Psychedelic 5-MeO-DMT induces slow waves in the brain of awake mice

In this edition of Sleep Science Friday, Dr. Lyudmila Korostovtseva (Chair of the ESRS Digital and Communication Committee) speaks with Dr. Benjamin Bréant about his recent study investigating the effects of the psychedelic compound 5-MeO-DMT on brain activity and behaviour in mice. 

The study reports the emergence of slow-wave activity typically associated with NREM sleep during behavioural wakefulness, alongside neuronal off-periods and suppression of theta rhythm. The findings indicate a dissociated brain state combining electrophysiological features of sleep with behavioural features of wakefulness. 

The study also examines effects on sleep homeostasis, including changes in slow-wave activity following sleep deprivation, as well as the involvement of serotonergic mechanisms, particularly 5-HT1A receptors. 

Transcript

SPEAKER_00 0:09

Hello everyone and welcome to our Sleep Science Friday podcast. Today we are speaking with Dr. Benjamin Brandt, who is the uh postdoc at Paris Graduate School for Physics and Industrial Chemistry in the lab of Karim Benchena. Before that, Benjamin worked clinical research with Isabel Arnold in Paris Brain Institute. And before that, he made his PhD with Vlad Bysovsky. And the results of his PhD study have been recently published in the Communication Biology. This research explores the effects of psychedelic, five, methoxy, and dimethyltyptamine on brain activity. And today we will discuss this research and how how it changes our understanding of brain activity. So, Benjamin, thank you very much for being today with us to share your insights and to explain your fascinating work. Before we go into details, could you briefly explain what question your study was trying to answer and what you found?

SPEAKER_01 1:18

So the project, the ideas about the project started in 2018 when we wondered one very simple question, which is what are the effects of psychedelics on sleep? See, in the psychedelic research blossomed in this, well blossomed boomed actually in the 60s, and psychedelics at the time were investigated for their potential therapeutic properties for a wide range of uh mental health disorders, um, going from anxiety, uh, depression, anxiety, depression. Uh, and there is addiction as well, so it's really, really a wide, wide range. Um, and then it stopped, and there was a few papers going on here and there um about psychedelics, what they did in the brain, what they did uh to animals' physiology. And well, roughly in 2015, that's like a couple more papers started to get out, and all of them went back to the whole uh psychedelics are potential, have potential therapeutic properties for all of these diseases. Um, but then with Vlad, we had one simple question. It's all right. We know from sleep research that a lot of mental health disorders have effects on sleep. And so surely if psychedelics had an effect on these mental health disorders, maybe they could restore some sleep phenotypes. And so that's how the how the how the project started. Um, so he published a paper just before with uh Christopher Thomas on psilocyin, which is a long-lasting psychedelic. And yes, he he he they showed they uh so yes, they showed that um psychedelics can have an effect on the an effect on the subsequent sleep episodes. However, psilocin is a very long, well very long, quite long-lasting psychedelic. It it the effects can last for hours. And so we weren't sure whether the effects on sleep were the still the still the effects of the psychedelics itself, the of the psychedelic trip, if I may say so, even though in rodents we don't know if they trip, um, or whether it was an effect of uh the previous wake experience. So we started the project with the idea in mind of analyzing the previous wake state, trying to see whether brain signals during the wake state were similar to that of a classical normal wake state. And then we wanted to use a very short-lasting psychedelic to make sure that these effects were confined to the wake state, so that when we observed and measured sleep architecture and brain states during sleep, we were in a brain and in a body that had virtually no more psychedelics in it and were close to physiological signals.

SPEAKER_00 4:05

Okay, thank you. That's fascinating. So you have already answered my next question about how does the psychedelic he chose differ from other widely used psychedelics such as psilocybin and LSD and green.

SPEAKER_01 4:20

But you may use if I if I may bring some precision as well. It's not just the timing, it's also the pharmacological structure. I won't go into details, of course, too. Um, but it's it's roughly the same class of drug, it has the same core, uh, but it doesn't activate like it activates a wide range of serotoninergic receptors. But although psilocybin and LSD mostly uh are mostly agonists of the serotoninic 2A receptors, 5 methoxy is mostly an agonist for the 5HC1A receptor, which is a small but noticeable difference.

SPEAKER_00 4:54

Yeah, but it makes a difference for your research, as I understand. Yeah. But you used mice for your experiments, and I'm a clinical doctor, so I always wonder what can mice teach us about brain states, which is relevant for human neurosciences? What about translational research?

SPEAKER_01 5:13

Well, I think they go hand in hand together. Uh so of course, if you want to understand humans' behavior and humans' brain states, humans are always the best subjects. But as far as my ethical concerns go, I don't think you can do much uh invasive studies in humans, um, so which is quite a strong limitation if you want to understand the networks. Um, so we can use mouse model and animal model to really go in depth about uh the underlying mechanisms of a wide range of things. Um, but yes, as I said in the brief introduction, we don't know whether mice are quote, tripping. Uh we don't know what mice experience when they're under psychedelics. We know what humans experience. Um, so all we can do is all right, take a bit of what we know about one species and try to apply it at the best as we could can to uh to the other species to try and go and go forward from there. Um yeah.

SPEAKER_00 6:12

I do believe that the dissociated brain state that you observe in mice uh is similar to one that can be observed in humans under the effect of psychedelics.

SPEAKER_01 6:23

Yeah. Um so the the first time we presented the study was in was after after the pandemic. Um and briefly after a paper went out um as well of people who done the same in humans, actually, and yeah, roughly the same activity were present. So we we think there is a good connection uh between the effects of five methodoxy on mice and on humans.

SPEAKER_00 6:48

Okay. So the dissociated brain state is a state which combines features of both wakefulness and sleep. Could you please explain it uh maybe more in simple terms for the general audience of our podcast?

SPEAKER_01 7:02

Yes, of course. Um so first of all, sleep. Uh so I know it's it's the ESRS, so we have a strong interest in sleep research. Um, but in simple terms, at least in mice, you can subdivide sleep into two substates. You have non-REM sleep on one hand, non-rapid eye movement sleep, and rapid eye movement sleep uh on the other. And the French like to call it paradoxical sleep. Um, it's relevant later, I promise. Um, and to differentiate whether the animal is awake or in sleep, we use different markers. Um, so in mice for wakefulness, we usually try to have electro um electroence photographic recordings and electromyographic recordings, and we want the brain activity that we can have through EEG recordings to be quite active. So you have on the on the on the traces uh you have fast activity, and as well on the electromyographic activity, so the muscle activity, as well as on camera, if you have it, you want the animal to do something. Um, it can be resting a bit, not moving, but otherwise the muscle activity remains quite strong. And during sleep, while you have very little muscle activity, the animal is just on a sleepy posture, quite immobile, and the brain activity changes quite drastically. So during non-REM sleep, uh you have mostly what we call slow wave activity. So if you look at the traces, you have large slow oscillations, um, and then during REM sleep, rapid eye movement sleep, you have an active brain state again. So the brain looks like the animal is awake, in simple term, um, and but the the the muscle activity is completely flat. It's called muscle atonia. And so by looking at these uh phenomena, you can infer through the signal what stage the animal is in. And when you inject five methods, you enter a strange realm because you don't really know. Well, it feels like the first time I saw the signals, I didn't know what stage the animal was in, because on one hand, on the EEG, I had a brain activity that had slow waves, just like non-RAM sleep, but on the video cameras and on the electromagic recordings, I saw the animal moving around. And so that's the key into the dissociation. You have a brain that is the brain activity that is in some way dissociated with the animal's behavior through our classical definition, of course.

SPEAKER_00 9:32

Thank you very much for this explanation. Do you think that this mixed brain state, this dissociated brain state, can be connected to how people describe their psychedelic experiences?

SPEAKER_01 9:44

I want to believe it is, but that's also because it's my research. Uh so that's pure speculation, of course. Uh we cannot, we haven't yet asked an animal how it was uh feeling uh under the influence of five methodoxy. Um but if you want to bridge the gap, well, sure, we we we can. Um slow waves, in a sense, are often associated with disconnection from the environment, in a s in a sense. Um, and so I wouldn't be surprised is actually at the root of this slow wave activity you could find some mechanism that were capable of um altering the way the animal or the human experience um what its surrounding its its daylife activity. Um so yeah, maybe a general state of you know, a general dissociated state, such as the one we observe, could explain the weirdness of the psychedelic state. Um especially because, and I haven't told that before, um in the interview, but believe me, it's in the paper. Uh, we don't just see an increase in slow wave activity, we also see a suppression of a certain rhythm uh that is commonly associated with some memory processes from the hypocampus and some uh uh spatial and temporal processing as well. Um so a shift in this pattern of activity in the brain could very well be um at the basis of the psychedelic trip. But that's just a speculation.

SPEAKER_00 11:19

Okay, so let's move closer to your findings and your results. What was the most surprising and lack of physiological result of your study?

SPEAKER_01 11:28

So that's what I just described, really. The just seeing slow waves, and it's not it's not just and it's been described before, that's in some some states you can have upon two slow waves, well, local local slower activity arising in an awake animal, but seeing them at such a global scale, virtually the whole brain is doing slow waves, just like in sleep. We were really puzzled by it, um, because we didn't think it would be possible for the animal to stay awake in the largest sense of the term, um, why the brain was doing such such strong uh activity.

SPEAKER_00 12:07

Yes, I also when I was reading your paper, it was very surprising for me. And there's so much uh um such evidence lower wave activity, and you described that the mice behaved normally, like normal waking uh mice. So and you also included. Yeah. And you also highlight that this slow wave activity was clearly seen in occipital EEG leads, yes, which I also find very surprising. Uh, usually you don't see that much slow waves on occipital regions. How would you explain or interpret this?

SPEAKER_01 12:43

Well, first of all, if you want to make the difference between humans and mice, um the the brain of a mouse is quite small. Um, and usually we are able to see slow waves just fine in the occipital uh part of the brain in mice. So there's already just that. But but you're right, slow waves are a more frontal phenomenon usually. Um and in subsequent analysis, I was expecting to see more slow wave in the frontal than in the in the occipital. But I think the key difference is um maybe in the frontal part of the brain there is already a you know a base, a basal slower activity that's present for the animal. So the increase can only go so far, whereas in the occipital parts there is more a wider range of faster activity going on, less slow wave actually. So maybe you know the step up is much higher just because of that, just because there is not that much um but I'm not sure about that actually. But we were we were kind of surprised that it it is a global, a global phenomenon at a very large scale.

SPEAKER_00 13:52

And how long did it last, this phenomenon?

SPEAKER_01 13:55

Well, that's interesting you ask, because even in the paper, I have conflicting results about it. Um so if you just do the injection, this phenomenon lasts for around 40 to 45 minutes, which is which um is roughly equal to the clearance rate of the of 5 methoxy. So we suspect that it's a pure pharmacological action. However, when you start doing experiments with other factors, when you do sound stimulation, when and I'll go in depth later, I suppose, uh, when you put some little cameras over their head, when you do some changes in the environment, for some reason we have some temporal differences between the frontal and occipital activity. So in the frontal, uh frontal slow wave activity, we will see the change lasting for about 20 minutes, and in the occipital part it lasts 40 minutes again. So we don't know where that changes come from. We don't know why it's not uniform everywhere. Um, I like to believe it's the effect of the environment on the on the drug, which we know you know, psychedelics have a strong uh dependency on the context uh for the trip in humans, so maybe that's an illustration of that, but we we're not sure.

SPEAKER_00 15:08

Yeah, but you also observe not only changes uh in these low wave activities during the um acute effects of this drug, but you also observed changes in sleep after the drug went off or wore off. And if I remember well, you observed the changes in REM sleep, like over presentation of REM sleep. So, how would you interpret this? And do you think it is important? It affects somehow the behavior?

SPEAKER_01 15:37

I believe it's it's important now. Whether it's relevant with my studies, we we don't know. Um, whether it's relevant with my uh interpretation of it, we have absolutely no idea. Um, but we believe it shows that there is something happening during wake. Um, so just to summarize, the effects of non-REM sleep are quite in existence. The mice seems to do after psychedelic, after fibantoxy injection, seems to do non-REM sleep just fine with the roughly the same duration, roughly the same electrophysiological markers. But for REM sleep, also the brain, although the brain waves are very similar, um, we increase REM sleep latency. So the animals spend more time in the wake state and the non-REM sleep state before entering REM sleep after 5 metrox injection uh compared to normal. And well, you can see in you can see it in different ways. Either when we did the injection, we induced a lot of stress on the animals, which is equally possible. Imagine suddenly you have a big hand coming from the sky injecting you with a weird drug, and suddenly you start seeing things. Um, yeah, that's surely undoubtedly quite a stressful event. Um, but another interpretation could be that actually what happens during the psychedelic trip, which we still don't really know, um, has some effects mimicking the function of REM sleep, and so you are decreasing artificially um REM sleep homeostasis regulation by decreasing REM sleep pressure because in FINA uh your the function of REM sleep has already been half half done.

SPEAKER_00 17:15

Yeah, this is really fascinating. Um, but let's now try to move more to methodology so that you could explain more about your study. And for me, it's always uh very interesting to know why um researchers choose certain methodology because you have applied different methods, quite complicated design, different uh states, um, sleep deprivation, and so on. So please explain like how you chose those, why you chose these combinations, and how did it um uh bring you to your results? What were the advantages of those?

SPEAKER_01 17:49

So it's all about sorry, it's all about going from one place to the other, right? So we saw something. We had quite an exploratory-driven um way of doing this project. So we saw something and we were like, all right. According to these results, what is the next question we have? So, first we saw the slow wave activity, um, and the next question was, all right, so are the animals really awake or is it some sort of weird state and the animal is not really understanding what's going on? So we did some behavioral analysis and some behavioral um experiments just to try and see if the animal was in were indeed awake and roughly aware of the environment, which they seem to be. Um, but then the next question was alright, we have slow waves. Now we know that usually slow wave during sleep is associated with sleep pressure, right? When you are sleep deprived, uh if you go to sleep after the slow wave activity, at least in mice, will be significantly increased compared to if you weren't sleep deprived. So of course we had slow wave activity during wake, so the question was does it decrease uh sleep pressure or does sleep pressure increase the slow wave activity during wake from five methoxy? Does it work both ways? So we did some sleep deprivation, then we did some injection of 5 methoxy. We observed the slow wave activity, we measured the slow wave activity during wake and during the subsequent sleep. And so what we found was uh that sleep deprivation actually doesn't increase the slow wave activity during wake, but that's 5-methoxy injection rescue the sleep deprivation phenotype. So we had a level of slow wave activity during non-REM sleep comparable um after sleep deprivation to the one before sleep, well, without sleep deprivation. So it led to the idea that potentially this slow wave can impact um sleep regulation a bit, or can if if if slow waves are um the basis for sleep restorative function, then maybe you know psychedelichoxy participates in this sort of this sort of restoration. And yeah. In a way, yes. Um so it's different because well, sleep pressure, the the increase of sleep pressure doesn't seem to increase their amplitude, which we would expect um it to be quite uh quite increased after sleep deprivation. Um but also if you look at the neuronal activity during these slow waves, it's well, and if you look at the slow wave intracortically, it's really a mix between awake and a sleep state, which is quite uh quite weird to see, um, where you still have some fast activity going on. Um but if slow waves are characterized by a moment where uh neurons are active and suddenly all synchronizing become inactive. So you have pairs of very nice neural silences, and we observe that in our slow waves with five methoxy. So that's why we always constantly um on the knife's edge being like, oh, it is sleep-like, but actually, no, there is some weight processes as well. Um, so we're navigating that as well.

SPEAKER_00 21:14

You also applied a very amazing technique, papillometry. Yeah, yeah. Could you explain why did you use it and what did it add to your findings?

SPEAKER_01 21:24

So the question behind that was okay, we have some sleep processes in the brain. Does it change arousal levels, uh, cortical arousal levels of the animal? And a proxy reader of that is the pupil size. Um, there are some very nice papers on humans and head fixed animals, where they show that actually pupil sizes change also with brain states. Um and so, usually to make it simple, the wider, the more dilated your pupil is, the more aroused you are, and the more constricted, the less aroused you are. Um But it hadn't been done, or very rarely done, in freely moving mice. So we had one issue. We know that psychedelics were infected, but psychedelics injection, the results of that are impacted by the environment and the context. So we didn't really want to change the context, we really wanted to stay into freely behaving mice. So we had to develop a new device to do so. So we just wrapped a very small camera to a thin sheet of aluminum, and voila. So it's a very light, it's a very it's a very light device and very convenient device. And you can clearly see you can also clearly see other behaviors, but we didn't put that in in the paper, and I didn't really do some analysis on that. But if you want to see how the snout is moving or how the whiskers are moving, like the camera resolution is actually good enough to do that. So we had some very good pilot data where I put some objects in the animal's environment, and you can see the animal just well behaving in ways that we weren't expecting without even five methods yet. So for behavioral experiments, I suppose this device could be quite interesting because it really makes you think that yeah, we experience the world in a certain way, we are mostly visual species, uh, but mice, their visual system is mostly for monitoring the environment and making sure there is no predation at the red sea. And all they do, the most exploration they do is with the whiskers. But anyway, I I digress. Um then we injected 5 methoxy, put the camera on the pupil, and so that the pupil were super dilated, um, which suggested a you know elevated state of arousal, which again was a paradox considering that we had a very strong slip signal in the in the in the brain.

SPEAKER_00 23:51

Yeah, that's amazing. I can imagine that you were really surprised to get such results. Given that complicated design and all those methods you used, were there any technological or methodological challenges that you had to overcome during the experiment? Your personal experience.

SPEAKER_01 24:07

Well, the first one was COVID, really.

SPEAKER_00 24:10

Yeah, that's true. That's true in all fields.

SPEAKER_01 24:15

In all fields. Um but yeah, well, the technical limitation was really this uh oculometer, um, because the only example of it being done in in um in a CBGly uh freely moving mice still had a strong apparatus connected to the animal. Uh so we were worried that actually the um the size uh and the weight of the oculometer uh wouldn't work really, uh, but it did, so we were happy. Um then we were also one of our biggest worries was well, of course, pupil sizes change with light. So if the animal suddenly looks at uh the the LED strips that we have to to eliminate the environment, well, surely we would see some pupil constrictions. Um but the effects of fibhoxy is so strong that that although we can see some microvariation in the pupil size, it it's it's irrelevant um for the for the for the experiment. Um and one limitation that we hadn't overcome with the oculometers was that well, in a lot of head-fixed paper, um the people, the the the scientists are analyzing pupil size through wake and sleep, and we're really eager to do it to see if it's you know if pupil sizes also changes um during wake and sleep in a freely moving animal. But we realize that uh the animal sleeps sleeps with their eyes open when they're in head-fixed apparatus, but with their eyes closed um in um in a freely moving setting, which um is a strong limitation when you try to merge the pupil, really.

SPEAKER_00 25:54

Yes, now let's talk a bit uh more about implications of your study. And as I told, I'm a clinician, so I know that some of the psychedelics are being investigated for their use in depression and post-traumatic disorder, and what the results of your study add to our knowledge about potential use of these um substances, and what can be the future uh implication of your findings.

SPEAKER_01 26:22

So I think our study really puts forward the importance of brain states. Um, as I mean, in sleep sciences we used to do it, right? That's the basic of our research. Uh, we look at the data, we score the data, and then we analyze the data. Uh, but in other fields, a little bit less so, even though there were a couple of papers on psychedelics where um rousal well behavioral states were sort of scored based on the animal's movements, which works in a way, um they weren't really classified with the scope and the eyes of sleep researchers that allowed us to really see that these sort of sleep-like slow waves. Um so now what does it mean? Well, still up for debate, I suppose. Um, it really shines that actually maybe having a global state um is what matters, having the brain in a certain state is what matters for the psychedelic to work. Um, there were a couple of papers that claimed that the psychedelic effect, the therapeutic effects of psychedelics, the potential therapeutic effects of psychedelics really lies within their capacity of um increasing plasticity in certain cortical areas, or at least changing the plasticity of these cortical sites. Um now, whether the slow waves are doing just that would be quite interesting because that's what they think, what some people think uh is the base mechanism of their restorative properties during sleep, right? Um so maybe that's what they do. Having sleep signals at a global scale during waste states might allow the brain to enter some sort of more basic standard state that allows the network to reconfigure themselves a certain way. And I will go a step further than this. Um what if you have that? What if you have a sort of malleable network, and then suddenly within that network you induce some wake signals, some signals coming from the environment, such as the one we observed. Then maybe the combination of the two, the combination of the slip signal and the wake signal could drive hypothetically some sort of plasticity in a certain way, which could explain why the therapeutic properties of psychedelics seems to only work or mostly work when there is a therapist present.

SPEAKER_00 28:49

Okay, so this is what we should be aware of and cautious of if we decide to use such substances for treatment. Yeah, or are there anything else that we should be aware of?

SPEAKER_01 29:01

Yeah, be careful at that. Um yeah, the environment is extremely important. Um and uh and things can easily go wrong if you're not in the right uh in the right setting, I suppose, according to the literature, uh human literature anyway.

SPEAKER_00 29:19

If you continue this study, I know that now we work in a different uh in a different field, but what would be the um future, the next step to study? Uh other substances, other behavioral um methods, or anything else?

SPEAKER_01 29:36

What would it dep it depends on your interest really? Uh if you're interested in psychedelics, of course, this uh results begs to be replicated with other sub other substances. Um so as we said in the beginning, five methods is quite different from other psychedelics. So maybe with LSD, with psilocybin, or with mescaline, maybe it it would be a good a good start to try replicating these results to see whether actually, yes, the the the this increase in slow wave activity is something inherent to psychedelics or if it's just a five method specific um element. But also the next step would be to try and see if these weird states that we observe, if if the source of dissociated state that we see is something that we can observe in other settings. Is it something that's only really psychedelics or only fibrethoxy uh dependent, or can we see it in other processes? And that's actually what I'm interested in mostly, trying to investigate as much as weird states as there are out there uh and see whether there are some common ground there to try and and really elucidate this uh this phenomenon.

SPEAKER_00 30:47

Yeah, this is really interesting. And thank you so much for taking time to talk about your research. And before we wrap up, if there is one key final message that you would like people to remember from your research, please share it with us now.

SPEAKER_01 31:05

One key message, um one key message concerning my study, I suppose. Um sorry, I'm taking a long time here to think. Um but one key message would be that everything is connected, everything is joined. Uh, and even though we as scientists and sleep scientists, we like to put stuff in boxes, we like to put brain states in boxes. Actually, the reality of things is uh it's more fluid uh than we think it is. And the beauty of complex behavior arises from this diversity of states.

SPEAKER_00 31:41

Thank you very much once again. Thank you for this fascinating discussion. Thank you for your for sharing your insights and explaining your work in this accessible way. Thanks also to all of you who have been here with us investigating the effects of psychedelics on brain state. Have a nice day.