This book proposes a new and innovative model for explaining why we dream, drawing on remarkable neuroscientific ideas and cutting-edge findings from research on sleep and dreams.
We will call this NEXTUP (Network Exploration to Understand Possibilities).
Simply put, it is a new theory that studies the meaning and possibilities of dreams.
We delve into how NextUp works, uncovering why the human brain needs dreams and offering new answers to four fundamental questions: what are dreams, where do they come from, what do dreams mean, and why do we dream?
--- p.10, from the "Preface"

There are many possible explanations for what happens in the brain when we dream.
In this book, we will explore all these possible explanations and see where they lead us.
There is no right answer, and explanations are not exclusive.
Sometimes, if you look at it a little more flexibly, it can all be reasonable.
But the most interesting explanation, both intellectually and scientifically, is the approach mentioned last, that dreams are memory processing.
--- p.27, from “Chapter 1: What is a Dream”

Freud's ideas and theories were certainly revolutionary, and The Interpretation of Dreams had a profound influence on dream research.
However, Freud's disdain and selective portrayal of dream theory and research that preceded his masterpiece obscured the valuable contributions of dozens of researchers before him, and scientific dream research virtually lost its momentum for the next fifty years.
Dream research before Freud was gradually relegated to the trash can and eventually forgotten by people.
So, we begin our journey into the science of dreams with the pioneers of dream research, some of whom have been forgotten.
It is the first step to reviving the achievements of those who deserve recognition.
--- p.36, from “Chapter 2: Early Explorers of the Dream World”

Do all of these dream theories align with Freud's assertions that "dreams are wish fulfillments" or "guardians of sleep"? Numerous dream studies have reached the simple conclusion that there is little empirical evidence to support Freud's claims of dream function.
Moreover, most scientists studying sleep and dreams have long since abandoned Freud's conceptualization of dreaming in favor of a streamlined, experimental model rooted in modern clinical and neuroscience.
But that doesn't mean that modern dream researchers have abandoned the notion that dreams have personal meaning, that they reflect the dreamer's waking anxieties, that they reference old memories, or that dreamwork is clinically useful.
All of these concepts have been and will continue to be innovative research topics.
It has little to do with Freud's dream theory itself.
--- p.58, from “Chapter 3: Did Freud Reveal the Secret of Dreams?”

When we compared dream reports obtained by waking participants during REM sleep with reports obtained by waking them during non-REM sleep, a surprising result emerged.
When participants were awakened from non-REM sleep, only 7 percent reported a "coherent and detailed description of the dream."
However, when awakened during REM sleep, 80 percent of the participants—more than 10 times more—reported consistent dreaming.
Dreams were no longer mystical mental phenomena emerging from somewhere hidden deep within the mind.
In an instant, the dream became a 'biological function'.
--- p.68, from “Chapter 4: The Birth of a New Dream Science”

Sleep helps solidify recently formed memories and prevents them from being forgotten or disturbed, but its functions are much more extensive.
The term 'memory evolution' draws attention to the numerous functions of sleep, as well as the fact that memory continually changes in various ways throughout life.
--- p.95, from “Chapter 5: Is sleep just a solution to drowsiness?”

As you can see, we've run into a much trickier problem than whether dogs dream.
The question is whether animals other than humans have consciousness.
Bob often surprises his students by saying that there is no scientific evidence that humans are conscious.
It's true.
Philosopher David Chalmers points out that “we think we know conscious experience very well, but in fact nothing is more difficult to explain.”
--- p.110, from Chapter 6, “Do Dogs Dream?”

In 2016, Levonsuo and his colleagues advanced the theory that dreams are alternative social simulations, arguing that the function of dreams is to simulate and reinforce "social skills, relationships, interactions, and networks relevant to the real world." Like the TST model, the social simulation theory of dreams argues that dream simulations enhanced our ancestors' survival and adaptability.

--- p.133, from Chapter 7, “Why Do We Dream?”

When we dream, our brain explores weakly connected networks to understand possibilities.
The brain explores more broadly than it does when awake, investigates less obvious connections, and finds hidden treasures in places it would never look while awake.
During bright daylight, when the brain is primarily focused on processing newly acquired sensations and the neurotransmitters in the brain are optimized for processing information in the here and now, it is difficult to determine whether newly identified associations are useful or "correct."
But that's okay.
There's no need to understand why the brain chooses these associations.
We don't even need to know whether the associations used to build our dreams are useful or not.
You don't even need to remember your dreams.
Because all the important work was done while we were sleeping.
While we dream, our brain discovers, explores, and evaluates associations.
And if some of these associations are deemed truly novel, creative, and potentially useful, the brain strengthens them and stores them for later use.

--- p.150, from “Chapter 8 Network Exploration for Understanding Possibilities”

Unlike classical music, there is no recapitulation at the end of a dream.
Like a good novel, the denouement is not connected to the beginning.
This pattern of dreams is valid.
Dreams rarely come to a clean conclusion.
The most common ending to a dream report is “And then I woke up from the dream.”
The dreaming brain doesn't compose the entire storyline.
In fact, because of the decline in norepinephrine we discussed in Chapter 8, NextUp cannot sustain a single plot narrative for long.
Instead, NextUp works by observing the "principle of proximity," weaving together a series of memories and network explorations.
Much like a cocktail party conversation, we move from topic to topic in a constantly unfolding narrative, always finding new, potentially useful connections.
--- p.186, from “Chapter 9: The Innumerable Contents of a Dream”

But rather than bringing in the entire episodic memory from the previous day's events and inserting it, the brain only brings in bits and pieces: objects, settings, characters, impressions, fleeting thoughts, and brief conversations.
Some of these daytime remnants combine with details from older, weakly related memories to form the details that make up a personal dream narrative.
--- p.220, from “Chapter 10: What Do We Dream of?”

True creativity, as discovered in dreams, arises from creative exploration of associated neural networks, where the brain identifies weak connections that are crucial for problem solving.
Whether this process can be considered true creativity becomes a problem when defining dream creativity.
Robert Franken, in his book Human Motivation, defines creativity as “the tendency to generate and recognize ideas, alternatives, and possibilities that are useful for solving problems, communicating with others, and entertaining ourselves and others.”
--- p.236, from “Chapter 11 Dreams and Inner Creativity”

But we do not see dreams as a mechanism that evolved simply to be interpreted.
The first reason this idea doesn't make sense is because we remember so few of the dreams we have each night.
The second reason is that among the dreams we 'remember', there are very few that can be interpreted by anyone, let alone so-called experts.
Therefore, it is important to distinguish between the biological and adaptive functions of dreams that occur 'vividly' while the dream unfolds and the uses of dreams, such as interpretation, creativity, or simple enjoyment, that we 'select' for the purpose of understanding the dream we remember after waking.
--- p.245, from “Chapter 12 Dream Work”

But dreams, and by extension the neurobiology of next-up, are too complex to be simply judged as success or failure.
Between the extremes of success and failure, there is a broad middle ground where sleep-dependent memory evolution occurs intermittently and with varying effects.
For example, 90 percent of people who develop PTSD after being exposed to trauma report nightmares that are similar in many ways to the traumatic event itself, but only half of the nightmares replay the traumatic memory.
Instead, post-traumatic nightmares may distort and reveal traumatic elements, metaphorically present the traumatic event, or relive the same distressing emotions—fear, sadness, helplessness—that were experienced at the time of the trauma without directly mentioning the actual traumatic event.
--- p.267, from “Chapter 13 Things We Encounter at Night”

Many people confuse the concepts of lucid dreaming and dream control.
But these two are different.
Although two experiences can and do occur simultaneously, being aware that you are dreaming may not allow you to change the direction of the dream, nor may you want to.
Conversely, you can intentionally change things in your dreams in ways that would be impossible in the real world, even if you don't realize you're dreaming.
Moreover, the term ‘dream control’ is inappropriate.
Lucid dreamers can consciously direct their actions in their dreams, but most can only 'influence' how the dream unfolds.
--- p.293, from “Chapter 14: Awake Mind, Sleeping Brain”

But another possibility is that the vague nature of dream memory, coupled with the associative nature of dreams (“I think there was something to do with cats…”), allows us to retrospectively recall a dream as being related to a particular topic, such as the death of a parent, even though they have nothing in common (“I felt really sad, like I lost something…”).

--- p.325, from “Chapter 15 Telepathy and Precognitive Dreams”