“Interoception: The Secret Ingredient” With Lisa Feldman Barrett, Ph.D.

Transcript of Cerebrum Podcast

Guest: Lisa Feldman Barrett, Ph.D., is co-director of the Interdisciplinary Laboratory at and Massachusetts General Hospital. She is a University Distinguished Professor of at Northeastern, with appointments at Harvard Medical School and Mass General. She is also Chief Science Officer for the Center for Law, Brain & Behavior at Harvard University. In addition to the books Seven and a Half Lessons About the Brain and How are Made, Barrett has published over 250 peer-reviewed, scientific papers appearing in Science, Nature Neuroscience, and other top journals in psychology and , as well as six academic volumes published by Guilford Press. She has also given a popular TED talk with over six million views.

Host: Bill Glovin serves as editor of Cerebrum magazine and as executive editor of the Dana Foundation. He was formerly senior editor of Rutgers Magazine, managing editor of New Jersey Success, editor of New Jersey Business magazine, and a staff writer at The Record newspaper in Hackensack, NJ. Glovin has won 20 writing awards from the Society of Professional Journalists of New Jersey and the Council for Advancement and Support of Education. He has a B.A. in Journalism from George Washington University.

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[Intro] Bill Glovin: When I first heard the word “interoception,” I immediately thought of a quarterback in football who throws the ball to the wrong team. Just because I edit a brain science magazine doesn't mean I still don't have an awful lot to learn about brain science. People much smarter than me told me interoception is one of the hottest areas of neuroscience and explained it to me. And rather have me try to explain it to you, we have someone who studies interoception and she can explain it and provide some context to what it means and its potential to help people.

Bill Glovin: Hi, I'm Cerebrum editor, Bill Glovin, and welcome to the Cerebrum Podcast, where we explore matters of brain science with leaders in the neuroscience field. Our podcast is sponsored by the Dana Foundation in New York City, and you can find all our content at Dana.org.

Lisa Barrett: It's become very apparent that disruptions in interoception are related to many illnesses, are involved in many illnesses, that normally we might think of as mental illnesses like depression, for 2 example, but actually that have a very strong metabolic basis—a very strong basis in the regulation of the body. ______

Bill Glovin: Today, we welcome in Dr. Lisa Barrett, co-author of our Cerebrum magazine feature, “Interoception: The Secret ingredient.” Lisa is co-director of the interdisciplinary affective science laboratory at Northeastern University and at Massachusetts General Hospital. She is a university distinguished professor of psychology at Northeastern, with appointments at Harvard Medical School and Mass General. She's also Chief Science Officer for the Center for Law, Brain & Behavior at Harvard, and the author of Seven and a Half Lessons About the Brain and How Emotions are Made. Welcome, Lisa. Our article is “Interoception, The Secret Ingredient.” For people who haven't read the article, can you briefly describe what interoception is, why it's important, and what's so secret about it?

Lisa Barrett: Sure. Thank you, Bill. Thanks so much for having me on your podcast. So I guess the best way to describe interoception is really to start with the contrast, which is exteroception. Right now, as our listeners are listening to our conversation, they are receiving changes in air pressure in the part of their ear called the cochlea, which is a sensory receptor for these changes. And their brains are translating or conjuring actually sounds that they hear and the meaning of those sounds based on that exteroceptive input. And actually, really, for your whole life, except for the times when you're sleeping. And even then, there's still some information from the world coming to your brain, through the surfaces of your body, from your eyes, from your ears, from your nose and your tongue and your skin and so on.

When we're awake, we're really aware of the consequences of that sense data, not all the time, but most of the time you see what's in front of you, you hear what's around you and so on and so forth. But at the same time, right now, as we're chatting with each other and as our listeners are listening, there's a whole drama really going on inside their bodies, inside our bodies. Blood is pumping. Lungs are expanding and contracting. Their heart is beating against your chest. Your gut is oscillating and contractions, and there's a huge variety of motor changes going on inside your body, which generates sense data. And we call that interoceptive sense data.

The really interesting thing about it is that for the most part, we're unaware that it's going on. And we say, Oh, I hope our listeners are unaware because if they're actually aware of all the sensory changes in their own bodies, then

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they're probably not able to pay attention to anything outside their own skin. We are wired in a sense, not really to be aware of every little tug and gush and contraction that goes inside our own bodies for this reason, actually. Philosophers call it tragic embodiment. That if you were aware of what was going on inside your body, you'll just be overwhelmed by it.

Nonetheless it's information that your brain is constantly receiving and your brain really requires that information in order to regulate your body efficiently, which is its major job, really. Brains didn't evolve so that we could think and see and feel and hear, they evolved to regulate the systems of our body and we think and feel, and see and hear in the service of that regulation. So the brain's main job is regulating the body and it needs that kind of constant stream of sense data from the body, which we call interoceptive sense data to do its job. And when it's not doing its job particularly well, when there are problems, manifest themselves as illnesses, physical illnesses or mental illnesses, usually there's a problem with interoception.

Bill Glovin: So when we're calling it the secret ingredient, it's because we don't even realize most of these things are going on. So that's the secret?

Lisa Barrett: Exactly. That's the secret. The human brain is this really interesting organ that is kind of like the master of deception. It seamlessly creates our experiences and guides our actions in ways that it doesn't really make itself aware of. We're really unaware of what our brains are doing on a moment-to-moment basis. For the most part, we're only aware of a very, very small proportion of the consequences of what our brains are doing. And interoception really falls into that largely unaware proportion of things, I would say.

Bill Glovin: I couldn't help, but wonder given the meaning whether or not the word “perception” has any connections.

Lisa Barrett: Yes. Well, typically scientists distinguish between perceptions of the internal world, meaning the internal body, what scientists sometimes call the internal mill you of your body that is all of the systems organs and so on. And the perception of the external world, which is called exteroception. So typically they kind of cleave perception into these two domains. And one of the things we talk about in the article is that actually, if you look at the anatomy of the brain and the functioning of the brain, that distinction is really kind of blurry.

Bill Glovin: Speaking of the anatomy, is there a part of the brain that regulates interoception?

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Lisa Barrett: Actually work from our lab and other labs have discovered that there's actually a very large distributed system in the brain that is important for interoception, for constructing and regulating these sensations. And what's really interesting about this discovery is that this very distributed system actually has many, many, many functions. So it's not that it sometimes does interoception and it sometimes does other things, it actually is while it's doing these other things, which include memory and exteroception, and regulating your body and a whole slew of psychological phenomena while it's doing these things, it's simultaneously constructing and regulating the sensations in your body.

Bill Glovin: There's quite a good illustration in the article that I guess shows that.

Lisa Barrett: We were really surprised. When we did this research, which we initially conducted on over 700 subjects, we replicated this finding with regular scanning procedures. And then we just replicated seven Tesla scanning procedures, which are much more precise, much more high resolution. We were really surprised to discover that there are several, what are called intrinsic networks in the brain that scientists, there may be thousands of articles on these networks, but the system for interoception includes two of these networks and the places in the brain where they overlap. And it's widely distributed across all of the cerebral cortex, all portions and also sub-cortical regions. So it's this very, very pervasive system at the core of your brain. And it's anatomically at the core and functionally it's at the core. So you could say metaphorically that your brain's representation of your body, your brain's modeling of your body is really at the core of your mind, even though you might not experience the world and yourself in that way.

Bill Glovin: When did interoception first appear on the radar of neuroscientists like you?

Lisa Barrett: Well, interoception was coined as a phenomenon, I guess you would say, really back in the late 1800s, early 1900s by one of the formative neuroscientists at the time, Sherrington, was the first person to formally define it, I would say. So interoception is not your awareness of your body, it's literally your brain's modeling of the sensory state of your body. And it's actually really hard to study. We can study people's awareness of their physical sensations, what you would call interoceptive awareness, so how aware are you of your heart beating, for example, how sensitive are you to temperature changes, but actually the modeling, the brain's modeling of the sensory state of the body is only, I would say recently had an uptick in interest in part because there are now new techniques to really over the last 10 or 15 years, there've been an increasing number of people who really, brilliant scientists who have discovered or

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invented ways of studying how the brain is tracking the various systems of your body and attempting to regulate them with the interoceptive sensory cues.

And I think alongside that, it's become very apparent that disruptions in interoception are related to many illnesses, are involved in many illnesses that normally we might think of as mental illnesses like depression, for example, but actually that have a very strong metabolic basis, a very strong basis in the regulation of the body.

Bill Glovin: It seems like it really ties into consciousness as well.

Lisa Barrett: It absolutely does. And in fact, there are philosophers who have written about interoception, although they don't call it this, but they do call it sensing the body as actually the basis of one of the most fundamental dimensions of consciousness, which is an animal's ability to distinguish itself from the rest of the world. So one of the first things that a nervous system has to do when an animal can move under its own steam, one of the first things that nervous system has to be able to accomplish is to distinguish the sensory consequences of its movements from the sensory consequences of other things happening in the animal's environment that are not a function of its own movements. So imagine a fish is in the water, and I'm using a fish as an example, because that's where vertebrates evolved, that's where our nervous systems evolved first. And fish have this sensory system. It's for touch that goes all the way down the sides of their bodies. It's called the lateral line system. And it's a sensory system for assessing changes in water pressure and vibrations in the water.

And when an animal swims, when a fish swims, of course there are going to be perturbations of this system, but also if prey is nearby or if a predator is nearby, there's also going to be perturbations in the system. And so the animal's nervous system has to be able to distinguish between the sensory consequences of its own movements from the sensory consequences that are due to some change in the world. And this ability of a nervous system to do this, and there's more than one way that nervous systems accomplish this, is the beginning of what philosophers would call presence, which is basic, basic, basic feature of consciousness. You could think of it as the me, not me distinction, because I'm able to sense my body, I'm also able to make the distinction between what's me and what's changing in the world that's not me.

Bill Glovin: What inspired you to study it?

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Lisa Barrett: A lot of neuroscientists who, particularly if they have a psychological background or they come from psychiatry or neurology, usually start with human experience, categories of human experience like emotions, like anger, sadness, and fear, or depression or or memory and so on. So they'll start with phenomena that people experience, and then they'll go looking in the brain for the physical basis of those phenomenon, but that's never really made a lot of sense to me. And in fact, that approach to trying to understand the physical basis of the mind has been criticized all the way back to . And I'm sure even before that, but William James was considered one of the founding fathers of modern psychology, really was very, very critical of that approach.

Lisa Barrett: I guess my approach has always been to look at the brain. So truly try to understand how is the brain structured, how does it work, how is it talking to the body kind of constantly, and then to try to figure out well, given that we have this kind of brain with this structure that works in this way, how can we get the kinds of experiences that we have and the kinds of behaviors we engage in out of a system like that. And when you look at the evolution of the brain, when you look at the development of the brain, even from embryological stages, when you look at the function of the brain, it's really clear that whatever else your brain is doing, it's regulating the systems of your body. And the metabolically efficient regulation of your body is key. And all sensory functions in your brain are in the service of motor functions. So if you couldn't feel touch on your skin, you'd have a really hard time moving your body in space.

And actually we use vision even in hearing also to allow us to navigate our lens in space and kind of move around. And the same thing is true for interoception and the internal movements of the internal environment of our body. So that got me really interested in asking questions about the basic neurobiology of interoception, but also is really kind of cool and interesting that I certainly don't experience every hug I give and every insult I bear as having something to do with the physical regulation of my body and my brain's tracking of the sensory consequences of that. But that is in fact, what is suggested by the anatomy and by the function.

Also, I would say I've always been really interested in studying and aspect, which is, not emotion, it's a feature of consciousness actually, which is just these simple feelings of feeling pleasant, feeling unpleasant, really worked up, feeling calm. These aspect of feelings are always with you. They're kind of like a barometer, if you will, of the state of your body, and is very much tied up with interoception, although trying to figure out exactly how mood, which is what we would colloquially call it, or affect is generated from

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interoception is the very, very basic question of consciousness that hasn't really been solved yet.

Bill Glovin: When you Google interoception, two areas that come up frequently are diet and autism. And I'm just wondering, how does the research have the potential to help people?

Lisa Barrett: First of all, disorders of interoception, and I'm not talking about necessarily your awareness of your body, like awareness of your heart beating, awareness of your breathing. I'm talking about your brain's tracking and your brain's modeling of the state of your body. That for various reasons turns out to be very important in understanding how that works and the ways in which that can go wrong. Turn out to be really important for pretty much almost every disorder, certainly every mental disorder that exists, but also metabolic disorders or disorders that have a metabolic basis, which include obesity and heart disease and diabetes and depression and anxiety and Alzheimer's disease, and probably Parkinson's and maybe some kinds of cancer.

So I guess my point is that usually what brings people to the doctor are symptoms that people can experience and observe. And these are the ones that scientists typically focus on at least initially, but there's a whole landscape of processing going on that bears on, or is related to how your brain is understanding the sensory conditions of your body that really is required to have a better picture of what's wrong in these diseases and also how to treat them and what they have in common. Normally you wouldn't think of obesity and heart disease and depression as having a hell of a lot in common, except the co-morbidity of these diagnoses is extremely high. And that's because they have underlying mechanistic problems that relate to interoception.

Bill Glovin: What is still ahead to be learned?

Lisa Barrett: So much, because as I said, it's very, very hard to study the brain's modeling of the sensory state of the body because it's actually very hard to measure some aspects of the body in ways that can be used in experiments on humans. And unfortunately, some of the work that's done on non-human animals, in non- human animal models is very, very relevant, but human brains have expanded and have elaborated circuitry and elaborated metabolic function in parts of the brain that are actually in these two networks and the sort of big system for interoception that may not be accessible to study with non-human animals.

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Lisa Barrett: So it means that we have to be able to become much more clever about really understanding ways to probe the state of the body in humans. For example, I can measure your heartbeat. That's easy. And now I can ask you, are you aware of your heartbeat? I can use a fancy technique to figure out whether you're aware of your heartbeat without asking you. But what I really want to know is how well is your brain tracking your heartbeat? How well is it tracking the sensory consequences of your heart beating? And it uses several systems to do this, some of which are interoceptive, but at least one of which is usually considered exteroceptive. So how do I do that? And it turns out that there is a way to do it, which involves measuring the electrical changes in your brain. You can measure those pretty easily, but it's really hard to localize where they are. Whereas, so you're using something like EEG or as opposed to FMRI, which is magnetic and based on magnetic changes, and you can't really find those electrical signals that way.

So then it turns out that you have to use both and they have to be special in terms of their precision. And the whole thing gets really complicated. What's really cool though, is I think we're really on the precipice of being able to crack some of those questions with the right funding and the right emphasis and asking the right questions now, because curiosity is the mother of invention, right? And now scientists are kind of clued in and really interested in developing these really, really cool techniques to be able to maybe finally get a better picture of what the brain is doing when it's taking care of your body.

Bill Glovin: Well, I think this conversation hopefully will wet the appetite of listeners to maybe go back to the article. Again, the article is “Interoception: The Secret Ingredient.” And our guest has been co-author, Lisa Barrett. And I can't thank you enough, Lisa, for your work on the article and for joining us on the podcast. So thank you very much.

Lisa Barrett: Thank you so much, Bill. It's been a pleasure to talk with you, and I really appreciate the opportunity to write about this and share this really fascinating neuroscience topic with people.

Bill Glovin: So all of our content and Lisa's article can be found at Dana.org, and want to thank you all for listening and we'll see you next time on the Cerebrum Podcast.