Chapter 1: What are the differences between speech and language?
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 ophthalmology at Stanford School of Medicine. And now for my discussion with Dr. Eddie Chang.
Chapter 2: How does the brain control the larynx and vocal folds?
Eddie, welcome.
Hi.
Hi, Andrew. Great to be here with you. Your main focus these days is the neurobiology of speech and language.
Chapter 3: What advancements are being made in speech neural prosthetics?
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? 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.
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 accent something, or it's a word that I have a particular difficulty saying, or I want to change the cadence, et cetera. So what in the world is contained in these brain areas? What is represented?
Chapter 4: How does AI enhance communication for paralyzed patients?
to me is perhaps one of the most interesting questions. And I know this lands square in your wheelhouse.
Sure.
Chapter 5: What ethical considerations arise from brain augmentation technologies?
Let's get into this, 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 speech corresponds to the communication signal. It corresponds to me moving my mouth and my vocal tract to generate words. And you're hearing these as an auditory signal. Language is something much broader.
So it refers to 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 the sentences? There's another part that we call syntax, which refers to how the words are assembled in a grammatical form.
Chapter 6: How does stuttering relate to anxiety and speech production?
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, reading.
Chapter 7: What tools are available for stuttering therapy?
Those are all important modalities for reading. Our research really focuses on this area that we're calling speech.
Chapter 8: How can auditory feedback improve fluent 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 tract that are picked up by the microphone in the case of this recording, but also picked up by the sensors in your ear, the very tiny vibrations. in your ear are picking that up and translating that into electrical activity.
It's such a complex feat. Some people would say it's the most complex motor thing that we do as a species is speaking, not the extreme feats of acrobatics or athleticism, but speaking.
And especially when one observes opera or people who freestyle rappers. And of course, it's not just the lips. It's the tongue. And you've mentioned two other structures, pharynx and larynx are the main ones. Can you tell us, just educate us at a superficial level, what the pharynx and larynx do differentially? Because I think most people aren't going to be familiar with that.
Okay, sure. I'll talk primarily about the larynx here for a second, which is that if you think about when we're speaking, 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. We fill up our lungs. And then we push the air out. That's a normal part of breathing.
What is really amazing about speech and language is that we evolved to take advantage of that normal physiologic thing at 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 at really high frequencies, like 100 to 200 hertz. And the reason why men and women generally have different 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 you take a breath in. As the air is coming out, the vocal folds come together and air goes through. That creates the sound of the voice that we call voicing. It's not just your voice characteristic, it's the energy of your voice.
It's 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 the air in particular ways that create consonants and vowels.
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 his words.
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