 I want to thank you all for coming this afternoon. I want to thank the organizers of the conference for inviting us to speak to you. My talk today is going to start with just sort of a brief description of my research program. So for the last few years I've been studying a phenomenon known as interception. So interception can be thought of as the awareness of the internal state of the body. It involves the detection by the brain of the numerous visceral, primarily visceral signals about things like heart rate and stomach distention, bladder distention, that when we integrate all these signals together we learn something about our internal milieu. It sort of tells us. So interception is important because it's one of the ways that our brains recognize our physiological needs and lacking interceptive awareness. It's difficult to organize behaviors to meet those needs. So this is a survival skill. So if you can't recognize that you're hungry, it's going to be hard to organize behaviors to go out and get food to meet that need. Now I've been studying interception for a while and Justin Feinstein was recruited to come to Tulsa, the Lawyert Institute for Brain Research, or LIBOR as we call it, and I was really excited about this. I've known Justin for a while and Justin started telling me about this new idea he had for studying interception. He said, you've got to try this out. You've got to try this thing called floating. I thought, that's kind of a little different, and Justin said, what this involves is you take off all your clothes and you get in a tank of salty water and it's completely black and there's no noise and you just lie there. And I thought, huh, Justin, I'm from Texas. I don't know if we do that sort of thing. And if you know Justin, you know that Justin is both enthusiastic and very good at convincing people to do things. And so Justin knew that I was going to be coming to visit my wife's family up in Portland, she's from here, and he got me in touch with this guy named Dylan. So Dylan, I could use my laser pointer and point to Dylan, Dylan is one of the owners of the float shop here. And I have to be honest and say that part of the reason why I was, I guess a little reticent to try floating when Justin first described it to me. I mean, I thought it sounded interesting, but I'm kind of like a sort of a by nature sort of anxious, ruminative person and the thought of being in that tank with my brain for 90 minutes with no iPhone or email or whatever to sort of distract myself, that didn't sound that pleasant, right? I sort of imagined that what was going to happen was I was going to get in there and start ruminating, and I think I'm causing too much feedback, sorry guys, that I'd start ruminating and just kind of boil off all the water, and it would just be me and the salt like crusted on the walls, right? And I talked with Dylan about this when I got there and I said, you know, what should I expect? And Dylan said the best thing. He said, man, just let it be whatever it is, just be with it. And that turned out to be great advice because I got in and this is what I discovered, right? Because know what this is, right? This is a float tank, right? You're in there. It's dark. There's not a lot of sound. And I get in the water and I'm lying there in the water and almost immediately I realized, oh yeah, this is what Justin's talking about, right? All of a sudden I could sense, I could be aware of certain bodily signals that I often found very hard to detect when I was just sort of out there in the world, right? And from the perspective of neuroscience, I was really interested in what are the brain systems that underlie this interesting float experience, right? So what I was doing in there was I was all of a sudden able to attend to those bodily signals. And that was really interesting and I felt like I was able to do it very well. And that was interesting because for a couple of years, my lab at LIBER had been developing tasks that study this exact interceptive attention inside an MRI scanner. So let me give you an example of what that entails. So in this visceral and interceptive attention task that you're going to see a lot of today. Subject sees on a computer screen that they can see inside the scanner, they see either the word say heart or stomach or sometimes they'll see the word bladder, right? And the job is to simply focus, while they see that word on the screen, focus on the naturally occurring sensations that they experience from that part of the body. Now we need a control condition, right, for that. And so for that we use what we call an exterreceptive attention task. So the subject sees a visual target on the computer screen and while that's on the screen they're supposed to engage in attention to this thing, this visual thing that's outside their body. Does that make sense? And they're doing all this while they're in an MRI scanner. And just to kind of give you a flavor of what brain regions turn out to be really important for this visceral and interceptive attention task, I'm going to tell you first about a study that we did just with healthy, 14 right handed healthy adults while they were doing the task. So just to be clear, because we're going to talk about this task in a couple of studies, I want you to understand exactly what's happening. So the subject's in the scanner and they see the word heart on the screen and their job is to focus, I think I'm being, three things to hold now. So their job is to focus on the beating of their heart when they see the word heart on the screen. If they see the word stomach on the screen, their job is to focus on the naturally occurring sensations they have in their stomach. So in this case, focus on the fullness of their stomach. Now this task uses, harnesses what we call in the neuroscience literature the attentional spotlight effect. So we've known for a long time, for decades now, that when someone focuses their attention on a specific sensory modality, say vision, for example, you get a potentiation or an increase in activity within the visual cortex, right, or you get a boost in terms of the activity of the sensory regions in the brain that underlie that modality that they're attending to. And our idea here was to use this attentional spotlight effect to identify the brain regions that underlie the processing of these body sensations. So essentially to get that attentional spotlight effect to reveal those regions to us. Now as our exteroceptive control condition, the subject saw the word target on the screen and they had to detect any time the word target moved from uppercase to lowercase letters, okay, so that's the exteroceptive condition. Now here's what we found. So what we observed was that the exteroceptive condition tended to increase activity in a portion of the dorsal anterior insula, which is this structure here, it's one on each side. Whereas the interoceptive condition tended to increase activity more posteriorly in the mid and posterior insula cortex, okay, now that was interesting to us because of what we know about the wiring diagram of the nervous system. So most of these signals from say your heart or from breathing or from your stomach, they travel up the vagus nerve to the brain, right, and when they reach the brainstem, so we would describe the vagus nerve as cranial nerve 10, so cranial nerve 10 comes into the solitary nuclear complex and then from there to a brain region, again in the brainstem called the peri-brakeal nucleus, then from there to the thalamus, and then out of the thalamus, the first place that these visceral interoceptive signals reach the cortex, which is the outer mantle of the brain that does a lot of the more elaborate processing in the brain. The very first place they hit the cortex is in the dorsal, mid, and posterior insula. So that was really exciting to us in light of what we found with our visceral and teresceptive attention task because all of a sudden we knew, yeah, we've got a task that allows us to map in awake humans visceral sensory cortex, right, this region of the brain that's a primary player in our perception of these signals. So the dorsal mid-insula is the first cortical representation for visceral and teresceptive signals conveying the state of the body. Now, dating back to William James, at least some psychologists have placed the physiological state of the body at the center of emotional experience. The idea here is that our experience of emotions is grounded in the physical effect, the physical feeling, the physical changes that happen in our bodies when we experience those emotions. And given that, more recently, others have proposed that the insula's role in interception should make it a player in emotion and in disorders of emotion. So you might think of the insula as the primary conduit for passing and teresceptive information into the brain for integrating the physical experience of our emotions. And if that's the case, then you might expect that emotional disorders would be associated with abnormal activity in this region of the brain, in the insula. And to explore this, we started doing research with patients with major depressive disorder, right. So major depressive disorder is a mood disorder that causes significant long-term impairment in mood and quality of life, right. Depression or major depressive disorder can manifest with lots of different types of symptoms, but the most common ones are a depressed mood in what we would call anhedonia, right. So anhedonia is a loss of interest in pleasure. But what most people don't realize is serious, sort of moderate to severe major depressive disorder is also associated with all sorts of somatic or body complaints. So depressed patients often experience chronic fatigue, headaches, heightened sensitivity to pain, they'll experience changes in their appetite and their eating behavior, and often a sense of sort of depersonalization, not being in touch with their bodies. So to understand, so given that, we thought this was an interesting and important model to look at for this visceral and teresceptive attention task and to look at maybe what the insula's role in interception might be. So we recruited 20 adults who were unmedicated, who had major depressive disorder, and then 20 adults who were healthy, who'd never had any sort of depression or psychiatric illness. And we asked them to perform this visceral and teresceptive attention task that I described a minute ago while they were in the scanner. And the first thing we did was we compared their brain activity while they're engaged in interception. But between these two groups, and when we look, for example, at what brain regions anywhere in the brain that show differences between these two groups in activity during heartbeat and teresception, one of the most prominent regions we observed was bilaterally the left and the right dorsal mid insula. The same region that I showed you earlier with the healthy control subjects, that seems to be the primary visceral sensory cortex. We also observed differences between the group in the amygdala, which is another region that's been associated with emotion. And in all of these cases, what we observed was decreased activity in, for example, the dorsal mid insula for heartbeat and teresception in the depressed subjects relative to the healthy control subjects. Now interestingly, this didn't just hold for heartbeat and teresception, it also held for stomach and bladder and teresception. So in heartbeat, stomach, and bladder and teresception, we observed statistically significant differences between the depressed group and the healthy control group. Now interestingly, the activity in the left insula was negatively correlated with depression severity. So what that means is that the activity in this region of the dorsal mid insula, when people were engaged in heartbeat and teresception, this heartbeat attention, was predictive of how ill they were. So the more abnormal your dorsal mid-insula activity was, the more severely depressed you were. And in fact, this relationship between dorsal mid-insula activity and depression severity appeared to be driven by the subject somatic complaints. So what we observed was that those individuals who had the most somatic complaints, those depressed individuals who had the most somatic complaints, meaning the report of the most headaches, chronic fatigue, changes in appetite, those sorts of things, those were the individuals who showed the most abnormal activity relative to healthy controls. So depressed subjects exhibit less activity within the dorsal mid-insula during interception, and as depression severity and somatic symptoms associated with depression increase, activation within this region of the dorsal mid-insula during interception becomes more abnormal. Now this certainly makes the case that interception plays a role in depression, but how does this relate to floating? Well, to get at that question, on the basis of these findings in healthy subjects and in patients with mood disorders, we think that we've got a task that maps this region that is involved in interception, interceptive attention. And we think that floating alters interceptive attention. I told you the story to begin with of my experience in the float tank. So we decided as part of the studies that we're doing, the float studies that we're doing at LIBER to include this visceral interceptive attention task. So the data I'm going to be showing you today, which again are preliminary. We're not finished with the study, but in the preliminary findings, what I'm going to be showing you is data from comparing the two groups. So we've got just by way of review, we've got a float group and we've got a chair group. And both of those groups, they perform at baseline this visceral and interceptive attention task. And then they also perform the visceral and interceptive attention task after repeated float sessions or repeated chair sessions. And what we want to know is we want to know are their brain regions, look anywhere in the brain, are their brain regions that show differences between those groups as a function of the time of measurement. And when we look at that, we observe, lo and behold, that the insulate is showing effects. So repeated floating, well, at the point of just looking at this map, you don't know exactly what's driving the effect. But you know that there's differences between the groups as a function of pre versus post training, there's a difference and it's in the insula, right? It's in the same region that we talked about. And now if we look at, for example, this spot right here, which is actually the same region of the dorsal mid insula that we observed in those earlier studies, what we see is that in the chair condition, pre versus post, there's really no difference in terms of the activity during visceral interceptive attention in those two conditions, those two time points. But in the float group, something significant is happening. There's repeated float sessions appear to modify the interceptive insula activity. And this is one of the things, again, this is preliminary, this is one of the things that we're going to continue to follow. And as we add subjects and we finish out the study, we're going to be looking to see whether or not this effect holds up. So neuroanatomy and brain imaging say that the posterior and mid insula is where many body signals reach the cortex. And this region is indeed implicated in some mental illnesses, right? So we talked about that. Now preliminary evidence suggests that repeated floating alters brain activity in the insula, I just showed you that. So, sorry, Justin showed you this slide last year and then I brought it up again. And I just want to put this up here again to just think about for a second what we think is happening in the float environment. So in the float environment, we are reducing the signals that come into the brain on different sensory modalities. So we're reducing vision, we're reducing the proprioceptive cues, we're reducing what you hear, we're reducing your tactile sensations, we're reducing how much you move, we're reducing certainly how much you speak, correct, because you're in there by yourself, hopefully. And as a result, what you're left with are your internal body sensations. The idea, the way I sort of think about this, and the data that Saib just showed you, I think really speak to this, is that it's almost as if you're increasing the signal to noise ratio of your interseptive sensations. By reducing all of these, the relative strength, relative to all the other sensory channels you have, the relative strength of your interseptive signals goes way up. So the float environment may facilitate the brain's processing of interseptive signals. And based on some new ideas about brain function, this facilitated interseptive processing may tell us something about the long term effects of floating. All right, so what do I mean by new ideas about brain function? Well, in the last 15 years, really, there's been kind of a paradigm shift happening in neuroscience, how we think about what the brain does. So the old way to think about the brain was that the brain was sort of a passive computational engine, right? The new way of thinking about what the brain does is that it's an active inference generator. So rather than passively simply receiving sensory inputs, right? Which was sort of the old way of thinking about that what was happening was sensory inputs would come into the brain. The brain was passively sort of waiting for those signals to come in. And then it would start doing lots and lots and lots of computations on those signals, right? Those sensory signals. And it would compute ultimately perceptions and you could think of it as those perceptions as causes of those sensory information. That rather than thinking about the brain as this sort of passive computational engine, the brain may instead act as a may actively predict the causes of sensations according to the principles of Bayesian probability. Now in a minute I'm going to explain what that means. So let's not get too far ahead of ourselves. Now at present, the empirical evidence for this sort of active inference account of brain function comes primarily from studies of the visual system, from auditory systems and from motor systems. But you really get a sense of how much this is sort of changing. How much this is sort of catching on in the neuroscience literature. This is a figure from Kenai and colleagues from 2014. And what they did was they just looked at the occurrences in the scientific literature, the co-occurrences in the scientific literature of the words Bayesian and brain. And you can see for a long time it's just down here, there's just nothing. And then all of a sudden, bam, there's like this exponential growth where this idea is catching a lot of people start to think, begin to think differently about how the brain functions. Now recently, as in like this year, a colleague of mine at Northwestern University in Boston, Lisa Feldman Barrett. Lisa and I proposed an implementation of this active inference account of brain functioning for interception and how the brain is aware and processes sensory information from inside the body. And we called it the EPIC model, and EPIC stands for Embodied Predictive Interception Coding Model. And that'll make a little more sense as I describe this model. So the idea goes something like this, that certain limbic brain regions issue predictions about the causes of body sensations according to Bayesian principles of active inference. We're gonna get to that in a second. And these predictions, what happens is these brain regions issue these predictions and send them to visceral sensory cortex, all right? And then in this visceral sensory cortex, it takes those predictions, those prediction signals, and then it also takes the incoming visceral sensory input from the body and it compares them. And it computes the difference between those two signals, and it sends that difference score or that prediction error back up to the prediction brain regions. And the prediction brain regions use that information and alter their predictions and send the next prediction down, right? And then it does the prediction error computation again, and then it sends it back to the prediction regions. You get this iterative loop where eventually you settle in on a best fit prediction for what the sensory, the cause of the sensory input is. The important point I want you to get from this is that the idea here is we perceive that which we predict. So your perceptions are actually your brain's predictions of the causes of the sensory input. So what brain regions are we talking about? Well, based on a lot of work looking at the connections among brain regions and the cellular structure of the brain regions, we think that these prediction regions, which would be in this figure in green, which are referred to as agranular cortex, that tells you something about their cellular structure. That these agranular prediction regions issue their predictions, send them to visceral sensory cortex, which is back in mid and posterior insula, which we saw that in the earlier studies. And that these regions then produce, generate those prediction error computations and send them back to the prediction regions. And then that's where you get that loop going back and forth between the regions. Now, the key point that I want you to get here is that these predictions are generated according to principles of Bayesian probability. All right, so I'm going to show you something. I don't want anybody to freak out, okay? I've been warned. I've been warned, like, don't, okay, just go with me. We're not gonna, there's not gonna be a test, all right? But I'm gonna talk with you about this equation, which is Bayes' theorem. And what I hope to show you is that something about this actually tells us something really interesting about floating and why floating has the effects that it does. So Bayes' theorem was sort of, came, generated by Thomas Bayes, who was a 18th century Presbyterian minister, his reverend Bayes. He also turned out to be a very good statistician and mathematician. And the idea behind Bayes' theorem is that the probability of an event is based on information related to that event. So let me walk you through this, all right? So you have some probability of a hypothesis given the evidence that's available to you. And then you have what we call the priors, right, or the prior. And that's the prior probability of that hypothesis itself. And then you have the likelihood of the evidence if the hypothesis is true and the prior probability that the evidence itself is true. The thing I want you to get from this is if you look over here, right? This prior, that tells you something about your past experiences, right? This tells you something about the evidence, right? That's the context, that's the current information, and particularly this likelihood term in the equation. It is telling you something about the quality of the evidence, right? So you could imagine, for example, that I have some sensation that I'm receiving from my lungs, from my breathing. And so I have to decide whether my breathing may or may not feel constricted and anxious. So to compute that, I'm gonna take the lifetime of experience that says my breath sometimes feels anxious, but at other times doesn't. And I'm going to include that along with how likely it is that I would have this breath sensation if I was anxious, right? And in the denominator here, we've got the prior probability that my breath feels the way it does right now. Now, if you take somebody who has an anxiety disorder, there's something interesting that begins to happen. So there's a lot of empirical evidence as well as sort of theoretical accounts from guys like Martin Pollis and Murray Steen that say that for reasons that we don't totally understand, we believe there's pathophysiology that cause in the body and in the brain that causes inter-acceptive signals to be noisy in individuals with anxiety disorders. And so as a result of that, right? The quality of these inter-acceptive signals are degraded relative to, say, a healthy control subject. Now in the context of Bayes, Bayesian probability, what that's gonna do is that's gonna have the function of shrinking the evidence, right? And the quality, the likelihood and quality of this evidence. And what that means is in your computation of how you feel, right? Your priors are going to carry relatively more weight in the computation of the posterior distribution, which is this term here. So as a result, your lifetime experience that says my breath often feels constricted and anxious is going to sort of carry more weight. And so we think this may account for why noisy inter-ception may lead to predictions of anxiety in patients with anxiety disorder. But now think about what happens in the float tank. So you go in the float tank and everything gets dark, right? And as we pointed out, we think that what happens in floating is that there is an increase in the signal-to-noise ratio of these inter-acceptive signals, right? Those signals get bigger and the quality, therefore, of those signals gets greater. And where is that gonna have its effect? It's gonna have it on this evidence term and the likelihood. And as a result, the relative contribution of your priors, of your past experience in the computation of the posterior is gonna go down. And you can think of it almost like, and to put it in colloquial terms, it's almost like the present moment, right? The present evidence is what's driving your experience more, right? And that's what happens in the float tank. It's a speculation on part. I really want to underline the word speculation, but we're gonna start to do studies to try and understand this. But I think this may account for why it is that so many people when they get in the float environment, in the float pool, begin to feel a sense of calm and sort of presentness. I told you, Bayes theorem can tell you something about floating. All right, so we have a good idea of which brain regions underlie interceptive sensation and perception. And many of the same regions are implicated in mood and anxiety disorders. We talked about those regions. Flotation seems to modulate interceptive awareness, possibly by increasing the signal to noise ratio of body signals. And as a result, flotation may have beneficial effects for some mood and anxiety disorders. But here's the thing, if we're gonna answer that, the question about whether or not that's the case, it's time to do the randomized controlled trials to find out for sure. And that's actually what's happening at Library Now. And that's what Saib was talking about earlier, and that's what Justin's gonna be talking about after the break. Thank you.