Dreams, Sleep, and Consciousness: Interweaving the Neurocognitive Theory of Dreaming with New Theories of Sleep and Consciousness

"For anyone curious about why we dream — and what those dreams might reveal about the mind — this book represents a significant and timely advancement.... a global milestone in dream research."

— Brain Dialogues Blog, Centre for Healthy Brain Ageing, University of New South Wales

Dreams, Sleep, and Consciousness is the first book since the beginning of the neuroimaging era in the mid-1990s that provides a scientifically based explanation of how dreams, sleep, and consciousness relate to each other. It begins with an existing and fully developed neurocognitive theory of dreaming. This theory specifies the neurocognitive network that supports dreaming, and explains the gradual development of dreaming in children, as well as the detailed quantitative findings on dream content using dream reports collected inside and outside of sleep-dream laboratories.

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The new "adaptive inactivity theory of sleep" that is used in this book explains why the sleeping brain is more activated at some times than others, which is the final necessary factor in making dreaming possible. The equally new "multistate hierarchical model of consciousness" drawn upon in this book offers an explanation for why consciousness occurs. The book reveals that the middle level of this three-level theory of self-knowing (autonoetic) consciousness encompasses the neurocognitive theory of dreaming into its middle level as a form of fact-knowing (noetic) consciousness.

This is also the first book on dreams, sleep, and consciousness that includes a full chapter on the sleep-onset process, which is important because brief periods of dreaming already appear during this process. It is also the first book on dreams and their relationship to sleep and consciousness that includes a chapter on the awakening process. This is relevant because people remain groggy and only semi-alert even though consciousness returns very rapidly following awakening, and this period of drifting waking thought is important in explaining why the majority of dream recall occurs shortly after the morning awakening.

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Chapter 1: An Introduction to the Three Theories Utilized in this Book

This chapter introduces the three theories that are interwoven in later chapters into a coherent account of the relationships among dreams, sleep, and consciousness — the neurocognitive theory of dreaming, the adaptive inactivity theory of sleep, and the multistate hierarchical model of consciousness. Each of the theories — which were created independently by three different empirically oriented psychological researchers — is overviewed as a preparation for the chapters that follow. The main takeaway points are, first, that dreaming occurs due to the activation of portions of the same neurocognitive networks that support imagining, daydreaming, mind-wandering, and visual mental imagery during waking.

Second, the imagination network is part of the "intermediate-level" of the multistate hierarchical model of consciousness during waking, which also processes newly arriving sensory information and sends it to the "higher-order network." In neurocognitive terms, the ability to imagine, the self-system, the semantic memory network, and several other cognitive capacities at the intermediate level are part of the "default network." The higher-order network, based on a neurocognitive network called the "frontoparietal control network," uses the updated information sent to it by the intermediate-level cognitive networks supported by the default network to make decisions and issue top-down commands.

Third, dreaming occurs during sleep because sensory information is mostly occluded, and the higher-order network, which is located in the frontoparietal control network, is relatively deactivated compared to the portions of the default network that are the primary support for the neurocognitive process of dreaming. Fourth, sleep is an adaptation that is unique to mammals and birds. It allows them to conserve energy at times when food is not easily found, and at times when predators are most active.

Chapter 2: The Unique Neurocognitive Network That Makes Dreaming Possible

This chapter discusses the specific neurocognitive network that supports dreaming when external stimuli are occluded and the higher-order network that makes decisions and issues top-down commands is relatively deactivated. At this point, people's imaginations can roam freely through their semantic memory banks and create the scenarios that we call dreams.

The chapter shows that blind people have vivid dreams based on other forms of sensory imagery, and it explains the unexpected discovery that young child do not dream with any frequency or complexity until the default network and several cognitive abilities have become more developed at about ages 9--11. The uniqueness of the neurocognitive network that supports dreaming is theoretically important because it is very different from the various neurocognitive networks that support hallucinations, recreational drug states, hypnotic states, and psychosis. This discovery reveals that dreaming, a routine everyday occurrence in teenagers and adults, can no longer be compared to any of these atypical altered states of consciousness, as was often wrongly done in the past.

Chapter 3: Findings on Dream Content in the Light of the Neurocognitive Theory of Dreaming

This chapter overviews the very solid findings concerning what people dream about. These results are based on a rigorous system of quantitative content analysis, the Hall/Van de Castle coding system. This coding system has been used by researchers from many different countries over the past 60 years. The findings using the Hall/Van de Castle coding system demonstrate that dream content is different from what is claimed based on clinical cases and popular accounts. The results lead to the conclusion that perhaps as many as 70--75% of dreams express personal concerns that are continuous with the personal concerns people think about during drifting waking thought. For example, they reveal how people conceive of their relationships with parents, siblings, and friends during waking life.

The chapter also discusses what are called "adventure" dreams. Adventure dreams are based on the imaginative use of people's general knowledge, which is stored in the aforementioned semantic memory network. Such dreams have little or nothing to do with people's lives or their waking personal concerns. The chapter also emphasizes that it is not easy to collect useful samples of dreams, which is one reason why so much popular information about dreams is exaggerated or wrong.

Chapter 4: Further Insights about Dream Content Based on Studies of Individual Dream Series

This chapter replicates, extends, and deepens the information that was presented in the previous chapter. It discusses what has been learned through quantitative studies of the hundreds — or thousands, in some instances — of dreams that a small percentage of people keep for their own personal reasons over the course of months, years, or decades. Only later do some of the few people who have kept dream journals decide to make them available to researchers. This is one main reason why dream journals are extremely useful — they were not meant for research purposes. (Dream journals are a type of "unobtrusive measure" that has proven to be very valuable in the social sciences.) Studies of over two dozen such dreams journals add the new discovery that most people's dreams are consistent over time from young adulthood to older ages.

At the same time, some studies of dream journals have been able to show how dream content can change when a person develops new personal concerns, or loses interest in a past personal concern, such as an infatuation with a person they recently met. All of these conclusions are demonstrated in this chapter through a quantitative analysis of over 4,000 dreams written down for two decades by a middle-aged adult woman. She also answered questions in interviews with the lead researcher after he and his assistants had finished with their quantitative studies of her dreams, which confirmed all but two of the researchers' numerous inferences. These two mistaken inferences turned out to provide evidence for the concept of "adventure" dreams, as is also explained in Chapter 4.

Chapter 5: Dreaming During the Sleep-Onset Process

This chapter provides the first full synthesis of the large amount of systematic scientific information that is available on the sleep-onset process, including what is known from studies of dreaming during the sleep-onset process. It first overviews the neurophysiological substrates that are involved in triggering sleep. The chapter then uses the findings from neuroimaging studies of the sleep-onset process to explain how the neurocognitive network that supports consciousness gradually becomes less activated and gives way to the imagination network based on the default network, which remains activated. The chapter uses results from awakenings in sleep-dream laboratory studies to show that participants begin to dream as the sleep-onset process unfolds.

These studies further reveal that dreaming increases over the course of the sleep-onset process, and that there are individual differences in when the participants report dreaming. Also, a few participants continue to think or to experience drifting waking thought, but do not dream. These studies are theoretically important because they show that dreaming can occur outside of sleep, which in turn reinforces the general idea that dreaming occurs in older children, adolescents, and adults whenever (1) external stimuli are occluded; (2) the neural substrates that support the higher-order network are relatively deactivated; and (3) the neurocognitive network that makes imagining possible remains activated.

Chapter 6: The Adaptive Inactivity Theory of Sleep

This chapter explains the adaptive inactivity theory of sleep in detail. In the process, it explains the very different sleep patterns of various kinds of mammals and birds. For example, one species of bats is awake only 3--4 hours a day and hibernates in winter. On the other hand, African bush elephants in the wild sleep on average only 2.1 hours per day. One species of seals has a sleep cycle that is much like that of humans when on land, but during its seven months in the ocean only one hemisphere at a time goes to sleep. It also entirely loses one stage of sleep, called Rapid Eye Movement ("REM" sleep), which is responsible for periodically reheating areas of the brain in land mammals and in birds during sleep. Moreover, some species of porpoises and dolphins do not sleep at all.

These and other studies demonstrate that sleep is an energy-conservation strategy that limits the search for energy supplies to the most propitious and safest hours within a species' ecological niche. This means other hypothesized adaptive functions of sleep, none of which is strongly supported by good evidence, or widely agreed upon, came later in the evolutionary history of mammals, and do not of necessity occur during sleep.

Chapter 7: Brain Temperatures, Activation Patterns, and Dreaming

This chapter demonstrates how well the adaptive inactivity theory of sleep explains several unusual features of human sleep, which were not fully known and understood before the publication in 2015 of a longitudinal study of sleep in three indigenous societies without electricity. These indigenous groups sleep on average only 5--7 hours a night, and they sleep longer in the winter than in the summer by almost an hour. Unlike other known primates, the human sleep cycle is linked to the temperature cycle, not the light-dark cycle.

The findings from the field study are then linked to laboratory studies of cerebral blood flow during human sleep, which in turn are consistent with the activation patterns during the sleep-onset process, REM sleep, and early morning NREM 2 sleep. This work sets the stage for showing that dream reports after NREM 2 awakenings are increasingly frequent toward morning, and are similar in content to those from REM sleep by the time of the morning awakening. When combined with the findings in Chapter 5 on dreaming during the sleep-onset process, this chapter again shows that dreaming occurs when the imagination network is activated and other neurocognitive networks are not.

Chapter 8: The Awakening Brain: From Dreaming to Consciousness

This chapter parallels Chapter 5 on the sleep-onset process in that it provides the first synthesis of the various neurophysiological and neuroimaging findings concerning the nature of the arousal process that leads to the morning awakening. It uses neuroimaging studies of the awakening process to show that very specific networks lead to the almost instantaneous return of consciousness, but people nonetheless feel groggy and often are not fully alert until several minutes after they awaken. The findings on post-awakening grogginess are very useful from the point of view of the neurocognitive theory of dreaming because this post-awakening period provides a context for the consolidation of the last dream before awakening into people's memories, and for the mind-wandering that often leads to dream recall.

The chapter then provides a more detailed explanation of dream recall than was possible in the past, based not only on numerous laboratory and non-laboratory studies of dream recall that began in the late 1950s, but also on more recent neuroimaging studies. The chapter also makes use of a small field study of everyday dream recall, as well as the large literature on memory consolidation during waking. In the process, the chapter suggests that roughly 95% of dreams are forgotten, or were never encoded into memory in the first place.

Chapter 9: Dreaming and Waking Consciousness

This chapter provides a detailed explanation for self-knowing (autonoetic) consciousness, based on the multistate hierarchical model of consciousness. This full statement of the theory makes it possible to explain more fully how autonoetic consciousness differs from dreaming, which is a form of noetic (fact-knowing) consciousness. The relationship between autonoetic consciousness and noetic dreaming is further demonstrated by showing how they develop in tandem in children between the ages of 5--7 and 9--11, which establishes both their similarities and their differences. Within the context of the multistate hierarchical model of consciousness, the rare occurrence of an awareness that the person is dreaming — called "lucid dreaming" — can be explained in terms of a small atypical expansion in the neurocognitive network that supports dreaming.

The fact that the neurocognitive network that supports dreaming does not have the same cognitive capabilities as the consciousness network has, provides a pathway for explaining several unexpected and contentious replicated findings from several quantitative studies of dream content, such as the rare inclusion of episodic memories in dreams, and the relative infrequency of emotions in dreams compared to the frequency of emotions during waking.

Chapter 10: Retrospect and Prospects

This chapter uses the research findings presented in the earlier chapters to assess traditional theories of dreaming and dream content from the pre-neuroimaging era. It provides evidence that no past clinical theory can explain any of the neuroimaging, developmental, or quantitative dream content findings presented in the book. Nor can a neurophysiological theory from the 1970s, which emphasizes the brainstem and REM sleep as the key to dreaming, explain any of the many new findings.

Just as important, the several adaptive theories of dreaming — which purport to explain the evolutionary value of dreaming — are refuted by the available evidence. This is especially the case for theories claiming that dreams are a form of rehearsal for improving social skills or for dealing with threatening situations. These claims do not fit with the relative lack of dreaming until ages 9--11, nor with the findings on the consistency of dream content over months and years. Nor does it fit with the nature of social interactions in dreams. As for theories claiming that dreaming is based on the process of memory consolidation, they do not fit with the complete lack of evidence for memory consolidation during REM sleep, nor with the fact that there is a relatively small amount of memory consolidation in NREM sleep.

The book ends with suggestions on how teams of dream researchers and neuroimaging researchers could replicate and extend past findings by first of all making use of cellphones equipped with voice-to-text apps that make field studies of dream recall possible, as well as the collection of large representative samples of dream reports. In addition, there is a new portable, low-cost technology — called HD-DOT (high-density diffuse optical tomography) — that can carry out neuroimaging studies outside of a laboratory setting. Finally, there are new AI-generated Large Language Models (LLMs) that have the potential to do automated Hall/Van de Castle codings in ways that are far faster and far less expensive than was possible in the past, although trained coders would have to make reliability checks for the foreseeable future.