t mean that it’s always a pleasure to interact with the baby, just that you are very motivated to learn about the baby, because the baby’s discomfort can be very distressing and the baby’s pleasure, very rewarding. The mother is not going to give up, like, “Oh, I don’t understand this baby.” Her wonderful motivation is going to keep her insistent despite the mistakes.
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