Hello, my name is Barbara and this is neuroscience amateur hour. Hello again. I know it's been a hot second since I lost produced an episode and a huge part of that is due to the fact that I'm now a graduate student of neuroscience. And far busier than I could have expected. But I've also honestly lost some momentum with the podcast and I'm out of practice when it comes to writing episodes. I'm trying my best to write new ones and when I have the time and I am active on my Instagram and email so please feel free to reach out if you have any specific questions. I promise you I will try and get to your message. So today I want to talk about dreaming something that is both scientifically fascinating and universal. Everyone dreams at every age and if you are at all like me, you assign meaning to your dreams. The loss of teeth indicates a loss of power, you failing a math exam in dream world means that you're stressed about work, a house is my mind for some reason and so on and so on. But what is the scientific basis of dreams? Can we quantify such a subjective experience in the activity of cells, circuits and systems? Also with regards to the structure of this episode, I'm going to start by looking at dreaming and sleep state and then I'm going to talk about brain waves and then a specific type of brain wave linked to eye movements during dreaming. Then the function of eye movements during sleep and finally the purpose of dreams and lucid dreaming. So let's dive in. So a common misconception about sleep is that dreams occur only during the REM or Rapid Eye movement stage of sleep. This assumption seems to have originated in a study from Azerinsky in Clipeman in 1955 where they woke up patients during REM sleep and found that 74% of them reported that they had been dreaming. In contrast, waking up subjects during other sleep stages meant that only 17% reported dreams. The paper that I'm referencing was published in 1955 by Clipeman and his student Eugene Azerinsky and it's linked in the citations. Thank you, you pen. And it's particularly important because it appears to be the first time that REM sleep is characterized at all. Prior to the publication of this paper, scientists assumed that falling sleep meant falling into a different brain state and that was all that there was to it. Now we modern neuroscience enthusiasts know that REM sleep is incredibly important but at the time Azerinsky was treading into uncharted territory or quote "going to Mars with a third of the Earth's surface still unexplored." It turns out that the assumption that we only dream during REM sleep is not true. Dreaming occurs during both REM sleep and non REM sleep and is associated with local decreases in slow wave activity in the brain. Also, don't get me wrong, we do the majority of our dreaming during REM, it's just not as clear cut as I expected, although very few things with the brain are clear cut. But let's channel a little bit more about those brain waves I mentioned. Once more, dreaming is associated with local decreases in slow wave activity in the brain. One group of researchers from Switzerland observed volunteer brain activity VA EEG while simultaneously awakening said volunteers during sleep stages and asking them to report on their dreams. They found that reports of dreaming were preceded by fewer, smaller and shallower waves and faster sleep spindles. So brain waves are rhythmic or repetitive patterns of neural activity across different brain regions. And for those of us that don't know, like me, a sleep spindle is a burst of coherent brain activity in the vicinity of 11 to 16 hertz. That means that during dreaming, your brain transitions from slow sleep waves such as delta waves which are in the vicinity of 1 to 4 hertz, or theta waves which are in the vicinity of 4 to 8 hertz to faster brain waves that resemble those that occur during wakefulness. And I guess that's one of the things that makes REM sleep and dreaming so fascinating. Your brain is technically sleeping, but the neural activity is similar as if you were actively interacting with and experiencing the world around you. Now one fascinating and signature thing about REM sleep is that it is characterized by the appearance of ponto-geniculo-oxypital or PGO monophasic waves. These are distinctive wave forms which result from propagating activity between the ponds, the lateral-geniculate nucleus, and the occipital lobe. And have been thought to be causal to dreams due to their stimulation of the cortex. Now as of 2017, PGO waves have been observed in cats, but not seen in humans. Although that makes sense since making progress in this area of research necessitates doing invasive recordings in human beings, which is a little unethical. Especially if you think about doing invasive recordings in three different locations across the brain, that's unethical on steroids. A little background on the three brain regions I mentioned, the ponds, the lateral-geniculate nucleus, and the occipital lobe. These are in fact scattered across the brain. The ponds is in the brainstem and is vital for sending information from your brain to your body to help you sense and interact with the world around you, and the other way as well. The lateral-geniculate nucleus sits somewhat near the ponds, specifically in the thalamus. This structure receives information from the eyes and sends it to the visual cortex. Last but not least, the occipital lobe sits at the very back of the head, and is primarily responsible for visual perception. This is the part of the brain that contains visual cortex. This is also effectively the pathway that visual information takes when it comes into your brain. Now, what could be the function of these PGO waves? How could they be causal to dreams as I mentioned before? These waves are thought to convey information about eye movements, from their mitoric sources in the brainstem to the site of visual processing. It could be that each PGO waves acts as a set amount of time during which visual information is experienced, and this serves as an instruction for the eyes to orient towards perceived stimuli. Or it could be that PGO waves are a corollary discharge from the retinal saccade, aka the movement of the eyes, and the wave is simply telling the rest of the brain that the eyes have in fact moved, and visual information is to be expected. So it looks like during dreaming, the brain is sending information about eye movements to visual processing areas. Some researchers have even called these PGO waves the "song sheets of the dreams". What could be the function of this? Is the brain generating visual information for dreams by telling your brain that your eyes are moving, even though they're not technically seeing anything? It's possible that your brain receives information about eye movements, and then generates hallucinations, or in this case, dreams, to create an explanation for this. Additionally, PGO waves are thought to be influenced by other brain regions like the amygdala, which is a limbic structure associated with emotions and memory, and may play a part in setting the emotional tone of a dream. And what are the eyes doing during sleep anyway? Now this question gets into one of my all-time favorite papers. So in 2022, Utah, Sanzai from Massimo Scanziani's lab at the University of California, San Francisco, published a paper in science titled "A Cognitive Process Occurring Durant Sleep" is revealed by rapid eye movements, where they examined with the rapid eye movements that will characterize the rapid eye movement or REM sleep stage are actually encoding. They asked, are these eye movements random, or do they reflect some sort of directed eye movements during dreaming? So what they did was they recorded eye movements in sleeping mice, while also simultaneously recording from head direction cells in the valeness. Now head direction cells are fairly cool in that they encode, or they change their activity, in response to the animal's actual head direction. So there's a specific firing pattern in these neurons for head pointed forward, and a completely different one for head pointed to the left. And what they found was that the direction and amplitude of the rapid eye movements during REM sleep reveals the direction and amplitude of ongoing changes in virtual head direction. So let's break that down. So when the animal's eyes are moving during REM sleep, and likely during dreaming, it's as if the animal is looking around a scene in its own mind, which is very, very, very cool. And if we connect all of these findings together, it seems like there's some emerging scientific evidence that the brain is generating some kind of visual scene when you dream, one which you virtually explore and interact with. And I would personally be very interested to find a paper that looks at whether your brain is generating a visual scene completely from scratch, or whether it's building it up off of your experiences during that day or your memories. And this might start to explain why and how dreams are so subjective, and how you might dream about things that maybe you would experience the day before. But I think that we're starting to drift away from the concretely neurobiological and into the psychological. So let's embrace it and start to think about what could be the purpose of dreams. The first hypothesis I want to talk about is the one that was actually proposed by Francis Crick and Graham Mitchison. If you're sitting there thinking why is that name familiar, it's because Francis Crick was one of the three individuals who, along with James Watson and Rosalind Franklin, discovered the double helix structure of DNA. But yes, Crick of DNA.
and Michelson proposed that dreams may act as an unlearning mechanism where uncertain modes of neural activity are erased by random activation of cortical connections. In a sense when you dream your brain isn't getting any new information from the world around it. Instead, it's parsing through the information that you've accumulated throughout the day and then deleting anything that it deems useless or parasitic. In the words of "crick" we dream to forget. Now this theory makes quite a bit of sense if you think about the fact that information is encoded by the activity of sets of neural networks. If there are unwanted patterns of activity from useless information, you might get dysfunction that comes in the form of schizophrenia or paranoia or anxiety. If you're curious to know more, I've actually cited the original 1983 paper in the show notes. While this theory is quite compelling, it leaves me wanting a little bit more. One question that I have is first of all, a lot of dreams follow story-like templates and that would make sense if we were simply trying to delete parasitic information. Although I guess I can acknowledge that maybe reactivating a neural network might result in a narrative, but I'm not positive that makes sense. I have some trouble believing this one. And I also had trouble finding any evidence outside of computer modeling that was in support of this theory. So another one, another theory titled the Activation Synthesis Theory, was proposed by Professor Alan Hobson and Robert McCarley of Harvard University in 1977. This theory posits that simply neural activity is taking place during REM sleep, and that dreaming is the brain's way of simply trying to make sense of what is potentially random activity. Now I like this theory because we know that at its core, the brain is a lean, mean, pattern matching machine. Even beings are fundamentally wired to find patterns in everything, even if there are none. So it makes sense that if there was random, spontaneous activity in the brain, we would attempt to create a story to make sense of it. But the reason I don't like this theory is because I don't think that there is ever really any random activity in the brain. And even Hobson himself agreed that their theory does not mean that dreams are meaningless. Instead they may serve the purpose of recombining cognitive elements to generate new ideas. But this theory does try away from the idea that dreams can serve some sort of function and memory or plasticity or development. If your curious Hobson went on to further elaborate his ideas on dreaming and what became known as the A model. Aemstance for activation, input source, and modulation, and provided a means of connecting how neurobiological mechanisms may affect cognition. If your curious, I've once again cited the paper in the show notes, but I won't dive too deep beyond this. Another potential function of dreams is brain development and plasticity. We know that we are very, very young. We have a ton of dreams. In fact, half or maybe even more than half of the time that we spend sleeping as children or infants is occupied by REM sleep. So it's possible and likely that dreaming plays a role in the plasticity of the brain, development during childhood, and the consolidation of memory. More slightly less neurobiologically focused functions of dreams include but are not limited to. They could be used to regulate emotions. Dreams offer you the chance to experience emotions that you would not normally experience, such as aggression or extreme fear. Dreams could also help you to predict a future brain state. I've always wondered about this one because I've periodically had dreams that have come true in some way, shape, or form in the future. And I felt a little bit like a mind reader, but it's possible that dreams are meant to cycle through possible futures so that you are prepared if you ever face the situation in the real world. There's even the concept of lucid dreaming, which is when you know that you are dreaming, when you are dreaming. While this has been reported by a great number of individuals, finding a neurobiological corollary is difficult to say the least. Learning dreams on their own is complex, but to study how one interacts with one's virtual environment seems nigh on impossible. But one way that researchers have approached the study of lucid dreaming is to ask study participants to somehow show that they are conscious, in a way that the researcher can measure. The best way to do that is to ask them to move their eyes in a specific pattern, which has effectively become the gold standard. Once the participants realized that they were dreaming, they began moving their eyes all the way to the left, and then all the way to the right, and then all the way to the left again, and so on, and so on. And this left right, left right signal is actually clearly discernible from background activity if you look at the trace. And this unambiguous metric allows researchers to quantify when someone is lucid dreaming, and then opens the doors for other measures of brain activity during sleep. Electrical recordings of brain waves and MRIs have shown that the regions of the anterior prefrontal, parietal, and temporal cortex could be involved in lucid dreaming. But I found that these studies are mostly underpowered and would benefit greatly from more participants and generally more data, and potentially more rigorous testing. Similar technical issues have found its studies that have attempted to link lucid dreaming sleep stages to specific brain waves in the alpha, beta, or gamma-vance. With regards to lucid dreaming, there exists the question, is it possible to trigger it? And the answer, once again, is complicated, but appears to be yes. It seems that acetylcholonest arrays, inhibitors, might be able to trigger lucid dreaming, such as the medication "donna-paisal" that "donna-paisal," which is used for the treatment of dementia and Alzheimer's disease. The only problem with these kinds of studies has been that they have not been conducted in a sleep laboratory, so it's difficult to validate lucid dreams without actually doing any kinds of recordings. If you're curious about this and want to read more, I linked a review by BeeBaird in the show notes, and it's both quite recent from 2019 and fairly in depth on the state of the field. But beyond pharmacological means, individuals have been trying to induce lucid dreaming in other ways, such as the mild technique or MILD, which stands for "Nomonic Induction of Lucid Dreams." This involves waking up after five hours of sleep and then developing the intention to remember that you are dreaming before returning to sleep by repeating the phrase, "the next time I am dreaming, I will remember that I am dreaming." It's kind of cool, right? Another similar method is called SSLID, or "Senses-Initiated Lucid Dream Technique." Similarly to MILD, this one involves waking up after five hours of sleep and then attempting to repeatedly shift one's attention between visual, auditory, and physical sensations before going back to sleep. Both MILD and SSLID appear to be similarly effective at triggering lucid dreaming. I also wanted to go ahead and highlight one of the pioneers of the field of lucid dreaming research, Stephen LeBerge, who is credited for developing MILD and conducting many of the other experiments in lucid dreaming I've discussed here. Having received his PhD in psychophysiology from Stanford in 1990, LeBerge has pushed our understanding of lucid dreaming for the past 30 years and has even helped to popularize it in the American media. Now as I was doing research into lucid dreaming, I was absolutely bombarded by blogs and videos and articles discussing the merits of it and how to trigger it. People credited their decreased anxiety, improved cognition, improved problem solving, and increased creativity to name a few qualities that are come as a side effect of doing lucid dreaming. But I also found this one article which I think raised an excellent point. What's the harm of doing so? Well, it could affect two things and maybe more. Our sleep quality and our psychological reality fantasy boundaries. It's very, very, very well established. The good quality sleep is crucial to our memory, emotional well-being, cognition, and more. Lucid dreaming could be looked at as an aroused state during sleep where there is increased activity in the prefrontal cortex and other brain regions, something that is generally suppressed during sleep. Those could frequent engagement in lucid dreaming deteriorates sleep quality over time. And especially if you think about those lucid dreaming induction methods I mentioned that deliberately involve waking yourself up after five hours. Furthermore, lucid dreaming could be kind of looked at as the blurring of boundaries between sleep and wake and between reality and dreaming. This kind of blurring of boundaries could theoretically be related to mental health disorders like schizophrenia or psychosis. So very long story short, we don't know enough about lucid dreaming at all. We need more research in this subfield. If lucid dreaming really does have mental health benefits, then we need long-term longitudinal studies with large populations and good sampling to understand how it affects a diverse set of individuals. And if it does potentially affect sleep quality or other aspects of our lives, well, we should probably learn more about that too before we get really, really excited and start marketing it for everybody. And if there are any aspiring neuroscientists out there with a passing interest in sleep and lucid dreaming, go pursue science. I want to know more about this personally. I'm looking at you, Bailey. Now, you might get to the end of the episode and sit there and think, "Dang, Barbara, didn't you miss the contributions of one very big scientist with some very strong opinions about dreams?" Someone who might go by the name of Sigmund Freud and publish the interpretation of dreams in 1899. I don't actually like the man very much, but I will throw in a little bit of a stuff here at the end. So Sigmund thought that dreams worry pathway and
to the unconscious mind. He believed that if we analyzed our dreams, we would get better insight into our motivations, our desires and wishes, even the ones that we're not acutely aware of. To him, dreams were like puzzles, full of seemingly nonsensical characters and dialogue and plotlines, but all of these could be dissected out and analyzed, and the symbolism of these dreams would give some clue as to the state of the personal psyche. It's important to recognize that many of Freud's ideas have not fared well with the passing of time, but if you want to dive more into this kind of historical approach to dream interpretation and psychology, I actually recommend reading into Ira Progoth. But that is a short look at the neuroscience of dreams. I hope that you enjoyed this episode and you learned something new. Dreams are deeply personal, complex and often nonsensical. It seems like something that would be insanely difficult to define scientifically, but it seems like the science is being done, and I'm really excited about any upcoming discoveries. I've obviously only been able to cover a really small part of the field of dream research, so maybe there is another episode on this topic in the future. As per usual, I've cited all my relevant sources and papers in the show notes, and you should keep an eye out on Instagram for any cool figures. Please rate, review, and subscribe, and if you have any questions, comments, concerns, queries, or complaints, please email me at
[email protected] or DM me a neuroscience amateur hour on Instagram. This podcast is available on every platform I could reasonably find except Pandora for some reason, so please recommend it to your friends and loved ones. And if you're feeling so inclined to financially support my work, please buy me a cup of coffee at buymeacoffee.com/nuracines. Also, if you have something you really want to learn about, contact me, and you might see an episode about it soon. Happy researching, and I'll see you again. you ain't.
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