Essentials: Improving Health With Stronger Brain-Body Connection

**Andrew Huberman** (0:00)
Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health and performance.
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are going to talk about our sense of self or what's called interoception. Interoception is our sensing of our internal landscape, things like our heartbeat, our breathing, and our gut. This discussion about sense of self and interoception has many important actionable items that relate to bodily health and brain health. Of all the topics I could cover, this thing that we call sense of self, which is also called interoception, has perhaps the most foundational level of importance for all that we feel, all that we do, and all that we are capable of doing. And I promise that if you can learn a little bit about the mechanisms of self-sensing, of understanding what's going on in your internal milieu, as we say, your internal environment, you will position yourself to do some very simple things that can lead to outsize positive effects on everything, from sleep to body composition, to mental focus, to mood, your ability to regulate stress, and indeed even your ability to heal and recovery from injuries of different kinds, brain injury and bodily injury. We have a system in our body that connects our brain to all of our bodily organs and connects all of those bodily organs to our brain. And that communication between brain and body in both directions creates a situation where either we are positioned to do things well, or we are positioned to do things poorly. So I really want to dive in and dissect what is this system of brain body communication? What does it look like? What are the actual neurons and connections? The system that's most often associated with this is our 10th cranial nerve called the vagus nerve. The word vagus relates to the word vagabond, which is to wander. And indeed the vagus nerve is a vast, enormous wandering set of nerves. So it's not one nerve. It's not like one fiber, one axon, as we say. So where do they go? Well, they leave the brain and the brain stem. The brain stem is kind of the back of your brain. If you touch the back of your neck, it's about three inches deep to where you're touching, the neurons that are there send information into the body to control your bodily organs. How fast your heart is beating, how fast you're breathing, how fast your digestion is occurring. Even things like whether or not you are going to secrete so-called killer cells, your immune cells from your spleen to go ward off bacteria. Now the neurons there don't know what to do unless they receive information about what's going on within the body. So everything from your intestines to your stomach, et cetera, and your spleen are sending information also up to the brain. There are two fundamental features of what's going on in your body that need to be communicated to your brain, these neurons in your brain stem, in order for your brain and your body to work together correctly. And the two types of information are mechanical information and chemical information. So when you think about your sense of self and your ability to understand what's going on in your body, if you feel good or if you feel bad, your sense of self is dependent on these mechanical phenomenon and these chemical phenomenon. If your gut is full or empty, whether or not your heart is beating fast or beating slowly, that's mechanical. And chemical information, whether or not your gut feels nice and whether, you know, when I say nice, I mean, whether or not it has a balance of acidity and alkalinity that feels right to you, or whether or not your gut feels off, it doesn't feel quite right, that's chemical information. So the first principle that everyone should understand about their sense of self is that they are sensing mechanical and chemical information about every organ in their body, except for one, and that's the brain. Your brain actually doesn't have pain receptors. It doesn't even have touch receptors. The brain is a command center. It helps drive and govern changes in the organs of the body. So, your organs are different. They need to tell your brain what's going on, and there are ways that you can control the mechanical and the chemical state of your organs in ways that are very powerful. So, let's talk about how you can adjust the mechanical and chemical environment of your organs in order to make your brain better, and how your brain can make the mechanical and chemical environment within your organs function better. Let's take one example of these and explain how mechanical and chemical information from this particular set of organs communicates to the brain and how that changes how our brain works. And the organ I'd like to focus on first are the lungs and the diaphragm. So, we're all familiar with our lungs, these two big bags of air, but they're actually not two big bags of air. They actually have little tiny sacks within them, actually millions of little sacks called the avioli of the lungs. The avioli of the lungs are like little tiny balloons throughout our lungs. Those little bags of air can fill up or they can deflate, right, just like your lungs overall can fill up or they can deflate. The diaphragm is a muscle and it sits below our lungs. And the way the diaphragm and the lungs work together is very interesting. The diaphragm is actually skeletal muscle, so it's just like a bicep or a quadricep. And the fact that it is skeletal muscle is important because it has a unique property, which is that you can control it voluntarily. How the diaphragm moves up and down determines how you breathe. How you breathe is also dependent on little muscles that are between your ribs, the intercostals and other muscles. When we inhale, these little sacks in our lungs fill up and our lungs expand. And when we do that, we take up space in our thoracic cavity and our diaphragm moves down, okay? When we exhale, the diaphragm moves up, the lungs get smaller, okay? This actually controls our heart rate and it works in the following way. Our heart actually has a little more space because the diaphragms move down. So the heart gets a little bit bigger, physically bigger, not in the emotional sense, but physically bigger. And as a consequence, whatever blood is in the heart flows at a slower rate because it's a larger volume. So bigger volume heart, same amount of blood inside the heart means slower flow. The brain registers that because there are a set of neurons on the heart called the sinoatrial node. That information is registered by the brain and the brain sends a message back to the heart to speed the heart up. So if you do long inhales or you inhale more vigorously, you actually are speeding your heart up. Now, of course you have to exhale as well. But for instance, if I were to inhale very long, like the entire time my heart rate is increasing. And then if I did a quick exhale, something else will happen. But if I kept doing that, my heart rate would increase. It's not going to increase linearly and forever, but it will increase with each inhale. Or I can simply make my inhales more vigorous and my heart rate will speed up. This is an autonomic and automatic relationship between the diaphragm, the lungs, the brain and the heart. Now, if inhales speed the heart up, what happens on exhales? When we exhale, the diaphragm moves up. The heart has less space, meaning it gets a little bit smaller, which means that whatever volume of blood is inside the heart moves faster through that smaller volume. That information is sent to the brain via these collection of neurons called the sinoatrial node. The brain then sends information via the vagus nerve back to the heart to slow the heart down. So while inhales speed up the heart, exhales slow the heart down. And you can leverage this in a very powerful way to set the conditions of your mind. If you want to be more calm, emphasize exhales. And the simplest way to do this is to emphasize exhales through what's called a physiological sigh. Two inhales, followed by a long exhale.