Dr. Eddie Chang: The Science of Learning & Speaking Languages | Huberman Lab Podcast #95

Andrew Huberman hosts Dr. Eddie Chang, chair of the neurosurgery department at UCSF, to discuss groundbreaking advancements in neuroscience, particularly focusing on speech, language, and movement disorders. Dr. Chang's work includes enabling communication for individuals with locked-in syndrome through AI and bioengineering, illuminating critical periods for language acquisition, and exploring how brain circuits govern speech and movement. They also delve into epilepsy treatments, the ketogenic diet's impact, and the potential of Neuralink. Chang's pioneering research bridges clinical practice and cutting-edge science, offering transformative solutions for neurological challenges.

• Dr. Eddie Chang discusses the concept of critical periods in brain development, which are times when the brain is particularly receptive to learning new things, such as languages.
• The research conducted by Dr. Chang in rodents suggests that environmental sounds can shape the auditory cortex and influence the duration of these critical periods.
• Raising rat pups in continuous white noise extended the critical period, delaying the maturation of the auditory cortex.

"One of the things we did was to try an experiment where we raised some of these rat pups in white noise... we found out that you could keep it open for months beyond the time period that it normally closes."

• This quote highlights the finding that exposure to white noise can prolong the critical period of plasticity in the auditory cortex, which may have implications for understanding how environmental factors influence brain development.

• The sounds we are exposed to, even from an early age, can significantly influence how our brain processes auditory information.
• Different environments, such as those with varying levels of noise, can shape speech and hearing abilities.

"It's really clear that those sounds that we are exposed to from the very earliest time, even in utero... actually will influence how these things organize."

• This quote underscores the importance of early auditory experiences in shaping the neural architecture related to hearing and language processing.

• The use of white noise machines for infants is widespread, but there is a need for further research to understand its long-term impact on brain development.
• While white noise can help soothe infants, it may also mask important environmental sounds necessary for normal auditory development.

"Parents are using white noise generators almost universally now... But I think that there is a cost, you know, to think a little bit about."

• The quote reflects concerns about the potential developmental costs of using white noise machines, suggesting the need for caution and further study.

• Dr. Chang's work involves understanding the distinct brain areas responsible for speech and language, which are complex and highly specialized functions in humans.
• Brain mapping during awake surgeries helps identify critical areas for speech and language to avoid during neurosurgical procedures.

"Some of these areas you stimulate, and altogether, you can shut down someone's talking."

• This quote illustrates the precision required in neurosurgery to avoid disrupting essential speech and language functions.

• Certain brain areas, when stimulated, can evoke specific emotional responses, such as anxiety or calmness.
• The orbitofrontal cortex and amygdala are involved in mediating emotional states through neural activity.

"There are other areas like the amygdala or parts of the insula that if you stimulate, you can cause an acute temporary anxiety."

• The quote demonstrates how targeted brain stimulation can induce emotional changes, providing insights into the neural basis of emotions.

• Epilepsy, characterized by uncontrolled seizures, can sometimes be managed with medication, but a subset of patients may require neurosurgery or brain stimulation.
• The ketogenic diet has been used to help control seizures in some patients, though its effectiveness varies.

"For some people, just like with some medications, it can be a life-changing thing."

• This quote highlights the potential impact of the ketogenic diet as a therapeutic option for epilepsy, particularly when traditional medications are ineffective.

• Seizures are caused by an imbalance in excitation and inhibition in the brain, leading to electrical storms.
• Absence seizures involve a temporary loss of consciousness where the individual may appear absent but can still stand and function.
• Temporal lobe seizures originate from the medial structures like the amygdala and hippocampus, causing unusual tastes, smells, or feelings of déjà vu.
• Nocturnal seizures occur during specific sleep stages and are influenced by circadian rhythms.

"Absence seizure is just one category of different kinds of seizures where 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."

• Absence seizures cause a temporary disconnect from consciousness while the person might still appear physically present.

"Temporal lobe seizures... oftentimes people, when they have seizures coming from that, they may taste something very unusual like a metallic taste or smell something like the smell of burning toast."

• Temporal lobe seizures can manifest as unusual sensory experiences due to their origin in brain areas responsible for processing taste and smell.

• Historically, Broca's and Wernicke's areas were identified as key regions for speech production and comprehension, respectively.
• Broca's area in the frontal lobe was thought to be responsible for articulation, while Wernicke's area in the temporal lobe was linked to understanding language.
• Recent findings challenge the traditional view, suggesting that language processing involves more complex and distributed brain networks.

"In historical times, how this works has been very controversial from day one of neuroscience... Modern neuroscience began when, actually, it was very much related to the discovery of language."

• The understanding of language processing in the brain has evolved significantly, moving from simplistic models to more complex interpretations.

"Nowadays, after, you know, looking at this very carefully over hundreds of patients, we've shown that surgeries, for example, in the posterior part of the frontal lobe, a lot of times, people have no problem talking at all whatsoever after those kind of surgeries."

• New research indicates that traditional models of language areas in the brain may not fully capture the complexity of language processing.

• Language functions are predominantly lateralized to one hemisphere, usually the left, especially in right-handed individuals.
• The left hemisphere typically houses language areas, while the right hemisphere may take on different functions.
• Handedness has a genetic component and influences the lateralization of language functions.

"If you're right-handed, 99% of the time, the language part of the brain is on the left side."

• Language processing is heavily lateralized to the left hemisphere in right-handed individuals.

"Handedness is not entirely but strongly genetic. So there is something that ties all of this, and what does handedness, for example, have to do with the part of your brain that controls language?"

• Genetic factors influence handedness, which in turn affects the lateralization of language functions in the brain.

• Bilingual individuals often use overlapping brain areas for different languages, though the processing can vary.
• Shared neural circuitry exists for processing multiple languages, but the exact mechanisms can differ between individuals.
• Bilingualism involves complex brain activity patterns that reflect the processing of different languages.

"For people that are bilingual and that learn two or more... do they use the same brain area to generate that language?"

• Bilingual individuals use shared brain areas for language processing, though the specific neural patterns may differ.

"The short answer is that with bilingualism, there are shared circuitry, there's this shared machinery in the brain that allows us to process both, but it's not identical."

• Bilingualism involves shared but distinct neural pathways for processing different languages.

• Speech involves the production of auditory signals, while language encompasses broader aspects like semantics, syntax, and pragmatics.
• The brain processes speech by decomposing sounds into frequencies, which are then interpreted as language.
• Brain mapping reveals that specific brain areas are tuned to particular speech sounds and features.

"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."

• Speech is the physical production of sounds, while language involves extracting meaning from these sounds.

"The cortex is the outermost part of brain where we believe that sounds are actually converted into words and language."

• The cortex plays a key role in transforming auditory signals into language comprehension.

• Speech production involves complex motor coordination, including the use of the larynx and pharynx.
• The larynx is crucial for voicing by bringing vocal folds together to create sound.
• Speech is considered one of the most complex motor functions, involving intricate control of various vocal structures.

"Some people would say it's the most complex motor thing that we do as a species is just speaking."

• Speech production is an incredibly complex motor function involving precise coordination of vocal structures.

"What the larynx does is that when you're exhaling, it brings the vocal folds together... when the air comes through the vocal folds when they're together, they vibrate at really high frequencies."

• The larynx's function is vital for creating the sound of the voice by vibrating vocal folds during exhalation.

• Vocalizations like crying or laughter are distinct from speech and involve different brain areas.
• Speech involves shaping breath and voice in the larynx to form words using the mouth, tongue, and lips.
• Primitive vocalizations are managed by brain areas shared with nonhuman primates, separate from language areas like Wernicke's.

"A vocalization is basically where someone can create a sound, like a cry or a moan, that kind of sound, and it also involves the exhalation of air."

• Vocalizations are simple sounds produced by the exhalation of air, distinct from complex speech.

• The primary auditory cortex has a systematic layout for sound frequencies, with low frequencies at one end and high frequencies at the other.
• Speech processing may bypass the primary auditory cortex, using a separate pathway.
• The organization of language areas like Wernicke's and Broca's involves a 'salt and pepper' map for speech features.

"There is a map of different sound frequencies... as you march backwards in that cortex, it goes from low to medium to high frequencies."

• Sound frequencies are organized systematically in the primary auditory cortex, supporting auditory processing.

• Plosives and fricatives are distinct classes of speech sounds produced by different articulatory movements.
• Consonant clusters, such as in the word "phthalates," combine plosives and fricatives, increasing pronunciation difficulty.
• Different languages have varying inventories of phonemes, influencing complexity.

"A plosive when the mouth or something in the oral cavity closes temporarily, and when it opens, that creates that fast plosive sound."

• Plosives are created by closing and releasing parts of the oral cavity, forming distinct sounds.

• Languages vary in complexity, with Russian and English being among the most complex due to consonant clusters.
• Early and immersive exposure to multiple languages enhances bilingual or trilingual proficiency.
• Social interactions are crucial for language acquisition, beyond just auditory exposure.

"The earlier, and the earlier is better, the more intense it is and the more immersive it is, the longer, you know, that you can be exposed to that is really important."

• Early and immersive language exposure is key to achieving fluency and reducing accents.

• Reading and writing are human inventions that map onto existing brain structures for speech.
• The visual word form area in the brain is specialized for recognizing written words.
• Reading maps to auditory speech processing areas, influencing language learning and dyslexia.

"Reading is once it gets through that visual cortex, it's going to try to map those reading signals to the part of the brain that's trying to make sense of sounds."

• Reading involves mapping visual input to auditory processing, crucial for language comprehension.

• Dyslexia involves difficulties in mapping visual words to auditory speech sounds.
• Treatments for dyslexia focus on enhancing phonological awareness and visual-auditory mapping.
• Skilled readers develop parallel routes for direct word-to-meaning mapping without phonological processing.

"It's very clear that there are many kids with dyslexia where the problem is a problem of a phonological awareness."

• Dyslexia often involves challenges in phonological processing, impacting reading skills.

• Language and speech naturally evolve over time, with changes in dialects and pronunciation.
• Social and environmental factors influence language change, challenging the notion of a 'proper' way to speak.

"Languages, and speech in particular, change over time, it evolves, and it can happen very quickly."

• Language evolution is a natural process, influenced by social and environmental dynamics.

• Foreign accent syndrome occurs when brain injuries alter speech intonation, mimicking other languages.
• Auditory memories are distributed across the brain, supporting language retention despite localized injuries.

"People have documented where, you know, patients have had strokes there, and after that, it sounds like they're speaking Spanish as opposed to English."

• Brain injuries can alter speech patterns, creating the illusion of a foreign accent.

• Brain-machine interfaces can decode speech signals from the brain, enabling communication for paralyzed individuals.
• The BRAVO trial aims to translate brain activity into speech for those with locked-in syndrome.
• The trial participant uses a brain implant to communicate, bypassing traditional speech pathways.

"We had identified all of these different elements that we could decode in epilepsy patients... we could decode all of the different consonants and vowels of English."

• Decoding speech elements from brain activity is a breakthrough for assisting paralyzed individuals.

• A participant in the BRAVO trial, paralyzed for 15 years, uses a brain implant to communicate.
• The trial explores whether speech signals remain intact in paralyzed individuals, enabling new communication methods.

"He had a very large stroke in the brain stem, and that turned out to be devastating... he couldn't speak or move his arms or legs."

• The participant's condition highlights the potential of brain-machine interfaces to restore communication abilities.

• The development of a brain-machine interface allows individuals like Pancho, who are locked-in, to communicate by translating brain activity into text.
• The system involves an electrode array implanted over the speech cortex, which transmits brainwaves to a computer that decodes them into words.
• Machine learning algorithms are used to interpret subtle brain activity patterns and translate them into text, although this requires extensive training.

"The port actually goes through his scalp, and he's lived with this now for the last three years. It is a risk of infection. These ports eventually have to become wireless in the future."

• The current brain-machine interface system involves a port that poses an infection risk, highlighting the need for future wireless solutions.

"We took those brainwaves, we put them through a machine learning or artificial intelligence algorithm that can pick up these very, very subtle patterns...and translate those into words."

• Machine learning algorithms are crucial for decoding brainwaves into text, capturing subtle patterns that are not visible to the naked eye.

• The first communication through the device was a significant milestone, involving weeks of training to accurately interpret brain signals.
• The system initially used a limited vocabulary of 50 words, with plans to expand this vocabulary over time.
• Autocorrect features, similar to those used in texting, help improve the accuracy of decoded messages.

"We created essentially all the possible sentences that you could generate from those 50 words...it's really helpful to have these other features like autocorrect."

• The initial system used a limited vocabulary, with autocorrect features enhancing the accuracy of decoded sentences.

"What was really amazing about it was you could really tell that he, like, got a kick out of that because he would start to giggle."

• The successful translation of brain activity into words had a profound emotional impact on the patient, demonstrating the potential for improved quality of life.

• The discussion on brain-machine interfaces extends to potential augmentation of brain functions, raising ethical and practical questions.
• While the focus is currently on medical applications, the potential for cognitive and physical augmentation exists, though it is not yet fully understood.
• Concerns include the invasive nature of some technologies and the societal implications of augmented capabilities.

"There's part of this that is not new at all. Humans throughout history have been doing things to augment our function, coffee, nicotine, all kinds of things."

• The pursuit of augmentation is not new, but the invasive nature of neurotechnologies presents unique challenges.

"We have not had the full conversations about, number one, is this what we actually want? Is this going to be good for society?"

• Ethical considerations are crucial in the development of brain augmentation technologies, including societal impacts and access.

• Facial expressions play a critical role in communication, enhancing the understanding of spoken words and emotions.
• The development of avatars that mimic facial expressions and speech movements could improve communication for individuals with disabilities.
• The integration of avatars in digital spaces could provide a more holistic communication experience.

"Facial expressions actually are a really important part of the way we speak...it's also seeing my mouth move and your eyes actually seeing my mouth move."

• Facial expressions and mouth movements are integral to effective communication, aiding in the perception and intelligibility of speech.

"We are thinking really about, for people like Pancho and other people who are paralyzed, what other forms of BCI can we do in order to help improve their ability to communicate?"

• The development of brain-computer interfaces aims to enhance communication for paralyzed individuals, potentially through the use of avatars.

• Stuttering is a speech condition affecting the fluency of word production, often exacerbated by anxiety but not caused by it.
• Treatment typically involves speech therapy to develop strategies for fluent speech, focusing on initiation and coordination of speech movements.
• Auditory feedback plays a role in stuttering, with changes in feedback potentially affecting fluency.

"Stuttering is a problem of speech, right? So the ideas, the meanings, the grammar, it's all there, and people stutter but they can't get the words out fluently."

• Stuttering is a speech disorder affecting articulation and coordination, not language comprehension or grammar.

"The main link between stuttering and anxiety is that anxiety can provoke it and make it worse."

• Anxiety can exacerbate stuttering, though it is not the underlying cause of the condition.

• Engaging in physical exercise, such as running, is crucial for mental well-being and performance, providing a mental reset and focus.
• The operating room serves as a sanctuary, allowing for intense focus and disconnection from external distractions.
• Music and audiobooks are used selectively to enhance motivation and focus during physical activities.

"For me, most exercise that I do, I really don't do for physical reasons. I do it for mental reasons."

• Physical exercise is primarily a mental health tool, essential for maintaining focus and well-being.

"The operating room, for me, is another space, kind of like running or swimming, where I'm disconnected from the rest of the world."

• The operating room provides a focused environment, akin to meditation, allowing for intense concentration on the task at hand.