"What are dreams? Where do they come from? What do they mean? And what are they for?". It's wonderful how the authors acknowledge that, despite thousands of years of wondering, clear answers have remained elusive – until perhaps now, in the twenty-first century. Now, some folks might come to a book like this thinking that a "science of dreaming" is a contradiction in terms, maybe believing that science can only study things you can see and measure in the physical world. After all, dreams feel so personal, so subjective, invisible to everyone but the dreamer, and often tricky even for the dreamer to recall clearly. Or perhaps others might feel that science could somehow diminish the wonder and mystery of dreams, maybe even believing that dreams are simply random electrical firings in the brain with no real meaning. But the authors? They strongly disagree with these ideas!. They believe science _can_ shed light on dreams, and that dreams are far from meaningless. So, how do they plan to guide us through this exploration? Well, they take us on quite a journey! They start by looking at how we, as children, gradually figure out what dreams even _are_. It’s not as simple as you might think!. Then, they whisk us back through the history of dream research, visiting early pioneers from the nineteenth century whose ideas strangely echo some modern scientific approaches. They touch upon the giants like Sigmund Freud and Carl Jung, presenting their work in potentially new ways. We learn about that groundbreaking discovery of REM sleep – that phase where our most vivid dreaming often happens. And they delve into what we currently understand about _why_ we sleep, setting the stage to debate the possible functions of dreaming itself. The book explores who dreams (pretty much everyone, including babies and possibly animals like dogs and rats, though we can't definitively _know_ for sure because of the subjective nature of dreaming!), when we dream (not just in REM, but in all sleep stages!), and what tends to show up in our dreams. They get into fascinating topics like the content of typical dreams, why some dreams keep coming back (recurrent dreams), sexual dreams, and of course, nightmares. Perhaps most excitingly, the authors promise to offer their very own, innovative model for _why_ we dream, pulling together insights from neuroscience, sleep research, and dream studies. This model is called **NEXTUP**, which stands for **“Network Exploration to Understand Possibilities”**. They believe NEXTUP will help us understand why the human brain has this seemingly essential need to dream and will provide fresh answers to those initial big questions about what dreams are, where they come from, what they mean, and what they're for. Along this journey, they challenge some common beliefs you might hold about dreams. For instance, they provide evidence that we don't _only_ dream during REM sleep. They suggest that not everyone dreams in black and white. And, perhaps surprisingly to some, they argue that our dreams are _rarely_ just driven by repressed desires. Here's a particularly intriguing claim: they suggest dreams _can_, in a sense, predict the future in a way we can't manage while awake. They also explore the fascinating idea that dreaming has a "cognitive basis," meaning there are reasons why our dreams can feel so incredibly real and even meaningful. The book even touches on what blind people dream about, how the brain conjures up images and concepts in dreams, and offers new insights into nightmares and other dream-related issues. Ultimately, they hope that even with these scientific advances, the world of dreams will retain enough mystery to keep us wondering. Let's start right at the beginning – defining what a dream even _is_. A dictionary might give you a simple definition like "a series of thoughts, images, or emotions occurring during sleep". This is a reasonable starting point, but as the authors cleverly point out, it just raises more questions! Like, where _do_ these thoughts, images, and emotions come from? How are they connected to what goes on in our minds when we're awake? And, of course, that big one: _Why_ do we do this at all?. Humans have wrestled with these questions forever. Dreams pop up in incredibly ancient texts, from the 4,000-year-old Epic of Gilgamesh to religious writings like the Old Testament and the Talmud, and philosophical works by Hippocrates and Aristotle. These ancient texts had a lot to say about dreams, often offering definitive, though frequently conflicting, answers. For instance, one of the earliest and simplest ideas was that whatever you experienced in a dream was _really_ happening. The authors share a lovely anecdote about a two-year-old girl who was terrified because she dreamt a puppet was in her crib and was convinced it was actually there. This brings up a crucial point: understanding dreams requires learning to distinguish between real and imagined events. As adults, we sometimes have fuzzy memories and wonder if something really happened or if we just dreamt it. The authors share a poignant example of a narcolepsy patient who had a dream of flying that felt so real, she actually threw herself down stairs, trying to fly. This highlights how incredibly real dreams can feel. Learning what dreams are is a process, especially for children. Children start by thinking dreams are real, then they grasp their unreality, then that they're private, and finally, that they happen inside their own minds. But even this process isn't always smooth; some kids might think their dreams are real _and_ visible to others in the room, or that the dream world is physically real _while_ they're in it. And yes, the authors note, some adults hold similar beliefs!. Our own experiences and what society tells us about dreams also shape our understanding. The scientific study of dreams really began to flourish in the mid-1800s. Philosophers started moving away from supernatural explanations and considered that dreams might originate from the dreamer's own mind. Competitions, like one proposed by the French Academie des Sciences Morales et Politiques in 1855, spurred research into questions like what mental faculties are active or change during sleep, and the fundamental difference between dreaming and thinking. These are still core questions today. Early dream explorers like Alfred Maury contributed ideas, such as the notion that dreams could occur instantaneously, or that dream actions were mechanistic but influenced by our past experiences and knowledge. Jean Marie Léon d’Hervey de Saint-Denys, another fascinating figure, meticulously recorded his own dreams and even experimented with lucid dreaming to study dreams from within. He proposed that dream images were visual representations of ideas, and the bizarreness of dreams came from how these images were elicited and combined, much like a train of thought can quickly change direction. A monumental moment in modern dream research was the discovery of REM sleep. In 1957, researchers found a strong link between REM sleep and vivid dreaming. When people were woken from non-REM sleep, they reported dreams only about 7% of the time, but from REM sleep, it was a stunning 80%. This discovery gave dreaming a biological basis, moving it beyond just a mystical mental phenomenon. REM sleep is characterized by rapid eye movements, a loss of muscle tone (atonia), and brain waves that look like wakefulness. This atonia is actually crucial to stop us from acting out our dreams. Sometimes this paralysis can happen while a person with narcolepsy is awake, causing them to collapse in a sudden loss of muscle control called cataplexy, often triggered by strong emotions like laughter. While REM sleep is dramatically different, we now know we dream in _all_ stages of sleep: N1 (sleep onset), N2, N3 (deep sleep), and REM. The authors use a broad definition of dreaming, including any mental experience during sleep – thoughts, feelings, or images, ranging from simple sensations to complex narratives. Even if we don't remember dreaming, it doesn't mean we weren't. However, dreams do differ depending on the sleep stage; REM dreams tend to be longer, more vivid, emotional, and bizarre than non-REM dreams. Hypnagogic dreams at sleep onset are often shorter, less bizarre, and more directly related to recent thoughts, sometimes lacking a clear narrative or self-representation. Studying dream content isn't easy because dreams are private. Researchers rely on dream reports collected after waking people from different sleep stages. This involves asking participants to describe everything they remember – sights, sounds, feelings, thoughts, and actions – without trying to interpret the meaning. Researchers have developed many ways to analyze these reports, using scoring systems to identify various features. For example, they might look for uncertainties in the report (like whether something was an ocean or a swimming pool), which could reflect forgetting or actual uncertainty within the dream itself. They've found that dreams are rarely exact replays of daytime events. One of the biggest questions remains: Why do we dream?. The authors playfully admit that the short answer to how the brain creates a dream, what function dreaming serves, and why we have to experience it for that function is currently "Not sure" for all three. But they have some compelling ideas!. How does the brain create a dream? It involves generating patterns of brain activity that represent the dream's content. Seeing something in a dream seems to involve similar brain activity patterns as seeing or imagining it while awake. The brain reactivates patterns from waking life to create images, thoughts, and emotions in dreams. It can even combine elements in novel ways, like imagining a green-skinned baseball player swinging a broom. Early theories, like the Activation-Synthesis Hypothesis, suggested that dreaming was the forebrain trying to make sense of largely random firing from the brainstem during REM sleep. While this highlighted brain activity during REM, it tended to view dreams as somewhat random and meaningless. However, newer research using brain imaging provides more clues. During REM sleep, areas involved in emotion (limbic system) become more active, while areas involved in logic and planning (prefrontal cortex) are less active. This helps explain why dreams are often emotional and can feel illogical. The preference for activating weak associations also contributes to dream bizarreness. Crucially, the authors argue that whatever the function of dreaming is, it must be happening _while_ we're dreaming, not just when we remember the dream later. Since we remember so few of our dreams, a function relying solely on recall wouldn't make evolutionary sense. This leads to their proposed model, **NEXTUP**. NEXTUP suggests that dreaming is a special way the brain processes memories during sleep, helping it find and strengthen connections between ideas that it wouldn't usually consider while we're awake. The brain starts with something recent or important, maybe a concern or a salient experience, and then looks for other memories – recent or old – that are only weakly associated with it. It then weaves these memories into a dream story that explores these unexpected links. The point isn't necessarily to find a concrete solution, but to discover novel, creative, or potentially useful associations. The brain evaluates these associations while we dream, and if they seem promising, it strengthens them for later use. This focus on weak associations is why dreams often feel bizarre. The strange combinations come from the brain deliberately exploring less obvious connections. Freud's idea of disguise and Hobson's idea of random synthesis are seen as different explanations for this bizarreness, but NEXTUP views it as a predictable outcome of this exploration process. The "understanding possibilities" part of NEXTUP relates to something called divergent thinking – the ability to come up with multiple potential solutions or ideas, rather than just finding a single right answer (convergent thinking). By creating narratives and exploring possibilities in the simulated world of the dream, the brain can gain new understanding. Even though we might not remember the dream, the work of finding and strengthening these novel associations has already happened. It's interesting that dreams often feel meaningful, even if we don't remember much. NEXTUP suggests this might be because the brain is deliberately biased to see potential value in the weak associations it's exploring in the dream. It gives itself a push to see these unusual connections as potentially useful. NEXTUP also proposes that dreaming serves different functions depending on the sleep stage. The authors connect dreaming to the Default Mode Network (DMN), a network in the brain active when our minds are wandering or recalling memories when we're not focused on a specific task. The DMN is also active during REM sleep. Some researchers even suggest REM dreaming is like "enhanced mind wandering". The DMN might help identify "ongoing, incomplete mental processes" or concerns that need more attention. At sleep onset (N1/hypnagogic), dreams tend to be shorter and more directly related to the thoughts we were having before falling asleep, often extending the DMN's work of identifying and tagging concerns for later processing. These early dreams might start the process of identifying associated memories, but the briefness suggests the deeper exploration happens later. NEXTUP saves its "best work" for REM sleep. REM dreams are longer, more vivid, emotional, and bizarre. They also tend to draw less on specific memories of events (episodic memories) and more on general knowledge and themes (semantic memories). This fits with NEXTUP's idea that REM dreaming generalizes from memory sources to create a more integrated understanding, exploring weaker associations that wouldn't normally be considered. The shift from non-REM to REM sleep across the night might reflect the brain moving from tagging concerns to actively exploring possibilities related to them. The authors bravely extend the NEXTUP idea to animals and babies. If dogs, rats, or babies dream, what function would it serve for them, given their simpler cognitive abilities?. They suggest that even with diminished abilities, animals and babies might still benefit from exploring possibilities within their limited cognitive world. They cite a fascinating rat study where the rat's "place cells" (neurons related to location) fired in patterns corresponding to maze paths the rat had _never_ taken in waking life, suggesting an exploration of possibilities. This is seen as the animal equivalent of NEXTUP at work. When it comes to the content of our dreams, people usually focus on the storyline, characters, and settings. While themes like missing a train or losing teeth are common across many people, the details are unique to each dreamer, pulling from recent "day residue" (bits of events, objects, or thoughts from the day before) and older, weakly related memories. This is precisely what NEXTUP predicts: combining recent and old memories via weak associations. But how do mundane daily experiences turn into dreams about being chased or having superpowers?. NEXTUP suggests that salient experiences or concerns, tagged by the DMN, act as a source, even if the specific memory isn't directly replayed. The brain then pulls associated elements to construct the dream narrative around this underlying concern. Dream narratives are seen as similar to how we use stories, art, or metaphors in waking life to explore and understand emotional experiences. Dreams also have a strong connection to creativity. Many famous creative insights, from inventions to songs, have reportedly come from dreams. While some of these might originate in the unique hypnagogic state right before sleep, the authors argue that NEXTUP's creative exploration of associations is happening more broadly, especially in REM sleep. Even if everyday dreams don't lead to Nobel Prize-winning ideas, they fit a broader definition of creativity as generating new possibilities. Given this potential, people are naturally interested in working with their dreams. The authors caution against the idea that every dream has a single "true" meaning that needs deciphering by an expert, partly because we remember so little of our dreams for this to be their primary function. Instead, the function happens _during_ the dream. However, they believe we _can_ use the dreams we _do_ remember for personal insight. Keeping a dream journal and using simple techniques like focusing on a problem before sleep (dream incubation) can help. Dream incubation might work by helping the brain tag the chosen problem as a concern for NEXTUP to potentially explore. When working with dreams, people often try to link dream content back to waking life. While difficult to do with certainty, the authors suggest that reflecting on the dream's content in relation to concerns can yield personal insights. This fits with NEXTUP's idea that dreams explore associations related to salient concerns and observe our reactions to these scenarios. The book also touches on fascinating dream-related disorders, viewing them as breakdowns in the complex, coordinated systems of the sleeping brain. These include things like narcolepsy (disrupted wake-sleep cycles and muscle control bleeding into wakefulness), REM sleep behavior disorder (acting out dreams due to lack of paralysis during REM), sleepwalking (complex behaviors during non-REM sleep, often involving a mix of real environment awareness and hallucinations), and epic dreaming (long, tedious dreams of repetitive activity leading to daytime fatigue). Studying these disorders offers valuable insights into normal dreaming and sleep function. Lucid dreaming – the state of knowing you are dreaming while it's happening – is also explored. Lucidity isn't all-or-nothing but exists on a continuum, from brief realization to full awareness and control. Lucid dreaming mostly occurs in REM sleep, and studies show increased activity and connectivity in frontal brain regions associated with self-awareness, similar to waking. These brain changes might actually _cause_ lucidity. Lucid dreamers can explore their dream world and even interact with dream characters, sometimes asking them questions. This highlights the remarkable way the brain creates a conscious, interactive world within the dream. Finally, the book addresses telepathic and precognitive dreams – dreams that seem to show distant events or foretell the future. While these feel powerful, the authors attribute them to either having prior information (conscious or unconscious) that allows the brain to predict possibilities, or simply to coincidence. The vagueness of dreams and our natural tendency to find meaning increase the likelihood of spotting connections after the fact. In wrapping up, the authors celebrate that dreaming is now a widely accepted area of scientific study. They hope their NEXTUP model, which integrates neuroscientific findings with the subjective experience of dreaming, provides a strong explanation for why we dream: to explain the past and predict the future, exploring possibilities to figure out "what's next up" in our lives. They beautifully suggest that this function, like great art, shows us what we cannot yet fully explain, enriching our lives and guiding us. The dreaming brain, creating these intricate virtual worlds and exploring endless possibilities, highlights that our minds are ceaselessly active, never truly sleeping. What a journey through the sleeping mind! It certainly makes you wonder about your own nightly adventures, doesn't it? Here are a few ideas and questions this exploration brings to mind: - If NEXTUP proposes that dreaming helps us explore possibilities related to concerns, could intentionally focusing on specific problems before sleep (dream incubation) actually enhance this process, beyond just tagging the concern?. - The book mentions the profound mystery of how the brain creates the _feeling_ of emotions and sensations in dreams without the corresponding bodily changes. How might future research delve deeper into the subjective experience of consciousness in dreams compared to waking life?. - Considering that the DMN, active during mind wandering and REM sleep, is thought to relate to thinking about the past and imagining the future, how might different types of daytime thinking (e.g., ruminating on the past vs. planning for the future) influence the _nature_ of the "possibilities" explored by NEXTUP in dreams? - The potential for future technology to record or even "read" dreams raises significant ethical and privacy questions. As this technology develops, how might societies grapple with the implications of accessing such a deeply personal and internal experience?