 But I'm pleased to present some new data, some new analyses, in fact, by an excellent student of mine by the name of Obata Alzubi, let me see if I could advance my slides here. So Obata actually came to my laboratory from Syria, and him and his family actually had to flee Syria in the middle of the horrible war there. And he decided to pursue his PhD in electrical and computer engineering at the University of Oklahoma. And when he came to my lab, he had no experience whatsoever doing functional neuroimaging analyses. But what was amazing about Obata is he picked it up. He's a really fantastic computer programmer. And what I'm going to present you today are some of the most advanced analyses that have ever been done on our float fMRI data. And the title of today's presentation is called Taking the Body Off the Mind, Decrease Functional Connectivity in Somatomotor and Default Mode Networks, Falling Flotation Rest. Now, before we begin, I'd like to just take a moment to reflect on what's happening right now on the West Coast. I hope everybody out there is OK. You know, the first seven years of the float conference were all in Portland. And as you could see, it's covered in smoke. The entire West Coast is on fire. And I grew up in California. It's so sad to see this. And I hope everyone's doing OK. I hope we could get some fresh air over to you guys soon. In fact, it's smoggy where I am right now in the middle of the country due to smoke that has actually crossed over to our area. And this is really showing us how interconnected we all are. You know, just this year actually, earlier in January, I was in Oregon in Salem, Oregon. And I presented my first TED Talk. One of these strange situations where you have to stand on a red circle with no notes whatsoever. It drove me nuts. I like reading my notes. But nevertheless, I wanted to speak about something important that I thought was happening in society. In the sense that more and more we're finding this constant connectivity is causing problems for our nervous system. And in this TED Talk, I discussed about how floating could offer an antidote to modern times. And I also discussed and showed some data about how the modern day nervous system craves disconnection. So I encourage you, if you haven't seen that, to go on YouTube and watch the talk. About a week or two before my talk in December of last year, they wanted to put up a blog post to discuss some of my work and they asked me a few questions. And so one of the questions they asked me was what does this year's theme vision mean to you? And I responded, the survival of our species depends on our ability to foresee the future and adapt to the oncoming challenges that face society. Without vision, we are the blind leading the blind. Reactively addressing issues once the fire has already started rather than proactively trying to eliminate such issues before they even begin. And little did I know the sort of fires that were going to appear in 2020 at the time of this. They actually asked me another question. They said, if you could instantly become an expert in something, what would it be? And for some reason back in December, I gave the following response. Immunology, as viruses and bacteria are the greatest threat other than ourselves to humanity. So here we are and all of these are bearing out. I think it's sad that our government couldn't have foreseen this. This was me reading the tea leaves back at the turn of the year. But my hope is that as a society and most importantly as a flow community, we will persevere and we will hopefully take floating to this next step of evolutionary development for our species, which I think it really is. So some good news. Last week, we received notice that a float paper published by the lead author, Dr. Saib Khalsa was accepted for publication in Frontiers in Psychology. This is the first anorexia float study that's ever been published in a peer review journal. And I think the journal title is perfect. It's a special issue on body representation and interoceptive awareness. It was as if this special issue was created with this paper in mind. And so hopefully the next week or two, the PDF will be fully available to anybody who wants that. And I spoke to Dr. Khalsa earlier today. He apologizes. He can't be there for this year's conference, but he's excited to come for next year's. So big congrats to Dr. Khalsa and the whole team for this great accomplishment. Now the study I'm going to be talking about today is a fMRI study. We have 48 healthy subjects who were randomized to either float three sessions in the float pool or three sessions in a zero gravity control condition, which we refer to as chair rest. All float sessions and all brain scans were 90 minutes in length. And really the first two floats were considered acclimation floats to get subjects used to the environment. And then immediately after the third float is when they had their post float brain scan. And right now what I could tell you is the data sets, the 48 data sets have all been through a lengthy quality assurance check. And so these were all the clean data sets in subjects who had both a pre rest MRI and a post rest brain scan. Now the control condition involves the zero gravity chair. It's an active condition obviously. And really what we're trying to control for are the effects of simple relaxation. So in both conditions, participants are laying supine. They're in a comfortable environment. They have minimal pressure on the spinal cord. They're alone in a quiet and dark room for 90 minutes. And we also try to control for expectancy effects. In fact, in both conditions, we read participants the same pre float instructions, and we explain the study in the same way. We say throughout the day, our brain is constantly being bombarded by sensory information from the external world. In this study, we aimed to understand what happens when the brain gets a chance to disconnect from this constant stimulation by floating in an environment with reduced levels of light and sound and reduced pressure on the spinal cord. So in terms of the subject demographics, we had pretty well matched groups. There's 24 subjects and in both in each group, their age and education and sex breakdown was was relatively well matched. There's no differences between them significant differences and all subjects had to pass a very thorough screening process. They were screened to be free of any psychiatric illness past or present and free of taking any drugs or medications. And all procedures were approved by the Western institutional review board. So in terms of this study, what we're focused on is what's known as resting state fMRI. So subjects will go into this giant magnetic donut shaped scanner. They'll see a little screen above their head with a cross on it and they'll be instructed to look at the cross with their eyes open and try to clear your mind and don't think about anything in particular. So this is the standard procedures for any resting state fMRI. The idea is that you're not actively doing any task. This gives you a little bit of idea about the different scanning parameters that we used in our study as well as the analyses. One thing I'd like to point out is we did control for both cardiac and respiratory related artifacts. A lot of resting state studies sometimes fail to control for these things and they could add a lot of noise to the data. We also used a rigorous set of statistical tests and we'll get into that in a little bit that correct for false positives. This whole idea of ACF correction that you see at the bottom means we're only looking for large clusters that would be deemed significant at a pretty conservative threshold. So let's talk about this analysis. This harkens back to what Obata did. It involves something known as multivariant distance matrix regression or what I'll refer to as MDMR. This is a technique that has been around since the turn of the millennium, but it was only recently used actually that study at the top was published in 2014. That was the first neuroimaging study where this particular analysis was applied. And then as you can see at the bottom there, there was a study that Liber actually published in 2018 using this method in resting state data from veterans with post-traumatic stress disorder. So the methods being developed, but I think there's some really beautiful aspects to this particular analysis that I wanted to highlight. So if you recall a couple years ago, a couple conferences ago, I presented some of our first analyses on the resting state fMRI data. And in those analyses, what we ended up doing is placing seeds, small six millimeter spherical seeds in different areas of the brain. And this is typically one of the common analyses for resting state fMRI data. But when you're taking the whole brain and focusing in on just a little tiny six millimeter spherical seed, you're missing out on all the amazing things that could be happening outside of that little seed, that tiny seed. And so I wanted an exploratory analysis that would allow me to inspect the entire brain as it is, rather than trying to pre-specify these little seeds. So this is a much more advanced and updated version of the analyses that I presented on a few years ago and that others in my lab have presented on. And it's a data driven hypothesis free technique that allows you to perform connectome wide association studies. And it provides a comprehensive voxel-wise survey of functional connectivity across the whole brain. And one thing to keep in mind, it is a relatively conservative approach. It uses a permutation test and it does this in order to minimize false positives. So in our case, the approach identifies voxels whose whole brain connectivity patterns vary significantly with a pre-specified variable. And what we specified was what are the hotspots that show a significant difference between the pre-float MRI scan and the post-float MRI resting state scan. And so that's really the analyses that we're going to be focusing on today. And following these permutation tests, which were repeated 10,000 times, what we did is we found those clusters that showed the biggest difference between the pre-float versus post-float scan within the same subject. And we focused on those seeds, which had at least nine voxels in MDMR space or 72 voxels in the original MRI space, fMRI space, which was two millimeters cubed. All right. So I've given you guys the background to get you to this point. Now, what did MDMR reveal about which brain areas are most impacted by the float experience in terms of resting state functional connectivity? So in this table, there's a list of brain regions. And you could actually see those brain regions plotted on the series of images. These are axial scans. But I think the most important point to take home from this is there were nine different clusters. And these clusters mostly were contained within what's known as the default mode network and the somatomotor network. And we'll get into each of those in great detail, so don't feel like you have to know what they are right now. And most of these changes happened, I would say, in the posterior section of the brain. So you could kind of see some of these regions highlighted here. Hopefully you could see my arrow. So what I want to do to sort of just give you a first past summary of what these look like in terms of the connectivity profiles across these nine MDMR seeds. On the left, you see the chair rest condition. And on the right, you see the float rest condition. And each of the points on the figure represent one of the nine MDMR clusters that showed a significant change from pre to post float. And one thing I will point out is this is showing you the correlation. Lines that are in red would signify an increase from pre to post float and connectivity and lines that are in blue would signal a decrease in connectivity from pre to post float. So without being ingrained with all the neuroscience knowledge that would be required to disentangle this figure, one thing I think all of you should be able to recognize is there are no red lines. There's not a single area or set of regions that show an increase in connectivity from pre to post float or pre to post chair. So that's interesting. I think that that's a finding by itself right there. The act of reducing environmental stimulation appears to be reflected by a decrease in functional connectivity within the brain, not an increase. The other thing I want you to take home from this is that the float condition in general shows a much more robust decrease in functional connectivity across these different brain regions. But especially between these three regions sort of highlighted in pink or red, which are part of the default mode. And these three brain regions highlighted in green, which are part of the somatomotor network. So there seems to be a decrease in connectivity, especially between these two different networks from pre to post float, you see it to some extent as well during the chair condition. But not nearly as robust of a response in terms of just the general number of reductions in connectivity. So what I'd like to do now is go into each of these sets of networks individually and show you what changed in the float condition and also what changed in the chair condition. So on the left hand side are the three MDMR seeds within areas of what's known as the default mode network. The default mode for those who have never heard of it are the areas of the brain that are most active when the brain is at rest and not engaged in any active task. It's one of the most well replicated findings in the history of functional neuroimaging in the sense that even after a five minute brain scan it's very easy to see these resting state networks appear and the default mode network typically appear when subjects are doing nothing but resting. So let's start at the top here I've tried to color code this for you guys circles in green are highlighting significant clusters in the somatomotor network and circles in red are highlighting significant clusters in the default mode network. So just to simplify things green circles signify somatomotor and red signify default mode network. And keep in mind these are all seeds in the default mode. So what we did in this analysis is using a t test as we place these seeds that MDMR told us would show a maximal change in connectivity from pre to post float. We actually looked at which clusters showed a significant change. The top row where you see here F signifies the float condition. The bottom row where you see C signifies the chair condition. So I think the first thing that we could see is in these default mode clusters whether it be the right superior temporal gyrus. The right posterior singulate or the left middle temporal gyrus. So this decrease in connectivity both between the somatomotor networks in green. And also within other structures of the default mode network as highlighted here in red. So these are highly significant changes. As you can see it's a broad swath of tissue I mean if you look at the posterior singulate which is really a hub of the posterior default network. You can see these giant changes that begin at the very ventral portions of the somatosensory courtesies going into posterior insula. And then transcend all the way to the most dorsal portions of somatosensory and somatomotor courtesies and this is a wide swath of cortical tissue. In contrast you really don't see much changes in these somatomotor courtesies in the chair condition. Once again you can see these robust changes in the pool condition when you're floating and then in the chair condition we're really not seeing much in terms of significant changes. Just to give you a little preview of what these somatosensory courtesies actually represent. To you what's known as the homunculus. This is one of the most well known discoveries in neuroscience. It goes back to the 1940s 1950s when a neurosurgeon in Canada by the name of Wilder Penfield opened up the brains of various humans who are undergoing different neurosurgical procedures and he started stimulating the areas of the brain that signified motor cortex or premotor cortex and the somatosensory cortex as shown here in blue. And if you cut those areas of the brain and sort of unfold them for you, this is sort of what this larger image shows which is a topographic map of the entire external perimeter of our body. And what Penfield found is that when you would say stimulate this area of tissue, the subject would report feeling a sensation in their lips. And if you go up just a little bit more and stimulate this area of tissue, they would feel something in their nose. And if you go up a little more and stimulate this area of tissue, they might feel something in their thumb. And likewise, if you stimulate the motor cortices in those same regions, instead of feeling the sensations, you'll actually start having those body parts moving reflexively without your control whatsoever. And so this somatosensory homunculus is actually well known. And you could kind of see the different areas of the body that are represented. And this crazy looking dude kind of shows you how much cortical tissue is represented for each of the parts of our body. And as you could see, most of our somatosensory representation in the brain is actually of our fingers and hands, as well as our lips, our mouth and our face. And much less is actually devoted to the body proper, if you will. The other thing to notice is as you get deeper and deeper into the folds of the sylvanes fissure and into the posterior insula here, the sensations are going deeper and deeper within the body itself, becoming more or less what I might refer to as interoceptive. In fact, you could even see here is in the folds, they're already starting to see some abdominal tissue. But as you get deeper, you might actually represent other visceral organs like the heart or the lungs, or even the vestibular system as another example. So when I look at the somatosensory system and when I look at these changes across the somatosensory cortices, it's really a representation of our entire body, both the outer surface of the body but then as you get into the posterior insula, the inner surface of the visceral organs. And so when you place the MDMR seeds in those three somatomotor clusters in the left post-central gyrus, the left posterior insula, and then in the right post-central gyrus. What's fascinating is the biggest changes once again that you see are reductions in connectivity with the default mode network, as well as other somatosensory structures. In the chair condition you do see some changes but quite a bit less. In the posterior insula you see dramatic reductions in the posterior cingulate, the hub of the default mode network, and to some extent you see some of those same reductions in the precuneus, which is also part of the default mode in the chair condition that overlap to some degree with what we're seeing in the pool condition. And then in the right post-central gyrus actually the chair condition shows some of the strongest drops with the default mode. So one final major data slide is the three other MDMR clusters. The top one is really part of the salience network, which I spoke a lot about a few conferences ago. We do see changes in the salience network and its connections with areas of the posterior insula, areas of the prefrontal cortex, which are part of the executive network, as well as areas of the precuneus, which are part of the default mode. So we are still seeing some changes in salience network. In this region of the less superior temporal gyrus the biggest changes are actually happening in executive areas as well as default areas. But let me draw your attention to this bottom area. This region of the left middle frontal gyrus, this is more or less the hub of the central executive network of the brain, the left dorsolateral prefrontal cortex. And what you see are dramatic reductions across the entirety of the default mode, both the medial prefrontal cortex and the posterior cingulate, in addition to other areas of the executive network. Just to sort of show you a different view of this. Most of the prior slides did not see changes in the medial prefrontal cortex, this area is kind of shown in blue here, with the exception of this one seed. The seed of course is in the left dorsolateral prefrontal cortex. And what you see is post float this dramatic decrease in connectivity between the left dorsolateral prefrontal cortex and the default mode network. Here's the interior hub. Here's the posterior hub following the chair condition. You don't see any of that. And I think this is perhaps one of the important findings of this study. And it's actually has some clinical relevance. This area of the left dorsolateral prefrontal cortex just so happens to be the same area of the brain that they're currently using to stimulate in what's known as TMS or transcranial magnetic stimulation. This is in patients who have chronic depression, and they're finding that with repeated sessions of stimulating this area of the brain, you could change the connectivity profiles with the default network. In essence showing something quite similar to what we're finding here. And so I think this is a very interesting sort of aspect of the findings, at least one of the findings. So let's summarize. This was a lot of information to take in. This study represents the first resting state functional nerve imaging investigation of flotation rest, a unique method for systematically reducing stimulation of the human nervous system. The resting state fMRI data was analyzed using MDMR, a statistically stringent whole brain searchlight approach aimed at finding peak clusters of connectivity change between the pre and post float brain scans. The results revealed that a 90 minute session of flotation rest elicit a consistent pattern of decreased resting state functional connectivity within and between posterior hubs of the default mode network, including the posterior cingulate and the precuneus, and its temporal parietal flanks and a large swath of cortical tissue centered around the somatomotor network, including primary and secondary somatosensory cortices extending into the posterior insulin. So that one sentence, I think nicely summarizes the thrust of most of the findings. Minus the slide I just presented earlier with the left dorsal lateral prefrontal cortex. One thing that I think is striking for me is floating reduces so many different sensory systems reduces the visual systems of the brain, the auditory systems of the brain, for example. Yet, the MDMR did not reveal significant changes in those sensory courtesies. We didn't see changes in primary or secondary visual courtesies or auditory courtesies. The areas of the brain that we're seeing changes in are the areas of the brain that represent the body itself. And I think that's really an important part of these findings. Another point that I think we have to acknowledge, and this is, I think, going to be sad for some of you, but the control condition, which was an active form of rest, showed a similar pattern of reduced resting state functional connectivity. And there were no significant group by time interactions. So even though on a lot of the slides and figures, I showed you that the float condition showed significant reductions in these sets of regions, whereas the chair condition did not. What this last statement actually says is even though one is showing a significant change and the other is not the differences between the two conditions were not significant. There could be a number of reasons for this. One is that it was a very active form of rest. So perhaps it's engaging changes in similar circuitry. But I think there's also another more likely reason, which is it turns out you need a lot of data to analyze resting state fMRI. Over the past year or two, there's been a few reviews and meta analyses that suggests that you need to actually study hundreds of people across dozens and dozens of minutes of resting state in order to have any degree of test retest reliability. These were new findings, actually new meta analyses that I didn't even know about when we first started this study. And what it suggests to me is that we were underpowered to detect a significant interaction. I think the changes that we are seeing from pre to post float are legitimate. We were powered to detect within subject changes, but the between subject changes having an end of 24 in each group I just do not think was enough. As you can tell from the figures that I showed you the direction of change is clearly favoring a greater reduction following float than the chair condition. Those changes we have to acknowledge were not significant. I just want to emphasize that. In conclusion, the default mode network resting state functional connectivity, which is reflexively heightened during states of resting weightfulness appears to be significantly reduced after a prolonged period of rest. The post float reduction in resting state functional connectivity observed between posterior hubs of the default mode network and the somatosensory courtesies suggests that flotation rest may reduce self reflective processes directed toward the current state of the body. Since flotation rest can significantly reduce muscle tension, it may be possible that the intervention directly alters the representation of this tension within the brain's body maps. Thus, reduced stimulation of the nervous system appears to be reflected by reduced resting state functional connectivity within the brain networks most responsible for creating and mapping our sense of self. And with that I'd like to close by acknowledging all my great collaborators over these years. Bobada who did a tremendous job with the MDMR analysis. And I'd like to point out, reminta Wilson and McKenna Garland, who are running our NIH funded clinical trial of floating in patients with anxiety and depression, and that should hopefully be completed within the next year.