More than an evolutionary waste of energy, dreams are one of the last mysteries of human cognition. Dr. Raphael Vallat, a neuroscientist and sleep researcher at UC Berkeley, explains what we know about what happens during REM sleep, why we have recurring nightmares, and even how that evening cocktail affects your dreams. Plus… the weirdest things some people do while they’re asleep.
Phil Stieg: I’m happy to introduce Dr. Rafael Vallat. He’s a neuroscientist at the Walker Sleep Lab in the Department of Psychology at the University of California, Berkeley. You will quickly notice he’s not from the United States, but from France. He came to the U.S. to investigate the impact of sleep on human health and decision making. More specifically, he is studying the production and recalling of dreams and their importance to our health. In a nutshell, dream processes are complex and probably good for you. We are here to understand why. Raphael. Welcome and thank you for joining us.
Raphael Vallat: Thanks for having me.
Phil Stieg: So let’s start off making sure we’re all on the same level. Can you tell us what is a dream?
Raphael Vallat: Sure. So in its simplest definition, a dream is a subjective and spontaneous experience that occurs during sleep and that we may or may not remember when we were awake.
Phil Stieg: So, does everybody dream?
Raphael Vallat: Yes, everyone dreams. But we do forget most of all dreams. I think people tend to underestimate the amount of dreams that they have during the night. Because if I were to wake you up, you know, several times during the night and ask you when you’re dreaming right now, you would actually remember many more dreams — than you do on a day to day basis.
Phil Stieg: Are there specific similarities between daydreaming and dreaming
Raphael Vallat: OK, so we know that there is a considerable overlap between dreaming and daydreaming. They share the same brain regions. They also share the same content. And some researchers also think that they could share possibly the same function, which is trying to integrate some memories and also regulate your emotion and also give you some Problem-Solving ideas and some and some creative thinking.
Phil Stieg: I always felt at a disadvantage. I had a friend that I would get together with and would always, in great detail, tell me about their dreams. And I the only time I ever have vivid dreams is when I take when I travel to Africa and take the antimalarial drug. And then I have these incredibly vivid dreams that I recall. So I always felt a little bit ripped off in that regard. And so the question is, why do some people recall so many of their dreams are so good at it and why are others not?
In terms of personality, we know that people will remember dreams more often, are typically more interested in dreams. And that’s probably one of the biggest factor to extend that difference. And we also know that there are some personality traits that are different between, you know, what I call the high dream recallers and the low dream recallers. High dream recallers, you know, people will remember them very often. Low dream recallers, those people will never recall them. So we know that high dream recallers typically are more creative people, but also more anxious. and low dream recallers have more the profile of engineers, you know, so more like ground-based people, I would say
Phil Stieg: So there’s my excuse. Got it.
Raphael Vallat: (laugh) One of the conditions that you need to remember your dream is that you need to wake up while you’re dreaming. And that’s the only way that you can actually have a chance of remembering your dreams. And so what we’ve what we’ve shown is that high recallers as an average, they tend to have more wakefulness. And so this leads to better chance of remembering your dream. Another point that is really critical to remember your dream, is to focus on dream as soon as you wake up, because we know that the dream memory fades away very quickly. And if you don’t make a conscious effort to focus on it when you wake up, then, you know, most likely you’re going to forget it in just a few minutes or a few seconds.
Phil Stieg: Can you tell me a little bit about the relationship between age and dreaming?
Raphael Vallat: First, we know that the ability to remember dreams decrease with age. So the older you have, the less likely you are to remember,
Phil Stieg: But do you dream less with age or you just don’t remember?
Raphael Vallat: We know that sleep is impaired with age and, you know, sadly, you typically sleep less as you get older. But we don’t know for sure if it’s a deficit in dream production or if it’s more the ability to remember them that is actually altered. And so we know that teenagers are probably the ones that remember the most the most dreams. And what is actually fascinating is that during development, when you’re a child, we know that dreaming is actually correlated with some cognitive abilities. So it seems like dreaming develops in parallel with, you know, cognitive development in in the child.
Phil Stieg: Everybody I know that is really a good memory caller is a woman. And I noticed that one of the one of the characteristics of a high dream recall is female, but there’s got to be something there. What do you know about that subject?
Raphael Vallat: We know that it’s true, actually, woman seems to recall more dreams than men. So if you compare the dream recall ability of children before their adolescence, they are the same. So no differences between boys and girls. But it starts to be different when they are teenager and then it stays on during, you know, during the entire during the entire life. So I don’t know if it’s related to some hormonal process that occurs during adolescence. I t might be related to some cultural and education differences between girls and boys, with girls being more encouraged to talk about their feelings. And, you know, the opposite being true for boys. We don’t know for sure. This is these are all speculations. We don’t know exactly.
Phil Stieg: Since you say we all really dream, just some of those aren’t good recallers, is there an advantage to recalling versus not recalling?
Raphael Vallat: For me, that’s the most important question in the research, the function of dreaming and whether you need to remember them or not, you know, to have an adaptive advantage. And I think I think the answer is probably no, because otherwise that would be the biggest mistake of evolution. If you if only the dreams that you can remember have a function, then it would be a huge waste of time, because we forget most of our dreams. I do think that dreams probably have a function, biological and maybe, you know, psychological function. But my guess is that we don’t need to remember them for that function to happen
Phil Stieg: Is there a biological or an emotional reason or a physiological reason for our body as to why we dream?
Raphael Vallat: In my opinion, — I don’t think there is a single function, you know, that would explain exactly why we dream. I think it’s similar to asking the question of why are we thinking is that, you know, is there a function of thinking?
Phil Stieg: So you’re saying that dreaming is an inherent function of the brain. It’s you know, it’s like, why do we breathe?
Raphael Vallat: Yes, I do think so. Some researchers have postulated that dreaming can be involved in emotional regulation as well as memory consolidation. And also forgetting, which is, you know, a very important part of our ability to remember things. We also need to forget things, you know, in order to have a good memory. There is also a theory that dream is essentially like a video game where you can simulate the world and see what the outcome is. You can rehearse different situations and conversations with people. So I do think that if there is the function of dreaming, then, you know, most likely there is there is some sort of a social aspect to it.
Phil Stieg: I wanted to touch upon the fact that there seems to be a lot of misinformation about dreaming. Everybody thinks that that occurs during REM sleep. And I’d like you to explain what is REM sleep, but then could you go into a little more detail about the sleep cycle and the importance of that?
Raphael Vallat: Yes, I’m so glad you asked this question. Sleep is divided into two broad stages. One of them is called Rapid Eye Movement Sleep. If you look at eye movements during that specific stage of sleep, then you see some very rapid eye movements. And the other sleep stage is called Non-Rapid Eye Movement Sleep. It’s not a very original name. (laugh)
We know that deep non-REM sleep occurs predominantly at the beginning of the night. And so this is when we see these huge slow waves in the brain activity. And rapid eye movement sleep mostly occurs at the end of the night. I actually much prefer the French name of rapid eye movement sleep, which is “paradoxical sleep”. And the reason it’s called paradoxical sleep is that if you look at the brain activity in rapid eye movement, sleep is it’s actually very similar to wakefulness. So there is almost no way just by looking at the brain activity to know if someone is actually asleep or awake
Phil Stieg: Is it true, though, that the dreaming only occurs during the REM component or kind of occurs through all these other cycles?
Raphael Vallat: We know that dreaming occurs in all sleep stages, and it’s just that you’re more likely to remember them after awakening from rapid eye movement sleep . And so when rapid eye movement sleep was discovered in the 50s, the pioneer sleep researchers were sure that they actually found the physiological basis of dreaming because, But it turns out that it was an oversimplification. And the truth is more complicated than that, because people do remember their dream actually in all sleep stages. We did a study and we would wake up participants in deep non REM sleep and even in, you know, deep non-REM sleep, which is supposed to be the sleep stage in which people, you know, almost never remember dream. Some of our participants were able to remember full vivid dreams with crazy stories. So I do think that, yeah, for sure we do dream in all the sleep stages.
Phil Stieg: Tell me a little bit about not getting enough sleep. You know, the fact that you said that REM sleep occurs early in the morning or at the end of your sleep cycle, if you set your alarm clock at five, when your body says sleep till seven, are you harming yourself or you’re cheating yourself out of a good dream? And is there an impact?
Raphael Vallat: So you are definitely depriving yourself of rapid eye movement sleep if you you know, you put your alarm clock too early in the morning. And by extension, you are also depriving yourself of, I would say, the most dream rich sleep stage. It’s not as simple because dreaming is a is a is a psychological experience and REM sleep is a physiological state. And there is not like a 100 percent match between the two.
Phil Stieg: What about for stress? Do you have to have REM sleep to decrease the cortisol levels, so you don’t, you don’t wake up stressed?
Raphael Vallat: Yes, REM sleep is also is also very important for cortisol levels and stress. That actually occurs during slow wave sleep, during deep sleep at the beginning of the night. That’s also when your heart rate is very low and you have a lot of benefits for your immune system, your cardiovascular system.
Phil Stieg: So tell me a little bit about dream types.
Raphael Vallat: One of the study that we did in our lab, we asked participants to record their dreams using a voice recorder and tell us h ow they thought that this dream was related to some experiences that they leave during their waking lives. And also we asked them to rate their dreams on a on a variety of scales, including emotion, intensity and, you know, the number of characters that were in your dreams. Were those familiar persons or, you know, unknown characters, what types of emotions were included in your dreams? So in other words, we are trying to use almost a statistical approach to dream content where we try to, you know, find patterns in in, you know, the typical dream content.
Phil Stieg: Is there any significance? Have you found the one particular thing that you measured correlates with either dream type or the frequency of dreaming?
Raphael Vallat: We know that vividness and bizarre ness of dreaming is usually correlated with the dream recall frequency. So your ability to recall them. And we know also that the typical dream content is actually quite consistent and stable within an individual across time, but also across different cultures, so, for example, we know that being chased by a monster or demon or failing an exam. So these are very, very common themes that you can actually find in a lot of dreams. We also know that concerns that you have that you are experiencing in your waking life at the moment are usually also incorporated into into your dreams.
A dream is essentially a mixture between mundane and unimportant events that occurred on the day before the dream and all the memories that are significant and more emotionally, emotionally charged. We actually saw that in the dreams that we analyzed, we we were able to show that about 40 percent of the of the memories that were included in those dreams were coming from the day before. And usually, you know, they would be very, as I said, mundane and not important. So, for example, you know, you’ve seen a blue truck yesterday. And so this could be incorporated.
Phil Stieg: So let me ask, is our recurring dreams, is that a common phenomena? And if yes, they are. What’s the significance of the recurrent dream?
Raphael Vallat: We have some theory about recurring nightmares. The common theory about nightmares is that they essentially represent a failure to regulate these traumatic experience. For example, you usually see these repeating nightmares in patients with post-traumatic stress disorder. And you know, they would usually relieve some very traumatic experiences that they experience, for example, at war. I t’s as if they brain during sleep is unable to down regulate the emotional aspect of that memory. I remember that one of one of our participants had recently lost one of their parents. Over the course of the study she dreamt about her deceased parents several times. And, you know, every time it was in in a different situation, in a different context. But, you know, the major theme of the dream was almost the same. And it was, you know, always related to, that loss.
Phil Stieg: So what impresses me is the way you do functional MRI scans on people that are dreaming. And I’m amazed that people can actually fall asleep in an MRI scanner giving all the noise. But can you just tell us what specific parts of the brain light up during dream episodes?
Raphael Vallat: What we know from a variety of studies is that when you’re in rapid eye movement sleep, you typically see activation in. In some regions that we think are very important for dreaming. So, for example, that includes the medial prefrontal cortex, the temporal parietal junctions on, you know,
Phil Stieg: So is that where the memory, is that were the memory of a dream comes from? The temporal lobes?
Raphael Vallat: So the yeah, part of. And there is also an activation of the hippocampus in, you know, in REM movements. And so we think that these yeah, the activation of the temporal lobes and the hippocampus is probably the source of the memory that you have in your dreams.
We talked about activation of brain regions, but we didn’t talk about deactivations and we know, for example, that the dorsolateral prefrontal cortex is deactivated during REM sleep. And this is an area that is very important for logical reasoning and self-awareness. And that could explain why typically when you’re dreaming, you’re completely, fully immersed in the dream experience. And also sometimes it’s very bizarre, and you can, for example, walk through walls. And, you know, it doesn’t it doesn’t seem weird or bizarre at the time. But then when you think about it, when you’re awake, you’re like, “oh, yeah, that’s actually very surprising. I’m not supposed to do that.”
Phil Stieg: Tell me what I can do in my daily life that might alter my ability to dream or recall them. What I eat important. Can I drink too much exercise? Things like that.
Raphael Vallat: Yeah, so avoid alcohol during the evening is probably, you know, my first advice
Phil Stieg: Altogether or just excessive?
Raphael Vallat: Altogether I should say, because alcohol is extremely detrimental to rapid movements. (and by the way, cannabis is the same) Put simply, it basically removes completely suppress your rapid eye movements. You should actually try to avoid alcohol in the evening or late in the night. That’s not an advice I should be giving. But if you want to still, you know, drink, maybe it’s actually better to drink in the morning so that it doesn’t affect it doesn’t affect your sleep at night, but. Yeah, for sure. So we know also that exercising is probably the best single way that you can improve your sleep together with sticking to a consistent sleep schedule. So waking up and going to bed every single day at the same time, even on the weekend, that’s, you know, doing that, exercising and avoiding alcohol is probably the three main things that you can do to improve your sleep today.
Phil Stieg: So is dreaming inherent, essential or beneficial or all the above?
Raphael Vallat: I think there must be there must be some sort of benefit from dreaming that is, you know, additional to the simple benefit of sleep or otherwise You know it would be kind of a waste in terms of evolutionary advantage. Why would it still be here, you know, after millions of years of evolution if it didn’t provide an actual benefit in addition to the simple fact of sleeping? One of the reasons I think that dreaming is so fascinating is that there is so much that we don’t know about it yet. And, you know, I always think of it as one of the last mystery of the human cognition that we need we need to understand. And I hope that with the development of new technologies and new algorithms and new methods to study dreams, we will we will be able to understand more about why we dream, what we dream when we dream.
Phil Stieg: Raphael Vallat, thank you so much, you’ve actually helped reduce my anxiety level. I thought that I was probably suffering from the fact that I don’t recall my dreams very well. And the other thing that I probably will take home from this is the fact that we really need to be more disciplined in regulating our sleep cycles so that, you know, if I did that, maybe I would recall more of my dreams. Thank you so much for being with us.
Raphael Vallat: Thank you for having me.