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Dr. Konstantina Stankovic on Huberman Lab: Why Noise Hurts

Ringing after concerts signals real damage. Hearing loss raises dementia risk; ear plugs and magnesium supplementation are two well-supported preventive tools.

Dr. Konstantina StankovicguestAndrew Hubermanhost
Oct 13, 20252h 27mWatch on YouTube ↗

EVERY SPOKEN WORD

  1. 0:00 – 3:27

    Konstantina Stankovic

    1. KS

      So now there's mounting evidence for a strong link between hearing loss and dementia. It's not that everyone with hearing loss will develop dementia. However, we are trying to identify who is at risk. Hearing loss is a huge problem. It currently affects one and a half billion people, and disables half a billion of them. And the World Health Organization estimates that another billion will be affected by 2050.

    2. AH

      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. My guest today is Dr. Konstantina Stankovic. She is a medical doctor and researcher, and the chair of the Department of Otolaryngology, Head, and Neck Surgery at Stanford School of Medicine. Today we discuss hearing and how to protect yours, as well as how to deal with common problems related to hearing, like tinnitus, or ringing of the ears, which is a very debilitating condition that many millions of people suffer from. Most of us don't think about our hearing very often, unless it's compromised, and yet we now know that our ability to hear clearly in many ways drives our ability to think and engage with the world, which is of course not to say that deaf people don't have excellent cognition and the ability to engage with the world, but they of course compensate for that hearing loss with the use of sign language and lip reading. Most people of course have the ability to hear, and yet don't know that even subtle deficits in hearing can lead to focus issues, mild cognitive impairment, and more serious hearing loss is directly related to dementia. And while until recently we thought about partial hearing loss as really something that accompanies aging, it turns out that for various reasons related to loud environments, the use of headphones, et cetera, progressive subtle hearing loss is occurring much earlier in people's lives, even as early as childhood. Today you're going to learn from one of the top experts in the world how your auditory system works. We'll talk about how it works from the time you were in your mother's womb, yes indeed, you could hear quite well even within your mother's womb, all the way through adolescence and into old age. And you're going to learn the specific things that you can do to protect your hearing. And I'm certain that you'll realize that some or many of the things that you're doing are subtly or not so subtly damaging your hearing, and fortunately, you can remedy that very easily. We talk about some of the behavioral protocols that are backed by science, as well as things like the use of magnesium to protect against hearing loss. And of course we talk about tinnitus, this very common condition of ringing in the ears and how you can remedy it. Thanks to Dr. Stankovic, this is both a fascinating and incredibly important conversation relevant to people of all ages. The information she shares is not covered in traditional public health announcements, but it absolutely should be, because it's not just about protecting your ability to hear, it's about protecting your brain function more broadly. So today's discussion is going to teach you about how your auditory system works, how to take care of it, how to remedy any partial hearing loss that you might have already experienced, and in doing so, how to take care of your brain health and cognition. 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, today's episode does include sponsors. And now for my discussion with Dr. Konstantina Stankovic.

  2. 3:27 – 10:58

    Hearing Loss, How Hearing Works, Types of Hearing Loss

    1. AH

      Dr. Konstantina Stankovic, welcome.

    2. KS

      Thank you.

    3. AH

      Most of us don't think about our hearing often enough.

    4. KS

      Mm-hmm.

    5. AH

      Except now everyone is using headphones or listening to things very loud, or most people are living in quite loud environments. I was in New York last week. I've been in Chicago, San Francisco. These are really loud cities. And even if one goes out into the countryside, you know, if you're listening to music loudly, which can be fun, feels good, if you like loud music, classical or rock and roll or otherwise, I have a feeling you're going to tell us that it's not good for our hearing and that losing our hearing is not good for a bunch of other things. Tell us about hearing loss. How do we avoid it?

    6. KS

      Absolutely. So hearing loss is a huge problem. It currently affects one and a half billion people and disables half a billion of them. And the World Health Organization estimates that another billion will be affected by 2050. So this is an enormous issue, and it's really underappreciated and stigmatized, and lots of people live in silence. For example, for those who have problems with their vision, they wear glasses and glasses can restore their vision back to normal, to the point that people now wear glasses even if they don't need them. It's a fa- it's a fashion statement. However, that's not the case for hearing loss, and it's because hearing aids are aids, like the name says. They don't restore hearing back to normal. So to answer your question, I think we really should review how hearing works. So the way we hear is when sound comes and travels down the ear canal, it vibrates the eardrum. The fancy term for it is the tympanic membrane. That sets in motion the smallest bones in the body. They're called the malleus, incus, and stapes, which is Latin for the hammer, the anvil, and the stir bone. As they vibrate, they set in motion fluids in the inner ear, and this is where these incredibly delicate sensory cells reside. They're called hair cells, but that has nothing to do with this hair. And as they deflect their sensors on top of their surface, which are called stereocilia, that leads to flow of ionic current and release of neurotransmitter and excitation of the auditory nerve, which then sends signals all the way to the brain. So in the inner ear...... occurs, this, m- it's called mechano-electrical transduction, because we are converting a mechanical stimulus into an electrical one. And there are two broad categories of hearing loss. One is the so-called conductive hearing loss and the other is sensory neural hearing loss. The conductive hearing loss a- affects the ability of sounds to be conducted to the inner ear. That can be if there is a hole in the eardrum or there's fluid behind the eardrum, or these hearing bones don't vibrate, they're frozen, uh, because of a disease process. There are surgical treatment options for that type of hearing loss, and non-surgicals, which include amplification with hearing aids. So that's an easier type of hearing loss to have. But the more common type of hearing loss is the sensory neural hearing loss. It's the one that originates from the inner ear. And why it's been so challenging to study and to crack that nut is because it's tiny. It's a tiny organ, it's encased in the densest bone in the body, and it's located deep in the base of the skull. You may even ask, "How tiny?" If you take a penny, then you'll notice that Lincoln is on a penny. So the human organ of hearing, which is called the cochlea, in cross-section, is the size of Lincoln's upper face on a penny.

    7. AH

      Wow, that's small.

    8. KS

      Super small.

    9. AH

      Mm-hmm.

    10. KS

      And that organ is filled with fluid. How much fluid? What's your guess? What's the volume of this inner ear fluid? It even has a fancy term, it's called perilymph and endolymph. There are two types of fluid. But that doesn't matter. What matters is the scale. So, how much fluid do you think there is?

    11. AH

      I- I'm guessing the equivalent of one, uh, less than one drop out of a, out of an eyedropper.

    12. KS

      That's pretty close. It's actually the equivalent of three raindrops.

    13. AH

      Okay.

    14. KS

      So about 140 microliters. So this is an organ that's amazing. It is the most sensitive sensory organ. It can detect displacements that are on the order of the diameter of a hydrogen atom. That's astounding. If you just think in terms of, um, electronic chips, the traces are now on the order of one nanometer, which is the size of five silicon atoms. But the ear can detect displacements that are one-tenth of that.

    15. AH

      So, at the angstrom level?

    16. KS

      Sub-angstrom level.

    17. AH

      Sub-angstrom?

    18. KS

      Sub-angstrom level. It's really phenomenal. And another example to really highlight the sensitivity of this organ, if you have a trained violinist, if they move their finger by only a micron, so that's a millionth of a meter, the ear can perceive that as a change in pitch.

    19. AH

      Amazing.

    20. KS

      You can't see that with your naked eye, but the ear can perceive it. So these examples really highlight how delicate this organ is. And another absolutely stunning thing about the, uh, ear is that there are these cells, they are sensory cells that we talked about, but they are called inner and outer hair cells. And what's special about these outer hair cells, they actually move, but they move at audio frequencies. So what does that mean? To put it in perspective, let's say that the heart beats at 60 beats per minute, which is one hertz. If the heart starts beating at two hertz, 120 beats per minute, that's arrhythmia, that could be life-threatening. Well, these cells in the inner ear move, in humans, up to 20,000 hertz, and in bats, up to 100,000 hertz.

    21. AH

      Wow.

    22. KS

      So this is to tell you how incredible this system is, and it's designed to let us detect sounds, and, uh, it's evolved so that we can detect sounds at any point in, uh, day or night. Sound travels through any media. Sound travels around obstacles. It's really essential for survival. There are species that don't even have vision, they're blind, and they're surviving superbly well because of their incredibly astute sense of hearing, like bats or moles.

    23. AH

      May I just

  3. 10:58 – 15:26

    Sound Waves, High vs Low Frequency, Communication, Importance of Hearing

    1. AH

      ask a question about sound waves themselves?

    2. KS

      Mm-hmm.

    3. AH

      Um, could you differentiate for us how high versus low frequency sounds, uh, travel further or have a greater propensity to impact the movement of, uh, the eardrum-

    4. KS

      Mm-hmm.

    5. AH

      ... um, which you bea- beautifully explained is the consequence of, uh, a bunch of mechanical, uh, features and the, the endolymph, and you said the other lymph?

    6. KS

      Perilymph.

    7. AH

      Perilymph.

    8. KS

      Mm-hmm.

    9. AH

      So I- I want people to get this image in their mind-

    10. KS

      Mm-hmm.

    11. AH

      ... that, uh, that sound waves, not voices-

    12. KS

      Mm-hmm. Yes.

    13. AH

      ... not music, but sound waves-

    14. KS

      Yes.

    15. AH

      ... uh, are traveling through space, uh, arrive to the ear, and then there are converted into a mechanical, uh, pressure that changes over time, like the beating of a drum, eardrum, that then is converted into pressure within this lymph fluid, which then moves these little hair, quote unquote "hair cells," which then activates neuronal signals, they go up to the brain and i- remarkably, I mean, to this day, I'm a, you know, neuroscientist, and it still blows my mind that then we perceive language, we perceive music, we recognize a cry versus laughter.And it all happens very, very fast. Um, I think most people don't think about hearing that way, and so could you, um, uh, explain for us the- the elements within sound waves that create this- this incredible architecture that we call the perception of hearing?

    16. KS

      Sounds as they set in motion the tympanic membrane, the eardrum, and then lead to motion of hearing bones. There are different modes of vibration depending on both sound intensity and frequency. Once they get transmitted to vibration within the inner ear, everything is tuned in the inn- inner ear. So the cochlea is a coiled organ. Uh, cochlea even means, uh, snail in- in Greek. So now if you uncoil it, then it's a tube, and high frequencies are encoded at the base close to the middle ear and low frequencies far away at the apex. And so when sounds- sound waves come in, if they have high frequency, they will cause primarily vibration at the base of the cochlea. If they have low frequency, they have to travel all the way up, and this is where speech resides, at higher frequencies. It's interesting that the l- high frequency, end of the cochlea tends to be more vulnerable to various insults like noise levels that you, uh, pointed out, certain drugs, uh, and aging. Now, in terms of, uh, music being so essential for being human and our ability to communicate, uh, this is a podcast, so it highlights how important our ability to communicate and hear that communication is essential. It can create vivid experiences. It can be very engaging even without seeing people. And looking at that throughout history, for example, Socrates in ancient Greece said, "Speak so that I can see you." And then in the medieval years, it was a French writer and, um, physician François Rabelais who said, "Of all the senses, hearing is the fittest for the reception of the arts, sciences and disciplines."

    17. AH

      Hmm.

    18. KS

      And then 500 years later, Helen Keller, who was both blind and deaf and is one of the most celebrated people of the 20th century said, "Deafness is a worse misfortune because it separates you from people as opposed to things." So that gets at your question of why is hearing important for us? It's important not only to communicate that's direct relevance, but there are indirect major effects on how we feel on our emotional, relational, and cognitive well-being.

  4. 15:26 – 18:40

    Sponsors: Wealthfront & Our Place

    1. KS

    2. AH

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  5. 18:40 – 22:59

    Sound Projection, Intensity, Speech; Moving Ears; Larger Ears

    1. AH

      zero risk.I'd like to return to this close relationship between what we hear and how we feel.

    2. KS

      Mm-hmm.

    3. AH

      But, um, before we do that, let's say I were in the wilderness-

    4. KS

      Mm-hmm.

    5. AH

      ... and I was lost and I was trying to find my way back and I was out of water, uh, and I spot somebody on the horizon, and I wanted to call out to them with the greatest probability that they could hear me.

    6. KS

      Mm-hmm.

    7. AH

      Would I call out in a higher pitched, lower pitched, or whatever my typical voice happened to be, assuming that I'm going to call out at the greatest intensity in either case? Which sound frequency is going to travel furthest and/or have the greatest likelihood of reaching somebody's ears and having them perceive it?

    8. KS

      You partly answered your question because sound intensity is the key, uh, and as humans, we can produce only sounds of certain frequencies. Uh, and throughout history, people have used horns. Horns really work.

    9. AH

      Mm-hmm.

    10. KS

      And so that, that would be the first thing that you do, and you can even create it like this yourself-

    11. AH

      Okay, put your hands on either side of your mouth.

    12. KS

      ... to, to project... exactly, to project. But if you have a longer horn, use that. That really works. In terms of our human ability to detect tones, in every species, it's a sensitivity curve. So, uh, when we test hearing in clinic, we test it only up to eight kilohertz, but we can hear up to 20,000 hertz. And it's because most of speech really lives below that frequency. Lots of speech lives between 250 hertz and 4,000 hertz. And if you speak at those levels, which we do because that's what we do as humans, uh, uh, women can have more high-pitched voices or children have, can have more high-pitched voices, but it's still in the range of optimal hi- uh, human hearing. That's what you would need to do. So then all you have to do when you're in a situation like that is speak as loudly as you can, and if you can, find a horn so that it amplifies.

    13. AH

      And if you don't have a horn, put your hand on either sides of your mouth-

    14. KS

      Yes.

    15. AH

      ... which we do intuitively.

    16. KS

      Intuitively, exactly.

    17. AH

      And if we need to hear something at a distance, we put our hand to our ear-

    18. KS

      Exactly.

    19. AH

      ... in order to create a temporarily larger ear.

    20. KS

      And that works too. It absolutely works. Our patients tell us it works. Uh, sometimes in the clinic, if people don't have a hearing aid and they're really hard of hearing and they don't know how to lip read, uh, and they don't want to be reading what's being written, that's what they do, and it really makes a difference.

    21. AH

      Because it's capturing the sound waves into a funnel.

    22. KS

      Yes. Exactly.

    23. AH

      Other animals, um, most, um, famously the desert fox or the fennec fox, have these-

    24. KS

      Mm-hmm.

    25. AH

      ... uh, really cute tall ears that they can direct-

    26. KS

      Yeah. Mm-hmm.

    27. AH

      ... uh, independently. Am I correct in thinking that some people can move their ears and other people can't? I don't think I can do it. Uh, I've never practiced it. It didn't seem like a worthwhile thing to try and, uh, generate that skill.

    28. KS

      No.

    29. AH

      But I know people, uh, that can move their ears either together or independently a little bit.

    30. KS

      Mm-hmm.

  6. 22:59 – 26:43

    Sounds & Emotionality; Tinnitus

    1. KS

    2. AH

      These days, there's a lot of content online about how different sounds can impact the emotionality of kids-

    3. KS

      Mm-hmm, mm-hmm.

    4. AH

      ... um, independent of learning, sort of innate sound-emotion relationships.

    5. KS

      Mm-hmm.

    6. AH

      Um, I actually don't know whether or not these, uh, uh, these posts are ethical or not. It's hard for me to know because what they show is babies, it's typically a series of clips with babies-

    7. KS

      Mm-hmm.

    8. AH

      ... where they'll say something. I forget what it is, and it's probably best that I forget so that people don't do this and try it-

    9. KS

      (laughs)

    10. AH

      ... 'cause I don't know the ethics around it. But they'll say something to their kid, um, and it's not a word. It's like, it's a, it's a sound, and the kid will suddenly either be terrified or suddenly be really happy, and there's no indication that that sound is a scary sound or a happy sound. It's not like they're, they're screaming at the kid or barking at the kid, so it seems to be that they're, people have learned to tap into these frequencies, um, and intensities, but it tends to be pretty low intensity, uh, at least by my listen of these things. Um, but very strong coupling of sound and emotion-

    11. KS

      Mm-hmm.

    12. AH

      ... independent of learning, and I say independent of learning because, of course, I hear certain pieces of music and they really move me emotionally, but I have a relationship to that music that I formed over time, uh, or it's similar to a, a different piece I heard over time. What is known about the convergence of sound information and emotion? And let's leave outside, you know, big loud bangs or, um, you know, high shrill things that really, like, impact our, our, um, pain system. Um, so is there, uh, something known about how different sounds impact emotionality?

    13. KS

      Oh, yes. Absolutely. The, uh, really, the brain has evolved to perceive and manage-... sensory inputs.

    14. AH

      Mm-hmm.

    15. KS

      And sound is one of these sensory inputs, and it's critical for emotional well-being. Uh, s- we have thus far talked about the periphery, what happens in the inner ear and how those signals are then transmitted all the way to the brain. Well, there are numerous relay stations from the ear to the brain, to the cortex. They h- they are in the, um, brain stem and midbrain all the way to the cortex. And these auditory pathways have very strong links with emotional pathways and the limbic system. And in fact, that's why music, hearing music can really move us. That's why, uh, remarkable speeches of impressive leaders can get people aroused and motivated to do something. Uh, so that link between hearing and emotion is really strong, well-established, and sometimes can be detrimental, for example, for people with tinnitus. So tinnitus, it's a phantom sound. It's produced by the brain typically in response to a reduced input to the brain. So the brain makes up the sound that it's normally not detecting. It's similar to phantom limb pain-

    16. AH

      Mm-hmm.

    17. KS

      ... where people don't have an arm or a leg, but they can still perceive pain in the limb that they don't have. So now, some people with tinnitus can just put it in the background. They can ignore it. They are reassured by knowing that it's not life-threatening and it's fine. But there are people who can't handle it. They are really severely disabled by it, and some are suicidal, s- which is a huge spectrum. And why is that? So clearly, uh, the- these circuits in the brain are differently connected for different people, and in some, that emotional component is really amplified.

  7. 26:43 – 32:19

    Painful Sounds, Hyperacusis, Phonophobia; Memory, Auditory Hallucinations

    1. KS

    2. AH

      Interesting. Um, many people have heard of ASMR-

    3. KS

      Mm-hmm.

    4. AH

      ... auditory sensory meridian reflex, I think it's called. Um, this is something that, uh, sure, there are accounts online where people will whisper or they'll scratch or they'll scratch a microphone. I won't do it here. Some people find certain sounds extremely pleasant. Other people find the same sounds extremely aversive. Um, actually, I was thinking for a moment about fingers on a chalkboard.

    5. KS

      (gasps)

    6. AH

      And it's enough to make me cringe.

    7. KS

      Yeah, yeah.

    8. AH

      Like, my- I tighten up. It's like- it's a- as if I'm ready to get, you know, hit by something. I think many people hearing this will imagine that sound. It's the same thing. Is the relationship between our- our cringing, our physical cringing, um, and these high-frequency sounds, is that a- a pain offset m- uh, mechanism? You know, in other words, um, in the visual system, if you just show someone a really bright light, they'll raise their hands.

    9. KS

      Mm-hmm.

    10. AH

      They'll turn-

    11. KS

      Mm-hmm.

    12. AH

      ... turn away.

    13. KS

      Mm-hmm.

    14. AH

      It's to protect their retinas.

    15. KS

      Mm-hmm.

    16. AH

      And it's a reflex.

    17. KS

      Yes.

    18. AH

      It's a hardwired reflex.

    19. KS

      Mm-hmm.

    20. AH

      And when we're sick, incidentally, um, there's a- this incredible reflex pathway that sort of becomes unveiled that we always have which gives us photophobia.

    21. KS

      Mm-hmm.

    22. AH

      Bright light that we normally might like-

    23. KS

      Mm-hmm.

    24. AH

      ... suddenly becomes aversive-

    25. KS

      Mm-hmm.

    26. AH

      ... and it can give us headache- headaches-

    27. KS

      Mm-hmm.

    28. AH

      ... and- and this kind of thing. Is there- are there similar pathways in the auditory system?

    29. KS

      There are. Uh, there's this phenomenon of hyperacusis or even phonophobia. Uh, and when it comes to hyperacusis, it c- frequently accompanies hearing loss. And really, what happens in people with hearing loss is that sounds have to be loud enough for them to hear them. But if they are too loud, that can be painful, very uncomfortable. So their dynamic range of hearing is reduced. And, uh, pretty much everybody with hearing loss experiences that. Now, to have a real fear of sound, uh, phonophobia, that's not common, and it's usually linked with some underlying mental health condition. It's more common in people with obsessive-compulsive, uh, disorder or personality trait and other conditions.

    30. AH

      It's so interesting how the- the timbre of somebody's voice, uh, leaves a mark on us-

  8. 32:19 – 39:15

    Concerts & Ringing in Ears, Hidden Hearing Loss; Tool: Safe Sound Threshold

    1. AH

      let's talk about hearing loss. Let's talk about what happens when we go to a loud concert, I, I fear I've done this, and, um, you get too close to the speakers or they're just turned up too loud and the acoustics of the room make it such that you have ringing in your ears the next day. If you have ringing in your ears after a concert or some other auditory experience, does that mean that some level of permanent damage was done?

    2. KS

      Possibly.

    3. AH

      (laughs)

    4. KS

      And why I say possibly is that until, uh, maybe 10 years ago, we thought that if you go to a concert like that, you have ringing in your ears, you may even feel like your ear is clogged and then it goes away, that that is temporary threshold shift. But now we know that some forms of temporary threshold shift are in fact permanent. Although your hearing may come back, and in fact we can see it on audiometric testing, we now know that the wheel has been set in motion where synapses that connect these sensory cells to neurons that contact them have been damaged or destroyed by loud sound. It takes them a long time to degenerate, and in fact, it's led to the concept of the so-called hidden hearing loss.

    5. AH

      Mm-hmm.

    6. KS

      So there is obvious hearing loss that you can measure on audiograms, but now we have a new appreciation for the type of hearing loss that you are describing and it's more common among young people, and if they go through standard audiometric testing, it'll be perfect. All of their audiometric thresholds are fine. However, they report that they cannot hear clearly in a noisy background or they have this tinnitus that they didn't have before. So what's now emerging from both animal and clinical data is that indeed there are anatomical correlates of this damage, and it typically involves synapses between sensory cells and neurons, or it may even involve hair cells and neurons themselves. Um, so what is the loud noise level? That was one of your questions. (laughs)

    7. AH

      Mm-hmm.

    8. KS

      Uh, for example, right now, we are speaking at about 60 decibel in terms of sound pressure level. And, and what does that mean? Decibel, it's a logarithmic scale because we had to compress an enormous scale that's really million-fold from the softest sound to the loudest sound we can, that we can hear. We compressed it to a linear scale that looks linear, it's not, but it's a logarithmic scale. So that's what DB is, and we can hear anywhere between zero to 120 decibel and louder. We can even hear a jet engine and that's 140 decibel. And to calibrate us, if I'm now speaking at around 60 decibel, to come here, I had to take a plane, uh, and the, uh, noise in the cabin is typically around 80 decibel. If you drive a motorcycle, it's about 100 decibel. If you go to a concert that you have referred to, it's not uncommon that it's between 110 and 120 decibel, and jet engine is around 140 decibel. And the loudest noise level ever achieved at a football stadium was in Kansas City, and it was 142 decibel. That is deafening. It's-

    9. AH

      Literally deafening?

    10. KS

      Literally deafening because it's, again, a logarithmic scale. So for every three decibel increase in sound intense- intensity, you have to halve the time exposure that's safe. So now back to your question, what is safe? Roughly speaking, 80 decibel is fine for eight hours, but for any three decibel increase, you have to halve it, which means 83 decibel is okay for four hours, 86 for two hours, 89 for one hour, 92 for half an hour. Well, most of music concerts that use amplified music are above 92 decibel.But it's not that everyone develops hearing loss, and it's not that we have to stop enjoying music concerts at all. It's just that we have to take precautionary measures. First of all, why does music have to be that loud? It's kind of a peer pressure phenomenon because most people don't even enjoy it when it's that loud, but they feel like they should because somehow, it's a kind of being youthful.

    11. AH

      I have an idea.

    12. KS

      Uh-huh.

    13. AH

      But it's just a speculation. Part of it, I think, is to drown out, um, other sounds in the crowd.

    14. KS

      Mm-hmm.

    15. AH

      In the same way that if you, uh, go to a party and they dim the lights on the dance floor, p- partially because of, uh, people's self-consciousness, but, uh, you know, you're- you're- people are more likely to dance when the- not every, like, movement of the dance is being detected, right, than bright lights and- Like, when the lights come up at the end of a- a night of dancing or bar, you kind of feel like, "Okay, party's over."

    16. KS

      (laughs)

    17. AH

      Right? And that's what they're trying to signal. So part of it is probably to drown out the micro-conversations, um, going around, and I think the other part is that, um, I do think that like with highly palatable food, uh, it, you know, there's been this sort of drift of setting higher and higher thresholds of what's normal and that people many times go to concerts 'cause they want to feel the music at the level of an intense sound wave, especially, you know, like, I mean, if you live in California, probably anywhere in the country, but you're familiar with someone pulling up next to you and- and really blasting the bass in their car and your whole car is shaking and they're obviously enjoying it and to you, it's aversive or you like it, d- depending on who you are. But most of the time, we don't want pe- other people's sound experiences encroaching on ours i- at that kind of, like, wh- whole vehicle level. So, um, yeah, I think it's this- this notion that we can't feel the music unless we, uh, unless it's very loud. Again, it's a speculation.

    18. KS

      There is something to it because it turns out that at loud enough sound intensities, the vestibular system is stimulated at all, a- a- as well.

    19. AH

      Mm-hmm.

    20. KS

      Uh, and there are experiments in, uh, animals that have shown this unequivocally. So there are vestibular or balance neurons-

    21. AH

      Mm-hmm.

    22. KS

      ... that actually respond to loud sound. Uh, so yes, there is a component of that.

  9. 39:15 – 43:44

    Concerts & Protecting Hearing, Tools: Ear Plugs, Magnesium Threonate

    1. KS

      However, we talked about initially how delicate this organ is. Again, it can detect sub-angstrom displacements.

    2. AH

      Mm-hmm.

    3. KS

      And now you are literally hammering it with this blast noise. It's like an elephant in a china shop.

    4. AH

      Yeah.

    5. KS

      And that is not good, and that's what contributes to some hearing loss. So what can you do to protect your hearing if you're going to a loud concert like that? Definitely wear earplugs. You can even measure sound intensities if you want to be very quantitative about it because now you have a rough formula. Uh, you can get a dB app on your phone. It's free. You can measure it. And let's say if it's 120 decibel at the concert you're using, then wear earplugs that provide at least 30 decibel of attenuation. When you buy these, uh, earplugs in a store, it tells you what, uh, degree of attenuation they provide, and it can be anywhere from 10 to 30. Musicians' earplugs usually provide about 14 decibel of attenuation. So clearly, that wouldn't be good enough for this event. Uh, and you have to put them in correctly because if they don't fit in, it doesn't matter what the number says, they're not protecting you. So, that's one thing that you could do. Another thing that you can do is take magnesium before going to a loud concert, and this is because studies have shown that magnesium can protect against noise-induced hearing loss, and, uh, the studies were done in countries where they have mandatory military service, and they literally grouped, uh, people into those who received magnesium before those exercises and those who didn't, and everybody was exposed to the same artillery and explosions as a part of preparation. Those who took magnesium beforehand had less hearing loss. Also, what measurements have shown in animal models is that after noise trauma is the levels of magnesium that change the most in the cochlea, in the organ of hearing, more than any other ion that's been studied. And also, what large scale human population studies have shown is that those with higher magnesium serum levels or higher magnesium intake, uh, tend to have better hearing. However, that needs to be further studied and replicated because the precise dose i- is really not known or the formulation, because as you know, there are many different kinds of magnesium and magnesium is good for your whole body, but depending on the formulation, it may be better for the gut versus the muscular skeletal system versus the brain. And different formulations have been studied in different scenarios. What we now think is that magnesium threonate, um, is most efficient in crossing the blood-brain barrier, so we think it's probably the best for hearing protection, but that study is yet to be conducted.

    6. AH

      Mm-hmm. Incredible. Um, I've been taking magnesium threonate for, gosh, well over a decade because I learned that it was the form that most readily crosses the blood-brain barrier. I was interested in the cognitive enhancing effects, uh, I take it about 30 to 60 minutes before sleep, and it does seem to make me a little bit- a little bit more drowsy and does seem to improve, uh, the architecture of my sleep-

    7. KS

      Mm-hmm.

    8. AH

      ... slow wave and REM sleep measured, et cetera. Um, I know a lot of people take magnesium bisglycinate as a- as an alternative. As far as I know, those are interchangeable, but I think it's wonderful if people are getting enough magnesium from their diet and if they need to supplement, they think about that. Um, I'm struck by...... these studies on magnesium because, you know, in the visual system, uh, the field of, of ophthalmology has, has been, uh, sort of reluctant to, um, embrace, uh, supplementation with things, except for a few things. Everyone knows you need enough vitamin A, you know, and, you know, carrots are good for your vision and this kind of thing. But it's a fat-soluble vitamin, so you don't want to overdo it. Um, but nowadays, there's a, kind of an emerging sense from some of our colleagues in ophthalmology at Stanford that some of the things, uh, found in supplement form actually can, uh, help protect the, the retinal cells, which is a sort of correlate of the, of the hair cells, uh, in the context of hearing loss.

  10. 43:44 – 47:30

    Magnesium Food Sources & Supplements; Migraines & Tinnitus

    1. AH

      So, um, I'm, I'm curious as to why magnesium would do this. Is it something about the, uh, the lymph, uh, that they, the sort of, uh, the chemical architecture of the, the cochlear environment? Is it happening at the level of the brain? Maybe we don't know, but it's, it's very interesting.

    2. KS

      I think it's probably both, at both, uh, levels. And by the way, going back to supplementation, really the best way is to have a healthy diet.

    3. AH

      Mm-hmm.

    4. KS

      And numerous studies have shown is that what we absorb through a healthy diet is better than supplementation. And supplements are not really strictly regulated in the way that other prescription medications are. So what the label says on a box could be all over the map.

    5. AH

      You need to go with a trusted brand. Some companies, um, get third-party testing.

    6. KS

      Yeah.

    7. AH

      But I completely agree that the supplement industry is replete with all sorts of things, especially, uh, for instance, melatonin.

    8. KS

      Mm-hmm.

    9. AH

      You know, the great sleep scientist, Matt Walker, uh, author of Why We Sleep, et cetera, uh, has cited, uh, experiments where they look at, um, bottles of melatonin labeled as one milligram, five, three milligrams, five milligrams, 10 milligrams. And the actual amount in one pill or capsule can be off by 85% in either direction.

    10. KS

      Yes. (laughs)

    11. AH

      In either direction, (laughs) either much less than you thought or much more. Actually, that reminds me to ask, is there any evidence that taking magnesium can help slow, reverse, or prevent tinnitus? Uh, because I know many people are really struggling with tinnitus.

    12. KS

      What is known is that for some people with tinnitus, in the setting of migraine-

    13. AH

      Mm.

    14. KS

      ... uh, magnesium supplementation really helps. As you know, magnesium, uh, can do magic for people with migraines, along with healthy diets and, uh, coenzyme Q10 and B complex or at least B12 vitamins. So that is the standard part of armamentarium to treat migraines. Uh, and some people with migraines have tinnitus during their exacerbations, as well as auditory fluctuations, and some people get really dizzy. And this is where thorough evaluation is really key, because someone may assume that the problem is in the inner ear, but the problem is really in the brain. And then going back to foods that are good for you, that are better than a supplement, given this unregulated nature of the supplements, uh, they include seeds and nuts and fish, especially salmon, and then green leafy veggies like spinach. They are all rich in magnesium. But it's all common sense. Basically, (laughs) what's good for your body is good for your hearing.

    15. AH

      Yeah. Although, uh, you know, having done many episodes on nutrition and talked to experts in nutrition, the number of people that really go out of their way to make sure they get enough green leafy vegetables, fiber-

    16. KS

      (laughs)

    17. AH

      ... and meet their protein quota per day, which, you know, nowadays, there's kind of controversy about how much protein. But, you know, most people just don't do the common sense things. So I think, uh, what I've learned is everyone, including myself, needs to be reminded to get sunlight, you know, set our circadian rhythm, not be on screens too late, get enough magnesium, ideally from food. I completely agree that supplements are useful in the context of when you're already doing things correctly with your nutrition. Or sometimes it's the case that when people are traveling or they're overly busy, they're just not paying enough attention to the foods they're eating.

    18. KS

      Mm-hmm.

    19. AH

      Uh, but that's not a long-term solution.

    20. KS

      Mm-hmm.

    21. AH

      Um, so I completely agree. Green leafy vegetables, (laughs)

    22. KS

      (laughs)

    23. AH

      ... uh, fish. Um, and this is, this information's now easy to find online, right?

    24. KS

      Yes.

    25. AH

      Which forms

  11. 47:30 – 53:19

    Tinnitus; Hearing Loss, Genetic & Environmental Factors

    1. AH

      of magnesium. So for people that have tinnitus or that don't want to get tinnitus, um, do you see any, uh, any harm in them, uh, kind of emphasizing magnesium intake through food and/or supplementation?

    2. KS

      That really hasn't been studied for any type of tinnitus. It's been studied in the context of migraine, and there, it really helps. And tinnitus, it's an umbrella term. Just like sensory neural hearing loss, it's an umbrella term.

    3. AH

      I see.

    4. KS

      It encompasses lots of different conditions. When it comes to hearing loss, there are already more than 200 genes identified to cause hearing loss, and that's the genetic component. But then there are environmental components to hearing loss, which includes noise trauma that we talked about, aging, infection. Lots of different, uh, infectious diseases can cause hearing loss, not only viruses from the herpes family, like herpes simplex virus, which causes a cold sore, or cytomegalovirus, which is the most common congenital infectious cause of hearing loss.

    5. AH

      CMV is very common, right?

    6. KS

      Exactly. CM-

    7. AH

      Something like 80 to 90% of adults in the United States carry CMV.

    8. KS

      Yes.

    9. AH

      What does that mean, that they, at one point, they had the, uh, CMV virus, and it, they felt it as a cold or a flu, but it was CMV?

    10. KS

      Yes.

    11. AH

      Mm-hmm.

    12. KS

      Indeed. And it, some of these viruses, they stay dormant and live with us forever. And then when the immune system gets weakened, then they can wreak havoc. And, uh, some of the other viruses from the herpes family, like Epstein-Barr virus, EBV, it's actually linked to cancer, d- different cancer types, including nasopharyngeal cancer.Um, so that's yet another cause of hearing loss, infectious hearing loss. Uh, then, uh, there is immunologic hearing loss when there is no infection but it's an inflammation, such as people with, uh, celiac disease or rheumatoid arthritis. They may have higher predisposition to developing hearing loss, not only because the little tiny joints in the middle ear becomes fi- become fixed and don't vibrate as well, but also because the inner ear is injured. So when we now say sensory neural hearing loss, we actually cannot specifically say exactly what's wrong.

    13. NA

      It's like a fever.

    14. KS

      E-

    15. NA

      Could come from any number of things.

    16. KS

      Exactly.

    17. NA

      Interesting.

    18. KS

      And the reason for that really goes back to the tiny size of the inner ear, to the point that if you image it using the current, uh, state-of-the-art imaging tools that include computer tomography or a CT scan or MRI, which is magnetic resonance imaging, you don't see cells in the living human inner ear. You just see a gray or white blob. Uh, and, uh, the organ is too small to be detectable by technologies of that resolution. Another issue is that you cannot biopsy it. It's so tiny that if you did tissue biopsy, you would destroy it. So that has really stimulated lots of very promising research in the area to improve diagnostics for hearing loss, which include both high resolution imaging of the inner ear and liquid biopsy, as opposed to tissue biopsy. And, uh, we have shown that if you take as little as half a microliter of that fluid perilymph, uh, we can detect molecular differences between, uh, mice with or without hearing loss. However, we have also collected this fluid from patients who undergo ear surgery. It's either when we perform cochlear implantation for those who are profoundly deaf, or we literally have to drill through the inner ear to get to the brainstem because they have a tumor such as a vestibular schwannoma or an acoustic neuroma, which is a tumor that causes hearing loss. So in these two instances, we can actually get inner ear fluid and we can study it and we can see differences. So I think that's a promising direction on the horizon. Another diagnostic possibility is genetic testing. That's relevant for people in whom, uh, there is a family history of hearing loss. But today, uh, when we, uh, test for known deafness-causing genes, it comes back definit- with a definitive answer only in 50% of people. And in another 50%, it often lists lots of variants of unknown significance. They are so common that we even use an acronym, VUSs. And some people will have tens, if not hundreds of these variants of unknown significance. So what do you make of that? You just shrug your shoulders and at this point we say, "Well, we don't know." But now one exciting research direction that we are pursuing with other investigators at Stanford and in collaboration with Google is to use AI to help us figure out which of these variants of unknown significance is actually significant. And by using those tools, we can establish the diagnosis in 80% of people. Uh, so now that's for hearing loss and you really asked about tinnitus, but this is really to tell you that both of these terms are huge umbrella terms and it's been super frustrating not having the ability to establish precise diagnosis to guide therapy. So tinnitus is an even bigger black box.

  12. 53:19 – 56:04

    Sponsors: AGZ by AG1 & David

    1. KS

    2. NA

      We've known for a long time that there are things that we can do to improve our sleep, and that includes things that we can take, things like magnesium threonate, theanine, chamomile extract, and glycine, along with lesser known things like saffron and valerian root. These are all clinically supported ingredients that can help you fall asleep, stay asleep, and wake up feeling more refreshed. I'm excited to share that our longtime sponsor AG1 just created a new product called AGZ, a nightly drink designed to help you get better sleep and have you wake up feeling super refreshed. Over the past few years, I've worked with the team at AG1 to help create this new AGZ formula. It has the best sleep-supporting compounds in exactly the right ratios in one easy-to-drink mix. This removes all the complexity of trying to forage the vast landscape of supplements focused on sleep and figuring out the right dosages and which ones to take for you. AGZ is, to my knowledge, the most comprehensive sleep supplement on the market. I take it 30 to 60 minutes before sleep. It's delicious, by the way, and it dramatically increases both the quality and the depth of my sleep. I know that both from my subjective experience of my sleep and because I track my sleep. I'm excited for everyone to try this new AGZ formulation and to enjoy the benefits of better sleep. AGZ is available in chocolate, chocolate mint, and mixed berry flavors. And as I mentioned before, they're all extremely delicious. My favorite of the three has to be, I think chocolate mint, but I really like them all. If you'd like to try AGZ, go to drinkagz.com/huberman to get a special offer. Again, that's drinkagz.com/huberman.

    3. AH

      Today's episode is also brought to us by David. David makes a protein bar unlike any other. It has 28 grams of protein, only 150 calories, and zero grams of sugar. That's right, 28 grams of protein and 75% of its calories come from protein. That's 50% higher than the next closest protein bar. These bars from David also taste amazing. Right now, my favorite flavor is the new cinnamon roll flavor, but I also like the chocolate chip cookie dough flavor, and I also like the salted peanut butter flavor. Basically, I like all the flavors. They're all delicious. Also, big news, David bars are now back in stock. They were sold out for several months because they are that popular, but they are now back in stock. By eating a David bar, I'm able to get 28 grams of protein in the calories of a snack, which makes it very easy for me to meet my protein goals of one gram of protein per pound of body weight per day and to do so without eating excess calories. I generally eat a David bar most afternoons, and I always keep them with me when I'm away from home or traveling because they're incredibly convenient to get enough protein. As I mentioned, they're incredibly delicious. And given that 28 grams of protein, they're pretty filling for just 150 calories, so they're great between meals as well. If you'd like to try David, you can go to davidprotein.com/huberman. Again, that's davidprotein.com/huberman.

  13. 56:04 – 1:04:36

    Individualization; Tinnitus Examination & Treatment, Supplementation?

    1. AH

      What you're saying is extremely important, both by virtue of what you're explaining in terms of the different types of hearing loss, new novel ways to detect hearing loss and hopefully treat hearing loss, but also that we lack, um, subtyping of what we broadly call hearing loss or sensory hearing loss or, or tinnitus. Uh, this is a, um, ubiquitous problem in, in the health space. Uh, I had our, our colleague, Mike Snyder from the Department of Genetics on, uh, just recently. That episode came out and, you know, he said, y- you know, we have to stop talking about, um, blood glucose responses, you know? Some people spike to potatoes. Other people spike to grapes. We actually have grape spikers versus potato spikers-

    2. KS

      (laughs)

    3. AH

      ... and they need different things. Same thing we hear fiber is great for us, and I agree. We need fiber.

    4. KS

      Mm-hmm.

    5. AH

      Some people experience a profound reduction in inflammation when they eat certain types of fiber. Some people experience significant inflammation, whole body inflammation when they eat other types of fiber.

    6. KS

      Mm-hmm.

    7. AH

      This was actually studied by Justin Sonnenburg and, and, uh, uh, Chris Gardner in their, uh, now becoming classic study about the value of low-sugar fermented foods, which were great for the microbiome, but the fiber group actually, the inflammatone in some people show marked increase. Do we say fiber is bad? No, it depends on the type of fiber.

    8. KS

      Exactly.

    9. AH

      And on and on.

    10. KS

      Yes.

    11. AH

      And we can talk about, it's like when people say colorblindness, I always say, "Well, like which kind?" (laughs) I mean, there's so many types of colorblindness. So, it's very important that, that you're highlighting this for vision as well. I, I definitely want to ask something about tinnitus, um, because I went into the literature a whi- this was a while ago, and just was trying to explore for what's being done or what's being, been tested in the nutrition and supplementation space, just because that was happening to be what I was looking at. And it seems that there are a few studies, I don't know how powerful these studies are, but a few studies that suggest that perhaps low dose melatonin might help. But then I realize it's very difficult to separate those out from improvements in sleep because the people were taking the melatonin before sleep.

    12. KS

      Mm-hmm.

    13. AH

      And then we know that anytime you sleep less-

    14. KS

      Mm-hmm.

    15. AH

      ... your inflammation goes up, you have a bunch of gut issues and whole body issues.

    16. KS

      Mm-hmm.

    17. AH

      So, is there any evidence that there's anything that people could safely experiment with? Perhaps magnesium if they choose through diet or supplementation or both? But is there any indication that people can take something or is it really the case that they need to go see a proper, uh, auditory neurophysiologist or clinician like you and get treated for tinnitus?

    18. KS

      Yeah, it's the latter-

    19. AH

      Mm-hmm.

    20. KS

      ... that they need to really be evaluated. And what studies have shown and systematic reviews and meta-analysis that none of this supplementation makes a difference for tinnitus.

    21. AH

      That's a real shame.

    22. KS

      It's a shame, and it's also potentially a methodological issue because again, everything was lumped under the same umbrella. But it is conceivable that different subtypes may respond to certain interventions, but because we don't know how to identify these subtypes, we are lumping them all together. So, when you lump them all together and put all studies together that have ever been done and perform meta-analysis, then it sounds like none of them make a difference. So, to the point that, uh, the American Academy of Otolaryngology Head and Neck Surgery really endorses two main interventions. One is amplification with a hearing aid for those who need it, and two is cognitive behavioral therapy. Those two interventions have actually shown to make a difference. There are other things that have been tried. Some people take things on their own. There is anecdotal reports of, uh, potential benefit, but that hasn't panned out in large-scale epidemiologic studies that have had the appropriate control group.

    23. AH

      Thank you for that. When Michael Kilgard was a guest on this podcast, he's auditory, uh, well, he's a neuroplasticity guy, but has spent most of his time in the, the auditory system, now vagus nerve system. He's from Mike Merzenich lineage.

    24. KS

      Mm-hmm, mm-hmm.

    25. AH

      Um, he emphasized that peoples, uh, who have tinnitus, uh, the fact that they think about it and pay attention to it tends to exacerbate the circuitry.

    26. KS

      Yes.

    27. AH

      Um, and it sounds like a brush off, but he really encouraged people to try and not think about it, try to distract themselves because that could help prevent some of the, you know, ramping up of the, the, what we call, as you and I call the gain of those circuits because, um... And, and people don't like that answer, and I can understand why they don't like it because, well, you won't want me to think about this loud ringing in my ears? And he's saying, "Yeah, until you, until you get a treatment, a proper treatment, uh..."... you need to try and not think about it, because thinking about it makes it worse. Which, of course, for some people, makes it worse-

    28. KS

      Yes.

    29. AH

      ... but nonetheless, I think it's a very important message, that if you have tinnitus, to do everything you possibly can to try and distract yourself from it and then pursue proper treatment.

    30. KS

      Exactly. And in fact, that's what we recommend in the clinic as well. And lots of people find it reassuring, because we first have to do complete and thorough evaluation, which includes examination of the ears, examination of the whole head and neck, hearing testing to make sure that there's no asymmetry or difference between the two ears. If there is a significant asymmetry, that triggers imaging or additional testing, like auditory brainstem evoked response testing. And imaging, it's typically MRI, and this is where we're looking for these tumors that could cause hearing loss. They're super rare, so I don't want people to be stressing out and thinking they have that, but it's important to rule out. Um, so, uh, indeed, once we find that there's, uh, no tumor, then we do try to reassure patients and explain that tinnitus is indeed a phantom sound produced by the brain and why it makes it. And the more you think about it, the more you reinforce that circuit, just like you said. So if you are occupied by other things or you have background noise, it lessens it. And we already know that this is true in terms of experiments that have been conducted, uh, and that has been shown by electrophysiology, by imaging, even in people. In people with tinnitus with normal audiometric thresholds, you can see hyperactivity in auditory centers in the brain, and in particular, the area that has been imaged is the inferior colliculus.

  14. 1:04:36 – 1:09:41

    Headphones, Tough vs Tender Ears, Children, Tool: Safe Sound Levels

    1. AH

      Um, I have to ask, with respect to headphones-

    2. KS

      Mm-hmm.

    3. AH

      ... how do I know if I'm listening to my headphones too loudly? Because I used to assume that if I use, I use corded headphones. I, I don't like the Bluetooth headphones for reasons, uh, related to, I, anytime I use the Bluetooth headphones, I get, um, a swelling of the lymph behind my ear, not the sort of lymph that we're talking about in the inner ear. And it's quite, um, quite consistent effect, and I think it's a heat effect. Some people say, "Oh, it's EMS," but I'm pretty sure it's a heat effect. So I don't, and I don't like them. I don't like having my ears plugged with those things. It doesn't sound as well to me as corded headphones. And I also was always losing the, the, uh, the non-corded ones. Um, I used to assume that there's no way that the phone manufacturer would let me turn up my phone loud enough to cause damage to my ears. How could that possibly be? Everything's regulated. But I recently learned that it's very easy to exceed the threshold of safety w- by going, uh, not even to the maximum volume of, of what I'm listening to.

    4. KS

      Yes, and, uh, it's so interesting, that observation that you have made, because these regulations are different in different countries.

    5. AH

      Hm.

    6. KS

      So even the same manufacturer of phones will set up the threshold at a lower level for the European market than for the American market.

    7. AH

      Wild.

    8. KS

      Because the assumption is that Americans like it louder.

    9. AH

      (laughs)

    10. KS

      And, um-

    11. AH

      They definitely talk louder than many, not all, but many areas of the world. I was recently in Italy-

    12. KS

      Uh-huh. (laughs)

    13. AH

      ... and, uh, went to this farmer's market. It was... And then I was indoors elsewhere. Uh, the Italians talk a lot.

    14. KS

      Yes.

    15. AH

      And they gesticulate a lot.

    16. KS

      Gestically.

    17. AH

      And the noise level got up there, but at one point, I was like, "Wow, you know, it's, it's, it's so pleasant." Um, it's not super loud. And then I landed in New York City, a city I love.

    18. KS

      Yes.

    19. AH

      And I was indoors, an environment shielded from outdoor sounds. I was like, "Wow, people are super loud here."

    20. KS

      Mm-hmm.

    21. AH

      And there are a couple other cities where I've really noticed that. And this isn't a knock on New York City-

    22. KS

      (laughs)

    23. AH

      ... um, but boy, Americans can be really loud.

    24. KS

      And to your question, it's not really the headphone style, it's really the sound level. And you can measure it. You can measure it on your DB meter, um, that you can download on your a- phone if you don't have it already. And th- again, the safe rule of thumb is 80 decibel is safe for eight hours. However, and then, and then for every three decibel increase in sound level-

    25. AH

      Halve that.

    26. KS

      ... you have to halve it. Um-

    27. AH

      But what if I don't use this decibel meter app? What if I'm lazy and I-

    28. KS

      So then, then, uh, if anyone can hear what you are listening to, uh, who is standing by you, it's too loud. So that's a good rule of thumb.

    29. AH

      Great. Uh, e- so parents, take note.

    30. KS

      Yes. E- exactly, take note. If you can hear your child's, uh, music or podcast that they are listening to through the headphones that they are wearing, too loud.

  15. 1:09:41 – 1:12:59

    Compounded Damage, Concerts & Hearing Loss, Tool: Ear Plugs

    1. KS

      levels.

    2. AH

      When I was in graduate school many moons ago, uh, I took a great auditory neuroscience class from Irv Hafter.

    3. KS

      Mm-hmm.

    4. AH

      Who's a-

    5. KS

      Yes.

    6. AH

      ... you know, kind of one of the-

    7. KS

      A legend. (laughs)

    8. AH

      ... a legend and a wonderful person and, um-

    9. KS

      Yes.

    10. AH

      ... uh, brilliant and a just a wonderful person, and he can move his ears. He pointed that out.

    11. KS

      (laughs)

    12. AH

      He could move his ears. Um, and I recall him describing something called the Two Hit Model, which has parallels to concussion where, and I get asked this a lot, you know, someone will say, you know, they had a bike accident or something hap- they had a slip and a fall or maybe they played a sport and they, they had a concussion. What should they do? And the first thing I always say based on my understanding of concussion and my, all my colleagues, our colleagues, um, support this statement is, "Don't get another concussion, especially not anytime soon." Now, people don't like that answer when it comes to a particular sport, but oftentimes the advice is, "You gotta stop playing the sport because if you get another concussion soon, you're gonna have serious issues down the line, maybe even sooner." But I recall Irv telling us about this notion that if you leave a concert and the next morning you notice that your ears feel like they're a little bit, um, clout- like you have earplugs in and you don't or if you hear a little bit of ringing in your ears, that you need to be especially careful about getting another high threshold sound arriving at your ears because the vulnerability is there-

    13. KS

      Mm-hmm. Mm-hmm.

    14. AH

      ... and two s- uh, subthreshold, um, insults-

    15. KS

      Mm-hmm.

    16. AH

      ... as they're called, right? Uh, to the cochlea, to the hair cells, each of which is not sufficient-

    17. KS

      Mm-hmm.

    18. AH

      ... to cause damage. If they're occurred too closely together in time, you can get very potent damage that's irreversible.

    19. KS

      Yes.

    20. AH

      And so I, I wonder if, um, it makes perfect sense in the context of-

    21. KS

      Yes.

    22. AH

      ... like concussion-

    23. KS

      Mm-hmm.

    24. AH

      ... which we raised as the parallel example. But, um, and he had some qu- some interesting experiments. I think these were done in Guinea pigs actually, but they also see this in industrial workers where they're getting, they have some ringing in their ears after a long week of being on the construction site, they'll go to a concert-

    25. KS

      Mm-hmm.

    26. AH

      ... and sure they could have gone to the concert at another time-

    27. KS

      Mm-hmm.

    28. AH

      ... and it wouldn't have been an issue. They certainly could recover from their work week, but you put those two things too close together in time-

    29. KS

      Mm-hmm.

    30. AH

      ... and they end up deaf.

  16. 1:12:59 – 1:15:56

    Transitioning Environments, Hyperacusis; In-Utero Hearing

    1. KS

      other may work.

    2. AH

      In the visual system, we know that if you're in a dark environment or a dim environment for a while, and you transition out of that environment, the eyes are particularly sensitive for-

    3. KS

      Mm-hmm.

    4. AH

      ... the first moments. Is that also true for the auditory system? So if I wear earplugs and then take them out, do I need to be especially careful about, um, w- in other words, are my ears more susceptible than they normally would be-

    5. KS

      Mm-hmm.

    6. AH

      ... if I'm coming from a very quiet environment or a noise cancellation headphone environment?

    7. KS

      Uh, they are. And the way we know that is from people who have hyperacusis that we alluded to before, and they are just so uncomfortable being in, uh, loud environments or even what we consider normal auditory environments-

    8. AH

      Mm.

    9. KS

      ... that they wear earplugs. But then when they pull them out, everything is unbearably loud. So in fact, the first thing in terms of counseling them, uh, we say, "Well, take out your earplugs. You have to get used to the normal listening environments." And, uh, we already know that the brain is amazing. It can get used to different stimuli, and it's important that it gets natural input so that it can work normally. Otherwise, indeed, it can calibrate, uh, in ways that are unhealthy.

    10. AH

      I know the fetus can hear.

    11. KS

      Yes.

    12. AH

      At what stage does the fetus begin to hear or sense, uh, w- mechanical waves at the level of the-

    13. KS

      In the-

    14. AH

      ... the- the cochlea.

    15. KS

      ... second trimester.

    16. AH

      Wow.

    17. KS

      And the organ of hearing is fully formed in utero, fully formed. It's-

    18. AH

      Babies come into the world ready to go.

    19. KS

      Listening, ready to go. And a- again, they hear in the womb. It's amazing.

    20. AH

      Amazing. So all this stuff about, uh, you know, mothers talking to their, uh, unborn in- uh, embryo and fathers too presumably-

    21. KS

      That's right.

    22. AH

      ... but especially mothers-

    23. KS

      Exactly.

    24. AH

      ... they have more opportunities for it.

    25. KS

      Exactly.

    26. AH

      Um, what are the thresholds? And the reason I ask is, I mean, can they hear a whisper? Can they... or, um, what can they hear?

    27. KS

      As you can imagine, challenging experiments to perform and some are based on electrophysiologic, uh, data and others are done based on imaging, and there's only so much you can do to pregnant women for safety reasons. So it's actually hard to precisely answer your question, but what is clear that the fetus can hear the mother's voice. So anything that's of that same intensity, the- the fetus can hear.

    28. AH

      For me, as somebody who's long been interested in and worked on plasticity, it absolutely has to be the case that the infant's auditory cortex is tuned to the precise frequencies and other aspects of mother's voice in particular.

    29. KS

      Mm-hmm.

    30. AH

      I mean, I think every mother would say, "Of course."

  17. 1:15:56 – 1:19:54

    Dogs & Sea Animals, Sound Pollution

    1. AH

      Um, second trimester.

    2. KS

      Mm-hmm.

    3. AH

      Wow. This might seem like a bit of an unfair leap, but, um, dogs-

    4. KS

      Mm-hmm.

    5. AH

      ... um, have very sensitive ears.

    6. KS

      Mm-hmm.

    7. AH

      Um, are we subjecting them to hearing damage? I know this is more for the veterinary crowd, but, uh, I- I'm about to get another dog and I would... uh, my last dog, I- he always seemed to ignore me no matter w- he was a bulldog, so that was part of his personality to pretend he couldn't hear.

    8. KS

      Mm-hmm.

    9. AH

      But, um, should we be more thoughtful about, um, the hearing of our cats and dogs and other animals?

    10. KS

      Of all animals, absolutely. And the s- most striking example is actually sea animals like whales and dolphins. All of that noise generated by, uh, big ships and motorized vehicles that are in the water are damaging their hearing and modes of communication th- to astounding and scary-

    11. AH

      Mm-hmm.

    12. KS

      ... ways. It- it's really unfair that we are doing that to the world around us. Uh, so now whales are getting lost because they communicate by sending and receiving these, uh, sound waves really long distances, miles away. And now you find them lost. They can't find their, uh, crew, the rest of their, uh, family, if you call it that, uh, and if they're in a quiet environment, the way they used to communicate before the modern industrial world, they function completely differently.

    13. AH

      Wow. So sound pollution in the ocean is a very real thing.

    14. KS

      Very real. Yes.

    15. AH

      Yeah.

    16. KS

      They- they- it's actually messing their navigation.

    17. AH

      Wow. It's- it's incredible 'cause it- I think, uh, the paper was published a few weeks ago that, um, light pollution is disrupting the duration over which songbirds are- are singing-

    18. KS

      Mm-hmm.

    19. AH

      ... and e- and it turns out they're singing longer throughout the year than they normally would, and everyone was, "Oh, nice, songbirds." But it's screwing up all the- the mating patterns-

    20. KS

      Mm-hmm.

    21. AH

      ... and the migration patterns-

    22. KS

      Mm-hmm.

    23. AH

      ... it's caus- I mean, we may see the eradication of many species, which I- I hope people realize is not just about being able to, um, see them in a zoo, it's- or- or appreciate a photograph of them. I- I mean, every animal impacts the ecosystem of another. So-

    24. KS

      Exactly.

    25. AH

      ... I think it's so important-

    26. KS

      Mm-hmm.

    27. AH

      ... what you're saying. Are there any efforts being made to try and, um, create limitations on where sound pollution or how much sound pollution can occur in the oceans? I know it's hard to regulate.

    28. KS

      It's hard because it's not even tightly regulated for people on land.

    29. AH

      Good point. Yeah.

    30. KS

      Uh, and there's a lot of room for improvement. For example, you have mentioned that you've traveled the world, you have noticed that in Western Europe, amplified music is not allowed on the streets.

  18. 1:19:54 – 1:26:26

    Hearing Loss, Dementia & Cognitive Decline; Tool: Slow Speech & Face Listener

    1. AH

      topics.

    2. KS

      That directly links to what you mentioned before, the importance of hearing for emotional, uh, communication, for relational wellbeing, and for cognition. So now there's mounting evidence for a strong link between hearing loss and dementia. It's not that everyone with hearing loss will develop dementia, so I really want the listeners to feel reassured that they don't need to run home and purchase hearing aids right away. I- it's just not the case. However, we are trying to identify who is at risk, and the standard tests, uh, are not that helpful in that regard because if you get just the standard audiometric testing, where you're in a sound booth and they play different tones and you raise your hand if you hear it, uh, and then you have a plot generated, it turns out that you can have 90% of neurons gone and your audiometric thresholds could be normal. And it's because the auditory system is so exquisitely sensitive that there is tremendous redundancy in it. And we talked about sensory cells, how they are connected to the brain by the auditory nerve. It turns out that there are 10 different nerve fibers contact a single sensory cell. Do you need all 10 of them to perceive sound? No, you need one. However, you need all 10 of them if you are in a noisy environment. So the l- g- going back then to the link between hearing loss and cognitive decline, uh, we are now using different tests to identify people who are at risk, and studies such as testing speech in noise or the ability to understand words in a noisy environment as opposed to in a quiet environment turns out to be helpful. It's not so simple. It's not there is one test that has perfect sensitivity and specificity, but the field has recognized the need to develop better hearing tests which are being developed.

    3. AH

      I love hearing that because I, no pun intended, because when I was a kid, I remember getting o- they would take you out of class, you'd get onto, it was typically a bus or a van, and you'd-

    4. KS

      Yeah.

    5. AH

      ... sit there and then you'd- you'd do the- the hearing test. Um, while that was appreciated, it was not very sophisticated. I like to know that there's been an evolution. Uh, that brings up an- an interesting scientific phenomenon as well which is the cocktail party effect.

    6. KS

      Yes.

    7. AH

      Uh, here, you and I are sitting in a room that is essentially silent except for a few noises, uh, around us, um, from time to time, but if we go to a loud environment, uh, within a few moments we can hold a conversation and- and essentially rule out all the other sounds. Do we know where in the brain that occurs? My guess is it's a circuit or network-wide phenomenon, but that's a brain thing.

    8. KS

      It's a brain thing, it's a circuit, uh, and it's absolutely central, uh, for understanding speech in noise. In fact, people with hearing loss typically experience problems understanding speech in noise. They have no problem in a quiet and facing you. In fact, that's a big m- uh, message for everyone who is listening, that it's more important to face someone and speak slowly if they have hearing loss than speaking loudly, I mean, th- than- than yelling. Uh, and so if someone, uh, has hearing loss, uh, and you are trying to talk to them with, uh, water running or a TV on or you are trying to talk to them from a different room, forget about it. You really have to face them and it has to be quiet and you have to slow down, and then they can really understand so much more.

    9. AH

      Thank you for that. I have a family member who is suffering from some moderate hearing loss, and I do notice that, uh, if there's anything going on in the background while we're on a phone call or even in person, it's- it's very dis- they get discombobulated, and they're very cognitively sharp. But the relationship between hearing loss and loss of cognition-

    10. KS

      Mm-hmm.

    11. AH

      ... what we call age-related dementia-

    12. KS

      Mm-hmm.

    13. AH

      Uh, people normally hear the word dementia and they think, "Oh, Alzheimer's," but the reality is we're all going to lose some cognition, um, speed or some other aspect of it, uh, with time, and, uh, it seems that vision loss and hearing loss are profoundly linked to age-related dementia. And I wonder if you could just, um, speculate, uh, on whether you think that has to do with how hearing loss in this case, you know, changes our behaviors and then causes loss of- of neurons in other areas of the brain in the same way that, for instance, if- if I had chronic ankle pain on my left side, I'd probably take the stairs less. I- I would at first probably push myself to do it, but at some point I would probably take the stairs less. So then you say, "You take the stairs less, you get less fit, cardiovascular fitness declines over time," and, you know, did- did the ankle actually cause the cardiovascular, uh, issue not directly but indirectly in the same way that if- if hearing is challenging, we're less likely to interact socially which also feeds back on dementia? Is that how it works or is there a direct link to unplugging some of the auditory input?

    14. KS

      We think that it's both.

    15. AH

      Mm-hmm.

    16. KS

      However, the direct link has not been established yet. Lots of studies are being done both in people and in animal models, uh, trying to real- es- really establish the direct link. Uh, so there-... data supporting it and refuting it, so that's why it's an active area of research. The indirect link is super well established because we know that hearing loss leads to social isolation, to depression, and cognitive decline. In fact, the cost of unaddressed hearing loss is the staggering nearly trillion dollars annually.

    17. AH

      Trillion?

    18. KS

      Trillion.

    19. AH

      With a T?

    20. KS

      Absolutely.

    21. AH

      Whoa.

    22. KS

      Yes. And it's because people have issues getting employed. They may not get the best jobs that they, uh, would like to be qualified for. All of arrangements that have to be done to make them as fully functional as possible are very costly. So indeed, it's an enormous problem that really needs more focus, more attention, and more research to develop new therapies.

  19. 1:26:26 – 1:27:38

    Sponsor: Joovv

    1. KS

    2. AH

      I'd like to take a quick break and thank our sponsor, Joovv. Joovv makes medical grade red light therapy devices. Now, if there's one thing that I have consistently emphasized on this podcast, it is the incredible impact that light can have on our biology. Now, in addition to sunlight, red light and near infrared light sources have been shown to have positive effects on improving numerous aspects of cellular and organ health, including faster muscle recovery, improved skin health and wound healing, improvements in acne, reduced pain and inflammation, even mitochondrial function, and improving vision itself. What sets Joovv lights apart and why they're my preferred red light therapy device is that they use clinically proven wavelengths, meaning specific wavelengths of red light and near infrared light in combination to trigger the optimal cellular adaptations. Personally, I use the Joovv whole body panel about three to four times a week, and I use the Joovv handheld light both at home and when I travel. If you'd like to try Joovv, you can go to Joovv, spelled J-O-O-V-V, .com/huberman. Joovv is offering an exclusive discount to all Huberman Lab listeners with up to $400 off Joovv products. Again, that's Joovv, spelled J-O-O-V-V, .com/huberman to get up to $400

  20. 1:27:38 – 1:30:12

    Lip Reading; AI-Enhanced Hearing Aids

    1. AH

      off. Do non-deaf, non-hearing impaired people lipread? Uh, are we always lipreading a little bit and we don't realize it?

    2. KS

      Some people are better than others-

    3. AH

      Mm-hmm.

    4. KS

      ... and, uh, as we've been discussing all along, it's not that one size fits all. All of us are a little different and some people are better at some things than others, and people lipread to different degrees depending on all sorts of things. Uh, th- their innate predisposition, their potential hearing loss that they may not even know, uh, their artistic nature where they are analyzing a face all the time-

    5. AH

      Mm-hmm.

    6. KS

      ... uh, their engagement and interest in what's being said. Uh, so going back to your question about the cocktail party environment. I- it's a problem for standard hearing aids in an environment like that because they tend to amplify everything, including that background noise. Uh, so that has led to a new generation of hearing aids that are AI informed and really are performing auditory scene analysis in real time to pick up signal from noise and, um, reduce amplification of the noise and, uh, reduce feedback. Uh, so that's an active area of research. The latest data, very promising. However, what's still needed is large scale controlled studies comparing traditional versus AI enhance- enhanced hearing aids. And indeed, that auditory scene analysis in a cocktail party environment is a problem. Uh, for example, directional hearing aids can address it to a point. I mean, hearing aids that have directional microphones if you know who you want to be listening to because then you face them. However, you may also want to be hearing someone who's talking behind your back and you don't realize it until you hear the first sentence or two that they have said.

    7. AH

      Mm-hmm.

    8. KS

      So if you have purely directional microphones, you're not even aware that that's happening. And that's why, uh, hearing aids with directional microphones are loved by some and not by others. So again, really all of this highlights that we are all a little different and it calls for personalized approaches that are tailored to a given individual's makeup and needs and preferences.

  21. 1:30:12 – 1:36:54

    Sleep, Tool: Earplugs; Hearing Yourself Speak, Superior Semicircular Canal Dehiscence

    1. KS

Episode duration: 2:27:42

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