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Dr. Jennifer Groh on Huberman Lab: How Gaze Reshapes Hearing

Groh shows thoughts are multi-sensory simulations running in sensory cortex; the superior colliculus links gaze direction to sound maps, altering what you hear.

Dr. Jennifer GrohguestAndrew Hubermanhost
Nov 10, 20252h 16mWatch on YouTube ↗

EVERY SPOKEN WORD

  1. 0:00 – 3:41

    Jennifer Groh

    1. JG

      What goes on in our brains when we think might be that we're running simulations related to the thought using that sensory, sensory motor infrastructure of the brain.

    2. AH

      Could you elaborate?

    3. JG

      So the theory is that, like, maybe when you think about a cat, for example, or you think the concept of a cat, that the mental instantiation of that, or the, the brain mechanism instantiation of having that thought is to run a little simulation in visual cortex that kind of includes what a cat looks like. A simulation in auditory cortex that, what does a cat sound like? And as I'm telling you this I'm, you know, I've used the word cat, um, what color cat are you thinking?

    4. AH

      I'm thinking of a, a gray cat, but I keep smelling kitty litter.

    5. JG

      Okay.

    6. AH

      'Cause my sister had cats and it drove me, the smell of kitty litter is just so aversive to me.

    7. JG

      Right. And s- (laughs) so you had no hesitation in telling me the color and adding an additional sensory quality. It provides an explanation for why you might, you know, be driving on the freeway and having to merge into difficult traffic and telling your, your passenger, "Okay, be quiet. I've got to, I've got to pay attention now." Like-

    8. AH

      Hmm. Mm-hmm. Mm-hmm.

    9. JG

      ... why would speech impair you from visual motor-

    10. AH

      Mm-hmm.

    11. JG

      ... if it wasn't all part of a kind of cognitive system that's, that's in operation, and maybe you need to shift some resources away from processing-

    12. AH

      Mm-hmm.

    13. JG

      ... the conversation and towards some, you know, actually dealing with the here and now sensory motor task?

    14. AH

      Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. (instrumental music plays) I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Jennifer Groh. Dr. Jennifer Groh is a professor of psychology and neuroscience at Duke University. Her laboratory studies how our brain represents the world around us, in particular how our different senses are merged in the brain so that we can focus and learn more effectively, including how our eye movements fundamentally shape not just what we pay attention to, but how they dynamically control what our brain is capable of. What she shares is fundamental to understanding how your brain works, and also how best to focus on and learn different types of information, not just information that you might read on a page, although including that, but also what you hear, what you remember, and the very thoughts you have about your life experiences. We also discuss thinking itself. In fact, we discuss what thoughts really are, and there Dr. Groh shares with us what is perhaps the clearest and most useful definition of what thoughts are and how you can control them. As someone who has been in the field of neuroscience for nearly three decades, I must say that her explanation of what thinking is, at the neural level, at the psychological level, and at the experiential level, is the most compelling and useful one I've ever come across. Today, Dr. Groh explains how to use your experiences, the information you encounter, and knowledge of how thoughts are built up in the brain to become a better thinker, and indeed smarter. I'm certain that the information you'll learn from Dr. Groh today is not like any other discussion you've heard about the brain or psychology. I'm also certain that it will be extremely useful for anyone wishing to better understand how the brain works, how their thoughts and emotions arise, and anyone who wants to get better at learning, thinking more deeply, or simply experiencing life with more richness. 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. Jennifer Groh.

  2. 3:41 – 7:42

    Sounds & Vision, Sensory Integration; Dynamic Maps

    1. AH

      Dr. Jennifer Groh, welcome.

    2. JG

      Thank you. It's great to be here.

    3. AH

      We've never had a proper conversation on this podcast about sensory integration. We've talked about vision, talked a little bit about hearing, little bit about touch, smell, taste, but we've never talked about how the senses come together, and that's critical to everyday life. Critical to perception.

    4. JG

      Absolutely.

    5. AH

      I know you focused perhaps mainly on the auditory system, but you really are a auditory-visual integration person. I know this because I've followed your work for a number of years.

    6. JG

      (laughs)

    7. AH

      So where in the brain do our eyes and our, our ears first come together to impact our perception of life? Like, we ... You know, the tea kettle is whistling or, you know, we hear a knock on the door, we know where the door is, we know where the tea kettle ought to be, but where do these things first collide?

    8. JG

      The story that is triggered by that question is a, a little bit long, so, uh, maybe I can start at the beginning of when I first got interested in this question.

    9. AH

      Mm-hmm.

    10. JG

      And so I was a college student. I was interested in neuroscience, but we didn't have a neuroscience, um, um, major, so, um, a couple of us talked, uh, a professor into offering a, a seminar in, in neuroethology and, and kind of like what he thought were sort of the coolest findings in neuroscience. Uh, and in that class, I learned about a, uh, study showing that, and I'm gonna, I'm gonna begin with the neuroscience nerdy lingo and then we'll unpack it.

    11. AH

      Mm-hmm.

    12. JG

      Um, that, uh, there's a brain structure called the superior colliculus, um, that's responsive to both visual and auditory stimuli, and that the responses to auditory stimuli depended on where the eyes were looking. Um, if you moved the eyes, the neurons' receptive field, the region in space where they were responsive to would shift, um, as the eyes moved. And that blew my mind. I could not get that out of my head, um, and it kind of set me on the track that, that I've been on ever since then.

    13. AH

      Mm-hmm.

    14. JG

      One of the things that was really interesting to me about it is that figuring out where a sound is with respect to where the eyes are looking is something that would be easy for us to do with a pencil and paper. You know, it's very simple math. If you know that, um, the sound is located, say.... uh, you know, 10 degrees to the right and your eyes are looking 10 degrees to the left, and that tells you that the sound is 20 degrees to the right of where your eyes are. Really not that hard to do. But from what I knew at that point, um, about how the brain represents this kind of spatial information, it seemed a big puzzle for how the brain might actually create these kinda moving representations of where the sound is located.

    15. AH

      Yeah, 'cause what you're talking about are dynamic maps.

    16. JG

      Yeah.

    17. AH

      Like, we have a... I think most people probably appreciate that we have a, a map of our body's surface.

    18. JG

      Right.

    19. AH

      A so-called homunculus.

    20. JG

      Yep.

    21. AH

      And so if w- one were to stimulate in a given region of the brain, you'd, uh, have the illusion of, uh, being touched at that location on the body. People perhaps have seen that, um, the more sensitive an area of the body, like the fingertips or lips or face, uh, or feet, the larger the representation in the brain. But what you're talking about is, is shifting maps depending on where the eyes move, and the eyes move quite a lot.

    22. JG

      They move quite a lot, exactly. And, and, uh, mostly we're not aware of this.

    23. AH

      Mm-hmm.

    24. JG

      Right? But if you think about it, every time your eyes move, the visual scene is shifting massively on the retina.

    25. AH

      Mm-hmm.

    26. JG

      But we don't even notice this.

    27. AH

      Mm-hmm.

    28. JG

      Um, and this is an indication that the brain is doing a ton of computation under the hood to give us that perceptual experience.

    29. AH

      Mm-hmm.

    30. JG

      Because if we were just representing reality, the reality would be these massively shifting, smeared visual scenes.

  3. 7:42 – 13:52

    Context & Mapping; Screens, Projection & Perception, Ventriloquists

    1. JG

    2. AH

      One thing that's so intriguing to me about the auditory system is, and the visual system, is the extent to which they can contract and dilate so fast.

    3. JG

      Mm-hmm.

    4. AH

      So for instance, if I'm, uh, like w- walking to get on public transportation of some sort, like a light rail or a subway, um, I'm walki-... I, you know, there's sound going by me, may or may not be relevant, but at some point, I sit down. Chances are, I open up a book or a computer, or these days people go into their phone. And we say, "Into the phone," because there's a lot of sensory information there, but th- our visual world and our auditory world just goes shoop-

    5. JG

      Right.

    6. AH

      ... into, you know, uh, a small box, and we expect whatever we're looking at to relate to the sounds that we're hearing in that small box.

    7. JG

      Right.

    8. AH

      But if somebody says, "Excuse me, do you have a ticket?" You, you know to look up.

    9. JG

      Right.

    10. AH

      We take this for granted.

    11. JG

      Mm-hmm.

    12. AH

      Like, most people might think of course you look up. Like, the sound is coming from over there, it's now a person. But we-

    13. JG

      Mm-hmm.

    14. AH

      ... all of a sudden, shoop, we can remap our visual auditory world and all the context-

    15. JG

      Yeah.

    16. AH

      ... in, like, milliseconds.

    17. JG

      Right.

    18. AH

      So is that all happening? Um, uh, we've been talking about superior colliculus at the, in the structure, the superior colliculus, uh, below our neocortex, meaning is it below our kind of conscious awareness?

    19. JG

      Uh, you know, gosh, I wish we knew where conscious awareness was.

    20. AH

      Mm-hmm.

    21. JG

      I think that's an open question.

    22. AH

      Mm-hmm.

    23. JG

      Um, and it... you know, the superior colliculus is important in this story because that's where the research began. It's not that that's where the binding of visual and auditory space, you know, is necessarily fully contained there and only there.

    24. AH

      Mm-hmm.

    25. JG

      I think it's a much bigger problem, and I think what you're describing is kind of, um, you know, a-another version of this kind of, um, capturing of, um, or integrating or connecting the information from one sensory system to another, that kind of shifting your resources around is something that happens in, in a few different contexts-

    26. AH

      Mm-hmm.

    27. JG

      ... like what you're describing. And I think one of the things that's really interesting about the phone or really any screen where you're watching a video is that the sound was never coming directly from the screen where you're looking at the visual image.

    28. AH

      Mm-hmm.

    29. JG

      You know, it's coming from somewhere else. Maybe you've got earbuds in, and it's coming from the earbuds. Maybe the earbud signal is simulating what the location should be, um, if it was really coming from the screen, but it's a simulation, it's not, not actually-

    30. AH

      Oh, yeah, that's-

  4. 13:52 – 16:53

    Sound Localization

    1. JG

    2. AH

      Is this something we learn during development?

    3. JG

      Partly, yes. Absolutely.

    4. AH

      Like, do kids come into the world understanding how to merge sight and sound, or, um, or is that a learned phenomenon?

    5. JG

      It has to be learned and it has to be continuously updated during the course of development until you reach your adult body size. So, let me back up a little bit and talk about, how do we localize sound? Especially when we're not talking about, you know, screens and video and movies and whatno- whatnot, but just, like, out there in the, in the real world. The way we tell where a sound is coming from is by the physics of the world causing differential delays for the sound to arrive at one ear versus the other. So, sound takes a certain amount of time. You know, a sound coming from over here will get to this ear before it gets to this ear. And it'll be slightly louder in this ear than in this one.

    6. AH

      Because it's just closer to that ear.

    7. JG

      It's closer, but also there's a, a kind of acoustic shadow cast by the head.

    8. AH

      Mm-hmm.

    9. JG

      So, the sound wave has to kind of come and then go around, and there's a little, you know, there's a little sort of dip in the sound intensity cast by the shadow of the head. I like to think about the timing cues because they're really easy to calculate. So, if you know how far apart your ears are and you know what the speed of sound is, then you can figure out, what's the delay for the sound, for sound to get-

    10. AH

      Mm-hmm.

    11. JG

      ... um, to reach this ear after this ear? I often take off my glasses to measure the distance between my two ears that way.

    12. AH

      Mm-hmm. Mm-hmm.

    13. JG

      And it's something like about a half a millisecond is the largest delay you can experience.

    14. AH

      Half a millisecond.

    15. JG

      Half a millisecond. So, this is tiny, and that is for the difference between a sound here versus a sound here.

    16. AH

      So, something from your right versus from your left.

    17. JG

      Exactly.

    18. AH

      Yeah.

    19. JG

      We can obviously detect much smaller sound separations than just l- totally left versus totally right.

    20. AH

      Mm-hmm.

    21. JG

      So, there's, you know, it's an incredible feat of computational power by the brain. I think maybe we should tell the audience, um, why, you know, your brow is f- uh, is furrowed and I'm excited about this.

    22. AH

      Mm-hmm.

    23. JG

      Because half a millisecond is less than the duration of a single action potential.

    24. AH

      Right, and we should just remind people, action potentials are the electrical signals that neurons use to communicate with one another. These are the, the, uh, the fundamental, um, way in which our brain works.

    25. JG

      Right.

    26. AH

      Without these, we're dead.

    27. JG

      It's the fundamental medium of communication, um, i- in the nervous system, as you say. So, it would seem totally weird for us to be able to pro- process sensory information that is faster than the duration of that minimum increment of, of firing. You know, there's some research about how exactly this can be done, and it involves things like lots of neurons firing together and really precise, uh, synapses that, um, cause minimal delay and very high temporal precision as the signals are going from one neuron to the next.

  5. 16:53 – 19:50

    Sponsors: Lingo & Wealthfront

    1. AH

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  6. 19:50 – 21:56

    Hearing Loss & Sound Localization, Ear Folds

    1. AH

      So, you know, if my finger snaps, uh, with my right hand, which is what I just did, you know, uh, intuitively I know that the... it's my right hand 'cause I did it, but-

    2. JG

      Yeah.

    3. AH

      ... my brain expects that sound to arrive more quickly to my right ear than my left ear.

    4. JG

      Right.

    5. AH

      And yet, for things directly in front of me, right at my nose, (fingers snap) the idea that it's right in front of me, it, it, let's say with my eyes closed, (fingers snap) I, I know to look in front of me. I know to expect it in front of me once I open my eyes.

    6. JG

      Right. Right.

    7. AH

      Are there conditions where we think we hear something from one location, but it's actually arising from another location that's outside an experimental context?

    8. JG

      Absolutely. So if you have hearing loss in one ear-

    9. AH

      Mm-hmm.

    10. JG

      ... uh, and one ear only, then, um, it, it's very difficult to localize sound.

    11. AH

      Hmm.

    12. JG

      It's not completely impossible. You would imagine that it would be completely impossible if the hearing loss was complete and if this timing difference and level difference were the only cues that we use.

    13. AH

      Mm-hmm.

    14. JG

      But actually, the ear has these little folds in them, and the folds filter the sound as it comes in, uh, and in particular, it alters the frequency content of the sound.

    15. AH

      Really? So these little dimples inside my ears-

    16. JG

      Yeah.

    17. AH

      ... are, are useful for something?

    18. JG

      They're useful, and your ears are different than my ears.

    19. AH

      Mm-hmm.

    20. JG

      Um, and so you are gonna be expecting a slightly different kind of fingerprint-

    21. AH

      Mm-hmm.

    22. JG

      ... of what the sound sounds like-

    23. AH

      Mm-hmm.

    24. JG

      ... as a function of location than I would be.

    25. AH

      Do people with damage to their ears have issues-

    26. JG

      Have issues with that?

    27. AH

      ... hearing? I mean, it sounds like, uh, sort of a, they must, um, but like the people I know that roll jujitsu-

    28. JG

      Yeah.

    29. AH

      ... like the wrestlers, their ears-

    30. JG

      Oh-

  7. 21:56 – 26:16

    Unfamiliarity of Hearing Your Own Voice; Tool: Bone Conduction Headphones

    1. JG

    2. AH

      If, if the auditory system is so sensitive, why is it that I don't really hear my own voice-

    3. JG

      Mm-hmm.

    4. AH

      ... um, or if I talk out one side of my mouth, like, I sort of know-

    5. JG

      Okay.

    6. AH

      ... what I'm doing, but it doesn't, doesn't throw me off.

    7. JG

      Doesn't sound quite right? Yeah, yeah.

    8. AH

      Doesn't throw me off.

    9. JG

      Yeah.

    10. AH

      And yet, most people have the experience of watching themselves or hearing themselves speak and it feels awkward.

    11. JG

      Yeah.

    12. AH

      We don't really like to-

    13. JG

      Yeah.

    14. AH

      I, I suppose there are some people on the planet that like to hear themselves speak, but most people don't.

    15. JG

      Yeah.

    16. AH

      Most people are not-

    17. JG

      Right.

    18. AH

      It, it sound... It's like we cancel ourselves-

    19. JG

      Yeah.

    20. AH

      ... out while we speak.

    21. JG

      Yeah.

    22. AH

      But then when it's coming at us from the front, it's like, it's o-

    23. JG

      It's weird.

    24. AH

      It's odd.

    25. JG

      Do you like listening to this podcast, or do you kind of like-

    26. AH

      Well, I listen to all the podcasts to see ways that I can improve.

    27. JG

      Yeah.

    28. AH

      Um, and I like the content that, that my-

    29. JG

      Yeah.

    30. AH

      ... guests bring on, and I like-

  8. 26:16 – 28:57

    Tool: Headphone Volume & Protecting Hearing

    1. AH

      a lot of questions about headphones and safety, and, uh, one thing that, uh, we resolved recently on the podcast, we had a guest on who's, uh, our chair of otolaryngology at Stanford, and she said that if your headphones are loud enough that somebody besides you can hear that there is a sound, not even the-

    2. JG

      Yeah.

    3. AH

      ... specific sounds-

    4. JG

      Yeah.

    5. AH

      ... uh, you are inflicting hearing damage.

    6. JG

      Right.

    7. AH

      Probably permanent hearing loss at some level. That, that-

    8. JG

      Yeah.

    9. AH

      She sets a pretty low threshold for, um, kind of like, "Be careful," but it seems important given that we now know hearing loss is correlated with dementia.

    10. JG

      Right.

    11. AH

      It makes sense. Less sensory information comes in, the brain probably says, "Oh, well, there's less stuff coming in," and starts-

    12. JG

      Right.

    13. AH

      ... turning off circuits. And then memory goes and attention goes, and there are other things obviously that can impact dementia, but, um ... So it's interesting. Um, the other question I get a lot, um, is, uh, about the Bluetooth-

    14. JG

      Mm-hmm.

    15. AH

      ... earphones. People want to know, are they safe? Is it safe to have this, like, Bluetooth arc o- you know-

    16. JG

      Oh, in-

    17. AH

      ... i- in your ears.

    18. JG

      In your ear?

    19. AH

      And, uh, we had a guest on here, uh, Matt MacDougall, who's the, uh, neurosurgeon at Neuralink-

    20. JG

      Mm-hmm.

    21. AH

      ... they're big on Bluetooth-

    22. JG

      Mm-hmm.

    23. AH

      ... there at Neuralink, but he said that the amount of, uh, radiation coming from those Bluetooth headphones-

    24. JG

      Mm.

    25. AH

      ... is considerably lower than the sort of radiation that you're exposed to all day, every day, so he wasn't concerned. Are you aware of any impact of heat? I'm not look- looking to go after EMF here if-

    26. JG

      Yeah.

    27. AH

      ... if there isn't anything there, but-

    28. JG

      Yeah.

    29. AH

      ... but of heat or of just having, um, EMF around-

    30. JG

      Around your ears?

  9. 28:57 – 37:24

    3D Sound, Sound Distance, Thunder, Earthquakes

    1. AH

      Like to talk about the experience of listening to something, music let's say-

    2. JG

      Mm-hmm.

    3. AH

      ... through headphones versus in the room.

    4. JG

      Mm-hmm.

    5. AH

      We don't think about it too often, but it's a totally different experience. In one case, you're hearing the sound in your head.

    6. JG

      Yeah. Right.

    7. AH

      Or even listen- You know, like your phone on speaker versus wearing ear- earphones.

    8. JG

      Right.

    9. AH

      The person's voice or the music is in, in your head-

    10. JG

      Right.

    11. AH

      ... as opposed to in the room.

    12. JG

      Right.

    13. AH

      And once you think about this difference, I, I simply can't go back.

    14. JG

      Uh-huh.

    15. AH

      It's like a-

    16. JG

      You like the full actual speakers, or do you-

    17. AH

      N- Well, now I-

    18. JG

      ... Do you like it in your head?

    19. AH

      ... try to listen to music in the room.

    20. JG

      Yeah.

    21. AH

      I find that to be a-

    22. JG

      Yep.

    23. AH

      ... better experience for me. But when I hear things with headphones, I now feel like, oh, like, the sound is coming from inside my head, and it, it's a little weird.

    24. JG

      Yeah. Yeah.

    25. AH

      I don't like it so much.

    26. JG

      Yeah. Right. It is possible to make sound that is coming from headphones f- sound like it is coming from outside, but to do that, you have to use all three of these sound localization cues. Um, things have to be, you know, to have a, a, an appropriate timing difference, an appropriate level difference across the two ears, uh, and to use the, the frequency filtering properties of, of the ear. And since everybody's ears are a little bit different, that last step is really hard.

    27. AH

      But there is 3D sound, right?

    28. JG

      Yeah.

    29. AH

      Like, we think about, like, three-dimensional vision is-

    30. JG

      Mm-hmm.

  10. 37:24 – 44:36

    Sound Integration; Sound Frequency & Distance, Warning Signals

    1. AH

      about this.

    2. JG

      It's incredible, right?

    3. AH

      This is a way that vision is so different.

    4. JG

      Yeah.

    5. AH

      I came up through vision science-

    6. JG

      Yeah.

    7. AH

      ... mostly. Um-

    8. JG

      Yeah, so did I.

    9. AH

      And ... right, I mean, there are certain wavelengths of light that can pass through our body, like-

    10. JG

      Yeah.

    11. AH

      ... long wavelength light. That's-

    12. JG

      Mm-hmm.

    13. AH

      ... relatively new findings. I think it's really interesting and it's very healthy for us, it turns out.

    14. JG

      Yeah.

    15. AH

      You know, mitochondrial health, et cetera. But light, in general, we're not used to thinking about light and wavelengths of light going through things, unless they're translucent or transparent, like a window. Sound is constantly bouncing off everything.

    16. JG

      We're in a hall of mirrors for sound all the time.

    17. AH

      But you experience me and I experience you during this conversation as one coherent sound. Even though we are ... biologically poised to detect half a millisecond differences in the a- arrival time of the two ears, there are much greater differences in the arrival time of my voice bouncing off the table versus the walls versus the ceiling versus direct path, but you integrate them.

    18. JG

      And I don't hear you as saying the same thing, you know, five different times, right?

    19. AH

      Right.

    20. JG

      You know, it's one integrated whole.

    21. AH

      And closing one's eyes doesn't change that. If I close my eyes and you speak-

    22. JG

      Right.

    23. AH

      ... I can register to the direct path. I infer that you're right in front of me. Of course I know that, 'cause my eyes were open a second ago. But all the versions of your voice arriving, bouncing off the different surfaces or arriving at my ears, and I don't ... it doesn't, it's not confusing and it's not jarring.

    24. JG

      Right.

    25. AH

      Like if somebody came over and touched my arm, and I felt it on my arm but also a little bit on the back of my neck and a little bit on my knee, that would be weird. That w- that would be odd. You know, and we can get these sensations. There are certain places on the back, for instance, that you can feel a subtle kind of phantom touch in your foot because of the way the neural circuits are organized. And with pain, we talk about this as, like, referenced pain. You know, for internal organs, there's, they're branches of, they're, uh, of nerves, such that, you know, uh, and this shows up in, you know, Eastern medicine but also Western medicine, like someone with a, with, like, liver pain-

    26. JG

      Mm-hmm.

    27. AH

      ... will register that in their shoulder, you know, and it, or-

    28. JG

      Yeah.

    29. AH

      ... and we think, "Oh, this is crazy." No, it's not crazy. The- there's actually branches that, that support that referenced pain. But we don't do this with hearing.

    30. JG

      Yeah.

  11. 44:36 – 47:39

    Sponsors: AGZ by AG1 & Our Place

    1. JG

    2. AH

      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. 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. If you'd like to try AGZ, go to drinkagz.com/huberman to get a special offer. Again, that's drinkagz.com/huberman. Today's episode is also brought to us by Our Place. Our Place makes my favorite pots, pans, and other cookware. Surprisingly, toxic compounds such as PFASs, or forever chemicals, are still found in 80% of non-stick pans, as well as utensils, appliances, and countless other kitchen products. As I've discussed before on this podcast, these PFASs, or forever chemicals, like Teflon, have been linked to major health issues such as hormone disruption, gut microbiome disruption, fertility issues, and many other health problems, so it's very important to avoid them. This is why I'm a huge fan of Our Place. Our Place products are made with the highest-quality materials and are all PFAS- and toxin-free. I particularly love their Titanium Always Pan Pro. It's the first non-stick pan made with zero chemicals and zero coating. Instead, it uses pure titanium. This means it has no harmful forever chemicals and does not degrade or lose its non-stick effect over time. It's also beautiful to look at. I cook eggs in my Titanium Always Pan Pro almost every morning. The design allows for the eggs to cook perfectly without sticking to the pan. I also cook burgers and steaks in it, and it always puts a really nice sear on the meat, but again, nothing sticks to it, so it's really easy to clean, and it's even dishwasher safe. I love it, and I use it constantly. Our Place now has a full line of Titanium Pro Cookware that uses the first-of-its-kind titanium non-stick technology. So, if you're looking for non-toxic, long-lasting pots and pans, go to fromourplace.com/huberman and use the code HUBERMAN. Right now, Our Place is having their biggest sale of the year. You can get up to 35% off all products now through January 12th, 2026. With a 100-day risk-free trial, free shipping, and free returns, you can try Our Place with zero risk, and you can see why more than one million people have made the switch to Our Place kitchenware. Again, that's fromourplace.com/huberman to get up to 35% off.

  12. 47:39 – 57:00

    Music, Rhythm, Community & Emotion

    1. AH

      So really, what we're talking about i- that I'd like to drill into even deeper across senses, but primarily with sound, is, you know, how space, uh, how the physical environment shapes our p- our perception of things.

    2. JG

      Yeah, yeah.

    3. AH

      Um, and I'm also very interested in the vi- the relationship between vibration and sound, given that our ears contain the apparatus to detect sound frequency but also, uh, have to do with, you know, balance and, and vibration.

    4. JG

      Mm-hmm.

    5. AH

      Most of us have had the experience of someone pulling up next to us in a car, blasting bass really loud-

    6. JG

      Oh, yeah.

    7. AH

      ... and our windows start shaking, and their windows-

    8. JG

      Right.

    9. AH

      ... start shaking.

    10. JG

      Right.

    11. AH

      Can we talk just about how objects have a, a, a resonant frequency?

    12. JG

      Right.

    13. AH

      I think this is pretty interesting-

    14. JG

      Right.

    15. AH

      ... and then people will inevitably want to know about how humans have a resonant frequency-

    16. JG

      Mm-hmm.

    17. AH

      ... and we do. I believe that certain frequencies of sound can shape our emotional state.

    18. JG

      Oh, sure. I mean, that's music, right?

    19. AH

      ... for example, right?

    20. JG

      For example.

    21. AH

      It just, for some reason, when we break it down to one frequency and it's not-

    22. JG

      Mm-hmm.

    23. AH

      ... um, packaged in music, people somehow think it's, like, woo or mysticism and it's-

    24. JG

      Mm-hmm.

    25. AH

      ... it's not.

    26. JG

      Mm-hmm.

    27. AH

      I mean, the, I'm fascinated by this, like, the gong, like, gongs as an ancient tool for j- well, trying to orient people's emotional state or signal.

    28. JG

      Mm-hmm.

    29. AH

      Like, if we hear (imitates gong) going, it sounds ominous, right? If we hear chirping of birds-

    30. JG

      Yeah.

  13. 57:00 – 1:02:37

    Music, Military; Courtship; Evolution of Music & Language

    1. JG

      and the other thing is that music plays a role in, um, in say the military and in war. I read somewhere that the military is the largest employer of musicians in this country.

    2. AH

      Interesting.

    3. JG

      Yeah.

    4. AH

      Makes sense.

    5. JG

      Well, you know, I thought, it was a surprise to me when I first-

    6. AH

      Yeah.

    7. JG

      ... first heard it.

    8. AH

      Yeah, surprising to me, but it, it makes-

    9. JG

      Yeah.

    10. AH

      I mean, somebody's gotta play Taps, usually that's one-

    11. JG

      (laughs)

    12. AH

      ... that's one horn though.

    13. JG

      Right, you get one-

    14. AH

      Right?

    15. JG

      Right. So, and I think the other, you know, possible angle for all of this is, you know, there are things in many species that are not o- obviously beneficial. Take the peacock for example, that, the, that enormous investment in plumage, in very colorful tail feathers is not something that is directly adding to the survival skills of the male peacock, but rather it's something the female peacocks like. Um, and so that tends to feed on itself too. So, that's another way that music could get into our, you know, panoply of human characteristics without necessarily directly leading to something like being able to get more food. Like, the rhythm thing gives us more food.

    16. AH

      Mm-hmm.

    17. JG

      People who are good at music might end up, um, with more offspring than people who, um, weren't good at music. That would be, that would be the sort of, uh, general idea behind that, that part of the theory.

    18. AH

      In many now older movies, um, typically it was a man singing to a woman.

    19. JG

      Mm-hmm.

    20. AH

      Or in the movie Say Anything, John Cusack-

    21. JG

      Yeah, with the stick.

    22. AH

      ... simply used a boo- a boombox, right?

    23. JG

      Yep. Yeah, right.

    24. AH

      Um, uh, or, um, poetry-

    25. JG

      Mm-hmm.

    26. AH

      ... creative works, but expressed out loud were the way that, um, courtship took place. Um, Erich Jarvis was on this podcast.

    27. JG

      Okay.

    28. AH

      I don't know if you know Eric-

    29. JG

      Yeah.

    30. AH

      ... at the Rockefeller.

  14. 1:02:37 – 1:09:48

    Ears, Visual & Auditory Integration, Sound Localization

    1. AH

      It, it's so interesting. I, so in the brain, uh, we haven't talked too much about brain structures yet, but maybe we can do that.

    2. JG

      Yeah, right. Yeah.

    3. AH

      Um, and not to fill people's minds with names of things, 'cause I always say like, it doesn't matter if it's called the superior colliculus or the superior schmaliculus. It doesn't matter unless-

    4. JG

      It doesn't matter.

    5. AH

      ... it, what, but what's interesting are the properties of these different brain structures.

    6. JG

      Right, right.

    7. AH

      So, um, I think about the ears as, you know, separating different frequencies of sound, and then there's a bunch of other important stuff. No disrespect to the auditory neuroscientists, but-

    8. JG

      Mm-hmm.

    9. AH

      ... but the, as you said, the, in the superior colliculus is where hearing and vision and the other senses come together. They're mapped onto one another.

    10. JG

      It turns out that the story is more complicated and more interesting than that. I got hooked on that particular study that I mentioned at the beginning. So this was auditory signals in the superior colliculus being affected by the position of the eyes at the time the sound was presented. And now our audience knows about how sound is localized. We haven't talked that much about how visual information is localized. I think 'cause mostly that's fairly obvious, that your, your eye is kind of a little camera and light hits a particular s- uh, location on the retina, and that retinal location tells us what the location of the visual stimulus is.

    11. AH

      Mm-hmm.

    12. JG

      But it tells us the location of the visual stimulus with respect to the direction the eyes are pointing. But our sound localization cues are with respect to, um, where's the sound with respect to the head. So this finding that neurons were responsive to sound but cared very much about the position of the eyes was really, you know, a startling finding when it first came about. When I set up my own lab, I basically set out to find out, well, where's, where does this computation happen? Where is the brain, um, incorporating information about eye movements into the processing of, of sound? You know, we, we knew from the literature was, okay, the superior colliculus is one of the places, but you know, does it, does it happen in the superior colliculus or does it happen in a different brain area? And so we kind of marched along the auditory pathway in brain areas that, I call them part of the auditory pathway because they're much more closely connected to the ear than to anything else, um, and because at the time nobody thought there were visual signals in these areas. We thought it was just auditory. That too turned out not to be true, but they're definitely much more auditory than visual. And what we found was that in each of these areas, eye movements affect the auditory signals there too, even though they weren't in this convergent structure of the superior colliculus. So we, we decided that it would take a long time to march through every brain area, and that it might be worth sort of jumping over a few brain areas and looking in the ear itself. So I need to give the audience a little bit more information about what, you know, what is possible in the ear and why that seemed like a reasonable thing to do. It has some little muscles in it. There are two muscles that control the bones of the middle ear, uh, and then inside the cochlea, there are, uh, cells called outer hair cells that can actually expand and contract, just the way a little muscle could.

    13. AH

      We should explain, the cochlear is this snail-shaped structure that has the, essentially the, we call them neurons, but these sensory cells that-

    14. JG

      Yes.

    15. AH

      ... that vibrate according to the frequency of the sound, and this is critical for our perception of sound.

    16. JG

      Exactly.

    17. AH

      And you have one on each side.

    18. JG

      You have one on each side. It's snail-shaped and it's connected. Uh, the vestibular, um, your balance structures are also connected to this as well. And to just describe the flow of information, you have, you've your, got your outer ear, you've got your ear canal, you have your eardrum, you've got these little bones that connect the eardrum to the cochlea, and so there's muscles that, um, that affect the motion of those little bones, and then there's cells inside the cochlea that can also act like muscles. These structures, um, get input from the brain. So we thought, well, if they're getting top-down input from the brain, are they getting a top-down input from the brain that carries information about, about the position of the eyes? You know, that it seemed like...... it seemed kind of like a wild possibility, but not completely out of left field. Like, there was a, a possible mechanism here that we could imagine. And the neat thing about this is that, um, we didn't have to do something like stick an electrode into these muscles because they're attached to the bones and attached to the eardrum. And so, if they were being manipulated by a top-down signal from the brain, they would tug these bones and then that would tug the eardrum, and when the eardrum moves, normally it moves in response to sound, but if it moves in the absence of sound, it's gonna make a sound.

    19. AH

      Mm-hmm.

    20. JG

      So, you could put a microphone in the ear canal to see whether or not anything was happening in connection with eye movements. And this too wasn't out in left field to do this, because, um, there's already kind of known signals generated by these kinds of structures that are measured by clinicians, by audiologists and, and otolaryngologists. Um, you can put a microphone in the ear and you can measure things called otoacoustic emissions. The-

    21. AH

      They basically ... your ears are making sounds, folks.

    22. JG

      Your ears are making sounds, folks.

    23. AH

      I know, I know, it's weird to-

    24. JG

      It's kinda wild.

    25. AH

      Some people make more of them than others.

    26. JG

      Some people make more of them than others.

    27. AH

      Yeah.

    28. JG

      Exactly. So, we wanted to know if any of these little sounds were being generated with eye movements, and I wouldn't be here telling you this story if it didn't turn out that yes, they do. So, we were able to measure that the eardrum is, is basically moving in connection with, with every eye movement, every saccadic eye movement. These are the fast, jerky eye movements. There's other kinds of eye movements and we haven't yet tested them. The signal is very precisely time-locked to the onset of the eye movement, and the effect, um, is different in the two ears so that if your eyes are moving to the left, the eardrum on the right is gonna kinda, uh, bulge inward then outward then inward. I might have this backwards, um, but whatever the right ear is doing, the left ear is doing the opposite, so that the eardrums are gonna be moving in the same direction. One is gonna be inward when the other is going outward.

    29. AH

      Like a wave.

    30. JG

      Like a wave, exactly. Like a wave, not like a, a, not like-

  15. 1:09:48 – 1:15:17

    Evolution of Visual & Auditory Systems, Music; Brain Controlling Vision

    1. AH

      Which would be the critical first step if the major goal of this integration of visual and auditory is for localization of sounds.

    2. JG

      Right.

    3. AH

      Because the, uh, you know, in, um ... As, uh, a neuroscientist, you know, like, there's so many different areas of neuroscience.

    4. JG

      Mm-hmm.

    5. AH

      Like, I used to marvel at, you know, you go to a meeting, you got people saying "consciousness" and working on consciousness.

    6. JG

      Mm-hmm.

    7. AH

      You have people trying to figure out how-

    8. JG

      Mm-hmm.

    9. AH

      ... a single photoreceptor works, or a single hair cell works.

    10. JG

      Yeah.

    11. AH

      And so, when I think about a sensory system-

    12. JG

      Mm-hmm.

    13. AH

      ... I think about layers of sophistication-

    14. JG

      Mm-hmm.

    15. AH

      ... and how they likely evolved. Like, very briefly, I mean, the visual system first evolved to detect light and dark on the order of 24 hours, so you know the difference between nighttime and daytime, which means even with the total inability to see objects, you are safer if you know when to stay in and when to go out. And then at some point, we evolved the ability to, um ... Probably motion detection came f- before the ability to send, to see detail-

    16. JG

      Yeah.

    17. AH

      ... 'cause it's way more important to know if something's-

    18. JG

      Yeah. Yeah.

    19. AH

      ... big and coming at you-

    20. JG

      Right.

    21. AH

      ... big and moving away-

    22. JG

      Right.

    23. AH

      ... or s-

    24. JG

      Or help you stay oriented, like, with respect to, like, knowing what's up and what's down-

    25. AH

      Right.

    26. JG

      ... and staying upright.

    27. AH

      That's right.

    28. JG

      Yeah.

    29. AH

      And just like, uh, the falling, uh, reflex is probably the most important reflex in the vestibular system-

    30. JG

      Mm-hmm.

  16. 1:15:17 – 1:16:45

    Sponsor: Helix Sleep

    1. JG

    2. AH

      I'd like to take a quick break and acknowledge our sponsor, Helix Sleep. Helix Sleep makes mattresses and pillows that are customized to your unique sleep needs. Now, I've spoken many times before on this podcast about the fact that getting a great night's sleep is the foundation of mental health, physical health, and performance. When we aren't doing that on a consistent basis, everything suffers. And when we are sleeping well and enough, our mental health, our physical health, and our performance in all endeavors improves markedly. Now, the mattress you sleep on makes a huge difference in terms of the quality of sleep that you get each night. How soft that mattress is, how firm it is, how breathable it is, all play into how well you'll sleep, how much deep sleep you get, how much rapid eye movement sleep, and it needs to be tailored to your unique sleep needs. So if you go to the Helix website, you can take a brief two-minute quiz, and it will ask you questions such as, "Do you sleep on your back, your side, or your stomach? Do you tend to run hot or cold during the night?" Things of that sort. Maybe you know the answers to those questions, maybe you don't. Either way, Helix will match you to the ideal mattress for you. For me, that turned out to be the Dusk mattress, D-U-S-K. I started sleeping on a Dusk mattress about three and a half years ago, and it's been far and away the best sleep that I've ever had. So if you'd like to try Helix, you can go to helixsleep.com/huberman, take that two-minute sleep quiz, and Helix will match you to a mattress that is customized for your unique sleep needs. Right now, Helix is giving a special offer to Huberman Podcast listeners of up to 27% off site-wide. Again, that's helixsleep.com/huberman.

  17. 1:16:45 – 1:22:37

    Physical Space & Sounds; Cathedrals, Sound Delay

    1. AH

      I wanna talk a little bit about physical spaces.

    2. JG

      Yeah.

    3. AH

      Recently, I was in New York and someone took me to Grand Central, where there are these incredible, um, arches in one of the hallways there.

    4. JG

      Mm-hmm.

    5. AH

      Um, people should check this out. It's really, really cool.

    6. JG

      It is beautiful.

    7. AH

      It's beautiful. I mean, you have this high ceiling main, kinda, chamber-

    8. JG

      Mm-hmm.

    9. AH

      ... room of the, of Grand Central. Um, and there's also a, a hallway off to one side where you can go into a corner-

    10. JG

      Mm-hmm.

    11. AH

      Do you know about this? Um, uh, and you can face into the corner-

    12. JG

      Uh-huh.

    13. AH

      ... like you were going to, you know, like you're facing the corner in shame, but you're not. And whoever you're with can go to the opposite diagonal corner.

    14. JG

      Oh, yeah. Yeah.

    15. AH

      The ceiling is shaped like a, a, somewhat of a dome.

    16. JG

      Uh-huh.

    17. AH

      It's contoured, but it's more or less a, a small-

    18. JG

      Right.

    19. AH

      ... a small dome. But you are easily 25 feet away from this person-

    20. JG

      Yep.

    21. AH

      ... that you're there with. Again, diagonal corner. And if you speak at a very, very low volume, they can hear you on the opposite side.

    22. JG

      Yeah. Yeah.

    23. AH

      And if they speak, you can hear them. And what's wild is there's a lot of noise in the environment.

    24. JG

      Yeah.

    25. AH

      This is Grand Central Station.

    26. JG

      Yeah. Yeah.

    27. AH

      And we played with this a little bit, like if high frequency sounds do s- seem to travel a little bit, a little bit better-

    28. JG

      Okay.

    29. AH

      ... in this, uh, i- environment.

    30. JG

      In that particular setting, yeah.

Episode duration: 2:16:34

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