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 opthalmology at stanford school of medicine today we are going to talk about our sense of self or what's called interosception interosception is our sensing of our internal landscape things like our heartbeat our breathing and our gut this discussion about sense of self and interception 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 interosception 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 millu as we say your internal environment you will position yourself to do some very simple things that can lead to outsized 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 etc 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 uh 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 of blood inside the heart means slower flow the brain registers that because there are 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 those double inhales are kind of important because what they do is they maximally fill all those little sacks in your lungs and then when you breathe out you're exhaling as much of the carbon dioxide in your system as possible when you make exhales longer you're slowing your heart rate you're calming down the opposite is also true if you inhale deeply or vigorously and then exhale less long or less vigorously you will increase your level of alertness through these purely mechanical aspects of your interosception it only takes two or three of those before you start to feel more alert and that's because your heart rate is increasing and actually if you keep doing that for 25 or 30 breaths of inhale deep short exhale you will start to secrete a lot of adrenaline you will actually feel as if you've had a couple espresso you will immediately wake up through purely mechanical means changing the way that you breathe emphasizing inhales or exhales or keeping them the same will change the way that your brain works how alert you are and how well you function in anything and again this doesn't mean that breath work has no value it's just simply to say that long extended protocols of breath work are simply they are truly simply just an exploration of this fundamental relationship between the mechanics of your internal organs and your brain and how your brain controls those internal organs so now i want to shift away from breathing and diaphragm and lungs and move toward another organ within our visca which is our gut so this includes our stomach and our intestines our esophagus and so forth it's been said before both by me and by others that we are but a series of tubes and indeed that's true believe it or not every system in your body is a tube your brain is actually a tube that connects to your spinal cord which is also a tube your digestive system starts with the tube at your mouth and of course goes down through your throat and then you've got all the elements of the stomach and the intestines and then it comes out the other end so you are but a series of different tubes your vascular system a series of other tubes the way your digestive system works is to communicate to your brain about the status of the mechanical pressures along this tube so within your stomach and your intestines etc and the chemical status of that tube at various portions within that tube to inform your brain about how your brain should control that tube so let's start with the mechanical sensing of your gut if you drink a lot of fluid or if you eat a lot of food your gut will fill up if there's a lot of that food pressure receptors communicate to the areas of your brain that are involved in feeding and will say "don't eat anymore you don't need to consume anymore." the converse is also true when these receptors signal to the brain that the gut is empty so when you find yourself at the refrigerator or you find yourself almost you know manically trying to get food of different kinds you're not even thinking about what you're eating because you're so hungry in part that's because the lack of food in your gut has sent that information to your brain and is driving particular fixed action patterns that are associated with eating so if you've eaten anything even if it's a small volume of food in the last hour to 3 hours it's actually a worthwhile practice to take a few moments maybe 10 20 seconds and actually just try and concentrate on sensing the neurons in your gut and how full you are the consequence of that is actually rather interesting it's been shown that the consequence of that is actually that you can better override the signals of gut fullness or emptiness so there are other ways that our guts communicate with our brain it's not just our stomach talking to our brain it's also our intestines talk to our brain the liberly lab the guy's name is steven lieberly he runs a lab at harvard medical school they discovered a category of neurons called the glp1r neurons and those neurons send little wires down into the intestines and deep into the stomach but mostly into the intestines and they sense stretch of your intestines and then those neurons send another branch so they have a branch in one direction senses what's going on in your intestines and they have another branch that goes up from your neck into your brain to either trigger the desire to eat more or to stop eating so these are really really cool neurons and they're basically stretch receptors and in addition to that the liberly's lab discovered neurons that detect nutrients themselves these neurons are activated by the presence of fatty acids amino acids and as a third food item sugars are coming from the foods that we eat these neurons will fire a lot to the brain that says "hey whatever you're doing up there do more of it." okay now the sugars are a little bit cryptic because when i say sugars or i say amino acids or i say fatty acids this has nothing to do with taste in fact beautiful experiments have been done by the bourhees lab and by other labs showing that even if you numb the mouth even if you gavage which is a really just a it's a fancy word for basically tube feeding you put a tube down in the gut you just deliver the food to the gut so you get no opportunity to taste it sounds pretty awful if you force feed by gavage or you numb the mouth these neurons don't care about the mouth they only care about the nutrients coming from these foods and then they signal to the brain hey do that thing do that thing where you lift that object we call a fork or a spoon do that thing where you drink the milkshake do that thing where you move your mouth like this not talking but do that thing where you swallow so that's how the nutrients in our gut control us and this is why for people that experience extreme sugar cravings or even mild sugar cravings replacing those foods with foods that have high levels of omega-3 or amino acids can reduce sugar cravings and i've talked about this on a previous episode but the point is these neurons don't really know taste they only know nutrients and so you can work with that system if you're if you crave sugar and i do believe that most if not all of us should be trying to limit if not eliminate simple sugars as much as possible most of the time then things like high omega-3 foods etc maybe even want to supplement with fish oil or something similar to get omega-3s there are other reasons for wanting to do that too can be very beneficial and here's what we're talking about is interosception it's your ability to sense your inner real estate but in this case by way of chemical signaling not by way of mechanical signaling so now i'd like to talk about another aspect of gut chemistry that has profound effects on the brain as well as on the immune system your gut needs to maintain a certain level of acidity or alkalinity for those of you without any chemistry background basically the low numbers on the ph scale that means more acidic the higher the numbers more alkaline so more alkaline means more basic and acidic means acidic your gut needs to be more acidic than essentially all other tissues of your body in order to function properly gastric juices are actually powerful modulators of brain state put differently one of the best things that you can do to have a healthy brain a well functioning brain and a healthy and well functioning body is to maintain proper gut chemistry and that's basically accomplished by getting the right level of acidity and alkalinity in your gut now this is not quack pseudocience what we're going to talk about now are peer-reviewed data that point to the gut microbiome and its relationship to acidity of the gut and how the gut microbiome can help enhance autoimmune function and various other aspects of brain and body health so within all the mucosal line tissues of our body we have what are called microbota little microorganisms that we didn't make that actually come from our environment or our food and live inside us and there are good microbiota and there are bad microbiota whether or not we have good microbiota or bad microbota depends on one thing and that one thing is how acid or alkaline the given mucosal tissue is what you essentially want to do is create an environment where the proper microbiota can thrive because when you do that you greatly decrease what are called inflammatory cytoines so these are things that are secreted both by cells within the body and cells within the brain to impact brain health and brain function and bodily health the simple way to adjust these things in the proper ratios is to adjust your gut microbiome the best way to adjust your microbiome is to ingest certain types of foods there was a study done by my colleague justin sonnenberg at stanford school of medicine they explored how different foods or different diets i should say impact the gut microbiome and inflammatory markers and what they did is they explored two types of diets one is a high-fiber diet and they compared that to diets that were unchanged except for the inclusion of a few to a few more servings of fermented foods each day and the takeaway message from this study is that the fermented foods far outperformed the high-fiber diet the bigger message is that all of us should be ingesting on a regular basis daily basis fermented foods of different kinds and why i say that is because the inflammatory markers went down the markers of autoimmune disruption went down and the chemistry of the gut therefore was adjusted in the appropriate ways and it's been shown in other studies that when the correct gut microbiota are present and these inflammatory markers are reduced cognition improves so ability to focus ability to sleep ability to ward off infection and wound healing all enhance so while today is about interception we're talking about sensing we're also talking about subconscious sensing we're talking about subconscious sensing of the millu of the body when the millu of the gut in the body is right then the brain and the immune system function very well it's very clear that's fermented foods and that's keeping the stomach slightly more acid than one might think you would want to so now i want to talk about two other forms of mechanical and chemical sensing that we very much can detect at a conscious level and those are fever and barfing so let's talk about barfing first barfing aka vomiting is when the contents of your guts run in reverse meaning when they go up from your stomach out the esophagus and mouth and onto whatever surface happens to be in front of you it's a terrible thing nobody likes to do it but it's a very interesting aspect to our biology because it reveals a beautiful and absolutely fundamental relationship between our chemistry and our brain so your brain is actually locked behind a gate and that gate is not your skull that gate is the so-called bloodb brain barrier it's absolutely fundamental that only certain molecules get across the bloodb brain barrier and that others don't and the reason for that is that most all 99.9999% of your neurons do not regenerate i don't care what you've read especially in the news recently about how psychedelics cause neurogenesis because they don't it's absolutely wrong psychedelics have effects on brain plasticity but they have nothing to do with neurogenesis at least no data support it but because you can't make new neurons you also can't damage the ones you've got or you shouldn't as much as possible and that's why you have a bloodb brain barrier or a bbb so the bbb as it's called prevents substances from getting to the brain however like any fence it is not always uniform along its length and there are little spots within that fence where chemicals can sneak across to the brain but through a beautiful design of some sort there are little holes in that fence and there are little neurons that sit right behind those holes and those neurons sense what the chemistry of the blood is so i'm guessing you probably didn't imagine that today's discussion about sensing the self would be sensing your own blood but you do there is a little area of your brain that's little indeed but is very very important called areama p o s t r e m a an area postramma is an area of the brain stem that sits right next to another brain area called the chemoceptor trigger zone and when the contents in your bloodstream are of a particular kind meaning when there are pathogens or it's too acidic the neurons in area and the neurons in the cheos receptor trigger zone trigger a bunch of motor reflexes in the abdominal wall that make you barf okay the contra the feeling that you need to throw up is triggered by these neurons in the brain stem and those neurons in the brain stem are triggered by the presence of certain chemicals and the reason why you don't have any bloodb brain barrier at that location is because postrea has to be there like a crossing guard making sure that everything that's coming through the blood is okay and if it even senses just the tiniest bit that things are off it's going to trigger that reflex some people the memory of or the thought of something like blood or vomit or use your imagination can actually trigger the vomit reflex and that's because these neurons in area are very sensitive to prior experience of interactions with negative things the neurons of area are there basically to keep your whole system safe so let's talk for a second about how to reduce nausea because nausea that salivation that feeling that you're going to vomit can be very beneficial in an in an adaptive circumstance like you've ingested something bad but some people experience nausea for other reasons there are good ways to regulate nausea and the ways they regulate nausea are very interesting they actually adjust the activity of these neurons in area postrema or they change the chemistry of the blood directly and many of you have heard this before perhaps but it turns out that there are good data 11 research studies were the ones that i could find peer-reviewed research studies with no bias so independent studies showing that ginger can cause a notable reduction in nausea how much ginger 1 to three grams and some of you will not be surprised to learn that cannabis can reduce nausea but cannabis thc and or it turns out cbd can reduce nausea and it probably does that by changing the threshold for firing of these neurons in area now let's talk about fever a fever is simply an increase in body temperature that increase in body temperature is triggered by neurons in the brain and those neurons in the brain are triggered by the presence of particular things in the bloodstream what sorts of things well toxins bacteria viruses when something bad gets in our system the body doesn't know it's bad it just knows it's foreign your body has this intelligence and that intelligence is to know hm these proteins are normally not seen in this region and then your body or the cells there i should say will release something that then will travel to the brain and will trigger an increase in body temperature so that your body cooks the bad thing or the cause of the bad thing it's really a beautiful adaptive mechanism so what's beautiful about the fever mechanism is that it looks a lot like the barfing mechanism basically you have a set of neurons that sit near the ventricles you are a tube a series of tubes and your brain has a hole down the middle and it extends down to the bottom of your spinal cord at the front it's called the ventricles and you have one ventricle a third ventricle along that third ventricle there's there are little neurons that can sense what's in the cerebral spinal fluid that fills the ventricle so in other words you have neurons that are sensing the chemistry of your cerebral spinal fluid and that have access therefore to the chemistry of your body because that cerebral spinal fluid is going up and down the brain and spinal cord but into that cerebral spinal fluid are signals about the various chemicals within the body so this is not a mechanical system this is a chemical system remember we're talking about mechanical information and chemical information accessing the brain the neurons that line these ventricles with cerebral spinal fluid go by a particular name they're called circumventricular organs meaning near circum ventricular near the ventricles and you have these organs and there are a set of neurons has a really cool name called the ovlt i don't know why i like that but i just like it it's the organum vasculosum of the lateral terminal organum vasculosum lateral terminalis ovlt are the neurons that respond to toxins and bad stuff in your bloodstream however minor or major what's going to happen is when those ovlt neurons are activated because you have something bad in your body or something bad is happening in your body they communicate with an area of the brain called the preoptic area of your hypothalammus and the preoptic area cranks up your temperature and tries to cook that bad thing now it's worth talking about fever for a moment and talking about thermal regulation because i think this actually could save some lives so if you are overheated to a point where you know you're getting up past 102 or 103 it's going to vary depending on person to person and certainly age you know kids some people think can tolerate higher levels of fever than adults but look you always want to be cautious about heating up the brain too much because once those neurons are gone they do not come back and neurons do not do well in very high temperatures once your body temperature starts getting up to 102 103 certainly 104 you are starting to enter serious danger zone this can happen through exercise in hot environments or an inability to escape heat because you don't have covering or adequate um ventilation or cooling it can also be because of excessive fever for whatever reason a lot of people think the way to deal with this is to put a cool compress on the back of the neck or to cool the torso it's very clear that that's the wrong response to try and cool off the body if you put a cold towel or you put an an ice pack on the back of the neck what you effectively do is cool the blood that's going to the brain and if you do that then your brain will react by turning up the crank in so to speak on the neurons in the preoptic area and will heat you up further and can cook your brain and organs further so what you want to do is as i've talked about before you want to cool the bottoms of the feet the palms of the hands and the upper part of the face now you can also cool the rest of the body but it's not okay to just stay under the covers and just cool uh you know the neck or something like that you really want to try and create a systemic or whole body cooling if the goal is to bring fever down now i want to turn our attention to interosception as it relates to feelings the way that interception is most commonly described and i want to highlight a term that many of you have probably heard which is the vegas nerve we talked about vegas a little bit earlier but the vegas nerve this vagabonding wandering nerve is involved in everything i've talked about up until now and the reason i saved it till now rather than mentioning all along is to highlight a specific point which is that whenever we hear about the vegas in popular culture it's like the vegas calms you down it'll mellow you out actually most of the time the vagus is stimulatory when you ingest foods with amino acids sugars or fatty acids the vagus nerve gets activated and triggers the release of dopamine and makes you more alert and go seek more of those foods or what led to those conditions when you feel nauseous it's rarely calming when you feel like you have a fever it's rarely calming so you're starting to get the picture that even though the vagus nerve is in the parasympathetic branch of the autonomic nervous system it's not a calming system it's a communication system and it's a motor system it communicates brain to body and body to brain and it changes the function of different organs now one thing that's important to highlight is that stress itself will alter the chemistry of your gut because of the ways that it shuts down the vagus nerve and quiets the neurons that communicate from gut to brain i want to say that again stress will disrupt your gut and make you feel not good poor digestion and just lousy because of the way that that it shuts down the vagus nerve and the neurons of your gut it doesn't mess up your gut it just doesn't let your gut get the signals up to your brain and it also then throws off the chemistry and then there's a whole cascade of effects the vagus nerve however is responsible for emotion and the way it does that is to pull to aggregate the conditions of your gut the conditions of your heart and the conditions of your breathing which includes your diaphragm and lungs and takes that kind of as a a collection of information and sends it to the brain and controls what we call your emotions now that might seem obvious to some people but to other people that might seem totally crazy you thought your emotions were because the market was down and you had invested or because something that you thought was going to happen is not going to happen whatever it is that bothers you you think of generally as a purely cognitive event but the brain doesn't really know what to do with that information it doesn't act directly on that information to create moods moods are created through the heart's response to reading that headline to the change in your breathing that's caused by someone that you love telling you that actually they're not interested in spending time with you anymore emotions can be good or bad or neutral so this thing that we call interception the sense of self i've been building up from very fundamental layers gut chemistry spleens immune systems autoimmune all of those things are plugging in like a series of ingredients in a recipe that gives rise to your mood and how you feel and that mood and how you feel is shown in one location in your body that other people can see and that's in your facial expressions and indeed there are now beautiful data showing that your face including the size of your pupils the tonality of your face how flushed you are or how pale you are even the degree to which you are frowning or smiling relative to other periods of time that is all an aggregate of or a reflection rather of your gut your heart and your breathing and the chemistry of your body and what's remarkable and this is where interception really really takes a leap into the incredible is that there are beautiful studies that show that for instance when we know somebody pretty well and they are going through some sort of experience of any kind our heart rate actually starts to mimic their heart rate our breathing starts to mimic their breathing even if we aren't conscious of their breathing somehow human beings are able to register the internal state of other beings and i think probably for animals too but certainly for other humans even at a distance and so your sense of your internal landscape is linked to others now you can enhance this interceptive capacity for how you feel and how others feel in other words you can start getting a better readout of your internal state by doing a simple exercise is what is really a tool and that is to learn to sense your heartbeats and i think this is one of the reasons why meditation is powerful when you stop taking in extterosceptive information information from the outside world by closing your eyes and focusing inward as they say you start paying attention to your breathing cadence you start directing your mind's attention to your heart rate and if you can start to perceive your heart beating you actually are very quickly strengthen the veagal connections between the body and the brain and so there's no real practice here there's no breathe this way or do this thing except to direct your awareness toward your heartbeat and some people can get very good at this very fast most people find that just by doing this for a minute or so every once in a while they start to tap into this sixth sense they start to notice when they don't feel quite right about something or somebody or some situation so this interceptive awareness can be tuned up with it used to be called veagal tone but i think that term doesn't take into account all the other things that are going on with the vegas so i don't really like that term it's more of an interceptive awareness so what i've effectively tried to do today is to give you a window into this incredible relationship between your viscera and your brain and your brain and your viscera all these organs of your body and i what i hope is that you'll appreciate that it's a system that you aren't just a system of tubes i said that in sort of inest i mean you have a lot of tubes and you are a system of tubes but that system of tubes is linked through the nervous system and those links work in very specific ways so whether or not you remember about pzo and all the glp1rs and all that stuff it doesn't really matter what i encourage you to do is start sort of pushing and pulling on the various levers within this beautiful system that we call the interceptive system this sense of self thank you for your time and attention and thank you for your interest in science [Music]