Dr. Leah Krubitzer is a professor of psychology at the University of California, Davis, where she is the head of the Laboratory of Evolutionary Neurobiology. Her research concerns the brain’s neocortex, the largest part of the cerebral cortex — involved in perception, memory, spatial reasoning and language, and comparative studies. As a part of comparative studies, Krubitzer looks at the brains of mammals to determine the brain’s gradual evolution across species by means of common ancestry. Brain World recently had the opportunity to talk with Krubitzer about her work, her interests, and the state of neuroscience today.
Brain World: So what got you interested in neuroscience?
Leah Krubitzer: Oh, God! [Laughs.] You know how some people are when they’re 10 years old and they decide what they want to be? Some people want to be a doctor or whatever. That was not me. I thought I wanted to be an artist. I was always interested in the brain but neuroscience wasn’t really even a word at the time, never mind having the option to study it. I went for my masters in audiology at Vanderbilt University, and was there for six months thinking I can’t do this, when people told me about this guy Jon Kaas, who’s one of the top comparative evolutionary neurobiologists studying the neocortex in mammals. He let people volunteer in his lab, and I had no idea who he was or what it was, but I volunteered in his lab for eight months. I loved it! Fell in love with what I was doing. I got to consider the comparative approach, got to understand evolution for the first time probably, so I transferred over to his laboratory — and here I am! I didn’t really have it charted out. When we worked in Kaas’ laboratory, we would do mapping experiments on the neocortex, so you’re sticking electrodes in the brain, amplifying the signal about 10,000 times — so you could see it and you could listen to it. If you ever participate in these experiments, it is the most thrilling thing to hear neurons respond.
BW: It seems almost as if the neocortex defines who we are.
LK: It’s a part of the brain that’s involved in hyperkinetic processes, perception, and decision-making, and other parts of the brain aren’t developed in those things. The brain also has parts involved in regulatory functions like heart rate and breathing, and has an intricate relationship with the rest of the body, but I would say the neocortex is that part that says who we are.
BW: What is evolutionary neurobiology?
LK: That’s a tough question, and depending on whom you’re talking to, they’ll give you a different answer. To me, the purpose of evolutionary biology is to understand the evolution of nervous systems. It’s trying to understand general principles of organization by means of common ancestry — changes in DNA sequence versus epigenetic changes. The problem is that the process occurs over generations and thousands or billions of years — so you can only study what evolution has produced: brains and bodies. I study the neocortex by looking at a number of brains and making inferences about the process where the different expressions of phenotypes come from as we age. I can’t get in to the mind of a great ape, but now I can see how it works — and then it’s really fascinating to learn that I can look into the neocortex of a cat or a horse, and think that despite how we always tend to put human beings on a pedestal, maybe there isn’t anything all that special about us; we’re just wired a little bit differently than other mammals.
BW: What would you say is the biggest breakthrough in evolutionary neurobiology so far?
LK: In my opinion, it’s the newer work looking at epigenetics. It’s really transformed how we think about the way changes in species happen over time. How we have changes in genes that affect changes in cortical activity, the size of cortical fields, how neurons respond, without changing gene sequence. These generate very large changes that can be passed on from generation to generation, but not by traditional evolutionary mechanisms — by epigenetic mechanisms. Think of how cultural and physical evolution intersect. You can have really large changes in the brain that can be passed down from generation to generation as long as the neocortex for that brain is consistent. You put that brain in a radically different environment and you’re going to get a new phenotype.
All this work has been really inspiring — they’re looking at behavior but this could really be the new frontier of neuroscience and evolution. It can even affect the way we raise our kids, and the rate that different brains can change even over the course of one lifetime, depending on the context. Whether it’s the system — being exposed to languages and culture — or sensory what we eat, the water we drink, the air we breathe — it’s this idea that genes don’t unravel in a vacuum, but unravel in a variety of different ways to generate radically different outcomes. It complicates things quite a bit — nature versus nurture. It’s the new take on nurture, and it’s incredible that we’re just starting to understand the mechanisms.
It’s probably one of the defining features of humans — we’re looking for that one thing or that gene that makes us who we are. Instead it’s how our genes our translated, that in a way we’re plastic, constantly in a state of change depending on how these genes unravel. Think about how now we’re interacting almost on a daily basis with machines and it’s going to change our brains — it’s going to reshape our motor and nervous system, our coordination, a lot of different things. It’s changing physical aspects of our brain. We’ve been around for 200,000 years but human behavior has changed radically — it’s only been about 200 years since the Industrial Revolution. The brain generates human behavior — so our brains must have changed radically, but there hasn’t been that kind of change in the DNA sequence. I think this is pretty exciting because it also allows us to appreciate how individual differences emerge in a population.
BW: Could you give an example?
LK: We do studies on parental rearing styles and how they actually change the brain — but think about everything a young brain encounters in its environment. You could say that you have loving parents, or have nonloving parents. These are all simply complex patterns of sensory stimuli impinging on the developing nervous system. So you could say love is temperature, love is touch, love is a cadence or an amplitude of voice. That packet of physical stimuli present during early development has a huge impact on how the brain is going to connect itself due to synaptic plasticity.
Imagine you’re in Aleppo and you’re developing, amid the civil unrest happening there right now. There’s going to be a radical difference in how you’re going to develop in early childhood as opposed to being born in Stinson Beach where the population is about 400 and people are just walking on the beach and taking hikes. Your response properties and neurons formed from those experiences are going to generate behavior. So if you were to take foster babies and switch places — between Aleppo and northern California — you’re going to change the phenotype. Or, with me, take social media: Facebook and Twitter, for example, I don’t really get it and I always wonder why we have to have it and feel like things were better when I was younger, but then I realize I can’t get it — because that’s not my brain. You see, we’re not wired that differently, and I can still learn, because my brain is still plastic — but it’s not the same way it was when it was still developing.
BW: What do you see in the future of human brain evolution?
LK: There’s a lot of people who ask that — and it’s really hard to say for sure. There’s going to be life on this planet long after we’re gone. We’ve done better than pretty much every other species — as we’re the only ones we know of who think about our own evolution, and can chart it back to the past and look at what’s happened and how far we’ve come since then. I was reading an article about mitochondrial repair in newborns — they did it in Mexico — and this opens the door for people altering the genes in a living, changing organism.
Science and technology are expanding at an astonishing rate and we’re only starting to think about the ethics involved. Changing the DNA in an organism for treating diseases is great — as long as it’s all done responsibly and doesn’t get out of control. When have humans ever not been able to not lose control? When you have this technology, you start to think about whether the internet should become its own entity — we need social networking, but how much should it expand? How much transparency should we have?
Of course, we’re going to think about the future; we have these frontal lobes that let us think about the future, where we stand and who we are on this planet Earth, whether we’ll have enough resources to keep going — but I’d say there’s reason to be optimistic in the future. The new generation seems to be very conscientious about things like addressing climate change — I see it in my students now, how passionate they are about these issues and really motivated for making life better for all of us on this planet. They give me hope — I write that in my letters of recommendation, “This person gives me hope.” [Laughs.] So we’ll see how it goes.
BW: What advice would you have for someone looking to pursue a career in neuroscience?
LK: I think being a scientist is the greatest thing. Careers in science are hard — it’s harder to get jobs, but there’s a lot you can do out there. If you get a degree or even a Ph.D., you can do what I do, looking at evolution and how human brains came to be what they are. It’s in our nature really. I do what I can to try and communicate my work to the public, going on lectures, and I feel we owe it to the public to explain what we do in a way they understand — that’s important to being an informed citizen. I think it’s really just in our nature to want to know if there’s life on Mars or to understand the universe and where we came from.
This article was originally published in the Winter 2017 issue of Brain World Magazine.
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