How the Brain Organizes Speech, Language, and Music: Insights from Neuroscience

Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and opthalmology at Stamford School of Medicine. And now for my discussion with Dr. Eric Jarvis. Eric, so great to have you here. Thank you. Yeah, very interested in learning from you about speech and language in terms of the study of speech and language and thinking about how the brain organizes speech and language. Uh

what are the similarities? What are the differences? How should we think about speech and language? There really isn't such a sharp distinction. Now let me tell you how some people think of it now that there's a separate language module in the brain that has all the algorithms and computations that influence the speech pathway on how to produce sound and the auditory pathway on how to perceive and interpret it uh for speech or for you know sound that we call speech. I don't think there is any good evidence for a separate language module. Instead, there is a speech production pathway that's controlling our larynx, controlling our jaw muscles that has built within it all the complex algorithms for spoken language. And

there's the auditory pathway that has built within it all the complex algorithms for understanding speech, not separate from a language module. And this speech production pathway is specialized to humans and parrots and songirds. Whereas this auditory perception pathway is more ubiquitous amongst the animal kingdom. And this is why dogs can understand sit ce boy get the ball and so forth. Dogs can understand several hundred human speech words. Great apes you can teach them for several thousand but they can't say a word. What do we understand about modes of communication that are like language but might not be what would classically be called language?

Right? So next to the brain regions that are controlling spoken language are the brain regions for gesturing with the hands. And that hand parallel pathway has also complex algorithms that we can utilize. And some species are more advanced in these circuits, whether it's sound or gesturing with hands, and some are less advanced. Humans are the most advanced at spoken language, but not necessarily as big a difference at gestural language compared to some other species. So, as you and I are talking here today, and people who are listening but can't see us, we're actually gesturing with our hands as we talk uh without knowing it. We're doing it unconsciously and if we were talking on

a telephone, I would have one hand here and I would be gesturing with the other hand without even you seeing me, right? And so why is that? Some have argued and I would agree with based upon what we've seen is that there is an evolutionary relationship between the brain pathways that control speech production and gesturing. Uh and the brain regions I mentioned are directly adjacent to each other. And why is that? I think that the brain pathways that control speech evolved out of the brain pathways that control body movement. All right? And um that uh when you talk about Italian, French, English, and so forth, um each one of those languages come with a learned set of gestures

that you can communicate with. Now, how is that related to other animals? Well, Koko, a gorilla who is raised with humans for 39 years or more, uh, learned how to do gesture communication, learned how to sign language, so to speak, right? But Koko couldn't produce those sounds. Koko could understand them as well by s by seeing somebody sign or hearing somebody produce speech, but Koko couldn't produce it with her voice. And so what's going on there is that a number of species, not all of them, a number of species have motor pathways in the brain where you can do learn gesturing, rudimentary language if you wanted, say, with your lens, even if it's not as advanced as humans, but they

don't have this extra brain pathway for the sound. So they can't gesture with their voice in the way that they gesture with their hands. One thing that I've wondered about for a very long time is whether or not um primitive emotions and primitive sounds are the early substrate of language. When I smell something delicious, I typically inhale more and I might say or something like that. Whereas if I smell something putrid, I typically turn away. I wse and I will exhale trying to not ingest those molecules or inhale those molecules. I could imagine that these are the basic dark and light contrasts of the language system. This kind of primitive to more sophisticated um pyramid of sound to language. Is

this a crazy idea? Do we have any uh do we have any evidence this is the way it works? No, it's not a crazy idea. And in fact, you hit upon one of the key distinctions in the field of research that I started out in, which is vocal learning research. Most vertebrate species vocalize, but most of them are producing innate sounds that they're born with. Uh that is babies crying, for example, or dogs barking. And only a few species have learned vocal communication, the ability to imitate sounds. And that is what makes spoken language special. When people think of what's special about language, it's the learned vocalizations. That is what's rare. So all the things you talked about, the breathing, the grunting and so forth, a

lot of that is handled by the brain stem circuits, you know, right around the level of your neck and below uh like a reflex kind of thing. So or even some emotional aspects of your behavior in the hypothalamus and so forth. But for a learned behavior, learning how to speak, uh, learning how to play the piano, teaching a dog to learn how to do tricks is using the forebrain circuits. And what has happened is that there's a lot of forebrain circuits that are controlling learning how to move body parts in these species, but not for the vocalizations. But in humans and in parrots and some other species somehow we acquired circuits where the forebrain has taken over the brain stem and now

using that brain stem not only to produce the innate behaviors or vocal behaviors but the learned ones as well. Do we have any sense of when modern or sophisticated language evolved amongst the primates which we humans belong to? we are the only ones that have this advanced vocal learning ability. Uh now when you it was assumed that it was only homo sapiens. Uh then you can go back in time now based upon genomic data not only of us living humans but of the fossils that have been found for homo sapiens of Neanderthalss of Dennisovven uh individuals and discover that our ancestor our human ancestors supposedly hybridize with these other homminid species. And it was assumed that these other homminid species don't learn how to

imitate sounds. I don't know of any species today that's a vocal learner that can have children with a non-vocal learning species. I don't see it. It doesn't mean it didn't exist. uh and when we look at the genetic data from these ancestral homminids that uh you know where we can look at genes that are involved in learn vocal communication they have the same sequence as we humans do for genes that function in speech circuits. So I think Neanderthalss had spoken language. I'm not going to say it's as advanced as what it is in humans. I don't know. Um but I think it's been there for at least between 500,000 to a million years.

Maybe we could talk a little bit more about the overlap between brain circuits that control language and speech in humans and other animals. You know, I was weaned in the neuroscience era where bird song and the uh the ability of birds to learn their tutor song was and still is a prominent field um sub field of neuroscience. And this notion of a critical period, a time in which language is learned more easily than it is later in life. And the names of the different brain areas were quite different. Um it one opens the textbooks we hear vernicks and brocas for the humans and you look at the bird stuff. I remember you know HBC a robust arch striatum area X right that's right. Uh how similar or

different are the brains brain areas controlling speech and language in say a song bird and a young ch human child. Yeah. So going back to the 1950s or and even a little earlier and Peter Mer and others who got involved in neuroethology, the study of neurobiology of behavior in a natural way, right? Um you know they start to find that behaviorally there are these species of birds like song birds and parrots and now we also know hummingbirds just three of them out of the 40some bird groups out there on the planet orders that they can imitate sounds like we do. And so that was the similarity. In other words, they had this kind of behavior that's more similar to us than chimpanzees have

with us or than chickens have with them, right? They're closer relatives. And then they discovered even more similarities, these critical periods that if you remove a child and you know this unfortunately happens where a child is feral and is not raised with human and goes through their puberty phase of growth, becomes hard for them to learn a language as an adult. So there's this critical period where you learn best and even later on when you're in regular society it's hard to learn. Well the birds undergo the same thing and then it was discovered that if they become deaf we humans become deaf our speech starts to deteriorate without any kind of therapy. Uh if a non-human primate or um

you know or let's say a chicken becomes deaf uh their vocalizations don't deteriorate very little at least. uh well this happens in the vocal learning birds. So there were all these behavioral parallels that came along with a package and then people looked into the brain Fernando Nataba my former PhD adviser and began to discover the area X you talked about uh the robust nucleus of the archopelium and um and these brain pathways were not found in the species who couldn't imitate. So there was a parallel here and then uh jumping many years later you know I started to dig down into these uh brain circuits to discover that these brain circuits have parallel functions with the brain circuits for humans even though they're by a different name like

brocas and linja motor cortex. And most recently we discovered not only the actual circuitry and the connectivity are similar but the underlying genes that are expressed in these brain regions in a specialized way different from the rest of the brain are also similar between humans and song birds and parrots. So all the way down to the genes and now we're finding the specific mutations are also similar. Not always identical but similar uh which indicates remarkable convergence for a so-called complex behavior in species separated by 300 million years from a common ancestor. And not only that, we are discovering that mutations in these genes that cause speech deficits in humans like in fox P2, uh if you put those same mutations or similar type of

deficits in these vocal learning birds, you get similar deficits. So convergence of the behavior is associated with similar genetic disorders of the behavior. Do hummingbirds sing or do they hum? Hummingbirds hum with their wings and sing with their searings in a coordinated way. There's some species of hummingbirds um that actually will um Doug Ashler showed this that will flap uh their wings and create a slapping sound with their wings that's in unison with their song and you would not know it, but it sounds like a particular syllable in their songs. uh even though it's their wings and their voice at the same time.

Hummingbirds are clapping to their song. Clapping with their they're snapping their wings together uh in unison with a song to make it like if I'm going da, you know, and I banged on the table except they make it almost sound like their voice with their wings. What's amazing about hummingbirds and I we're going to say vocal learning species in general is that for whatever reason they seem to evolve multiple complex traits. You know this idea that evolving language, spoken language in particular comes along with a set of specializations. When I was coming up in neuroscience, I learned that I think it was the work of Peter Marlor that um young birds learn song birds learn their

tutor song and learn it quite well. But that they could learn the song of another tutor. In other words, they could learn a different, and for the listeners, I'm doing air quotes here, a different language, a different bird song, different than their own species song, but never as well as they could learn their own natural genetically linked song. Yes, genetically linked meaning that it would be like me being raised in a different culture and um that I would learn that the other language, but not as well as I would have learned English. This is the idea. Is that true? That is true. Yes. And that's

what I learned growing up as well and talked to Peter Mer himself about before he passed. Um he had this he used to call it the innate predisposition to learn. All right. So um which would be kind of the equivalent in the linguistic community of universal grammar. There is something genetically influencing our vocal communication on top of what we learn culturally. And so there's this ba balance between the genetic control of speech or a song in these birds and the learned uh cultural control. And so yes, if you were to take um you know um I mean in this case we actually tried this at Rockerfeller later on. Take a zebra fininch and raise it with a canary. It would sing a song that was sort of like a hybrid in between. We call it a

caninch, right? uh and vice versa for the canary because there's something different about their vocal musculature or the gen or the circuitry in the brain. And with a zebra finch, even with a closely related species, if you would take a zebra finch uh young animal and in one cage next to it place its own species, adult male, right? And in the other cage place a Bengal finch next to it, it would preferably learn the song from its own species neighbor. But if you remove its neighbor, it would learn that bangal finch very well. Fantastic. So there's it has something to do with also the social bonding with your own species. That raises a question that I based on something I also heard but I don't have any uh scientific

peer-reviewed publication to point to which is this idea of pigeon not the bird but this idea of when multiple cultures and languages converge in a given geographic area that the children of all the different native languages will come up with their own language. I think this was in island culture maybe in Hawaii called pigeon which is sort of a hybrid of the various languages that their parents speak at home and that they themselves speak and that somehow pigeon again not the bird but a language called pigeon for reasons I don't know harbors certain basic elements of all language is that true is that not true what is going on here is cultural evolution remarkably tracks genetic

evolution. So if you bring people from two separate populations together that have been in their separate populations evolutionarily at least for hundreds of generations. So someone speaking Chinese, someone speaking English. Uh and that child uh then's learning from both of them. Yes. That child's going to be able to pick up and merge uh phonms and words together in a way that an adult wouldn't because why? they're experiencing both languages at the same time during their critical period uh years in a way that um adults would not be able to experience. And so you get a hybrid and the lowest common denominator is going to be what they share. And so the phonms that they've retained in each

of their uh languages is what's going to be I imagine used the most. So we've got brain circuits in songirds and in humans that in many ways are similar perhaps not in their exact wiring but in their basic contour of wiring and genes that are expressed in both sets of neural circuits in very distinct species that are responsible for these phenomenon we're calling speech and language. I mean what are these genes doing? Uh, one of the things that differ in the speech pathways of us and these song pathways of birds is some of the connections are fundamentally different than the surrounding circuits. Like a um a direct cortical connection uh from the areas that control vocalizations in the cortex to the motor neurons that control

the larynx in uh humans or the serrings in birds. And so we actually made a prediction uh that since some of these connections differ, we're going to find genes that control neuro connectivity uh and that specialize in that function that differ. And that's exactly what we found. Uh um genes that control what we call axon guidance and form in connections. And what was interesting, it was sort of in the opposite direction that we expected. That is some of these genes, actually a number of them that control neuro connectivity were turned off. in the speech circuit. All right? Uh and it didn't make sense to us at first until we started to realize the function of these genes are to repel connections from forming. So repulsive molecules and

so when you turn them off, they allow certain connections to form that normally would have not formed. So it's a so by turning it off, you got a gain of function for speech, right? Um uh other genes that surprised us were genes involved in calcium buffering neurop protection like a parvamine or heat shock proteins. So when your brain gets hot these proteins turn on and we couldn't figure out for a long time why is that the case and then the idea popped to me one day and said ah when I heard the larynx is the fastest firing muscles in the body. All right. In order to vibrate sound and modulate sound in the way we do, you have to control, you have to move those muscles, you

know, three to four to five times faster than just regular walking or running. And so, um, when you stick electrodes in the brain areas that control learn vocalizations in these birds and I think in humans as well, uh, those neurons are firing at a higher rate to control these muscles. And so what is that going to do? You're going to have lots of toxicity in those neurons unless you upregulate molecules that take out uh the extra load that is needed to control the larynx. And then finally a third set of genes that are specialized in these speed circuit are involved in neuroplasticity.

Uh neuroplasticity meaning allowing the brain circuits to be more flexible uh so you can learn better. And why is that? I think learning how to produce speech is a more complex learning ability than say learning how to walk or learning how to do tricks and jumps and so forth that dogs do in terms of plasticity of speech and the ability to learn multiple languages but even just one language. What's going on in the so-called critical period? And then the second question is if one can already speak more than one language as a consequence of childhood learning is it easier to acquire new languages later on.

Actually the entire brain uh is undergoing a critical period development not just the speech pathways and uh so it's easier to learn how to play a piano. It's easier to learn how to ride a bike for the first time and so forth as a young child than it is later in life. The brain can only hold so much information. And if you are undergoing rapid learning to learn to acquire new knowledge, you also have to put memory or information in the trash like in a computer. You only have so many gigabases of memory. Plus also for survival, you don't want to keep forgetting things. And so the brain is designed I believe to undergo this critical period and solidify the circuits with what you learned as a

child and you use that for the rest of your life. And now the question you asked about if you learn more languages as a child, can you is it easier to learn as an adult? And that's a common uh finding out there in the literature. There are some that argue against it, but for those that support it, the idea there is um you are born with a set of innate sounds you can produce of phonms and you narrow that down because not all languages use all of them. And so you narrow down the ones you use to string the phonms together in words that you learn and you maintain those phonms as an adult. And here comes along another language that's using those phonms or in different combinations

you're not used to. uh and therefore it's like starting from first principles but if you already have them in multiple languages that you're using then it makes it easier to use them in another third or fourth language. So it's not like your brain has under has maintained greater plasticity is your brain has maintained greater ability to produce different sounds that then allows you to learn another language faster. What about modes of speech and language that seem to have a depth of emotionality and meaning but for which it departs from structured language? I think of musicians like there are some Bob Dylan songs that to me uh I understand the individual words. I like to think there's an emotion associated

with it. At least I experienced some sort of emotion and I have a guess about what he was experiencing. But if I were to just read it linearly without the music and without him singing it or somebody singing it like him, it wouldn't hold any meaning. So in other words, words that seem to have meaning but not associated with language but somehow tap into an emotionality. Absolutely. So, so we call this difference um semantic communication, communication with meaning and effective communication, communication that has more of an emotional feeling content to it. I believe you know based upon imaging work and work we see in birds

when birds are communicating semantic information in their sounds which is not too often but it happens versus uh effective communication sing because I'm trying to attract the mate my courtship song or defend my territory it's the same brain circuits it's the same speech like or song circuits are being used in different ways there's several other points here I think it's important for the those listening out there to here is that when I say also this effective and um semantic communication um being used by similar brain circuits it also matters the side of the brain uh in birds and in humans um there's there's left right dominance uh for learn communication learned sound communication uh so the left in us humans is more dominant for

speech but the right has a more balance for singing or processing musical sounds as opposed to processing speech. Both get used for both reasons. And so when people say your right brain is your artistic brain and your left brain is your thinking brain, this is what they're referring to. Uh and uh so that's another distinction. The second uh thing that's useful to know is that all vocal learning species use their learn sounds for this emotional effective kind of communication, but only a few of them like humans and some parrots and dolphins use it for the semantic kind of communication we calling speech. And that has led a number of people to hypothesize that the evolution of spoken language of speech

evolved first for singing uh for this more like emotional kind of made attraction like the Jennifer Lopez the Ricky Martin kind of songs and so forth. Uh and then later on it became used for abstract communication like we're doing now. I'd love to chat a moment about facial expression many of which are subconscious. We are all familiar with the fact that when what somebody says doesn't match some specific feature of their facial expression that it can um call you know that mismatch can cue our attention.

Yeah. So how does motor circuitry that controls facial expression map on to the mo the brain circuits that control language, speech and even bodily and hand movement? Yeah. You ask a great question because we both know some colleagues like Winrich Frywald at Rockefeller University who study facial expression and the neurobiology behind it. Non-human primates have a lot of diversity in their facial expression like we humans do. And what we know about the neurobiology of brain regions controlling those muscles of the face is that these non-human primates and some other

species that don't learn how to imitate vocalizations, they have strong connections from the cortical regions to the motor neurons that control facial expressions. And even though it's more diverse in these non-human primates, there was already a pre-existing diversity of communication, whether it's intentional or unconscious, through facial expression in our ancestors. And on top of that, we humans now add the voice uh along with those facial expressions. So it's like an email, too. You're you're emailing and someone says something by email. someone can interpret that angrily or gently uh and it be becomes ambiguous. The facial expressions get rid of that ambiguity.

I'm so glad you brought that out because my next question was and is about written language. What is the process of going from a thought to language to written word and what's going on there? What do we know about the neural circuitry? What I think is going on is to explain what you're asking is about that I'm going to take it from the perspective of reading something. You read something on a paper. The signal from the paper goes through your eyes. It goes to the back of your brain to your visual cortical regions eventually. That visual signal then goes to your speech pathway in the motor cortex in front here in Brocas area. And you silently speak what you read in your

brain without moving your muscles. And sometimes actually if you put electrodes EMG electrodes on your lendial muscles even on birds you can do this you'll see activity there while reading or trying to speak silently even though no sound's coming out. And so your speech pathway is now speaking what you're reading. Now to finish it off that signal is sent to your auditory pathway so you can hear what you're speaking in your own head. That's incredible. And this is why it's complicated. Oh, and then you got to write, right? Okay, here comes the fourth one. Now, the hand areas next to your speech pathway is got to take that auditory signal or even the adjacent motor signals for speaking and

translate it into a visual signal on paper. So, so you're using at least four brain circuits um which includes the speech production and the speech perception pathways to write. Stutter is a um particularly interesting case. What is the current neurobiological understanding of stutter and are what's being developed in terms of treatments for stutter? Yeah. So we actually uh accidentally came across stuttering in songirds and we've published several papers on this to try to figure out the neurobiological basis. The first study we had was a brain area called the basil ganglia or the what's the strium part of the basil ganglia involved in coordinating movements learning how to make movements when it was damaged in these in this in

the speech-like pathway in these birds. What we found is that they started to stutter as the brain region recovered and unlike humans they actually recovered after three or four months. And why is that the case? Because bird brains under goes new neurogenesis in a way that human or mammal brains don't. Uh and it was the new neurons that were coming in into the circuit uh but not quite you know with the right proper activity uh was resulting in this stuttering in these birds. uh and after it was repaired not exactly the old song came back as a after the repair but still it recovered a lot better and it's now known they call this neurogen neurogenics stuttering in humans uh with damage to

the braz ganglia or some type of disruption to the basil ganglia at a young age also causes stuttering in humans and even those who are born with stuttering uh um it's often the basil ganglia uh that's disrupted than some other brain circuit and we think the speech part of the basil ganglia. Can adults who maintain a stutter from childhood uh repair that stutter? There are ways to overcome the stuttering through um through uh you know behavioral therapy. Uh and I think all of the uh tools out there have something to do with sensory motor integration. Uh controlling what you hear with what you output in a thoughtful controlled way helps reduce the stuttering.

Texting is a very interesting evolution of language. I wonder sometimes whether or not we are getting less proficient at speech because we are not required to write and think in complete sentences. Mhm. What do you think is happening to language? Are we getting better at speaking, worse at speaking? And what do you think the role of things like texting and tweeting and shorthand communication, hashtagging, what's that doing to the way that our brains work? Uh texting actually has allowed for more rapid communication amongst people. It's more like a use it or lose it kind of a um thing with the brain. The more you use a particular brain region or circuit, the more enhanced it's like a muscle. Uh the

more you exercise it, the more healthier it is, the bigger it becomes and the more space it takes and the more you lose something else. So I think texting is not decreasing the speech prowess or the intellectual prowess of speech. It's converting it and using it a lot in a different way in a way that may not be as rich in regular writing because uh you can only communicate so much nuance in short term writing. But um whatever that whatever is being done, you got people texting hours and hours on the phone. So whatever your thumb circuit is going to get pretty big actually for those listening who are interested in getting better at speaking and understanding languages. Are there any

tools that you recommend? Should kids learn how to read hard books and simple books? Uh what do you recommend? Should adults learn how to do that? Everyone wants to know how to keep their brain working better, so to speak, but also I think people want to be able to speak well and people want to be able to understand well. Yeah. What I've discovered personally, right, is that so when I switched from uh pursuing a career in science from a career in dance, I thought one day I would stop dancing. Um but I haven't because it I find it fulfilling for me. And there have been periods of time like during the pandemic where I slowed down on dancing and so forth. Um and when you do that you realize okay there

parts of your body where your muscle tone decreases a little bit and somewhat and or you could start to gain weight or I somehow don't gain weight that easily and I think it's related to my dance if that's that's meaningful to your audience. But what I found is in science we like to think of a separation between movement and action and cognition. And there is a separation for you between perception and production. Cognition being perception, production being movement, right? But if the speech pathways is next to the movement pathways, what I discover is by dancing, it is helping me think. It is helping keeping my brain fresh. It's not just moving my muscles. I'm moving or using the circuitry in my brain to do

control a whole big body. You need a lot of brain tissue to do that. And so I argue if you want to stay cognitively intact into your old age, you better be moving and you better be doing it consistently, whether it's dancing, walking, running, and also practicing speech, oratory speech and so forth, or singing is controlling the brain circuits that are moving your facial musculature. And it's going to keep your cognitive circuits also in tune. And I'm I'm convinced of that from my own personal experience. This has been an incredible conversation and opportunity for me to learn. I know I speak for a tremendous number of people. And I just really want to say thank you for joining us today. You are

incredibly busy. It's clear from your description of your science and your knowledge base that you are involved in a huge number of things. Um very busy. So, thank you for taking the time to speak to all of us. Thank you for the work that you're doing. Thank you for inviting me here to get the word out to the community uh of what's going on in the science world. Well, we're honored and very grateful to you, Eric. Thank you. You're welcome.