S3E2 - Francesca Siclari - Parasomnias and dreaming

Hello and welcome to the Sleep Science podcast. I'm Penny Lewis, a new scientist specializing in sleep and memory and the presenter of this show. In the podcast we talk about all things related to sleep, from dreaming and sleepwalking to what sleep does for our brain and body and how we can get more out of our sleep. Hello everybody. Today we're extremely lucky to have Dr. Francesca Siclari with us. She's a neurologist and she's an expert in sleep and she has a particular interest in parasomnias like sleepwalking as well as an interest in dreams. Francesca is a research group leader at the Netherlands Institute for Neuroscience and I think we're going to have a really interesting discussion. So Francesca, welcome to the show. Thank you. Thanks for having me. It's really great to have you here. I have lots of questions for you. I was having a look at, you know, some of your work and the first thing that I wanted to ask you about is your recent work on parasomnias. So you have this really exciting paper and I wondered if you would start by telling us what parasomnias are. Yes, of course. So the term parasomnia comes from the Greek and means a long sleep basically and refers to abnormal behaviors or experiences that occur during sleep. There are different types of parasomnias, parasomnias that occur in different stages of sleep and the ones I was particularly interested in in the study refer to are non-rem parasomnias. So parasomnias that occur mainly actually in deep sleep and there's a group of parasomnias that occurs in the stage that is called arousal disorders and that comprises sleepwalking. So people who basically have an incomplete awakening out of deep sleep and then start to walk around but also sleep terrors when there are bigger manifestations of fear. So screaming and having a frightened facial expression and also confused arousals, that's when a person just has this partial awakening during deep sleep and appears confused. Wow, so it's actually lots of different kinds of parasomnias but the one that you focused on in this paper was more the sleepwalking, is that right? Well actually these three types of parasomnias, they occur often in the same individual and the boundaries are really fluid actually between the different types. So in this study we included mostly patients with sleepwalking or sleep terror but many of them had both. So this is something that I get asked about a lot and I never you know have the information to give the right answer so I'm just going to ask a little more here. Can you explain the difference? Sleep terror, is that the same as night terrors? Yes, absolutely. What actually is involved in that? During a night terror basically a person appears to be waking up during deep sleep and starts to appear very scared so basically they can be screaming involved, frightened facial expressions, they can also leave the bed, they appear to be in great great distress and when you look at the brain waves during sleep terror, those people although they appear awake actually have sleep waves in their recordings so they are still asleep in a way, it's a hybrid state between wakefulness and sleep. It's very common in children like all non-rim parasomnias so many children up to 10% have actually one type of non-rim parasomnia and then usually it goes away with age but in some people it can even persist into adulthood or even occur for the first time while being an adult. And when you say they still have sleep waves do you mean slow waves or is it non-rim sleep? Yes slow waves yes that are typical of non-rim sleep. There have been studies of non-rim parasomnias that have captured episodes while patients actually had electrodes in the brain those were epileptic patients that did these recordings for other reasons but the researchers happened to capture episodes of parasomnia of non-rim parasomnia and they found actually that these people technically were both asleep and awake so some areas of the brain showed patterns of wakefulness as if they were awake and other areas of the brain showed the brain waves that are typical of deep sleep so it's a hybrid state actually. And do we know what causes it? So definitely in children maturational factors enter into play we also know that it runs in families so if you have someone in your family who is sleepwalking for instance you have a higher chance to sleepwalk we haven't fully identified the genes that are involved in in this condition and then actually it's conceptualized usually as something that occurs when a series of factors that are called precipitating factors make your brain really want to stay asleep like for instance if you have not slept well or not slept enough for many days in a row then when you go eventually go to sleep then if you have this predisposition and a sleepwalking episode is more likely to happen because your brain really wants to stay asleep and then when at the same time there are factors that want to wake up your brain like noise sudden noises or even stress then the brain gets himself into a mode where on the one hand it wants to stay asleep but on the other hand it wants to wake up and that's when these episodes occur where the brain basically gets stuck between sleep and wakefulness that's how it's usually conceptualized it's so interesting and it's so interesting that it also tends to happen more in kids i mean i know you say it's developmental so maybe their brains haven't figured out that balance between sleep and wake so much absolutely that's what the idea is it also goes perhaps with the observations that sometimes kids can be extremely difficult to wake up completely depending on when you wake them up so there might be a natural resistance to complete awakenings yeah and just all of what you've said now it's kind of true for all parasomias so because we started talking about night terrors but actually the balance between sleep and wake and the fact that it's more prevalent in young children this is true for all of the kinds of parasomias that you mentioned right for these non-run parasomias yes for arousal disorders absolutely yeah so i'm just going to ask a little bit more kind of general questions on this because there's so much interesting stuff here i've read things about people actually committing crimes in their sleep you know there are these kind of court cases from the past where someone got up and drove 30 miles and i think killed his wife and and you're you're nodding so i know that these are familiar to you other people have killed bed partners that so there have been crimes for instance there are also things like night eating where people go to the fridge and they eat copious amounts you know this is all in their sleep they're not aware of it are these different than the other arousal parasomias or is it part of the same thing no so violence and eating can occur within these non-run parasomias there's a whole range of behaviors that can occur fortunately violent behaviors are rare but they can occur and obviously when this happens this is terribly dramatic because those people are obviously in an altered state of consciousness cannot be made responsible for their actions and it's also very difficult in a legal setting to determine whether whether someone had a parasomnia episode retrospectively and also whether a person actually is a sleepwalker or not because there are many sleepwalkers that don't display any episodes for months and months and months and we don't have a very clear marker to say okay this person is a sleepwalker as opposed to someone who pretends to be one so there's a big legal complexity involved in these cases of violent behavior which fortunately are rare but whenever I see a patient in the sleep clinic I really make them aware of this possibility and we discuss what can be done actually to prevent the violence in this context and what can be done well it's actually we try and prevent the consequences of the violence or the occurrence of parasomnia episodes typically having a very regular sleep schedule is something that we advise people to do not to be sleep deprived also sleep in a calm environment without noises without disturbance sometimes we use videos in patients home videos to see what they actually do during the night and I was surprised to see that sometimes episode can be provoked by pets just a cat jumping on the bed at the right moment or things like that so obviously having a bedroom environment that is free of such disturbances is important we advise people not to sleep on high beds because sometimes they can fall down injure themselves during the episode remove any dangerous objects from or furniture from the bed environment for example in the united states it's also weapons are an issue some people have weapons near near the bed also in some cultures it's common a common thing to have the door open also the the front door of the house and some children actually have died because they just ventured outside in a sleepwalking state so these are like common sense measures that need to be taken to reduce the risk of injury during these these episodes I mean it's really scary actually and I guess because these these personas are more common in children it's not uncommon that a child would get up and walk around so surely having the door is closed is an obvious thing you could do or the windows also I have had cases of patients where they jumped out of the window that is also they can be really dramatic fortunately as I said it's rare but it's better that the patients are informed yeah and I mean of course it's interesting now we're just kind of thinking about it what's involved here and it's interesting to hear about these things so is there any explanation for why a simple thing like you know getting up and walking or talking would turn into a violent behavior do we have any idea why that would happen is it perhaps linked to a dream or do we just not know okay that's interesting so that partially relates also to the reason that I started studying this phenomenon more in detail what I actually wanted to know is what a sleepwalker what what they experience actually during their episodes and while interviewing a lot of them it became clear that violence can occur in a variety of instances for example sometimes they can reflexively hit another person that is approaching because they are sometimes in a state where they misinterpret reality so a bad partner is actually interpreted as being someone else and often their experiences or these misinterpretation have a bit of a negative connotation and suddenly it becomes someone who's dangerous and who wants to harm them and then they defend themselves sometimes this can also happen reflexively without them wanting it or having actually the intention because the state of consciousness is actually quite variable in some cases there appears to be very little experience associated with their behaviors as if they were a bit in automatic mode and at other times they really have an intention in mind that is often related to something that thing that appears like a dream scenario so violence can occur in these cases and sometimes simply injury can occur because they interact with things that are not there for instance they might lean on something and then lose their balance and fall because in their dream they're leaning on something that they perceive but that is not there in reality or for instance I had a patient who was convinced that he was at work and he was sleeping under a pitched roof and then he was actually getting up and hit his head against a pitched roof because in his head he was at work he wasn't in his bed sleeping and so yes this is a bit the context where injuries can occur and so it sounds like you've been working with these patients for some time and through seeing multiple cases and multiple things that happen it made you would it be correct to say that it made you start to wonder what's driving this where it's coming from and that's what caused you to do some of the experiments that you've done yes absolutely that was one reason and then the other reason is that I had heard that often patients actually acted during these episodes according to a dream scenario and I'm also very much interested in dreams and usually a dreaming person doesn't reveal anything about their dream in real time right if a person looking at you dreaming doesn't see anything of that dream unless you record the brain waves and even then you don't really see the content of the dreams and parasomias by definition actually have visible behaviors and I was very interested in relating this behavior to actually the experience of the person and I wanted to know okay is this behavior always a reflection of a dream going on as was suggested by some or can this behavior sometimes truly occur without any experience at all you know in a purely automatic mode and how complex can it be I thought the best way to really know is to ask patients okay with respect but especially to record these episodes in the lab and as soon as the episode is over just talk to the person because yes these episodes we also know they're very easily forgotten like dreams and so I really wanted to have the the chance with my team to interview them directly after the episode and and ask them okay what did you just experience if anything and also we wanted to know can we see something in their brain activity in their brain waves does this look like dreaming or does this look like other patterns that these were the questions we were interested in there's such interesting questions and and really kind of wide open I think until your work I mean there hasn't been much on these kind of questions right tell me a bit about the experiments that you then chose to do because I know it's been a series of experiments sure so the first thing I actually did and that was when I saw these persons in in my consultation is to set aside some time about two hours and really ask many questions about the experience so that's what they remember just over lifetime and by doing that it became apparent that the level of consciousness actually appeared to be variable in non-reparation on the episode there were some patients telling me you know I never know what I'm doing actually when I'm doing it and when someone wakes me up after it I don't have the impression that I experienced anything and then there were examples of patients telling me a very elaborate dream and that their actions during the episode reflected what was going on in the dream so I saw that was a certain variability and then another thing I discussed with them in these interviews is do they actually perceive their environment do they see or not and there again their answer suggested that it's variable there were patients that could easily interact with others during the episode they could have conversations that could avoid obstacles that could seek out really specific objects in a location for instance I had a patient who had an episode where he dreamt that his dog was dying of thirst a dog it wasn't wasn't even his dog and so he went to the kitchen and he got a little bowl filled it with water and put it next to the bed and the detail that I love is that he didn't want the water to splash on the floor and so he put a little towel under the under the bowl so you see very intentional actions where they are connected to their environment and then their cases were basically everything the whole environment is hallucinated so they move actually through fully imagined environments it can be their workplace as in the example before it can be a volcanic landscape it can be a jungle whatever that is really has nothing to do with their real environment and then that's where they also get hurt because they are functionally blind actually they bump into objects because they don't see them they see something else and so there's a whole range actually of sensory disconnection so sometimes they're connected to the real environment and sometimes they're connected to an imaginary environment and sometimes there's something in between where they in some rudimentary form I think perceive the environment but they misinterpret it so they can know that a person is there but they don't recognize this person as their bed partner or their wife but they think it's someone else or they take an object for another they might just carry a plate but think this is a cactus or a plant or something else so so there's a whole spectrum of how connected they are actually to the environment and is that again explained by just the fact that parts of their brain will be in different states so and that could be different in every case in every person like exactly the mixture of which parts of the brain are awake and asleep and in other states of consciousness that was the next question I had I knew it was variable but what determines this variability and that's why we invited these patients over to the sleep lab to actually record their brain activity and see if any pattern could explain these differences and so what we did it was quite a tiring protocol for everyone these these patients came to the sleep lab and then we just recorded them a night with high density EEG so EEG recordings that record the electrical activity of the brain we use many many electrodes to really cover all the brain areas 256 so we call this high density EEG so the patient slept with this EEG net and they had a really long cable which allowed them to move around in the room so they could sleepwalk if they needed to and the first night we just observed them and some of the patients presented episodes and after the episodes we would immediately interview them through intercom we were sitting in another room you could see the video we filmed them and then we would ask them through intercom what did you just experience or what was going through our mind was the exact questions and then after this night we had actually another night in the lab where they weren't hooked up and they were not allowed to sleep so we really wanted to mimic a bit the situation that favors these episodes and so wanted to increase the sleep pressure by keeping them awake and only letting them go to sleep the next morning and then when they entered a deep sleep so slowly that's when most of the episodes happened we would play very strong arousing sounds actually in some cases this induced the episodes and then again we would interview actually the the patients about their experiences so what kind of sounds I mean strong arousing sounds you mean like unpleasant sounds or just loud sounds it's like a very loud beep and it's quite strong and yes in some cases the patients walk up just normally just a normal awakening in some cases they presented an episode and that's when we went interviewed them about their experiences several observations we made that that I found interesting so the first observation was that indeed whether you will experience something or not during an episode depends on how activated your brain is when we played a sound when parts of the cortex so the the outer part of the brain were active and particularly the parts involved in dreaming that we had seen in another study to be involved in dreaming then patients were more likely actually to report a dream as if the brain was in a state where it could create a dream and whereas when there were the more slow waves there were so the more sleep-like the activity was in the entirety of the brain the less likely it was that they experienced something so we saw a relation actually between the degree of activation of the brain and the experience the presence of experience actually of conscious experience how do you measure activation you're talking about particular frequencies of activity or yes so we chose the very low frequencies and the very high frequencies obviously this is something we do once this data acquisition is finished um and basically we look at the low frequencies that are more sleep-like and the high frequencies that are more wake-like i'm simplifying a bit here and then we compare basically the instances where patients reported an experience and the instances where patients did not report any experience so when they were doing things and afterwards when we work when we asked them about that they said there was nothing basically there was nothing in my mind so they don't remember doing anything basically well they have three different possible answers i was experiencing something and then can relate the content the option of saying well there was something but i don't remember what i don't remember any content and the option i have the impression that was absolutely nothing and that was actually the minority of cases only about 20% of of cases participants reported this option and when we looked at the brain activations the brain activations between the presence of experience and the no experience were different then when we compared the brain activity associated with the recalled experience and the the ones where they did not remember the content but they had the impression that they had experienced something so to me it suggests that obviously this is debatable but i truly have the impression that in some cases there's no experience and those were very short episodes quite stereotyped quite similar while in the longer ones there were more complex most of the time they experienced something and could remember it we interpreted to be three different scenarios forgotten experience but also possibly behaviors without any experience at all actually so when you say short and long what kind of duration are we talking about we're talking about like one minute versus five minutes or no it's more in seconds so a short one would be five seconds very short like could be a short scream or looking around or just appearing very perplex or saying things and the longer one then would be 20 seconds that was our average actually or 25 but in the lab we didn't have any episodes they were much longer than that and when you talk about the low frequency and the high frequency so i think i mean some of our audience will know about the different frequencies so i think by low frequency you mean like slow waves yes so elements that are typical of slow wave sleep of sleep actually absolutely yeah and and high frequency do you mean gamma or well there were so many movement artifacts that we couldn't go up to gamma so we we used better instead okay and so did i understand correctly that for the episodes where they reported that they knew they were doing something they had some kind of a mentation or dream or awareness they had a higher beta high frequencies and lower low frequencies yes so it's the ratio between them is it so they had a higher ratio between high to low frequencies and if they didn't if they weren't aware of anything they had the opposite so they had the higher low frequency yeah exactly it's not exactly the ratio but both we found both lower frequencies and higher high frequencies when they had an experience and so how do you interpret that well we know that the very low frequencies in the brain activity they represent so-called slow waves and we also know that during slow waves the thalamocortical neurons in the brain they become silent before showing activity again become silent they go into this on off rhythm and it's possible that when a big part of the brain actually shows these silences that this could actually interrupt the exchange of information across different brain regions and that is thought to be at least from a theoretical perspective a main prerequisite of consciousness so different parts of the brain can only communicate when there's no silence that interrupts them so it's kind of like bites are being taken out every time you have a trough in one of these big slow oscillations and those bites I guess what you're suggesting is that might be enough for you just not to have any consciousness at all yeah the more they are the more widespread they are across the brain then the less likely it is I think that the patients have a conscious experience we also found that it matters where they are in the brain and we found that if they are more in the posterior regions especially the visual areas then they will describe less fewer conscious experiences and how about the higher frequency activity does it matter where that is similar exactly so again if it's higher frequency is in the kind of visual areas then they're more likely to and when people describe experiences do they how do they describe them is it often a kind of a visual thing or is it just say you know I I knew that I was doing this this or it was I was in this situation or is it yeah what do they say yeah so in about 80% these experiences were about something that was going to happen something mostly negative for instance we had a patient who had a six month old baby at home that was the reality and during the episode we saw him actually getting up and looking through the bed sheets looking under the bed and screaming for help and then when we asked him what did you just experience he said well I was looking for my baby my little one I thought she had fallen off the bed and I couldn't find her and I screamed for help so exactly what we actually saw so often about an an impending danger basically another patient we saw her getting up in the bed and reaching actually towards the wall touching the wall and saying no no no don't die please and then she told us that she was actually saving trying to save ladybugs from falling and from dying so often there was the idea that something was going to happen and another interesting observation in this context is that we played these really loud sounds to provoke the episodes and in only very few cases I think it was 11% the sound actually figured in the report most of the time they had the impression that something dangerous was happening but it had nothing to do with the sound actually I found this very interesting because it it actually suggests that your brain during this state or even during sleep perhaps is more sensitive to the meaning of the sound or the potential danger associated to the sound than to the actual auditory content because most dreams and that relates to a question were actually visual most of the time they had more the visual hallucinations than the auditory ones so the sound just didn't didn't figure anywhere it's so interesting do you think it it's partly because the sound you chose I mean I know it was loud and annoying but it wasn't kind of a a meaningful sound it was just a beep do you think it might have been different if you had chosen a meaningful negative sound like a scream or I don't know a dog growling or possibly it would be interesting it would be absolutely interesting to try that but perhaps it's really the brain in this day just makes the difference between dangerous potentially or not and then in this case I think elaborated on the danger but it would be a very interesting experiment I think to do so there is a kind of a older theory I think about k complexes which are basically if you play a sound during deep slow wave sleep there are these huge oscillation responses to the sound and as I remember there is this theory that k complexes are the brain kind of being aroused by the sound checking whether it's a dangerous thing and then deciding that it's okay and going back into a deep sleep does this kind of fit with or relate to your findings you think we actually saw that when they experienced something we saw more of these k complexes just before whether we gave a sound or not so that's also interesting I don't know if that's the function of k complex so we definitely saw a k complex like presence before the episodes when they reported something yeah okay I mean it's very hard to know what those are really doing I just I thought I saw a parallel there but maybe it's going too far yeah yeah I wouldn't know if that's exactly the function of k complex I couldn't say but we saw k complexes associated yeah with these episodes what also was interesting is that even when we didn't play any sound sometimes in the spontaneous episodes the patients had the impression that someone had just talked to them or that they had the sound the episode would start like huh what did you say or like like the start will reaction a little bit so whatever we do with the sound I think it mimics very well what happens spontaneously even if we don't play any sound and the episodes happen yeah but you're just using the sounds to kind of bring the episodes on in the lab condition exactly now I know that you've done a lot of work on dreams as well and you said at the beginning that part of your motivation for this work was to kind of look at the relation between the parsomnias and the dreams would you consider these can I call them mentations that they were having that they were putting would you consider these dreams and how does this tie in to the work that you have done on dreams yeah so if we look at the phenomenology I think they can be considered dreams so all the core features of dreams are there in these experiences that the the participants described in their full-fledged expression we have the hallucinatory character with many visual hallucinations but also auditory ones just like in dreams we have false ideas so basically during the episode the person believes in a different reality not in the current reality of lying in a bed so that's similar as in dreams where we get caught up in in scenarios without questioning them we have yeah the absence of insight so these parsomnias episodes even if you tell them during the episode you're having a parsomnias episode the people will protest they will get angry they will say no I'm not this is real this is real that's what happens so they really have our denial about the hallucinatory nature of their experiences and in a dream most of the time we don't realize we're dreaming apart from lucid dreams but that's a notable exception so we have that and people also call them dreams so it it makes sense to consider them dreams there are two things that are different from ordinary dreams it's the fact that they can interact with their environment and they can partially perceive the environment which we don't do during normal dreams our dreams have nothing to do with our environment most of the time although they can sometimes be influenced and in parsomnia episodes there is a relation so there they could partially connect it to a certain degree and then another interesting thing is that the themes of the dreams associated with parsomnia episodes are very similar one to another so many patients tell me exactly the same stories this seems to be a stereotype contents about the impending dangers insects in the bed I know that when they tell me about the insects in the bed it's probably a non-reparsomnia it's so typical that actually within patients but also between patients they tell very often there or at least they remember the same the same dreams so that's a bit different from from normal dreams and also what we've seen with the studies they the no experience episode appear to differ from the dream episodes just like during normal sleep the dreaming differs from the non-dreaming so at least in terms of brain activity they appear to share similar signatures we don't still understand fully what what these signatures represent actually but there seems to be a parallel there now if we look at also the the content of the dreams are more similar to the non-rem sleep dreams on average so we have REM sleep where the brain is very active where the eyes move under close eyelids and that is very prominent in the morning and most dreams we remember are actually from that stage normally those are the story-like dreams with very very vivid vivid images the non-rem dreams can be like that but on average they're shorter they're more conceptual they're more closer to reality and that's what the parasomnia dreams are also more similar to but it makes sense because the parasomnia episodes occur in non-rem sleep but i would say one of the conclusions i have is that i think it's a good model to study dreaming because we can see actually what they're dreaming about in real time when they have these conscious experiences are you waking them up after their experience or do they spontaneously wake up or at what point are they actually reporting their dreams some patients actually gave us a signal when they were back when they realized they were having an episode one clapped and in a sense and told us okay it's over i'm realizing i just had an episode i'm ready to talk about it but that was the exception most of the time they would have the episode and then they would go back into a sleeping position again and that's when we came in and what we interviewed them and asked them about their experiences but it's usually a matter of a few seconds after the episodes you did wake them up at that point yes that we interviewed them in some cases they were gradually had returned to a normal waking level and in some cases were in this they were in this hybrid state and then we brought them to to full consciousness and would they then go back to sleep and possibly have another episode yes okay so i mean i think you've convinced me that these are dreams and that they fit all the criterion for dreams but what you didn't talk about is actually the eeg evidence for this so i know that you have you know prior studies where you looked at what the brain is doing during dreaming and there are signatures for that as well and i assume that the activity was quite similar during these states is what you've seen previously is that right exactly so i did a previous study with my colleagues at the University of Wisconsin where we woke up normal sleepers during their sleep and asked them what they were experiencing and we found that some instances they were they could tell us just like the sleepwalkers what they were experiences in other cases they said there was nothing i had no experience and when we compared these instances regardless of whether it was REM sleep or non-relief we saw a greater eeg activation so a greater activation of the the cortex probably in posterior brain regions when they were dreaming as opposed to when they were not having any experiences and that's exactly what we found also in the sleepwalkers and so is that the beta frequency again yes it's the low frequencies that were lower and the high frequencies that were higher and the high frequencies yes in the dream study was the gamma but also the beta and in this case we could only go up to beta because the gamma was too um artificial yeah but so the point is that the kind of eeg signature was roughly it matched what you would expect for dreaming based on that prior study yes yeah it's so interesting were some of your participants children or were they all adults no we only did this in adult but it would be absolutely fascinating to do this in children already it's more frequent and then there are some studies suggesting that children do not experience the episodes like adults children much more often say that they were not experiencing anything compared to adults and many patients actually related yes when i was a child i didn't remember anything or think i didn't experience anything and i only started to have the dreams with my episode much later when i was older so that was a common thing the patients reported why would that be well if we think that indeed the slow waves reflect processes that interfere with consciousness we know that children have much bigger slow waves so have have more slow asleep so i would expect that during episodes they would also have more slow waves and possibly these processes interfere with the generation of these of of the complex dream experiences so it kind of goes back to what we said about the troughs of this low waves kind of taking bites out of that mentation and when you say the generation of the dream experiences so can i push you a little bit more on what might be happening there so if you didn't have so many slow waves how do you think those dream experiences are generated and and also remembered because you have to not only experience them but remember them when you're woken up right yes so this is a big question obviously we we still don't know actually what we know is that the dream experiences they seem to activate similar areas and are waking experiences when we see something a dream we see an activation in the visual areas just like we see it during wakefulness we saw for instance that when you dream of a face then the face area in the brain it's called the face who's from area that recognize faces is more active as opposed to when you don't see a face similar to in to wakefulness actually so it's as if we had seen that the screen on which the dream movie is projected is the same so we have a screen same as in wakefulness but in wakefulness how do the images get there through the senses we see your face so it goes through the eyes during dreams the senses are more or less shut so the face must come from somewhere else and where this happens in the brain that's of the question we still don't know how this relates to memory processes that might go on in the brain the study that we did in sleepwalkers well at least some experiences appear to be induced by the sound because it was a confabulation around an arousing stimulus that then unfolded into a longer dream so the question we're looking at in my lab now is what role do arousal systems play in the generation of dreams but this question is is still open and it's the big question I think yeah I think it's a big question and I'm not sure if I actually understood that answer so I mean the role of the arousal systems as in okay so the sounds trigger something and then and then you have some kind of a perception you know whether it's auditory or the sound just triggered something and then you have a visual perception as it sounds like a lot of people did and then that's in the cortex but that is getting then saved into the hippocampus maybe as an episode or I mean do you think about those kind of dynamics yes that's even more complex but yeah I don't know how it plays out then at the level of the hippocampus but I think it is conceivable that arousal systems might pray alone even in the generation of dreams so arousal system is in the sense of activations in the brain stem and one of the original hypotheses on dreaming by Alan Hobson's that is a bit outdated now but I don't think the role of a arousal system could should be totally excluded in the generation of dreams then how it relates to the hippocampus I don't know but what we did in the sleep on case is we induced arousing experiences that were secondarily enriched as a dream probably that's at least what the description suggested and we know that arousal systems are active during sleep spontaneously even without us playing any sounds and do these almost periodic activations will play a role in the generation of dreams we still don't know it might just help to remember a dream for instance there are many possibilities yeah so it's a very it's a tricky question it's a tricky question we have by no means proven anything it just opens I think even more questions all of what you said is so fascinating I just ask you two other quick things so we haven't talked really about REM sleep could you maybe just tell us a little bit about the REM sleep parasomnias so parasomnias can occur either in non-REM sleep like arousal disorders sleepwalking sleep terrors confusion arousals those are the non-REM parasomnias and then there are also REM sleep parasomnias I hope the most known is called a rapid eye movement sleep behavior disorder also rvd rvd is a condition that occurs as the name says during REM sleep normally during REM sleep we have very low muscle activity probably this relates into a functional muscle paralysis and the general idea is that this prevents us from acting out our dreams and there are conditions where this muscle paralysis is lost and where people actually have excessive muscle activity and even very complex behaviors and often if you wake up these patients and ask them what they were experiencing they will tell you very specific dreams with goal directed actions that match the behaviors that you see now this is a different type of parasomnia because it occurs in REM sleep so more frequent in the second part of the night and also the age group and the cause of this parasomnia is very different so while non-REM parasomnias or the confusion arousals occur very frequently in childhood and then really diminish in adulthood the REM sleep parasomnia so the rvd is more frequent in people after 50 and it can also be the first sign of some neurodegenerative disorders like for instance Parkinson's disorder or other other disorders in this group called synnucleopathies so it can be the first time even before other signs of the degenerative orders appears they can already have this the sleep disorder so the rvd which is an important sign for clinicians actually and that's the most common REM parasomnia is it yeah some people also count nightmares as a REM parasomnia but that's again different yeah I have a question about nightmares so you know there is this idea that in REM sleep you can't have bodily responses like autonomic responses we call them so you know increases in your pulse rate sweating of your palms things like that because the balance of neurotransmitters means that those systems are kind of offline but I believe that when people have nightmares they do have those responses can you comment on that at all yes so there are actually very few nightmares recorded in the lab so I think the question is still open and I also think that within REM sleep heart rate can be very variable and yes in humans the sweating responses can be reduced although not completely abolished like in animals but there can be some variation but there also cases described where the mental content the nightmare did not match the the other measures like heart rate so it's still an open question I haven't seen a good study where a nightmare was actually captured in the sleep laboratory and these variables were studied at the moment where the nightmare has supposedly occurred okay so we we don't know basically it's another thing that remains for us to study which is great because there's plenty of work for us to do yeah okay well thank you so much I mean this has been fascinating and I've learned a lot thank you for having me you've been listening to the sleep science podcast with me Penny Lewis and our special guest Dr Francesca Cichlari for more information about the podcast check out our website and if you enjoy the show please feel free to like us on Twitter now from me and all my colleagues at the naps lab in Cardiff thanks for listening and sleep well