Huberman LabThe Science of Learning & Speaking Languages | Dr. Eddie Chang
EVERY SPOKEN WORD
150 min read · 30,097 words- 0:00 – 3:00
Dr. Eddie Chang, Speech & Language
- AHAndrew Huberman
(uptempo music) Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today my guest is Dr. Eddie Chang. Dr. Eddie Chang is the chair of the Neurosurgery Department at the University of California at San Francisco. Dr. Chang's clinical group focuses on the treatment of movement disorders, including epilepsy. He is also a world expert in the treatment of speech disorders and relieving paralysis that prevents speech and other forms of movement and communication. Indeed, his laboratory is credited with discovering ways to allow people who have fully locked-in syndrome, that is, who cannot speak or move, to communicate through computers and AI devices in order to be able to speak to others in their world and understand what others are saying to them. It is a truly remarkable achievement that we discuss today, in addition to his discoveries about critical periods, which are periods of time during one's life when one can learn things, in particular languages, with great ease, as opposed to later in life. And we talk about the basis of things like bilingualism and trilingualism. We talk about how the brain controls movement of the very muscles that allow for speech and language and how those can be modified over time. We also talk about stutter, and we talk about a number of aspects of speech and language that give insight into not just how we create this incredible thing called speech or how we understand speech and language, but how the brain works more generally. Dr. Chang is also one of the world leaders in bioengineering, that is, the creation of devices that allow the brain to function at super physiological levels and that can allow people with various syndromes and disorders to overcome their deficits. So if you are somebody who is interested in how the brain works normally, how it breaks down, and how it can be repaired, and if you are interested in speech and language, reading and comprehension of information of any kind, today's episode ought to include some information of deep interest to you. Dr. Chang is indeed the top of his field in terms of understanding these issues of how the brain encodes speech and language and creates speech and language, and as I mentioned, movement disorders and epilepsy. We even talk about things such as the ketogenic diet, the future of companies like Neuralink, which are interested in bioengineering and augmenting the human brain, and much more. One thing that I would like to note is that in addition to being a world-class neuroscience researcher and world-class clinician, neurosurgeon, and chair of neurosurgery, Dr. Eddie Chang has also been a close personal friend of mine since we were nine years old. We attended elementary school together, and we actually had a science club when we were nine years old focused on a very particular topic. You'll have to listen in to today's episode to discover what that topic was and what membership to that club required. That aside, Dr. Chang is an absolute phenom with respect to his scientific prowess, that is, both his research and his clinical abilities, and he's one of these rare individuals that whenever he opens his mouth, we learn.
- 3:00 – 7:19
Levels, Eight Sleep, InsideTracker, Momentous Supplements
- AHAndrew Huberman
Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Levels. Levels is a program that helps you see how different foods affect your health by giving you real-time feedback on your diet using a continuous glucose monitor. I started using Levels about one year ago, and the Levels monitor allowed me to see how different foods change my blood sugar level or my blood glucose level, which turns out to be immensely important for being able to predict how, for instance, certain foods will affect your energy level, your ability to exercise, your ability to recover from exercise, and how it will affect other hormones like testosterone, estrogen, thyroid hormone, and so forth. The other thing about using a Levels monitor is that it gave me insight into how food and exercise and other activities and even how well I was sleeping or how poorly I might happen to be sleeping impact my blood glucose levels. It even taught me that the sauna, that generating a lot of heat in my body was changing my blood glucose levels, which turned out to inform how I should shift my eating patterns, foods I should eat, timing of eat, and so on and so forth. Really gave me great insight into how all of the important aspects of my health were interlocking and affecting one another, not just how food was impacting my blood glucose. So if you're interested in learning more about Levels and trying a continuous glucose monitor yourself, you can go to levels.link/huberman. That's levels.link/huberman. Today's episode is also brought to us by Eight Sleep. Eight Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity. I started sleeping on an Eight Sleep mattress cover a few months ago, and it is simply incredible. In fact, I don't even like traveling anymore (laughs) because they don't have Eight Sleep mattress covers in hotels and Airbnbs. One of the reasons I love my Eight Sleep mattress covers so much is that, as you may have heard before on this podcast or elsewhere, in order to fall and stay deeply asleep, you need your body temperature to drop by about one to three degrees, and I tend to run warm at night, which makes it hard to sleep and sometimes wakes me up in the middle of the night. When you sleep on an Eight Sleep mattress cover, you can program the temperature of that mattress cover for specific times in the early, middle, and late part of your night so that the mattress stays cool, and as a consequence, you sleep very, very deeply. It also tracks your sleep, so it's paying attention to how many times you're moving, how deep your sleep is. It gives you a sleep score, all wonderful data to help you enhance your sleep, and of course, sleep is the foundation of mental health, physical health, and performance, which makes an Eight Sleep a terrific tool for enhancing not just your sleep, but all aspects of your life really. If you're interested in trying an Eight Sleep mattress cover, you can go to eightsleep.com/huberman to check out the Pod 3 cover, and you can save $150 at checkout. Eight Sleep currently ships to the USA, to Canada, the UK, and select countries in the EU and Australia. Again, that's eightsleep.com/huberman to save $150 at checkout.Today's episode is also brought to us by InsideTracker. InsideTracker is a personalized nutrition platform that analyzes data from your blood and DNA to help you better understand your body and help you reach your health goals. I've long been a believer in getting regular blood work done for the simple reason that many of the factors that impact your immediate and long-term health can only be analyzed with a quality blood test. One problem with a lot of DNA tests and blood tests, however, is you get data back about levels of metabolic factors, levels of hormones, et cetera, but you don't know what to do with that information. InsideTracker makes interpreting your data and knowing what to do about it exceedingly easy. They have a personalized platform where you can go and you can see those levels of hormones, metabolic factors, lipids, et cetera, and they point to specific nutritional tools, behavioral tools, supplement-based tools, et cetera, that can help you bring those numbers into the ranges that are optimal for you. If you'd like to try InsideTracker, you can go to insidetracker.com/huberman to get 20% off any of InsideTracker's plans. Again, that's insidetracker.com/huberman to get 20% off. The Huberman Lab Podcast is now partnered with Momentous supplements. To find the supplements we discuss on the Huberman Lab Podcast, you can go to live momentous, spelled O-U-S, livemomentous.com/huberman. And I should just mention that the library of those supplements is constantly expanding. Again, that's livemomentous.com/huberman. And now for my discussion with Dr. Eddie Chang. Eddie,
- 7:19 – 13:10
Neuroplasticity, Learning of Speech & Environmental Sounds
- AHAndrew Huberman
welcome.
- ECEddie Chang
Hi. Hi, Andrew.
- AHAndrew Huberman
Great to be here with you. This has been a long time coming. Just to, uh, come clean, uh, we've known each other since we were nine years old.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
But then there was a long gap in which we didn't talk to one another. I heard things about you, and presumably, I don't know, you heard a thing or two about me-
- ECEddie Chang
(laughs)
- AHAndrew Huberman
... uh, for better or for worse. Uh, and then we reconnected years later when I was a PhD student and you were a medical student, and we literally ran into each other in the halls of University of California, San Francisco, where you're now the chair of neurosurgery, so, uh, it all comes full circle. When you were at UCSF, you were working with Mike Merzenich, and I know that name might not be familiar to a lot of people, but he's, uh, sort of synonymous with neuroplasticity, the ability of the brain and nervous system to change in response to experience. So for our listeners, I would just love for you to, uh, give a brief overview of what you were doing at that time, because I find that work so fascinating and it really points to some of the things that can promote and maybe hinder our brain's ability to change.
- ECEddie Chang
Oh, wow, that's fantastic. So we did bump into each other, uh, serendipitously back then, and at the time, I was a medical student at UCSF studying with Mike Merzenich. In particular, I was studying how the brain, uh, organizes when you have patterns of sound, and, uh, in particular, we were studying the, the brain of rodents and trying to understand how different sound patterns organize the frequency representation from low to middle to high frequency maps in the brains of baby rodents. And one of the things that I was very interested in was trying to understand how the patterns of the natural environment, let's say the vocalizations of the environment that the rat pups were raised in or just the natural sounds that they hear, how that shapes the structure of the brown- of the brain. And one of the things we did was to try an experiment where we raised some of these rat pups in white noise, continuous white noise that was essentially masking all of those environmental sounds.
- AHAndrew Huberman
And what was the consequence of animals being raised in white noise environment?
- ECEddie Chang
Well, one of the things that we didn't expect but we found which was quite striking is that there's this early period in brain development where we're very susceptible to the patterns that we hear or see. In, in neuroscience, we call this a critical period or a sensitive period, and we have this for our eyes, but we also have it for our ears. And, uh, one of the most striking examples of this is that any human can essentially grow up in a, a culture where they hear different speech sounds from one language to another, and it's like after a couple of years, you lose sensitivity to sounds that are not part of your native language and you have high sensitivity for, for the languages of your native culture, and, um, that's pretty s- pretty extraordinary that human brain has that flexibility yet at the same time has that specialization for language. And so we were trying to think about how do we model this, for example, in, in rodents who obviously don't speak, but we're just understanding how sounds and environmental sounds modulate and organize auditory cortex. And one of the things that we found that was quite striking was that if you basically mask environmental sounds from these rat pups, the critical period, this sensitive period where it's open to plasticity, it's open to change, it's open to reorganization, that actually, that window can stay open much, much longer, and it... And in one way, it sounds like that's a good thing, but on the other hand, it, it's also, um, a retardation, it's actually, uh, it slowed the maturation of the auditory cortex. It was ready to close when these rat pups were really young, but by raising them in white noise, we found out that you could keep it open for months beyond the time period that it normally closes. And so I think one of the things it taught me was that it's not just about the genetic programming that specifies some of this sensitive period, but it's also a little bit about the nature of the sounds that we hear that help keep that window for the critical period open and closed.
- AHAndrew Huberman
It's fascinating. And I know it's difficult to make a direct leap from animal research to human research, but if we could speculate a little bit, um, I can imagine that some people grow up in homes where there's a lot of shouting and a lot of inflection, uh, maybe people are very verbose-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... maybe pe-... others grow up in a home where it's quieter and more peaceful. Uh, some people are going to grow up in cities. I just came back from New York City, it's like all night long, there's honking and sirens and it's just non-stop. And then I return here where it's quite quiet at night. Can we imagine that the human brain is going to be shaped differently depending on whether or not one grows up in one environment or another? And would that impact their tendency to speak in a certain way as well as hear in a certain way? What do we know about that?
- ECEddie Chang
Well, I think that it's, from my perspective, it's really clear that those sounds that we are exposed to from the very earliest time, even in utero, in the womb, where the sound is hearing the mother or father or friends around while in the womb actually will influence how these things organize and, um... And so there's no question that the sounds that we hear are going to have some influence, and those sounds are going to structure the way that those neural networks actually lay down and will forever influence how you hear sounds and speech, and language is probably one of the most profound examples of that.
- AHAndrew Huberman
I get
- 13:10 – 17:26
White Noise Machines, Infant Sleep & Sensitization
- AHAndrew Huberman
a lot of questions about the use of white noise during sleep, in particular, people want to know whether or not using a white noise machine or a machine or a program that makes the sound of waves for instance, if it assists their infant in sleeping, is it going to be bad for them because it's flooding the auditory system with a bunch of essentially white noise or disorganized noise? Do we have an answer to that question?
- ECEddie Chang
Not yet. I think that what you're asking is a really important question because parents are using white noise generators almost universally now and for good reasons. You know, it is hard, uh, to have kids up at night. I've got three kids of my own and was very tempted to think about how to use some of these tools to just soothe them and get them to bed, especially when I was like so tired and exhausted, um, but I think that there is a cost, you know, to think a little bit about. You know, we don't- we're not exposed to continuous white noise naturally. There is a value to having really salient structured sounds that are part of our natural environment to actually have the brain develop normally, so whether or not that has an impact, you know, while you're sleeping, it's not clear. I don't- I don't think that those studies have been done. What was really clear was that if you raise these baby rats in continuous white noise, not super loud but just enough to mask the environmental sounds, that that was enough to keep, you know, the auditory cortex, the part of the brain that hears, uh, in this really delayed state which could essentially slow down the development and maturation of the brain.
- AHAndrew Huberman
And one could probably assume that slowing the maturation of areas of the brain that are responsible for hearing might, I want to underscore might, impact one's ability to speak, right? Because isn't it the case that if people can't hear, they actually have a harder time enunciating in- in a particular way? Is that right?
- ECEddie Chang
Yeah.
- AHAndrew Huberman
If I were to not be able to hear my own voice, uh, would my speech patterns change?
- ECEddie Chang
Well, I think part of it is that over time we develop sensitivity to the very specific speech sounds in a given language and the sensitivity improves as we hear more and more and more of it, and then on the other hand, we lose sensitivity to other speech sounds at the same time. But as part of that process, we also have, um, a selectivity, uh, again, a specialization even for those sounds, uh, even relative to noise, noisy backgrounds and things like that. I- I tend to think about it like what is the signal to noise ratio and so the brain has its own ways of trying to increase that signal to noise ratio in order to make it more clear. Part of that is how we hear and how it lays down a foundation for that signal to noise ratio and so you can imagine a child that's- that's raised continuously in white noise would be really deprived of those kind of sounds that are really necessary for it to develop properly. So I think with regard to, um, those tools for babies, I think we- we should study, we should try to understand this definitively. I think what we saw, rodents would tell us that there is potential, you know, things that we should be concerned about, but again, it's not really clear if you're just using at night whether it has those effects.
- AHAndrew Huberman
Here's the critical question that a number of people are going to be asking is did you decide to use a white noise machine or not to help keep your, uh, any of your three children asleep?
- ECEddie Chang
Yeah. Well, um, I think the short answer is no. I mean, I- I obviously did a lot of work thinking and work on this and thought about it carefully, but there are other kinds of noise or I- I wouldn't even call it noise, other sounds that you can use that can be equally soothing to a baby. Um, it's just that white noise has no structure and what it's doing is essentially masking out all of the natural sounds and I think the goal should really be about how do we replace that with other more natural sounds that structure the brain in the way that we want to be more healthy.
- 17:26 – 24:26
Mapping Speech & Language in the Brain
- ECEddie Chang
- AHAndrew Huberman
Well, I know that after you finished your medical training, you went on to, of course, specialize in neurosurgery and, uh, last I checked, you spend your- most of your days either running your laboratory or you're in the clinic or running the department and your clinical work and your laboratory work involves often removing pieces of the skull of humans and going in and either removing things or stimulating neurons, um, tr- treating various, uh, ailments of different kinds but your main focus these days, of course, is the neurobiology...... of speech and language. And so for those that aren't familiar, could you please distinguish for us speech versus language in terms of whether or not different brain areas control them? And I know that there's a lot of interest in how speech and language and hearing all relate to one another.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
And then we'll talk a bit about, for instance, emotions and how facial expressions could play into this, or hand- hand gestures, etc. But for the- the uninformed person, and for me, to be quite, uh, direct, what are the brain areas that control speech and language? Wh- what- what are they really? And- and especially in humans, how are they different? I mean, we have such sophisticated language, um, compared to a number of other species. What- what- what does all this landscape look like in there?
- ECEddie Chang
Yeah. Well, um, that's a fascinating question, and I'm going to just try to connect a couple of the dots here, which is that in that earlier work during medical school, I was doing a lot of what we call neurophysiology, putting electrodes into the auditory cortex and understanding how the brain responds to sounds, and that's how we actually mapped out these things about the sensitivity to sensitive periods. That experience, uh, with Mike Merzenich and thinking about how plasticity is regulated in the brain, in particular about how sound is represented by brain activity, was something that, you know, was really formative for me. And because I was a medical student, I was going back to my medical studies, um, it was that in combination with seeing some awake brain surgeries that our department is really well-known for. Uh, one of my mentors, Mitch Berger, really pioneered these methods for taking care of patients with brain tumor and be able to do these surgeries safely by keeping patients awake and by mapping out language.
- AHAndrew Huberman
So they're talking and listening, and you're e- essentially in conversation with these patients while there's a portion of their skull removed and you are stimulating or in some cases removing areas of their brain, is that right?
- ECEddie Chang
That's- that's exactly right. And the only thing off there is it's not essentially, it's- it is just that. The only difference between the conversation that I might have with my patient who's undergoing awake brain surgery is that I can't see their face and they can't see my face. Uh, we actually have a sterile, um, drape that actually separates the operating field and they're looking and interacting with our neuropsychologist, but I can talk to them and they can hear my voice and vice versa, and it's a really, really important way of how we can protect some of those areas that are really critical for language, at the same time, uh, accomplish the mission of getting the seizures under control or getting a brain tumor removed.
- AHAndrew Huberman
And is that because occasionally you'll encounter a brain area, maybe you're stimulating or considering removing that brain area, and suddenly the- the- a patient will start stuttering or will have a hard time formulating a sentence? Is that- is that essentially what you're looking for? You're looking for, um, regions in which it is okay or not okay to probe?
- ECEddie Chang
Exactly. So the first thing that we do is that we use a small electrical stimulator to probe different parts of the areas that we think might be related and important for language or talking, or even movements of your arm and leg. That's what we call brain mapping. And we use a small electrical current that's delivered through a probe that we can just put at each spot, and the areas that we're really interested in are of course the areas that are right around the part that is pathological, the part that's injured or the part that has a brain tumor that we want to remove. So we can apply that probe and transiently, meaning temporarily, activate it. So if you're stimulating the part of the brain that controls the hand, the hand will move. Uh, it will jerk. Sometimes a fist will be made, something like that. Uh, other times, while someone is counting or just saying the days of the week, you can stimulate in a different area that stops their speech altogether. That's what we call speech arrest. Or if someone is looking at pictures and they're describing the pictures and you stimulate a particular area, they stop speaking, or the words start coming out slurred, or they can't remember the- the name of the object that they're seeing in the picture. These are all things that we're listening really carefully while we apply that, uh, focal stimulation. That's what we call brain mapping.
- AHAndrew Huberman
Uh, what are some of the more, uh, surprising, or maybe even if you want to offer one of the more outrageous examples of things that people have suddenly done or failed to be able to do as a consequence of this brain mapping?
- ECEddie Chang
Well, I think the thing to me that has been the most striking is that, you know, some of these areas you stimulate and altogether you can shut down someone's talking. So a person says, "I wanted to say it, but I couldn't get the words out." And even though I've seen this thousands of times now, it's still exciting every time that I see it because it's- it's exciting because you're seeing the brain. It's a physical organ. It's part of the body. Um, outside of the veins on top of it, doesn't look like, uh, a machine. But when you do something like that and you focally change the way it works and you see that because a person can't talk anymore and they say, "I know what I want to say, but I couldn't get the words out," you're confronted with this idea that, that that organ is the basis of speech and language, and way beyond that, obviously, you know, for all the other functions that we have for thinking and- and feeling, our emotions, everything. So that to me is a constant reminder of, you know, um, this really special thing that the brain does, which is compute, uh, so many of the things that we do, and in particular in the area around speech and language, generating words, something that is really unique to our species.... um, is, is just extraordinary to see. Again, even though I've seen it thousands of times, it's just having that connection, because it doesn't look like a machine, but it is doing something that is quite complicated, precise and remarkable.
- AHAndrew Huberman
Do you ever see
- 24:26 – 30:19
Emotion; Anxiety & Epilepsy
- AHAndrew Huberman
emotional responses from stimulation in particular areas? And do you ever hear or see emotional responses that are associated with particular types of speech? Because for, I, I would, for instance, curse words-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... uh, are known to, uh, people with Tourette's often will curse-
- ECEddie Chang
Sure.
- AHAndrew Huberman
Not always, but, uh, sometimes they'll have tics or other things.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
And, but, um, what I learned from a, a colleague of ours is that, um, curse words have a certain structure to them. There's usually a heavy, uh, or kind of a sharp consonant up front, right?-
- ECEddie Chang
Mm-hmm.
- AHAndrew Huberman
... that, uh, allows people, at least a- as it was described to me, to have some sort of emotional release. It's not a, a word like murmur-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... which has a kind of a soft entry.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
Here, I'm not using the technical language.
- ECEddie Chang
Yeah. Yeah.
- AHAndrew Huberman
And, uh, you pick your favorite curse word out there, folks. I'm not going to, um, shout out any now or say any now, but that certain words have a, have a structure to them that because of the motor patterns that are involved in j- in saying that word-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... it, you could imagine has a, an emotional response unto itself. So when stimulating or when blocking these different brain areas, do you ever see people get angry or sad or happy or more relaxed?
- ECEddie Chang
Oh. Well, um, definitely I've seen cases where you can e- invoke anxiety, stress, and I think that there are also areas that you can stimulate and you can also evoke, um, the opposite of that, sort of, like, a calm state.
- AHAndrew Huberman
Y- I think that brain area is, is slightly hyperactive in you. Uh, or at least-
- ECEddie Chang
(laughs)
- AHAndrew Huberman
... more than, uh, than me. In all the years I've known you, you've, you've always been, at least externally, a very calm person. I mean, I always find it amusing that you work on speech and language and you have-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... a very calming voice. Right? Um, and I'm being really serious. I think that there's a huge variation, yeah, right? I- in terms of how people speak and their, their, how they accent words.
- ECEddie Chang
Absolutely. Yeah. So there are areas, for example, um, the orbital frontal cortex that we showed, that if you stimulate there... The orbital frontal cortex is a part of the brain that's above the eyes. That's why they call it orbital frontal, uh, meaning it's above the eye or the orbit, and in the frontal lobe. And it's this area right in here. Uh, it has really complex functions. It's really important for learning and memory. But one of the things that we observed is when you stimulate there, it, people tended to have, um, a reduction in their stress. And it was very much related to their state of being, meaning that if someone was already kind of feeling normal and you stimulate there, it didn't do much, but if someone was in a very anxious state, it actually relieved that. And then we've seen the corollary of that, which is true too, which is that there are other areas like the amygdala or parts of the insula that if you stimulate, you can cause an acute temporary, uh, anxiety, a nervous feeling. Or if you stimulate the insula, people can have an acute feeling of disgust. So, um, you know, the brain has different functions and these different nodes that help process the way we feel. Uh, certainly, I think that, to some degree, neuropsychiatric conditions reflect an imbalance of the electrical activities in these areas. Um, one of the things that was something I will never forget was taking care of a young woman with uncontrolled seizures. Uh, we call that epilepsy. It's a medical condition where someone has uncontrolled electrical activity in the brain. Sometimes you can see that as convulsions, where people are shaking and lose consciousness. There are other kind of seizures that people can have where they don't lose consciousness, but they can have experiences that just come out of nowhere, and, uh, it's just a, it's a result of electrical activity coming from the brain. And, um, about six years ago, I took care of a young woman who was diagnosed psychiatrically with anxiety disorder for several years. It turns out that it wasn't really an anxiety disorder. It was actually that she had underlying seizures and epilepsy activating a part of her brain that evokes, you know, anxious feelings.
- AHAndrew Huberman
How did, how was that discovered? Because I know a lot of people out there have anxiety. I mean, how-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... with, in the absence of a brain scan, um, how would, or why would one suspect that maybe they have a, a tumor or, or some other, um, condition that was causing those neurons to become hyperactive?
- ECEddie Chang
Yeah. That's really important because so many people have anxiety, and the vast, vast majority are not having that because they're having seizures in the brain. I think one of the, the ways that this was diagnosed was that, um, the nature of when she was having these panic attacks was not triggered by anything. They would just happen spontaneously, and that's what can happen with seizures sometimes. They just come out of nowhere. We don't fully understand what can trigger them, but they weren't things that were typically anxiety-provoking. This is something that just happened all of a sudden. And because you brought it up, this is not something that you can see on an MRI. We could not see and look at the structure of her brain with an MRI, that she was having seizures. The only way that we could actually prove this was actually r- putting electrodes, uh, into her brain and proving that these attacks that she were hav- she was having were localized to a part called the amygdala, it's a medial part of the temporal lobe, which is here, and, um, associating the electrical activity that we were seeing on those electrodes with the symptoms that she, she had. And she ultimately needed a kind of surgery where she was awake, um, in order to remove this safely.
- 30:19 – 33:01
Epilepsy, Medications & Neurosurgery
- AHAndrew Huberman
Speaking of epilepsy, uh, a number of people out there have epilepsy or know people who do. Uh, are the drugs for epilepsy, um, satisfactory? You know, I think about things like Depakote and-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... you know, and adjusting the excitation and inhibition of the brain. I mean, are there good drugs for epilepsy? We know there are not-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... great drugs for a lot of other conditions, but, um... And how often does one need neurosurgery, uh, in order to treat epilepsy, or can it be treated ex- um, most often just using pharmacology?
- ECEddie Chang
Yeah. Great question. Well, um, a lot of people have seizures that can be completely controlled by their medications. A lot. Uh, but there's about a one third of people who have epilepsy, which we define as anyone who's had three or more seizures, um, that, you know, about a- a third of them actually s- don't have control with all of the modern medications that we have nowadays. And some of the data suggests that if you have two or three medications, it actually doesn't matter necessarily which of the anti-seizure medications it is, but there is data to suggest if you've just tried two or three, the fourth, fifth, sixth, and beyond is not likely to help control it. So, um, we are in a situation unfortunately where a lot of the medications are great for some people, but for another subset, they can't control it and it comes from a particular part of the brain. Now fortunately, in that subset, there's another part of that- that group that can benefit from a surgery that actually either removes that part of the brain, and nowadays we'll use stimulators now to, um, sometimes put electrical stimulation in that part of the brain to help reduce the seizures.
- AHAndrew Huberman
And you said a third of people with epo- epilepsy might need neurosurgery.
- ECEddie Chang
Well, what I, what I mean by that is, like, they continue to have seizures that are not controlled by all the medications, and there's going to be another subset of those that, uh, may benefit from a surgery. It's probably not that whole third. It's a subset of that. It's just to say that epilepsy can be really hard to get fixed, and, uh, for people where the seizures come from one spot or, you know, a- an area, then surgery can do great. If it coming from... If it comes from multiple areas or if it comes from the whole brain, then we have to think about other methods to control it. Fortunately, nowadays, there's actually other ways. Um, surgery now to us doesn't just mean removing part of the brain. Um, half of what we do now is use stimulators that modulate the state of the brain that can help reduce the seizures.
- 33:01 – 34:56
Ketogenic Diet & Epilepsy
- ECEddie Chang
- AHAndrew Huberman
I've heard before that the ketogenic diet was originally formulated in order to treat epilepsy, and in particular in kids.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
Is that true? And why would being in a ketogenic state with low blood glucose reduce seizures?
- ECEddie Chang
That's a great question, and, um, to be honest, I don't know actually if it was originally designed to treat seizures. But I can tell you for sure that for some people, just like with some medications, it- it can be a life-changing thing. It can completely change the way that the brain works, and it's not something that's for everybody. But for some people, there's no question it has some very beneficial effects. I think it's to be determined still, like, why, why and how that works.
- AHAndrew Huberman
I've heard similar things about the ketogenic diet for people with, uh, Alzheimer's dementia, that, um, there's nothing s- particularly relevant about ketosis to Alzheimer's per se, but because Alzheimer's changes the way that neurons metabolize energy-
- ECEddie Chang
Mm-hmm.
- AHAndrew Huberman
... that shifting to an alternate fuel source can sometimes make people feel better, and so a number of people are now trying it. But it's not as if, um, blood glucose and having carbohydrates is causing al- Alzheimer's. People get confused often that- that just because something, uh, can help doesn't mean that the opposite is- is harming, uh, somebody. So I find this really interesting. Uh, uh, sometime I'll check back with you about what's happening in terms of, uh, ketogenic diets and- and epilepsy. But it- you said that in some cases it can help. Has that observation been made both for children and for adults? Because I thought that originally the ketogenic diet for epilepsy was really for pediatric epilepsy.
- ECEddie Chang
Yeah, that's right. So a lot of its focus has really been on kids, uh, with epilepsy. But certainly it's a safe thing to try, so a lot of adults, you know, will try it as well.
- AHAndrew Huberman
Interesting. I'd like
- 34:56 – 36:10
AG1 (Athletic Greens)
- AHAndrew Huberman
to take a quick break and acknowledge one of our sponsors, Athletic Greens. Athletic Greens, now called AG1, is a vitamin mineral probiotic drink that covers all of your foundational nutritional needs. I've been taking Athletic Greens since 2012, so I'm delighted that they're sponsoring the podcast. The reason I started taking Athletic Greens and the reason I still take Athletic Greens once or usually twice a day is that it gets me the probiotics that I need for gut health. Our gut is very important. It's populated by gut microbiota that communicate with the brain, the immune system, and basically all the biological systems of our body to strongly impact our immediate and long-term health. And those probiotics in Athletic Greens are optimal and vital for microbiotic health. In addition, Athletic Greens contains a number of adaptogens, vitamins and minerals that make sure that all of my foundational nutritional needs are met, and it tastes great. If you'd like to try Athletic Greens, you can go to athleticgreens.com/huberman and they'll give you five free travel packs that make it really easy to mix up Athletic Greens while you're on the road, in the car, on the plane, et cetera, and they'll give you a year's supply of vitamin D3 K2. Again, that's athleticgreens.com/huberman to get the five free travel packs and the year's supply of vitamin D3 K2.
- 36:10 – 41:08
Absence Seizures, Nocturnal Seizures & Other Seizure Types
- AHAndrew Huberman
I'm curious about epilepsy, uh, for another reason. Um, I was taught that epilepsy is an imbalance in the excitation and inhibition in the brain. So you think about these electrical storms-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... that give people either grand mal, you know, shaking and kind of convulse- and convulsions.
- ECEddie Chang
Right.
- AHAndrew Huberman
But, uh, years ago I was reading a book, a wonderful book actually, Einstein in Love by Dennis Overby. It was about Einstein and his more, um, I guess his personal life. But in-People who knew him claimed that he would sometimes walk along and then every once in a while would just stop and kind of stare off into space for anywhere from a minute to three or to five minutes.
- ECEddie Chang
Hmm.
- AHAndrew Huberman
And it was speculated that he had absence seizures. What is an absence seizure? And the reason I ask is I, um, occasionally will be walking along, and I'll be thinking-
- ECEddie Chang
Yeah. (laughs)
- AHAndrew Huberman
... about something and I'll stop, but I, in my mind, I- I think I- I'm thinking during that time, but I realize that if I were to see myself from the outside, it might appear that I was just kind of absent. What is an absence seizure? Because it's so strikingly different in its description from, say, a grand mal convulsive seizure.
- ECEddie Chang
Sure. Well, um, like I mentioned before, depending on how the seizure activity spreads in the brain or how it actually propagates, if it stays in one particular spot and doesn't spread to the entire brain, it can have really different manifestation. Uh, it can represent really differently. So absence seizure is just one category of different kind of seizures where, um, you can lose consciousness basically, and what I mean by that is that you're not fully aware of what's going on in your environment, okay? So you're sort of taken offline temporarily from consciousness. But you could still be, for example, standing, and to people who are not paying attention, they may not even be aware that that's happening.
- AHAndrew Huberman
What are some other types of seizures?
- ECEddie Chang
Well, um, you know, I think some of the other kinds are, the classic ones are temporal lobe seizures. So these are ones that come from the medial structures like the amygdala and hippocampus. Uh, oftentimes, people, when they have seizures coming from that, they may taste something very, uh, unusual, like a metallic taste or smell something like the smell of burning toast, something like that. Um, there are some people will, uh, with temporal lobe seizures will have deja vu. They will have that experience that you've been somewhere before, but, um, that's just a precursor to the seizure. And it just highlights that when people have seizures coming from these areas, they sometimes hijack what that part of the brain is really for. So the amygdala and hippocampus, for example, are really important for learning and memory. It's not surprising that when people have seizures there that it can evoke a feeling of deja vu or that it can evoke a feeling of anxiety. Um, and, um, in the areas that are right next to it, for example, uh, these areas are really important for processing, uh, smell. So, uh, these areas are right next to each other, so you can have these kind of complex set of symptoms, the weird taste, the smell of toast, and then a feeling of deja vu. That's classic for temporal lobe seizure, and it's because those parts of the brain that process those functions are right next to each other.
- AHAndrew Huberman
I'm told that I've had nocturnal seizures and I've woken up sometimes from sleep having felt as if I was having a convulsion, a sort of sense of buzzing in the back of the head.
- ECEddie Chang
Hmm.
- AHAndrew Huberman
Um, this happened to me two or three times in college. My girlfriend... Um, well, I woke up and my girlfriend was very distraught, like, "You were having a seizure." I was having a full convulsion in my sleep. Uh, what are... D- Is that correct? Are there, is there such a thing as nocturnal seizures? What do they reflect? They eventually stopped happening, and I couldn't tether them to any kind of life event. I wasn't doing any kind of combat sport or anything at the time. I wasn't drinking alcohol much. It's never really been my thing. Uh, what are nocturnal seizures about?
- ECEddie Chang
Oh, uh, well-
- AHAndrew Huberman
And do I need brain surgery? (laughs)
- ECEddie Chang
(laughs) Um, nocturnal seizures are just another form. Like, again, epilepsy and seizures can have so many different forms, and, uh, not just like where in the brain, but also when they happen. And there are some people who, uh, for whatever reason, it's very timed to the circadian rhythm.
- AHAndrew Huberman
Hmm.
- ECEddie Chang
There's actually not just happening at night, but a certain period at night when people are in a certain stage of sleep that the brain is in a state that it's vulnerable to- to having a seizure. And so that's basically just one form of that. Again, it's not just about where it's coming from, but also when it's happening and how that's timed with other things that are happening with the body.
- AHAndrew Huberman
Interesting. Well, it eventually stopped happening, so I- I stopped worrying about it.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
But, um, I haven't had seizures since.
- 41:08 – 53:23
Brain Areas for Speech & Language, Broca’s & Wernicke’s Areas, New Findings
- AHAndrew Huberman
Returning to speech and language. Uh, when I was getting weaned (laughs) in neuroscience, I learned that we have an area of the brain for producing speech and we have an area of the brain for comprehending speech.
- ECEddie Chang
Mm-hmm.
- AHAndrew Huberman
What's the story there? Is it still true that we have a Broca's and a Wernicke's area? Um, those are names of neurologists presumably or neurosurgeons-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... that discovered these different brain areas. Um, maybe you could familiarize us with some of the- the sort of textbook version of how speech and language are organized in the brain. Maybe share with us a little bit of the lesion studies that led to that understanding, and then I would love to hear a bit about what your laboratory is discovering about how things are actually organized, because from some discussions you and I have had over the last year or so, it seems like... Well, let's just be blunt. It seems that, uh, much of what we know from the textbooks could be wrong.
- ECEddie Chang
Well, um, I- I love that question because, for me, it's very central to the research we do and it's where the intersection between what we do in the- in the laboratory and our research interfaces with what I see in patients. And one of the things that fascinated me early on in my medical training was, in doing some of these brain mapping or watching 'em with my mentor or taking care of patients that had, you know, brain tumors in a certain part of the brain, was that a lot of times what I was seeing in a patient did not correlate with what I was taught in medical school, and-You know, some people will think, "Well, um, this might be an exception." But after you see it for a couple of times and if you're kind of interested in this problem, it poses a pro- you know, it poses a serious challenge to what you've learned and how you think about how these things, um, operate. And that actually got me really interested in trying to figure this out. Because earlier, we talked about just this extraordinary thing that the brain is doing to create words and sentences, and that's the process by which I'm getting ideas out from my mind into yours. It's an incredible thing, right? It's the basis of communication, um, um, high, high information communication between two individuals that's really unique to humans. So in his- in historical times, it... How this works has been very controversial from day one of neuroscience. Um, a long time ago, people thought the bumps on your head corresponded to the different faculties of the mind. So, for example, if you had a bump here, it might be corresponding to intelligence or another one over here, you know, to vision and these kind of things. Um, that's what we nowadays call phrenology, and, um, that was kind of the starting point, a lot of that has been, of course, debunked but when you see those little statues of different brain partitions on someone's head, that's essentially what... how people were thinking about how the brain worked back then, um, a couple hundred years ago. Modern neuroscience began when... actually, it was very much related to the discovery of language. So modern neuroscience, meaning moving beyond this idea that the bumps on the scalp corresponded to the faculties of the mind, but there were things that actually were in the brain themselves and they weren't corresponding to things that you could see superficially like on the scalp or, um, externally, that it was something about the brain itself. I mean, it seems so obvious now (laughs) but back then, this was the big academic, you know, debate. And the first observation that I think really was really impactful in, in the area of language was an observation by a neuros- neurosurgeon, a French neurosurgeon named Pierre Broca. And what he observed was that, uh, in a patient, not that he did surgery but that he had seen and taken care of, that the person couldn't talk, and in particular, they called this individual Tan because the only words that he could produce was, "Tan. Tan." For the most part, he could generally understand the kind of things that people were asking him about, but the only thing that he could utter from his mouth were these words, "Tan. Tan." And what eventually had happened was this individual passed away, and the way that neuroscience was done back then was basically to wait until that happened and then to remove the brain and to see what part of the brain was affected in this patient that they called Tan. And what Broca found was that there was a part in the left frontal lobe. So the frontal lobe is this area like I described earlier which is behi- you know, up behind our forehead up here, and in the back of that frontal lobe, he claimed that this was the seat of articulation in the brain. He literally used something like that in French, "The seat of articulation," meaning that this is the part of the brain that is responsible for us to generate words. About 50 years later, the story becomes more complicated with a German neurologist named Carl Wernicke, and what Wernicke described was a different set of symptoms in patients that he observed a different phenomenon where people could produce words but a lot of the wor- and they were fluent in the sense that they had, like, um, they sound like they could be real words but from a different language, for example. And some of us call that, like, word salad or jargon. It's essentially they were essentially making up words but it was not intentional. It's just the way that the words came out. But in addition to that, he observed that these people also could not understand what was being said to them. So, uh, you, we could be having a conversation and I'd be asking you, "Uh, am I a woman?" and you might nod your head, you know, just because you're not processing the question, you know? And so, um, here are two observations. One is that the frontal lobe is important for articulating speech, creating the words and expressing them fluently, and then a different part of the brain called the left temporal lobe, which is this area right above my ear, that is an area that I think was, um, claimed to be really important for understanding. So the two major functions in language, to speak and to understand, were kind of pinned down to that, and we've had that basic idea in the textbooks for, you know, over 200 years.
- AHAndrew Huberman
Certainly what I was taught.
- ECEddie Chang
Is that right?
- AHAndrew Huberman
Oh, every... Yeah, and certainly-
- ECEddie Chang
Well-
- AHAndrew Huberman
... what we still, we still teach-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... undergraduates, graduate students, and medical students that.
- ECEddie Chang
Well, that's what I learned, too, in medical school, and what I saw in reality when I started taking care of patients was that it's not so simple. Um, in fact, part of it is fundamentally wrong. So just in a nutshell-Nowadays, uh, after, you know, looking at this very carefully over hundreds of patients, we have shown that surgeries, for example, in the posterior part of the frontal lobe, a lot of times people have no problem talking at all, at all, whatsoever after those kind of surgeries, and that it's a different part of the brain that we call the precentral gyrus. Um, the precentral gyrus is a part of the brain that, uh, is intimately associated with the motor cortex. The motor cortex is the part of the brain that has a map of your entire body so that it has a part that corresponds to your feet, it has a part that corresponds to your hands, but then there's another part that comes out more laterally on the side of the brain that corresponds to your lips, your jaw, your larynx. And we have s- seen that when patients have surgeries or injuries to that part of the brain, it actually can really interrupt language. So it's not as simple as just moving the muscles of the vocal tract, but it's also important for formulating and expressing words. So that's Broca's area that I think the field now recognizes, not just because of our work, but many other people that have studied this in stroke and beyond, is that the idea that that is the, the basis of speaking in Broca's area is fundamentally wrong right now, and we have to figure out how to correct the textbooks that we kind of understand that so that we can continue to, to make progress. Now, in terms of the other major area that we call Wernicke's area in the posterior temporal lobe, um, that has held, held f- uh, I think quite legitimately for some time. So that is an area that you have to be super careful when you do surgery there. That's an area where if you have a mistake there and you cause a stroke or you remove too much of the tumor there, you go too far beyond it, then the person can be really, really hurt. Like, they'll have a condition that we call aphasia, where they may not be able to understand words, they may not be able to, uh, remember the word that they're, that they're trying to say. They, they know what they're trying to say, but they can't remember the precise word that goes with the object that they're trying to think of. They may even produce words that I described before are like word salad or very jargony. So ins- you know, they might say something like, "Tamirinai." That's not a real word, but it sounds like it could be, you know? And that's just because that part of the brain has some role not just in understanding what we hear, but also actually has a really important role in sending the commands to different parts of the brain to control what we say.
- AHAndrew Huberman
Not long ago, you and me and my good friend Rick Rubin were having a conversation about medicine and science, and Rick asked the question, "What percentage of what you learned in graduate and/or medical school do you think is correct?" And you had a very interesting answer. Would you share it with us?
- ECEddie Chang
Um, I don't know. I don't remember the exact, but I, I would say that, um, with regard to the brain in particular, I would say about 50% gets it right and accurate and is helpful, but another 50% is just the approximation and oversimplification of what's going on. The example that we talked about, language, just an example of that. It's just, um, there are things that make it easier to learn and easier to teach and easier to even think about, and that's probably why we continue teaching in the way that we do. But I think as time goes on, the complexity of, of reality of how the brain works is, um... Well, first of all, we're still trying to figure it out, and second of all, it, it is complex and it is, it's still incomplete story.
- AHAndrew Huberman
It's early days. And we'll, we'll get into some of the technical advances that are allowing some correction of the errors that the field has made, and look, no disrespect to the brain explorers that came before us and, uh, the ones that come after us will correct us, right? That's the way the game is played. But, um, what I'm hearing is that there are certain truths that people accept and then there's, um, about half of the information that is still open for debate and maybe even for complete revision. One
- 53:23 – 59:05
Lateralization of Speech/Language & Handedness, Strokes
- AHAndrew Huberman
thing that I learned about language and the neural circuits underlying language is that it's heavily lateralized, that these structures, Broca's and Wernicke's and other structures in the brain responsible for speech and comprehension of speech, sit mainly on one side of the brain, but they do not have a mirror representation or another ar- equivalent area on the opposite side of the brain. And for those that haven't, um, poked around in a lot of brains, um, certainly, you, Eddie, have done far more of that than I have, but I've done my fair share in non-human species and a little bit in humans, almost every structure, almost every structure has a matching structure on the other side of the brain. So when we say the hippocampus, we really mean two hippocampi, one on each side of the brain. But language, I was taught, is heavily lateralized, that is that there's only one. So that raises two questions. One, is that true? And if it is true, then what is the equivalent real estate on the opposite side of the brain doing-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... if it's not doing the same function that the one on the, say, the left side is performing?
- ECEddie Chang
Well, that's one of those things that is, again, like, mostly true, not 100%. And what I mean by that is that, um, it's complicated. So for people who are right-handed, 99% of the time, the language part of the brain is on, on the left side.
- AHAndrew Huberman
And what is the equivalent brain area on the right side doing, if it's not doing language?
- ECEddie Chang
Well, you know, the thing that's incredible is if you look at the right side and you look at it very carefully, either under an MRI or you actually look at the brain under slides in a microscope, it looks very, very similar. It's not identical, but it looks very, very similar. All the gyri, which are the, the bumps on the brain that, you know, have the different contours and the valleys that we call sulci, those all look basically the same, like there is a mirror anatomy on the left and right side. And so it's not been so clear what's so special actually about the left side to, um, to house language. But what we do know, and this is what we use all the time in assessing and figuring out, you know, this before surgery, is if you're right-handed, 99% of the time, the language is gonna be on the left side of the brain.
- AHAndrew Huberman
Is handedness genetic in any way?
- ECEddie Chang
Yes.
- AHAndrew Huberman
I mean, when I was ... grew up, I ... a pen or pencil was ... or crayon was placed into my hand presumably or I started using my ... My father was left-handed, and then, uh, where he grew up in South America, they've, they forced him to r- to force himself to become right-handed. They actually used to restrict the movement of his left hand, so he was forced to write. So, um, and then you have hook-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... hook lefties-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... and hook righties, and-
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... um, I know this is a deep dive, and we probably don't want to go into every derivation of this.
- ECEddie Chang
(laughs) .
- AHAndrew Huberman
But f- so for somebody who's left-handed, naturally just starts writing with the left hand, there's some genetic predisposition to being left-handed?
- ECEddie Chang
Absolutely. No question about it. Handedness is, is not entirely, but strongly genetic. So, uh, there is something about ... that ties all of this. And what does handedness, for example, have to do with where, the part of your brain that controls language? Well, it turns out that the parts that control the hand are very close to the areas that really are responsible for the vocal tract. Uh, again, part of the motor cortex and part of this brain area called the precentral gyrus. And there are some theories that because of their proximity, um, that these parts of the brain might develop together early in utero and they might have a head start compared to the right side, and because they have a head start, that things solidify there. This is one theory of why this happens. In people who are left-handed, it still turns out that the vast majority of people have language on the left side, but it's not 99%, it's more like 70%. So if you're left-handed, still more likely that the language part of your brain is gonna be on the left side, but there's gonna be a greater proportion, maybe 20, 30%, where it's either in both hemispheres or on the right side. And just to make this a little bit more interesting, is that when people have strokes on the left side, and if they're lucky enough to recover from those strokes, sometimes that involves reorganization, this term that we call plasticity earlier, where the areas around where the stroke take on that new function in a way that they didn't have before. That can certainly happen in the left hemisphere. But there are also instances where the right hemisphere can also start to take on the function of language, where it ... when it was once the left and then transfers to the right. So the thing that I, I think about a lot is that, that the machinery probably exists on both sides, but we don't use them together all the time. In fact, we may strongly bias one side or the other, just like we use our two hands in very, very different ways. It's a little bit the same with the brain. Well, it's because of what we do with the brain that actually is why we use the hands in different ways. And the same thing goes for language, which is, again, the substrates, the organ, the language organ, the part of the brain that process it probably has very similar machinery on the left side as the right, and the right may have the capability to do it. But in real everyday use, the brain specializes one of the sides in order for us to, to use it functionally. That's, that's a theory.
- AHAndrew Huberman
You're bilingual,
- 59:05 – 1:01:18
Bilingualism, Shared Language Circuits
- AHAndrew Huberman
correct?
- ECEddie Chang
Yeah.
- AHAndrew Huberman
You speak English and Chinese?
- ECEddie Chang
Yeah.
- AHAndrew Huberman
For people that are bilingual and that learn two or more lang- well, bilingual is two obviously, but learn both languages, or let's say more languages from an early time in life, do they use the same brain area to generate that language? Or perhaps they use the left side to speak English and the right side to speak Chinese. Do we know anything about bilingualism in the brain?
- ECEddie Chang
I think we know a lot about bilingualism in the brain. The answers are still out there, the final answers on it, and part of the answer is yes, absolutely, we use some parts of the brain, um, very similarly. Uh, we actually have a study in the lab right now where we're looking at this, where people who speak one language or another or bilingual, uh, and we're looking at how the brain activity patterns, uh, occur when they're hearing one language versus the other. And what's striking to see actually is how overlapping they really can be. Even though the person may have no idea (laughs) of the language that they're hearing, um, the English part of the brain is still processing that and maybe trying to interpret it through, uh, an English lens, for example. So the short answer is that with bilingualism, there are shared circuitry, there sh- there's this shared machinery in the brain that allows us to process both. Um, but it's not identical. Um, it's the sh- it's the same part of the brain, but what it's doing with the signals can be very, very different. And what I mean by that precisely is not the instantaneous detecting of one sound to the next but-... the memory of the sequences of those particular sounds that give rise to things like words and meaning, that can be highly variable from one individual to the next, and those neurons are very, very sensitive to the sequences of the sounds even though the sounds themselves might have some overlap between languages.
- AHAndrew Huberman
Fascinating. Okay, so we've talked about brain areas and a little bit about lateralization. I want to get back to the hands and some things-
- ECEddie Chang
Right.
- AHAndrew Huberman
... related to emotion in a little bit. But
- 1:01:18 – 1:12:38
Speech vs. Language, Signal Transduction from Ear to Brain
- AHAndrew Huberman
maybe now we could go into those brain areas-
- ECEddie Chang
Okay.
- AHAndrew Huberman
... and start to ask the question, what exactly is represented or mapped there? And for people who perhaps aren't familiar with brain mapping and representation and receptive fields, perhaps the simplest analogy might be the visual system, where I look at your face, I know you, I recognize you, and certainly there are brain areas that are responsible for face recognition. But the fact that I know that that's your face, and for those listening I'm looking at Eddie's face, the fact I know that that's your face at all is because we are well aware that there are cells that represent edges and that represent dark and light, and those all combine in what we call a hierarchical structure. They sort of build up from basic elements as simple as little dots, but then lines and things that move, et cetera, to give a coherent representation of the face. When I think about language, I think about words and just talking. If I sit down to do a long podcast or I think about asking you a question, I don't even think about the words I want to say very much. I mean, I have to think about them a little bit, one would hope, but I don't think about individual syllables unless I'm trying to in- you know, accent something or it's a word that I have a particular difficulty saying where I want to change the cadence, et cetera. So what's represented in the, in the neurons, the nerve cells in these areas? Are they representing vowels, consonants, and how do things like inflection, like, I occasionally will poke fun at up speak-
- ECEddie Chang
Mm.
- AHAndrew Huberman
... but there's a, I think a healthy (laughs) , a normal (laughs) , uh, version of up speak where somebody's asking a question like, for instance, "What is that?" That's an appropriate use of up speak, as opposed to saying something that is not a question and putting a lilt at the end of the sentence. Then we call that up speak, which it doesn't fit with what the person is saying. So what in the world is contained in these brain areas, what is represented, um, to me is, is perhaps one of the most interesting questions, and I know this lands square in your wheelhouse.
- ECEddie Chang
Sure. Let's get into this, uh, Andrew, because this is one of the most exciting stuff that's happening right now is understanding how the brain processes these exact questions. And you asked me earlier, wh- you know, what is the difference between speech and language, uh, speech corresponds to, um, the communication signal. It corresponds to me moving my mouth and my vocal track to generate words, and your hearing these is an auditory signal. Language is, um, something much broader. So it refers to, uh, what you're extracting from the words that I'm saying, we call that pragmatics, and sort of, are you getting the gist of what I'm saying? There's another aspect of it that we call semantics. Do you understand the meaning of these words and, uh, the sentences? There's another part that we call syntax, which refers to how the words are assembled in a grammatical form. So those are all really critical parts of language, and speech is just one form of language. There's many other forms, like sign language, uh, reading. Those are all important modalities for reading. Our research really focuses on s- on this, this area that we're calling speech. Again, the production of this audio signal, which you can't see but your microphones are picking up. There are these vibrations in the air that are created by my vocal track that are picked up by the microphone, uh, in the pa- in the case of this recording, but also picked up by the sensors in your ear. The very tiny vibrations in your, uh, ear are picking that up and translating that into electrical activity. And what the ear does at the periphery is translates all sounds into different frequencies. So its main thing to do is to take, uh, a speech signal or any other kind of sound and decompose it, meaning separate that sound into different kind of signals. And in the case of hearing, what it's doing is separating it out into low, middle, high frequencies at a very, very high resolution. It's doing it very quickly and it's doing it in a really fine way to separate all of those different sounds. So if you look at the periphery near the nerve that goes to your ear, those nerve fibers, some of them are tuned to low frequencies, some of them are tuned to high frequencies, some of them are tuned to the middle frequencies, and that is what your ear is doing. It's taking these words and splitting them up into different frequencies.
- AHAndrew Huberman
And for those of you out there that aren't familiar with thinking about things in the so-called frequency space, um, base tones would be lower frequencies and high-pitched tones would be higher frequencies, just to, to make sure everyone's on the same page. So, uh, th- the sound of my voice, the sound of your voice, or any sound in the environment is being broken down into these frequencies. Are they being broken down into very narrow channels of frequency or are they, um, I want to avoid nomenclature here, um, or are they, uh, or are they being binned as fairly broad frequencies? 'Cause we know low, medium, and high, but, um, for instance, I can detect whether or not something's approaching me or, or moving away from me depending on whether or not it sweeps louder (imitates sound)
- ECEddie Chang
Yeah.
- AHAndrew Huberman
... or (imitates sound) right?
- ECEddie Chang
Yeah.
- AHAndrew Huberman
Towards or away. It's subtle, but, and of course it's combined with what I see and my own movement, but, um, how finely sliced is our perception of the auditory world?
- ECEddie Chang
Oh, e- extraordinarily precise. I mean, we take these millisecond cues-... the millisecond differences between the sound coming to one ear, let's say your right ear versus your left, to understand what direction that sound came from. Those are only millisecond differences, and that's how precise this works. But on the other hand, um, it does a lot of computation on this, it does a lot of analysis as you go up, and a lot of our work is focused on the, the part of the brain that we call the cortex. The cortex is the, the outermost part of brain where we believe that sounds are actually converted into words and language. So there's this transformation where at the ear words are decomposed and, you know, turned into these elemental frequency channels, and then as it goes up through the auditory system, hits the cortex, there are some things that happen obviously before it gets to the cortex, but when it gets to cortex, there's something special going on, which is that that part of the brain is looking for specific sounds, and specifically, what I mean by that is the sounds of human language, so the ones that are the different consonants and vowels in a different language. One of the ways that we have studied this is looking in patients who have epilepsy, and in a lot of these cases where the MRI looks completely normal, we have to put electrodes surgically on a part of the brain. Uh, the temporal lobe is a very, very common place where we've done a lot of our work looking at how the temporal lobe processes speech sounds, because we're looking for, uh, where the seizures start, but then we're also doing brain mapping for language and speech so we can protect those areas. We want to identify the areas that we want to remove to cure someone's seizures, but we also want to figure out the areas that are important for speech and language to protect those so that we can do a surgery that's effective and safe. And so in our research, and why it's become a really important addition to our knowledge is that we have electrodes directly recording from the human brain surface. Uh, a lot of technology we work with right now is recording on the mil- on the order of millimeters, and they can order, they can record millisecond time resolution of neural activity. And what we see is extraordinary patterns of activity when people hear words and sentences. If you look at that part of the brain that we call Wernicke's area in this part of the temporal lobe, this whole area lights up when you hear words or speech. And it is not in a way that is like a general light bulb warming up, and it's generally lit up, but what you actually see is something much, much more complicated, which is a pattern of activity. And what we've done in the last 10 years is t- try to understand what does that pattern come from, and if we were to look at each individual site from that part of the brain, what would we see? What parts of words are being coded by electrical activity in those parts of the brain? Remember, the cortex is using electrical activity to transmit information and do analysis, and what we're doing is we're eavesdropping on this part of the brain as it's processing speech to try to understand what each individual site is doing.
- AHAndrew Huberman
And what are those sites doing? Or could you give us some examples of what those sites are doing? So for instance, are they sites that are specific for, or we could say even listening for consonants or for vowels or for, uh, inflection or for emotionality? What's in there?
- ECEddie Chang
Okay, well-
- AHAndrew Huberman
What makes these, what, what makes these cells fire?
- ECEddie Chang
Yeah. What gets them excited?
- AHAndrew Huberman
Yeah.
- ECEddie Chang
What gets them going is hearing speech. In particular, there are some of these really focal sites, again, just on the order of millimeter or at some level single neurons, that are tuned to consonants, some are tuned to vowels. Some are t- tuned to particular features of consonants. What I mean by that are different categories of, uh, consonants. There's a class of consonants that we call plosive consonants. This is a little bit of linguistic jargon, but I'm going to make a point here with that is that certain classes of sounds, when you make them, it requires you to actually close your mouth temporarily.
- AHAndrew Huberman
Hmm. Now, I'm going to be thinking about this. So plosive, like plosive, like saying the word plosive does, requires that.
- ECEddie Chang
Exactly. So what's cool about that is that we actually have no idea what's going on (laughs) in our mouth when we speak. We really have no idea.
- AHAndrew Huberman
Some people definitely have no idea. (laughs)
- ECEddie Chang
Yeah. (laughs) Well, not just, like, in terms of what you're saying sometimes-
- AHAndrew Huberman
Sure.
- ECEddie Chang
... but actually, like, how you're actually moving-
- AHAndrew Huberman
Right.
- ECEddie Chang
... you know, the different parts of vocal tract. And I have a feeling if we actually required understanding, we would never be able to speak because it's so complex. It's such a complex feat. Some people would say it's the most complex motor thing that we do as a species is, is this speaking, not, you know, the extreme feats of acrobatics or athleticism, but speaking.
- AHAndrew Huberman
Well, and especially when, uh, one observes, you know, uh, opera or, um, people who, you know, freestyle rappers, you know, and, and of course, it's not just the lips, it's the tongue.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
And, and you've mentioned two, um, other structures, pharynx and larynx are the main ones that they-
- ECEddie Chang
Yeah.
- 1:12:38 – 1:17:37
Shaping Breath: Larynx, Vocal Folds & Pharynx; Vocalizations
- AHAndrew Huberman
can you tell us, just, uh, just educate us at a su- at a superficial level what the ph- ph- pharynx and larynx do differentially? 'Cause I think most people aren't going to be familiar with that.
- ECEddie Chang
Okay, sure. So, um, I'll talk primarily about the larynx here for a second, which is that if you think about when we're speaking, um, really what we're doing is we're shaping the breath. So even before you get to the larynx, you got to start with the expiration.So we fill up our lungs and then we push the air out. That's a normal part of breathing. And what is really amazing about speech and language is that we evolved to take advantage of that normal physiologic thing, add a larynx, and what the larynx does is that when you're exhaling, it brings the vocal folds together. Some people call them vocal cords. They're not really cords, they're really vocal folds, they're two pieces of tissue that come together and a muscle brings them together. And then what happens is when the air comes through the vocal folds when they're together, they vibrate, uh, at really high frequencies, like 100 to 200 hertz. Yours is probably about 100 hertz. The average-
- AHAndrew Huberman
Whereas yours is 200? (laughs)
- ECEddie Chang
(laughs) No, no. Uh, ours is, most male voices are around 100, okay, and then the average female voice around 200 hertz.
- AHAndrew Huberman
Well, and as you know, I've always had the same voice.
- ECEddie Chang
Yes, yes, the same.
- AHAndrew Huberman
This is, uh, was a point of shame when I was a kid.
- ECEddie Chang
(laughs)
- AHAndrew Huberman
Folks, my voice never changed. I always had the same voice. This is a discussion for another time.
- ECEddie Chang
Yeah. Well, it's a great voice, uh, you know, a great baritone voice. But I know in your voice it's a low frequency voice, and the reason why men and women generally have different, um, voice qualities is it has to do with the size of the larynx and the shape of it. Okay, so in general, men have a larger voice box or larynx, and the vibrating frequency, the resonance frequency of the vocal folds when the air comes through them is about 100 hertz for men and about 200 for women. So what happens is, okay, so you're taking, you take a breath- breath in, and then as the air is coming out, the vocal folds come together and the air goes through. That creates the sound of the voice that we call voicing, and that's the energy of your voice. It's not just your voice characteristic, it's the energy of your voice is coming from the larynx there. It's a noise. And then it's the source of the voice, and then what happens is that energy, that sound goes up through the parts of the vocal tract like the pharynx into the oral cavity, which is your mouth and your tongue and your lips, and what those things are doing is that they're shaping this- the air in particular ways that create consonants and vowels. So that's what I mean by shaping the breath. It just starts with this exhalation. You generate the voice in the larynx, and then everything above the larynx is moving around, just like the way my mouth is doing right now, to shape that air into particular patterns that you can hear as words.
- AHAndrew Huberman
Fascinating and, uh, immediately makes me wonder about sort of more, um, primitive or non-learned vocalizations like crying or laughter. Babies will cry. Babies will show laughter. Are those sorts of, uh, vocalizations produced by the language areas like Wernicke's, or do they have their own unique neural structures?
- ECEddie Chang
Yeah, interesting question. So we- we call those vocalizations. Um, a vocalization is basically where someone can create a sound like a cry or a moan, um, that kind of sound, and it also involves the exhalation of air. It also involves some phonation at the level of larynx where the vocal folds come together to create that audible sound. But it turns out that those are actually different areas. So people who have injuries in the speech and language areas oftentimes can still moan, they can still vocalize, and it is a different part of the brain. I would say an area that, uh, even non-human primates have that can be specialized, you know, for vocalization. It's a different form of communication than- than words, for example.
- AHAndrew Huberman
The intricacy of these circuits in the brain and their connections to the pharynx and larynx, uh, is, uh, just, it's almost overwhelming in terms of thinking about just how complicated it must be, and yet some general features and principles are starting to emerge from your work and from the work of others. If we think
- 1:17:37 – 1:20:26
Mapping Language in the Brain
- AHAndrew Huberman
about that work and we think about, for instance, Wernicke's area, if I were to record from neurons in Wernicke's area, um, at different locations, would I find that there's any kind of systematic layout? For instance, in terms of we've talked about sound frequency, we know that low frequencies are represented at one end of a structure and high frequencies at the other. This is true actually, at least from my earlier training, within the- within the ear itself, within the cochlea, the early work of von Bekesy and from cadavers, right? They actually figured this out from dead people, which is incredible. Uh, a fascinating literature people should look up. Um, and in the visual system, we know that, for instance, you know, visual position where things are is mapped systematically. Neur- in other words, neurons that sit next to each other in the brain represent portions of visual space that are next to each other in the real world. What is the organization of language in areas like Wernicke's and Broca's? For instance, um, I think of the vowels A, E, I, O, U, uh, as a kind of a coherent unit, but do I find the A neurons are next to the E neurons are next to the, uh, or the val- the A, E, I, O, U? Is that vowel representation also laid out in order, or is it kind of salt and pepper? Is it random?
- ECEddie Chang
That's been one of the, like, most important questions we've been trying to answer for the past decade. So, uh, there is a part of the brain that we call the primary auditory cortex, and the primary auditory cortex is deep in the temporal lobe. And if you looked at-That part of the brain, there is a map of different sound frequencies. So if you look at the front of that primary auditory cortex, you'll find low frequency sounds, and then as you march backwards in that, that cortex, it goes from low to medium to high frequencies. It's organized in this really nice, nice and orderly way. And it turns out there's just not just one, there's, like, mirrors of that, um, tone frequency map in the primary auditory cortex. The areas that are really important for speech, uh, are on the side of that, and we now think that speech can go straight to the speech cortex without having to go through the primary auditory cortex, that it has its own pathway to get to the part of the brain, uh, that processes speech. And when we've looked at that question about is there a map, the short answer is yes, there is a map, and it is, um, but it is not structured, uh, universally across all people in a way that we can clearly see right now. It is like a salt and pepper map of the different features in speech. So
- 1:20:26 – 1:25:07
Plosives & Consonant Clusters; Learning Multiple Languages
- ECEddie Chang
before we talked about these sounds that are called plosives. You make a plosive when the mouth or something in the oral cavity closes temporarily, and when it opens, that creates that fast plosive sound. So when you say, um, dad, um, or, um, you know, the ball, like the B in ball, that kind of thing, you will notice that your, your lips actually close, and then it's the release of that that creates that particular sounds. Okay. So those are the sounds that we call plosives. Those are like ba, da, ga, pa, ta, ka. Those are a certain class of consonants that we call, uh, plosive sounds. There's another class of sounds that we call fricatives in linguistics. Fricatives are created by turbulence in the, the airstream as it comes out through the mouth, and the, and the, the way that we make that turbulence is getting the mouth and the lips to close almost until they're completely shut or putting the tongue to near the teeth to almost get it completely shut, but just have a narrow aperture. That creates a turbulence in the airflow that we perceive as a high frequency sound. So those are the sounds like shuh, and thuh, those kind of things. Those are, if you look at the frequencies, they're higher frequencies, and those are created by specific movements that you constrict the airflow to create turbulence and we hear it as shuh, suh, thuh.
- AHAndrew Huberman
So if I say that?
- ECEddie Chang
Exactly.
- AHAndrew Huberman
And as opposed to a plosive where I'd say explosive?
- ECEddie Chang
Right.
- AHAndrew Huberman
I'm now, of course I'm emphasizing here.
- ECEddie Chang
Yeah.
- AHAndrew Huberman
Well, this explains and, uh, something and solves a mystery which is recently, I've been fascinated by the work of a, of a physician scientist, um, back east, uh, Dr. Shanna Swan who's done a lot of work on, um, things that are contained in pesticides and foods that are changing hormone levels, and she refers to phthalates which is spelled P... (laughs) So it's both a plosive and a thuh.
- ECEddie Chang
Yeah. Yeah.
- AHAndrew Huberman
So it's combining the two, and it's one of the most difficult words in the English language to pronounce, um, second only perhaps to the correct pronunciation of ophthalmology. (laughs)
- ECEddie Chang
Yeah. (laughs)
- AHAndrew Huberman
So it's a combination of a, of a plosive and one of these thuh sounds, and that's probably why it's difficult.
- ECEddie Chang
That's exactly right. In fact, um, we have a term for that that's called a consonant cluster. So sometimes syllables will just have one consonant, but when we start stacking certain syllables in a sequence and there's rules that actually govern which consonants can be in a particular sequence for a given language, um, that be- that makes it more complicated. And certain languages have a lot more consonant clusters than others. So for in-
- AHAndrew Huberman
For instance?
- ECEddie Chang
So for instance, Russian, for example, has a lot of constant clusters. English has a lot of them. There are other languages, um, that have very, very few, uh, for example, Hawaiian. Hawaiian has an inventory of about 12 to 14 different phonemes, 14 different consonants and vowels. English, on contrast, has about 40, uh, different consonants and vowels. So languages have different inventories. They can overlap for sure, but different languages use different sound elements, combine and recombine those elements to give rise to different words and meanings.
- AHAndrew Huberman
Can we say that there is a most complicated language out there, or among the most complicated? Would it be Russian?
- ECEddie Chang
It's definitely high up there. English is up there too, actually. Yeah. German as well.
- AHAndrew Huberman
And in terms of learning multiple languages during development, my understanding is that if one wants to become bilingual or trilingual, best to learn those languages simultaneously during development, ideally before age 12 if one hopes to not have an accent in speaking them later. Is that correct or do you want to revise that number?
- ECEddie Chang
Well, basically, the earlier and the earlier is better, uh, the more intense it is and the more immersive it is. Uh, the longer, you know, that you can be exposed to that is really important. A lot of people can get exposed to it early and basically lose it. Even though it's "during that sensitive period," unless it's maintained, it can be very easily lost. Then I think another aspect of it that's very interesting is, um, some of the social requirements for it too. It's pretty clear that you can only go so far, um, just listening to these sounds from a tape recording or something like that. There's something extra about real human interactions that activates the brain's sensitivity to different speech sounds that allows us to become specialized for them for a given language.
- 1:25:07 – 1:28:33
Motor Patterns of Speech & Language
- ECEddie Chang
- AHAndrew Huberman
So returning to the, the what's mapped, what, what the representations are in the brain, I'm starting to get a, a picture now based on these plosives and these thuh sounds. Uh, and what I find so interesting and logical about that is it maps to the motor structures and the actual pronunciation of the sounds, not-... necessarily to the meaning of the individual words. Now, of course, it's related to the meaning of the individual words, but it makes good sense to me why something as complex as language, both to understand and to generate, would map to something that is essentially motor in design because as you point out, I have to generate these sounds and I have to hear them generated from others. However, there's reading and there's writing, and writing is certainly motor, reading involves some motor commands of the eyes and etc. Where do reading and writing come into this picture? Are they in parallel with, as we would say in neuroscience, or are they embedded within the same structures? Are they, um, part, part of the same series of, of computations?
Episode duration: 2:34:23
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