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Jeffrey D. Sharon, "The Great Balancing Act: An Insider's Guide to the Human Vestibular System" (Columbia UP, 2025)
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- [00:00]
Jeffrey Sharon
Limu Emu and Doug.
- [00:03]
Marshall Poe
Here we have the Limu Emu in its natural habitat, helping people customize their car insurance and save hundreds with Liberty Mutual. Fascinating. It's accompanied by his natural ally, Doug.
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Gregory McNiff
Uh, Limu is that guy with the binoculars watching us.
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Jeffrey Sharon
Cut the camera.
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Gregory McNiff
They see us.
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Jeffrey Sharon
Only pay for what you need@libertymutual.com Liberty Liberty Liberty. Liberty Savings vary unwritten by Liberty Mutual Insurance Company and affiliates Excludes Massachusetts.
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Marshall Poe
Hello, everybody. This is Marshall Poe, the founder and editor of the New Books Network. And if you're listening to this, you know that the NBN is the largest academic podcast network in the world. We reach a worldwide audience of 2 million people. You may have a podcast or you may be thinking about starting a podcast. As you probably know, there are challenges basically of two kinds. One is technical. There are things you have to know in order to get your podcast produced and distributed. And the second is, and this is the biggest problem, you need to get an audience. Building an audience in podcasting is the hardest thing to do today. With this in mind, we at the NBM have started a service called NBN Productions. What we do is help you create a podcast, produce your podcast, distribute your podcast, and we host your podcast. Most importantly, what we do is we distribute your podcast to the NBN audience. We've done this many times with many academic podcasts and we would like to help you. If you would be interested in talking to us about how we can help you with your podcast, please contact us. Just go to the front page of the New Books Network and you will see a link to NBN Productions, click that, fill out the form and we can talk. Welcome to the New Books Network.
- [01:38]
Gregory McNiff
Welcome to the New Books Network. I'm your host, Gregory McNiff, and I'm excited to be joined by Jeffrey Sharon, the author of the Great Balancing Act, An Insider's Guide to the Human Vestibular System. The book was published by Columbia University Press in the United States in December of 2025. Jeffrey Sharon is the Director of the Balance and Fall center and an associate professor in the Otology, Neurotology and Skull Based Surgery Division at the University of California, San Francisco. I selected the Great Balancing act because it reveals how one small, often overlooked part of the inner ear affects nearly every aspect of human life, from movement and perception to memory and emotion. It's both a scientific and a philosophical exploration, and I think listeners will be fascinated by how this, quote, hidden system shapes everyday experience. Basically, it's a book that connects anatomy to meaning. Hello, Jeff. Thank you for Joining me today to discuss your book.
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Jeffrey Sharon
Thank you so much for having me.
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Gregory McNiff
Jeff, why did you write the Great Balancing act and who is the target reader or audience?
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Jeffrey Sharon
So, I'm a physician, and I care for patients with a variety of vestibular disorders that cause vertigo, that cause dizziness, that cause imbalance. So, um, I've always approached the vestibular system from that standpoint. Um, but trying to expand my knowledge and learn more and more about the vestibular system, I found that there was this pretty interesting story out there that just hadn't been told before about the history of the vestibular system, about its evolution, about how it's important not just for medicine and health, but for normal functioning, for thinking. It's important for pilots taking off from an aircraft carrier. It's important for astronauts going up into space, because a system that's fundamentally designed to sense gravity doesn't do that well in outer space. And it seemed like it was a good time to try to weave it all together into a story about this. As you say, kind of forgotten part of our inner ears and forgotten sense that turns out to be pretty important.
- [03:55]
Gregory McNiff
Yeah, that's a great, great introduction to the, to the book, Jeff, and just curious in terms of target audience, obviously any med students or individuals interested in anatomy, biology, hearing would really benefit from this. Was there anyone else, patients, or even friends and family, where you thought, I want to make this field more accessible because it's so, so important to us.
- [04:19]
Jeffrey Sharon
The aim of the book is that it should be accessible to anyone who enjoys thinking about science, thinking about neuroscience. Understanding the world around us has some creativity and a nice place to read, like a hammock or a little book nook or something. Definitely those invested in the field, you know, those who care for patients with vestibular disorders, neurologists, ENT doctors, patients who suffer from the horrible disorders that the vestibular system creates might find the book particularly appealing. But I really wrote it for the general public.
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Gregory McNiff
Yeah, no, I can totally concur. It is very accessible to the general public. As someone who has no medical training, and I want to talk about later, you do interweave your own personal experience and candidly, your personality into the book, which I really enjoyed, and we should talk about that. But let's start at the beginning. Jeff, what is the vestibular system?
- [05:21]
Jeffrey Sharon
The vestibular system jokingly referred to as the sixth sense because it's not the sense you're taught about in kindergarten. It's not hearing, it's not vision. It's not touch. It's our inner ear's ability to sense movement, to sense gravity, and to sense rotations and turns and tilts and things like that, and the parts of the brain that help process that information. Even though we don't think about the vestibular system as often as we should, it turns out that you need a vestibular system. And by that I mean an aircraft has a vestibular system. Half of the instruments in the cockpit are really an analog of a vestibular system where it tells the pilot if the plane is tilted or turned. Well, your brain needs the same ability. Your iPhone also has a vestibular system. That's how it knows when it's upright and switching from portrait to landscape, because it needs to know how it is oriented in space. And it turns out this ability to know how you are oriented in space and also how your head and body are moving throughout space is critical for normal functioning and for getting around the world.
- [06:36]
Gregory McNiff
Yeah, absolutely. And you give some great case studies, and I think we all would agree with what you just said. You do introduce a number of terms in the beginning of the book. And for the audience, I'll just apologize right up front. I probably either get the pronunciation wrong or certainly the definition. But, Jeff, I want to ask you about one of these. Somoto sensation. Could you talk briefly what that is?
- [06:57]
Jeffrey Sharon
Yeah. And I do. I do want to disclose to the audience, you know, this is supposed to be a fun book. It is a book with a glossary. And when you're writing a book, and maybe that's an inherent disconnect there, when you're writing a book about science, I think the question is what level to write it at. And I wanted to write it at a level where we didn't miss some of the interesting details because we were too scared to wade into them. But we also don't lose everyone, and we bring everyone up to speed quickly. And I settled on what I thought was a reasonable compromise. Somatosensation is a fancy medical word for touch. So it basically refers to our ability to sense touch. Now, when you break it down, there's a lot of different forms of touch. One of them is just feeling the ground beneath your feet. That's kind of a pressure sensation. One of them is temperature, one of them is pain, um, and then one of them is vibration. And also we can sense the position of our joints within space, meaning, I know even without looking, if my arm is outstretched or if it's crawled inwards. And that's called proprioception. Another big word, which is a subset of this other fancy word, somatosensation, which, again, is just a synonym for touch. But, you know, in. In medicine, we have to have our big words. I apologize for that, but that's. Things are. I bring up somatosensation because it's one of the critical components of balance, Meaning we talk about balance as being one of the parts of the vestibular system, but balance is a multisensory effort, meaning it's vision helping us balance. It's somatosensation with touch, especially on the bottom of our feet, helping us balance. And then the inner ear, sensory systems, sensing the sway, the movement, the turning, that helps us balance. And all of those come together in an integrated fashion in the brain to help us balance.
- [09:10]
Gregory McNiff
Yeah, excellent definition, not surprisingly, and I will point out the book is very fun to read. And Jeff does say at the beginning of one of the later chapters, half a medical school, I guess, is the training, and the other half is learning the terminology of language. So don't feel bad if you're in the second half. You sort of nailed it, Jeff, that the vestibular system touches on a number of different functions, and there is some relationship between hearing and balance. They seem very closely intertwined. Could you talk about why that is? And the vestibular system, it is in the inner ear, is that correct?
- [09:45]
Jeffrey Sharon
Yes. So it's in the inner ear. Interestingly, it's surrounded by some of the densest bone in the body. So that, number one, maybe makes my job a little bit difficult as a surgeon who operates in that area. But number two, it provides some interesting insights because there are extinct animals, you know, there are dinosaurs that we can see their inner ears because it's protected by that dense bone. So it survives hundreds of millions of years later. So it's a fairly small organ. You know, the hearing bones are by far the smallest bones in the human body. When you look at the one that sits atop the inner ear, the stapes bone, it was so small, the Greeks didn't know about it. You can see it with the naked eye, but it's kind of hard to see with the naked eye. It's only in 17th century Italian anatomists that you really start seeing the stapes bone, even described when you look across the inner ear. It's basically the way I think about it is there's a fundamental cellular technology that's present in the inner ear, and evolution has found a number of interesting uses for it. Right. So keep in mind we are animals, we have to hunt for food, we have to reproduce, we have to be safe at night. So we have to take advantage of the physical properties of Earth and by our special senses, gain advantage over other animals. And that's why almost every animal has a pair of eyes, is because it's such a useful ability to see light and electromagnetic spectrum. Well, it turns out that the ability and the need to sense gravity is almost universal. You know, plants have a vestibular system. It's a rudimentary one. It just enables them to sense gravity, but they need to know which way is up. Jellyfish have a rudimentary vestibular system because they need to know where the surface is. And, you know, mice, monkeys, humans, elephants, we all have a vestibular system. And it all starts with this primitive need to sense gravity. It's hard to move without knowing which way is up and this primary orientation. So if you look at an inner ear, it's a very interesting shape, but the middle part is where you have the gravity sensing organs. And that's the evolutionarily, the oldest part of the inner ear. It's kind of the center of the inner ear. And there's an irony there. This center part is called the vestibular, the vestibule. And the vestibule just means the entry chamber. And it's named that way because no one realized when it was first discovered that it actually had its own purpose. They thought it was just the entry hall into the organ of hearing, the cochlea, but it actually has its own purpose. So the name vestibular actually belies how little importance the whole system had from a historical perspective within that. So you have this ability to sense gravity, and that's enabled through these specialized cells called hair cells. And we have found two other uses for them also in the inner ear. One is sensing hearing and one is sensing head turn. So the semicircular canals, the three semicircles that come off this central chamber, sense head turns. And the other part, the coiled snail, which is what cochlea means in Greek, is where the hearing happens. And it all happens in the same area because these hair cells are able to sense microscopic fluid movements, and therefore it makes sense to house them in the same area. Now, that creates some interesting problems because sometimes the same diseases affect both. So they're like roommates. And when you have a leak and both roommates get affected because the whole apartment floods, that can happen with, say, an inner infection that causes hearing loss and imbalance.
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Gregory McNiff
Yeah, and great, you hit on a number of key themes. There, particularly the scientists whose shoulders we stand on. These hairs you talk about are just absolutely fantastic as sensing organisms. I want to go into that, but I want to briefly circle back to discussion of the evolution of the vestibular system. And you referenced this theme of form follows function two or three times throughout the book. Could you just expand on that again in the context of the ability to sense gravity is the key here? How did evolution help us get where we are?
- [14:29]
Jeffrey Sharon
Right, yeah, this is something that. It was a realization to me. When you start to look and you begin to not just memorize a bunch of facts because you're in med school and you gotta pass the test, but you take a step back and you start to say, can I appreciate the holistic structure of what this sense is trying to do? I think you begin to see that if you understand the design, you understand the need, you understand the purpose, then you can understand the predictable failures that happen. And that's what a lot of these diseases are. And suddenly what seems to be mysterious isn't mysterious anymore because you say, oh, I understand it. We need to sense gravity. How do we sense gravity? We sense gravity. It's a simple design. It's basically a plumb line, right? We have something heavy inside our inner it. It settles in a gravity dependent position. And therefore the hair cells, which can sense when something's pushing or tugging on them, that's their fundamental role, can sense where the heavy stuff lies. What is the heavy stuff? The heavy stuff is the ear crystals you've heard about. So the ear crystals are 2.7 times denser than anything around them, and they always settle in a gravity dependent position. Okay, so now I understand that we have ear crystals, but now I can extrapolate that and begin to understand the diseases. Right? So if I have a gravity sensing organ right next to an organ that senses head turns, what happens when the crystals end up in the part of the inner ear where they're not supposed to be, the part that's supposed to sense head turns? Well, when you move your head relative to gravity, then it tricks your brain into thinking you're spinning around really, really fast. And that's. We call the loose crystals disease, which we also name by a big medical name, the acronym bppv. But it's a predictable outcome of knowledge of the system and its functioning. And I think there's interest in that because it's an elegantly designed system. And there's something kind of wondrous to behold when you understand how its form follows its function.
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Gregory McNiff
No, absolutely. It's a beautiful description. I want to hit on a few more terms here. You talk about the cochlea, the organ of hearing. You describe that as beautiful. Why do you think that?
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Jeffrey Sharon
Why do I think that? When you look at it and you see a 3D reconstruction of it, it's this elegantly curled spiral. The inner ear really has the most interesting shape of almost any part of our body. And then when I show patients their scans were in the, I like to point it out because I show them here, look at this little spiral that you have. And then I show them their canals. And I say, look at this little circle that you have. You don't realize your head has three interlocking circles inside of it, the width of each millimeter across of these circles. And why do you have three interlocking circles? Well, very simple answer, right? There's three axes of movement. And if you want to be able to sense any type of head movement, you need three interlocking circles. So how are they arranged? They have to be arranged at right angles to each other to be able to sense any type of head movement. And that's what evolution provides. So I think that there is something elegant to it. You know, the mammalian inner ear provides the best hearing of any animal on earth. Right. We can hear orders of magnitude in terms of sound loudness and also the frequency of sounds. A normal human can hear sounds from 20Hz to 20,000Hz. It's this remarkable range. You know, a chicken can hear up to 1000Hz. It's nowhere close to what we can hear. And that is enabled by this elegant design. And I could go into it further even, because it's actually even more remarkable how we're able to hear these soft sounds. Some researchers have calculated that we can sense microscopic movements that are smaller than the width of an atom. That is the sensitivity of this system. And it. And you could sense. Okay, that's a useful evolutionary thing to sense when the lion is stepping on the leash as it's approaching your campground or whatever it is. But we have this remarkable ability to hear very, very soft sounds.
- [19:20]
Gregory McNiff
Yeah, that's absolutely amazing. I want to just ask you a follow up question about these semicircular canals and particularly this endolymph movement. Could you talk about what that is as it relates to the fluid and the crystals?
- [19:35]
Jeffrey Sharon
Absolutely. So we talked about the hair cells in one part of the inner ear being responsible for sensing gravity. And that's because the crystals sit atop them. Just picture a layer of crystals on top of some Jelly on top of hair cells. So whenever you tilt your head relative to gravity, the crystals start shifting. The hair cells sense that within the semicircular canals, we have a different orientation of the hair cells. So picture a circle, and then there's just one area in the circle where you have the sensory part, the part that actually does the sensing, and it's a bunch of hair cells. And then they. They stick their little microscopic hairs into this jelly like substance that's basically like a wall that blocks off the inside of the circle. And the way this works is pretty ingenious and pretty simple. So basically, if I turn my head one way or another, the fluid is inside. Your ear has inertia. Inertia just means it wants to stay where it is. Inertia is why when you take a cup of water and you suddenly move it really quick, the water wants to stay where it is and you spill everywhere. Right. So the same thing happens inside our inner ears. The fluid has inertia. It wants to stay where it is, and it pushes against that wall that's blocking the inside of the canal. And because the hair cells are embedded inside that wall, they sense every time the wall is stretched one way or another. And that wall is called the cupula. And that's how the semicircular canals work.
- [21:13]
Gregory McNiff
That is absolutely fascinating. So one more question on this. On one hand, you talk about the symmetry of the semicircular canals, but is there also an asymmetry? It felt like in one section of the book, you're talking about when we turn to the left versus when we turn to the right, there's a positive or negative reaction. And I was a little surprised because you do talk about the geometry and the symmetry, and I would have expected that horizontal turn to have an equivalent reaction. Can you maybe expand and more intelligently explain to the audience what I'm asking you?
- [21:48]
Jeffrey Sharon
Yeah, absolutely. Yeah, an excellent point. Yeah. So there is a beautiful symmetry that happens with these six canals able to sense the head turns in any direction. And interestingly, interestingly enough, one of the cardinal features of the vestibular system is to keep our vision steady when we move. So each of the canals is roughly in the same plane as one of the. Guess how many eye muscles we have. Six. Each eye has six muscles, six semicircular canals. Not a coincidence. It's because there's cardinal axes of movement and because the vestibular system needs to control your eyes when you're running so that the world doesn't bob up and down. So that it can counteract each movement. That's the symmetry. The asymmetry you're alluding to is interesting. And let's approach this from a design principle standpoint, right? So nerves can only do one thing. They can fire, right? So they send a signal by depolarizing the inside of the cell. That means making it less negatively charged. And then they send neurotransmitters that then continue this nerve signal along. Well, if you want to be able to sense head turns, but you want to be able to sense them when you turn to the right or to the left. How do you design a system that can encode right movements and left movements when the only thing the nerve could do is just fire, send an action potential, send a nerve spike. And the solution the body has is to have a resting rate of nerve firing. So instead of the nerve being quiet, it's constantly sending signals. It's sending a hundred spikes per second. So it's going boop, boop, boop, boop, boop, boop. If you listen to it all the time, it is not a quiet nerve. And therefore, when you turn your head to the right and we're talking about the right side canal, it gets excited, it starts sending more signals. It goes from boop, boop, boop to boop, boop, boop, boop, boop, right? It's a lot more signals. When you turn to the left, the signals start going down. Well, it turns out there's an inherent asymmetry because of that, right? So if you're sending spikes at 100 spikes per second, that's how often the nerve's firing. You can go to zero. That's as low as you can go. You cannot go past zero. On the other hand, you could go up to about the rate that nerves can fire. And it turns out that nerves have a refractory period, meaning there is a maximum rate that they could fire because they need about 2 milliseconds to recover from having all those cations, meaning the positively charged ions rush into the cell and send off the nerve signal. So they could go up to 4 or 500 spikes per second, but that's about it. So that's an asymmetry. I could go down 100 or up 3 or 400. And because of that, an excitatory signal, meaning a signal that I'm getting the spikes to increase rather than decrease, is a more powerful signal, and that's the asymmetry. But it does allow us to study each canal in isolation because of that asymmetry. Because otherwise, when I Turned your head to the right and there was a problem. I wouldn't know if the problem was in the right canal or left canal, but because of that asymmetry, I can say, oh, no, the problem's in the right canal.
- [25:15]
Gregory McNiff
Well, that is fascinating the way it's able to distinguish the right and the left on the horizontal plane relative to, I guess, the binary function of the neuron firing at a certain level. I wanted to follow up because you have this great point about the hair cells, and you basically say the hairs of the inner ear responding to a Lorenz force. Could you briefly explain what that means? And again, that was very mind blowing. Yeah.
- [25:40]
Jeffrey Sharon
Oh, this is an interesting story. Actually, a lot of people don't know this story. One of my friends and colleague, Dr. Brian Ward at Johns Hopkins was integral to this story and some of his other colleagues. But basically, as Brian told me the story, one of the kind of grandfather figures in the field who had made a lot of seminal discoveries, his name is Dr. David Z. And he's at Johns Hopkins, would spend some time in Italy, and he spent some time with a researcher who noted that when a normal human gets inside an MRI machine, their eyes start twitching back and forth, and we call a rhythmic twitching of the eyes nystagmus. And so, you know, a lot of us would just say, huh, that's interesting. But these are scientists, so they have to say, well, okay, why does that happen? Why do eyes twitch when you get inside an MRI machine? And so it became a subject of inquiry. So then when David Z. Got back to Johns Hopkins, he worked with several other scientists, including Dale Roberts, and they started putting people inside MRI machines, and they found that if you didn't have a vestibular system, you didn't see any eye twitching. But if you do have a vestibular system, they did see the eye twitching. And they worked on this problem practically and also mathematically and thought that the most likely explanation was that, you know, there is this electrical field generated by the utricle, and when that interacts with the magnetic field of the MRI scanner, because recall that an MRI scanner works with basically a large magnet that aligns protons in your in hydrogen atoms that would produce a resting rate of force, so called the Lorenz force, that would then push against the semicircular canals and cause then nystagmus. And Brian later did some experiments with some mice without utricles, and they don't have the nystagmus. So he feels pretty confident that it is this Lorenz force idea, and that's why people get dizzy inside an MRI scanner.
- [27:50]
Gregory McNiff
Oh, that was absolutely amazing. You talked about the utricle, which is part of these otoleep organs. And Jeff, please get my pronunciation correct here. Which you describe as being critical for balance, sensing gravity, and detecting linear acceleration. But you also suggest maybe on the clinical side, they're often underestimated or underappreciated. Could you maybe explain why that might be?
- [28:16]
Jeffrey Sharon
Probably the short answer is probably because we don't have a great way to quantify them. And also there's probably a little bit more redundancy with those organs in terms of having the corresponding pair in the other ear. But these are critical organs. They're evolutionarily the oldest part of the inner ear. And there's a lot of patients who come in with unexplained symptoms who say, no, I'm not dizzy. I feel kind of floaty. I feel unmoored, I feel ungrounded. I feel like I'm just not well attached to the ground. Right. And then you think about it and you say, well, what would it feel like if your gravity detecting system was wonky and you didn't have enough of those crystals? And so people have done studies and said, actually that floating, gravityless sort of sensation does seem to correlate with utricular dysfunction, but it's a harder system to study. We have, for instance, a great bedside test that enables us to look at each of the canals and see if it is functioning properly or not by studying whether or not eyes can stay on a target during a quick head movement. We don't have a perfect bedside test for these gravity sensing organs. We have some okay, tests. One of them is we have people align a light bar or something similar with gravity to test their perception of verticality and of gravity. And then we have a complicated test that we do in the lab, which I won't bother with the acronym, but it's called a VEM test, and it does assess those organs, but in a very roundabout way, through sound. And actually, it tells us a bit more about the structural integrity of the inner ear than the organs that the test is designed to sense. So probably we need better diagnostics for these and we need to keep them on our radar.
- [30:23]
Gregory McNiff
That's really interesting. You referenced us coming to understand the vestibular system. Sort of late to the game. And you have a nice history where you talk about individuals like Scarpa, Florenz, Baramy, and I want to ask you about him. Could you maybe hit the highlights? I'd like you to Start with, like, Raimoni Kadyal, who I think his writings were. I'm sorry, his pictures, his drawings are beautiful. Could you talk about him and maybe some other individuals who you think are sort of key contributors to our understanding of the vestibular system?
- [30:55]
Jeffrey Sharon
Yeah, absolutely. You know, and I was a neuroscience major in college, and I always recall one day the professor came in and he sung a song about Ramon y Cajal. And it was the song about how he drew the brain. And it's. The song has stuck in my head for a long time.
- [31:15]
Gregory McNiff
If you'd like to sing the song, feel free.
- [31:17]
Jeffrey Sharon
Oh, no, no, no. I wouldn't torture your audience like that. But he really did draw the brain. So he used an innovative stain because neurons can be hard to see with just the normal stains. So he used a stain developed by Golgi to really, for the first time, in detail, see the different layers of the brain, the different senses that we have. And he helped describe the structure of the brain. You know, we know that the cortex has a number of layers. The cerebellum has a number of layers. The hippocampus, where memory is stored, has a number of layers. And there's characteristic cell shapes and how they're connected to each other in those layers. That really was the pinnings of modern neuroscience coming out of his experiments. So that was really important. And he helped prove, actually, ironically, using the stainless steel that Golgi had developed to disprove Golgi's theory, and then helped prove that our brain is comprised of billions of interconnected neurons that talk to each other, but they're not physically connected. There's a small space between them and they communicate with each other. The story of vestibular science, a lot of it is late 19th century, so pretty recent. Some of the biggest figures, actually, we know some of their names just because they're popular for some of their other discoveries, like Mach, for instance, was important. He helped figure out that it's acceleration that the inner ear senses and not velocity, which has very interesting implications for vestibular illusions. Breuer, who is known as one of the colleagues of Freud who helped develop psychoanalysts, was actually interested in vestibular system. And Barinet, who led a very interesting life, was the only person ever to win a Nobel Prize for a vestibular discovery.
- [33:28]
Gregory McNiff
No, that was a fascinating section, the way we sort of learned about the vestibular system, sort of in the sort of fits and starts approach. You spoke about the brain, and this is one that I found really interesting. Parts of your book here. At one point, you quote, I guess, a researcher, Barbara Tversky, in her book Nature of Thought, talking about maybe the relationship between the vestibular system and the brain, and particularly helping us think. You write, the foundation of thought is motion and space. Could you maybe talk a little bit more about how the vestibular system is connected to how we think and maybe even consciousness?
- [34:08]
Jeffrey Sharon
Yeah. So this one is not something you would expect directly, but it's something that we're learning more and more about each passing year. So, number one, a surprising number of patients with vestibular disorders come in and say that they can't think clearly, and they call it brain fog. And they want their brain fog to be better. And so that's item number one. Item number two is the fact that if you remove the vestibular system of, say, a mouse, they have trouble forming a mental map of the world around them. Right? So they basically, we all need to do this, but it's literally, you know, rats in a maze or mice in a maze, experiments where they need to find the food and then they need to find home. And when you don't have a vestibular system, you can't remember where things are relative to other things. You cannot form a mental map. So this gets to how our brain forms a mental picture of the world around us. Right. You know, I know where I live. I know where the supermarket is. Relative to that, I know where the overpriced coffee shop is. So I need to know where everything is relative to other things. And it turns out that our heads do that through some specialized cells called place cells and called head direction cells. And place cells are basically our internal gps. You know, if I'm in my house, one cell will mark it. If I'm at work, another cell will market. So it's literally a GPS system. And inside our heads and head direction cells are cells that tell us which way we're facing, you know, north, south, east, and west. And both of those cells rely on vestibular information. They simply do not work without vestibular information. So we cannot form a mental map of the world around us without the vestibular system. In the chapter you're alluding to, we want to take this one step further. So when we think about, you know, our evolution, we clearly needed to be able to understand where home is, where the food is, where shelter is, things like that. But then when we talk about ideas, we oftentimes talk about ideas as being closely related, ideas as being far apart. You know, we have to think outside the box. You're way off base. I'm getting closer to understanding. All the language we use about ideas seems to imply that we have this mental architecture landscape for putting things into this virtual space. And that's part of the way we can understand different things. And the argument then is that we might be using some of the same brain areas that we use for mental navigation, for abstract thought. And we see that, and we've done some interesting studies, even in my own patients, where we will look at brain fog and then we will treat patients for vestibular disorders and we find that brain fog actually gets better. So afterwards, when we assess them and it's questionnaires, it's self reported stuff, we find that we can make the brain fog better by treating the underlying vestibular disorder.
- [37:34]
Gregory McNiff
Yeah, that is another fascinating section. I want to hit on that idea of brain fog because I did jump ahead in an earlier section. When you're describing the vestibular system, you actually say language has failed the vestibular system. Could you briefly comment on that?
- [37:49]
Jeffrey Sharon
Yeah. So we don't have a word for someone who can't. Who has a broken vestibular system, basically. So we have a word for someone who can't see. Right. The word is a blind person. We have a word for someone who can't hear. The word is a deaf person. But we don't have a word for someone who can't accurately use their vestibular system. My dad would probably say, no, no, we have a word, that word is a klatz. But that's not precisely what it is. Right. We don't even have a word for the ability to sense head movements. Which is why I always feel so, like awkward or clunky trying to explain this. I say, oh yeah, we have a system in our head that senses linear accelerations. What does that mean? Meaning like you go up and down in an elevator, you could sense that. But I don't have a word. You know, my colleagues who study hearing stuff just say, oh yeah, you can hear with your ears. But what is the word for being able to sense accelerations, Rotational accelerations. So language has not provided the word's nest to describe the vestibular sensation. And someone without a vestibular system, you know, is someone with a deficit similar to someone who can't hear or someone who can't see. So we need. It would be nice to have a word to be able to describe that.
- [39:19]
Gregory McNiff
Yeah, no, hopefully your research will bring us closer to that. On the brain, there was One other. There are many fascinating sections, but one that, again, really stuck with me. You. You suggest our brains are wired to do calculus. And I realize that might be tongue in cheek, but we talked about Mach earlier. Acceleration, velocity, position. Could you expand on that? Why you think we're wired to do calculus whether we appreciate it or can do it at exam time?
- [39:47]
Jeffrey Sharon
It's a bold statement, but I'm going to stand by it. Everyone's brain can do calculus. So let's go back to Mach. Mach figured out that the vestibular system senses acceleration. It does not sense velocity. And that's actually a pretty important feature to understand. So picture a common vestibular scenario where I am trying to keep my eyes on something. I'm looking at an apple in a tree, and I want to keep my eyes on it, but I move my head to the right. So my vestibular system says, oh, let's move your eyes to the left to counteract, to balance out the head movement so that I could keep staring at this apple, which. The apple in my eye. It's caught my interest. I want to keep my eyes on the apple. Well, the vestibular system senses acceleration, right? So it senses when I've quickly moved my head over, right? But that would mean that the eyes at first will quickly dart to the apple. No problem, right? Well, there is a problem. The problem is, how do my eyes stay on the apple, right? Because eyes have a natural elastic tendency to drift back, to be pulled back to the center position. So if I just had a vestibular system sensing gravity, I would look at the apple for a second, and then my eyes would dart away from it. So in order to keep my eyes pushed out against the elastic forces of my eyeball trying to pull them back to center, our brain has to enhance the vestibular system. And that's a system inside the brain called the neural integrator. And the neural integrator, you might remember, integration is one of the functions that we do in calculus where we convert acceleration to velocity, we convert velocity to a position sense. So we literally have a circuitry in our brain performing calculus and changing the signal so that our eyes, instead of looking at the apple for a second, can continue to look at the apple by continuing that neural discharge. And this goes back to the basic theme of the book. If we understand that, now we understand a problem. So if there's a problem with that, sort of the part of the brain, we call that the leaky integrator. And the leaky integrator problem means that when your eyes are looking off to the side and they have trouble maintaining that eccentric position and they bob back and forth, they cause nystagmus because that integrator is malfunctioning. When did making plans get this complicated? It's time to streamline with WhatsApp, the secure messaging app that brings the whole group together. Use polls to settle dinner plans, send events, send invites and pin messages so no one forgets mom 60th and never miss a meme or milestone. All protected with end to end encryption. It's time for WhatsApp message privately with everyone. Learn more@WhatsApp.com this episode is brought to you by Indeed. When your computer breaks, you don't wait for it to magically start working again. You fix the problem. So why wait to hire the people your company desperately needs? Use Indeed's sponsored jobs to hire top talent fast. And even better, you only pay for results. There's no need to wait. Speed up your hiring with a $75 sponsored job credit@ Indeed.com podcast terms and conditions apply.
- [43:30]
Gregory McNiff
Yeah, I found that absolutely amazing. And it sounds like it is more than just a cute concept, but our brains are really hardwired to do that type of those kind of type of mechanics. We've talked about a few diseases. I think the one that everyone's familiar with is vertigo. Could you briefly talk about what that is and then follow up you suggest? I think up to half your patients come in with anxiety that also exhibit vertigo functions. I found that very interesting. Mamie, could you touch on why that is?
- [44:02]
Jeffrey Sharon
So vertigo has a definition. It has a medical definition. Not everyone, and this includes a lot of physicians, have read the papers that try to define it, but definitions are provided by a wonderful society, actually named after one of the characters we discussed. So Robert Barinet, the only person to ever win a Nobel Prize for his work on the vestibular system, has a society called the Barinet Society. And they are very active to this day. Have a great meeting and they provide definitions for different things. So vertigo is defined as an illusory sensation of movement. So it's when you think that you or the world are. Is moving in some way, could be spinning, could be rocking or swaying, when that is not indeed occurring. So it's the vestibular equivalent of saying seeing flashing lights when there are none, which would be a visual illusion or hearing a sound when there is none. We usually call that tinnitus. Right. So that's what vertigo is by definition. There are quite a few vestibular diseases, you know, A lot of my own research focuses on what's probably the most common one, which is a variant of migraine that causes dizziness. A lot of people don't even realize that that can happen, that migraine itself can cause dizziness and vertigo, but is actually very, very common. Almost everyone has someone in their lives who suffers from, we call it vestibular migraine or migraine related vertigo. But there is a curious feature of the vestibular system which is maybe not so curious when you think about the fact that we have to balance well. If we don't balance well, we're at risk of falling. Falling doesn't seem like a big problem until you realize that falls are a leading cause of morbidity and mortality in the elderly. And falls are a huge health concern. And basically every organism, it's a primitive, primal function to be able to safely navigate the world. And if we lose that ability, we lose our trust in the vestibular system. It makes sense that that would be associated with some level of anxiety. The story there isn't fully understood, and it probably relates a bit to some of these neuronatomical connections and certain brain neurochemicals that are prob related to both vestibular and anxiety. But it is a fact that there's more anxiety in the vestibular population than you would initially expect. And therefore it's an important part of any holistic treatment to try to address all aspects of any disease.
- [46:53]
Gregory McNiff
One of the most poignant sections of the book, again, you really insert your personality in a good way. And I want to circle back on that towards the end. But is the discussion around Meniere's disease and you write, quote, we don't understand the disease, therefore the most effective treatments are destructive in nature. Could you talk about that?
- [47:12]
Jeffrey Sharon
Yeah. So Prosper Minier was a Parisian who kind of shook the medical world when he started arguing in the French Academy of medicine in 1860 or so that the inner ear could cause vertigo. And no one thought it could at that time. They thought vertigo just came from the brain, from congestion on the cerebellum, et cetera. And he made a cohesive argument with some histology and cases that no vertigo could arise from the brain. So 1860 is now 2025, and we still, still don't know what causes Meniere's disease, and we still don't have any. We have zero FDA approved treatments for Meniere's disease. So this is something that's a huge gap. It's something that we're learning more about. There are some intriguing new ideas with this. And we're trying to approach Meniere's and learn about it in different ways. One of the fundamental issues with the Earth is we can't biopsy it. Right. It's too small. But a lot of the way medicine learns about different diseases is biopsying it. But if you biopsy someone's inner ear, you destroy it completely. So there's no room for biopsy. Every other organ you can biopsy. You can even biopsy the eye sometimes because there's some redundant areas. But you cannot biopsy the ear. People think you can't biopsy the brain. I work with neurosurgeons. We biopsy the brain all the time. We biopsy lungs, we've obviously liver, but we don't have the ability to biopsy the ear. And that means a lot of the ways we understand these diseases is by looking at post mortem histologic sections to try to infer what went on when someone was living. And that, I think, has slowed down the progress in my field dramatically.
- [49:13]
Gregory McNiff
Yeah, that's a very interesting point. And shout out to all the mice and monkeys and I think pigeons who have helped us contribute very much. Appreciate that. Jeff, in the latter part of the book, namely Part 4, labeled the Future, you talk about certain technologies and where you see this subsector of the medical profession going. Could you briefly describe the science behind the cochlea implant and vestibular implants and how close you think we are to basically restoring hearing to our natural capabilities?
- [49:51]
Jeffrey Sharon
Yeah, so, yeah, it's an interesting moment in time. And that was part of my impetus for writing the book as well, is we're coming up on some new technologies within the last few years that just simply didn't exist. So I'll talk about implants because we have a chapter about the vestibular implant which is coming. I'll talk about genetic treatments because we now have the ability for the first time in the last year to cure a specific form of inherited deafness with a gene therapy. This has been proven in human beings. This wasn't true a few years ago. This is incredibly exciting times. And then the last chapter, I talk about space. I do have a childhood fascination with space and the vestibular system, A system fundamentally designed for terrestrial animals does not do so hot in space. So the chapter I decided to end on. So the cochlear implant is arguably the most successful neural prosthesis of all time. It enables routinely meaning, you know, this is something that ear surgeons like myself do on a Weekly basis, we put in an implant in someone. I typically do adults. So someone who's had hearing their whole life, they've lost hearing, and then we put an implant in their head, and we can restore the ability to hear. We can bypass the cochlea when it's no longer working. And recall that neurons just work on electricity so you can electrically stimulate neurons. And we use fancy sound processing algorithms to recapitulate what a normal cochlea does and to stimulate the cochlear nerve fibers to restore someone's ability to hear. So that is something. The work started in the 1950s, commercially, became available in the 90s. Technology's been getting better, and now in 2025, more than half a million, I don't know the exact number of people worldwide, have been implanted with a cochlear implant. And it's a truly remarkable thing. It's why many of my colleagues went into the field. And I'll routinely get messages back from patients, you know, who will say, Dr. Sharon, I forgot that raindrops made a sound.
- [52:22]
Gregory McNiff
Oh, that's wonderful.
- [52:23]
Jeffrey Sharon
It's. Yeah, it's really the most heartwarming stuff you could imagine. And it makes our days just fly by because they're great when we're helping people. So simple concept, okay? If we can take a microphone, sound processor, mini computer, and directly bypass a broken cochlea and restore a sense of hearing, why can't we do that with a sense of balance? Why can't we take. It wouldn't be a microphone. It would be an accelerometer and gyroscopes and directly stimulate the nerves in the semicircular canals and restore someone's balance reflexes, the cardinal reflexes of having their body be steady when they walk and having their eyes be steady when they walk. And work on this began with some lab experiments in 2000, and then a number of teams worldwide have been working on this for the last 25 years. Two very notable teams. One is where I did my training at Johns Hopkins. One of my mentors, Dr. Charlie Della Santina, has done remarkable work, and he has an ongoing human trial. So right now, humans have been implanted with a vestibular implant. And his results are really remarkable. And the other major team, which has done amazing work as well and shown a number of firsts, is a combined effort in Europe between Zurich and Maastricht. And they've done amazing work as well and showed that you can restore some of these cardinal vestibular reflexes with a implant. So this is going to happen. This is a future treatment of when your vestibular system doesn't work anymore, especially in both ears. So bilateral vestibular loss. And they've shown that they can restore the eye movements and they can make the balance better and they can make patients lives better. So the future technology, I don't know exactly when it'll be commercially available, but it is coming.
- [54:29]
Gregory McNiff
And Jeff, could you briefly talk about gene therapy and regenerative medicine and restoring hearing? I think you compare it to us understanding DNA and the 50 years to get where we are, and we could be looking at a similar trajectory for these therapies for hearing.
- [54:47]
Jeffrey Sharon
So what we know right now is the more we understand the fine structure of these hair cells, their supporting cells, the little hairs which we call stereocilia, these fancy ion channels that pull open when the stereocilia move. We understand that there's specific proteins, meaning little microscopic machines who have jobs to do with regard to those hair cells to keep them functioning normally. And we now know about 200 different genes that when altered, can cause hearing loss. There are some that are very common, you know, in white populations. One particular mutation accounts for about a third of all cases. And then there's others that are more rare. And actually a number of teams around the world, I was just at a research meeting and one of the teams was sharing the results. But a number of teams around the world, including the US and China, have shown that for one specific mutation, the mutation is called otoferlin. It's actually not the most common one. It's about 1% of all congenital hearing loss. You can give someone gene therapy and that's a surgery where you intentionally infect their inner ears with a virus. Because recall that viruses are great for transporting genetic material, getting into cells, and having that genetic material replace the faulty instructions inside the cell to give it new instructions so it can make functional proteins. And that has been shown after years of animal work where it worked to restore hearing in humans. And this was huge news. There have been front page articles about this. And this is the world we live in now, where for the first time in history, we're now able to treat hearing loss with a gene therapy. And so now it's this precipice that we're looking out over and saying, if we could do this for one, what about the other 199? And many genes are shared between the vestibular system and the hearing system. So we're going to have to see what sort of vestibular benefits we could get if Someone's born with a faulty vestibular system.
- [57:02]
Gregory McNiff
Yeah. That was amazing. I want to. Before we move on, I do want to ask you about moving into space and extraterrestrial travel. Clearly, we weren't designed for that. Is the only way we sort of progress and live in space some form of evolution or do you think there's a technology or any way we can counteract the fact that our vestibular system just wasn't made for life and space?
- [57:29]
Jeffrey Sharon
Right. And just to highlight the problem. So we have two parts to the inner ear. We talked about the gravity sensing part, and the other part, the semicircular canals. The semicircular canals actually work fine in space because space has inertia. Right. That's why on Star Trek they always need to have their inertial dampeners and stuff. So that principle is fine. Your semicircular canals work fine in space. What doesn't work at space is the gravity sensing portion. And that's because the crystals, which are supposed to be heavy and pushed down on the hair cells, just float up in microgravity. There's nothing keeping them down. They float around the same way the astronauts do. And that is very disorienting. So this is an open secret of NASA. But basically, I actually talked to one astronaut about this. I have a friend, and her brother happens to be an astronaut. So I've asked him about this. And they say that when you get into space, half of all astronauts just start vomiting and they get confused as to where they are, and they think that they're upside down. They think they're falling when they're not falling, and their brains don't know what to do with this altered sensation. But it goes beyond that. You know, the astronaut I talked to said that he would get routinely lost in the International Space Station, especially when doing the spacewalks outside, and that it was really dangerous. And the thought there is that without the pull of gravity, without this orienting vector, it's hard to form this mental map of the world around you. And that therefore the astronauts, even though it's a pretty small area, the International Space Station, gravity really helps our brains be able to think and be able to form a mental map of the world around us in terms of if we're going to try to travel to different stars. I do talk in the book about animals who develop in space. They don't develop normal vestibular systems. So this has been studied. Jellyfish and rats have gestated and been born in space. And they don't balance correctly, the jellyfish don't swim correctly. They need that back and forth information about the vestibular system to properly develop. I suspect that we really did evolve for life on Earth. We're probably going to need artificial gravity if we want to travel between the stars. Yeah.
- [60:05]
Gregory McNiff
Wow, that's amazing. I want to shift to the end of the book. It's more of a practical chapter. You label it advice for patients. Jeff, if someone is suffering from vertigo or some of these diseases we talked about, how should they select a doctor? What do you suggest they. How do they approach that selection? And what should they expect?
- [60:26]
Jeffrey Sharon
So modern healthcare is a confusing maze of different specialties. Different healthcare insurers, different hospitals, different doctors. And probably nowhere is the problem more confusing when trying to figure out who you should see for your vestibular problem. So I would tell patients a few things, right? The first is that there's two specialties in medicine who can treat vestibular disorders. That's neurology. The doctor is dedicated to the brain and the nerves, and ear, nose and throat. Like myself, the doctor is dedicated to the ear. But there's a problem, because when you have a symptom that is right at the border between the brain and the ear, sometimes patients can fall right into the crack between them. And then you have a neurologist saying, well, I don't think it's your brain. And you have an ear, nose and throat doctor saying, I don't think it's your ear. And where does that leave the patient? Not knowing where to go and who to seek. So we do need more vestibular specialists in the country. We need to have a new generation of doctors who are focused on the vestibular system because the stakes are staggering. About 5% of all emergency room visits and primary care visits are for dizziness or vertigo. So it is this humongous part of medicine that doesn't have enough providers in it. I would tell patients, if you're not getting the answers from the first person you see, try to do some online research and figure out is there a vestibular specialist in my area, could be a neurologist, could be an otolaryngologist, and can they evaluate me and try to treat me. The other thing to know is, with the loose crystals, physical therapists, and some physical therapists have received some subspecialty training in vestibular disorders. They can be very, very helpful for that process. So keep physical therapists in mind as well, because a lot of vestibular problems can be made better with Physical therapist.
- [62:38]
Gregory McNiff
Oh, that's great. And I should mention you have resources. And this is chapter 15 advice of patients where they can go and do further research. Last question, Jeff. I talked about your personality, and clearly we got a sense for it in this interview. There's the humor and the spin doctor, the one hit wonder. I love the Windows operating error chapter. And I'll just say this. You referred to the rats navigation. Guests were random. Quote, like my wife. I'll let you deal with that when the book comes out. But also, a fair amount of empathy comes out in the book. Again, you talk about suffering through the entire education process. Just quote, in return for the privilege of caring for your fellow humans. And you stress throughout the book the importance of listening. I've even read your online reviews where they cite how great you are as a listener for a young med student or someone in their residency. Could you briefly just talk about, you know, the science and the knowledge and the understanding is great, but mainly sort of that patient doctor connection for a minute.
- [63:39]
Jeffrey Sharon
Oh, this is. This is critical. I'm happy you asked about this. You know, from a writing standpoint, you know, I believe part of the goal is education, but it has to be fun. We have to try to entertain. And I find humor is just a great way to do that. So, yeah, I think every chapter in the book is a pun. I tried to throw in humorous examples, things like that, just to liven things up. And I try to do the same with my lectures, because if we're going to go together on a journey into whether or not your brain can do calculus, I think we got to keep it as fun as possible, as interesting as possible. Empathy is essential to medicine. It's really critical. Our patients come to us in this unique moment of vulnerability where they're scared, they can be worried, they don't know what's going on, and they're looking at you and they're not sure, is this person gonna even take me seriously, whether or not they could help me, Are they gonna take me seriously? Are they gonna take the time to understand what I'm going through, who I am, and at least try their best for me? And I find that that is essential. We have to make that human connection. We have to show that we care. And fundamentally, we do care. I find medicine to be this great privilege we have because we're seeing people at this vulnerable stage, and we can be there for them during the journey. And that's incredibly rewarding to us to be able to help someone when they're going through a really tough time with a disease or an unexplained symptom.
- [65:27]
Gregory McNiff
Yeah, I think we'd all hope to have a doctor who approaches our health like you do. It's wonderful just hearing you say that. Like I said in the book, it comes across very well. That concludes our interview. Again, the book is the Great Balancing Act, An Insider's Guide to the Human Vestibular System by Jeffrey Charon. Jeff, thank you so much for your time and writing. Such a really thought provoking and just mind expanding book. I mean, just what you cover relative to what we know and all the advancements, the learnings, the technology, everything. It really was a wonderful read. Thank you very much.
- [66:07]
Jeffrey Sharon
My pleasure. Great to talk to you, Sam.