Greiz is a town along the White Eister River on the eastern edge of Thuringia, a few kilometres from Saxony and 50 kilometres from the Czech Republic. The town square is next to an expansive English garden, with a castle looming on the hill above. This region of Thuringia is known for its many forests and mountains. It is also known for its ancient cities and the Wartburg Castle, which is now a UNESCO World Heritage Site.

Huda Zoghbi is an expert on the genetics of neurodevelopmental disease. Zoghbi and her research group uncovered the genetic basis of a classic postnatal neurodevelopmental disorder, Rett syndrome. It is a puzzling disorder in girls who develop normally for the first year of life or more – reaching milestones like walking and talking – and then undergo a regression at around one to two years of age. The developmental deterioration coincides with the timing when there is a switch from net synapse formation to synapse elimination. As a medical resident, Zoghbi became fascinated with understanding what is happening in Rett syndrome.

While REM sleep is the phase of sleep from which dream reports are most reliably elicited, dream reports can also be elicited from any other stage of sleep, including sleep onset and N3 SWS. Reports after awakenings from NREM stages of sleep tend to be shorter, less emotional, and less visually vivid than reports obtained from REM – but we do get reports of “dreams” from NREM sleep states. Indeed, you can get dream reports without REM when REM is chemically suppressed via antidepressant medications. Just as dreams can occur without REM, REM sleep can occur without dream reports. About 20 percent of awakenings after a REM episode results in no dream report. Activation of REM, therefore, does not necessarily eventuate in a dream or at least a dream report. In addition, children who have abundant REM do not consistently report dreams until visuo-spatial and cognitive skills have matured enough to support reporting of visual narratives (Foulkes, 1982). Similarly, patients with lesions in the orbitofrontal cortex, basal forebrain, and near the occipitotemporoparietal junction sometimes report complete cessation of dreaming (Solms, 1997). In addition, Solms emphasized that disconnection of the ascending meso-limbic-cortical dopaminergic tracts from their termination sites in ventromedial frontal lobes could also lead to the loss of dreaming. Given that this tract is associated with instinctual appetitive drive and motivational states, it seems reasonable to conclude that this dopaminergic system may participate in the generation of some dreams. The loss of dreaming in these patients is not due simply to an inability to recall dreams, as their basic memory and recall abilities are largely intact. REM physiology as measured by sleep EEG is normal in these individuals, thus REM is still operating.

Although we know a lot about sleep, there is no scientific consensus on its function or functions. Its functions, however, must be extraordinarily significant, given that it renders us vulnerable to predators each time it overcomes us. It is involuntary. Everyone must eventually succumb to sleep or die. We must have it as surely as we must have oxygen, food, and water. But we do not know why.

The most common definition of dreams among scientists appears to be that dreams are sleep-dependent cognitions (Table 7.1). They are thoughts and mental images that occur during sleep. If, however, dreams are sleep-dependent cognitions, then they require sleep if they are to occur. If REM sleep can erupt or invade daytime consciousness and REM-related mentation can occur with that daytime eruption, then we can get dreams or dreamy thoughts and images while awake. Indeed, that is what we call daydreams. Even if we cannot strictly claim that dreams are always sleep dependent, they nevertheless typically occur in association (even when daydreaming) with a brain state (REM) that is normally activated during sleep.

At the dawn of the twentieth century, Freud presented his theory of dreams in his landmark work The Interpretation of Dreams. Freud’s basic claim was that the dream was a hallucinated wish fulfillment. Recent memories and imagistic fragments called day residues provide raw material for dream images that then activate motivated content and affects or wishes, and these wishes conflict with the waking ego and so must be disguised by the dream censorship mechanisms. The dreamwork mechanisms (condensation, representation, displacement, etc.) take the basic content carrying the desire or motivational wish and construct elaborate disguises around it (via secondary revision) while still attempting a hallucinated fulfillment of the wish. Up until the discovery of REM sleep in 1953, most scholars and scientists studying dreams operated within this Freudian framework. Carl Jung broke with the framework and presented his own theory of dreams as simulations that compensate for some aspect of the personality or psychic structure of the individual. Jung also postulated the appearance of mythic archetype in dreams, consistent with Freud’s claims concerning reenactments of the Oedipal tragedy and transgression in dreams.

If we want to know about the neurobiology of sleep, we need to very briefly summarize the main features of the neurobiology of wakefulness. In Figure 4.1 the main components of the networks that activate and maintain wakefulness are diagrammed. Two major pathways are shown in Figure 4.1. One (in yellow), rooted in the ascending reticular activating system (ARAS), shows that activating impulses ascend from ARAS via the via the thalamic-relay nuclei as well as reticular nucleus of the thalamus. This input is coming from acetylcholine (ACh)-producing neuronal groups, which are located in the Pedunculopontine and laterodorsal tegmental (PPT/LDT) nuclei of brainstem. The second major group of neurons (in red) are located in noradrenergic (NA) locus coeruleus (LC), serotoninergic (5-HT) dorsal and median raphe nuclei, dopaminergic (DA) periaqueductal gray matter (vPAG), and histaminergic (His) tuberomamillary neurons (TMN). The largely cholinergic groups are in mutual inhibitory balance with the large aminergic sertoniergic/noradrenergic groups. Additional cortical input also originates from the GABA or Ach neurotransmitter containing basal forebrain (BF) neurons as well as from lateral hypothalamic (LH) peptidergic neurons that contain the melanin-concentrating hormone (MCH) or orexin (hypocretin) (ORX).

Forty million Americans are afflicted with chronic disorders of sleep. Sleep disorders cause 38,000 cardiovascular deaths and cost over $16 billion annually. Indirect costs of accidents, property destruction, litigation, hospitalization, and death add another $50–$100 billion. Worldwide, about 10 percent of the population meet diagnostic criteria for insomnia disorder. Obstructive sleep apnea (OSA) is becoming more ubiquitous as the obesity epidemic enhances risk for OSA. Recurrent episodes of not breathing (apnea) or reduced airflow (hypopnea) during sleep leads to an almost constant daytime state of a brain starved for oxygen. It is likely that some 10 percent of the general population has OSA but that is probably a low estimate given that OSA is likely severely underdiagnosed, particularly among African Americans, overweight individuals, and older adults. Sleep disorders also carry huge consequences for mental health. For example, 65–90 percent of adults with major depressive disorder (MDD) report sleep problems, and 90 percent of children with depression report disturbed sleep. It is not just that sleep problems result from mental health problems, sleep problems can precipitate or help cause mental problems.

Dreaming both reflects the stage of life in which we find ourselves and influences the character of that stage of life. For example, adolescence would not be adolescence without the wild, melodramatic, passionate, and swirling epic dreams teens have that center around those existential questions of “who am I” and “W\why am I here?,” etc. We will see in this chapter that dreaming appears to reflect and perhaps promote waking social interactions of the dreamer, and this is true across the entire lifespan of the dreamer from toddlerhood right through to death. Of course, that is not the whole story. Dream content across the lifespan involves far more than social interactions, but it is a striking and consistent fact that simulations of social interactions are a constant feature of dream life throughout the life cycle. If we want to understand the development of dreams and dream content across an average human lifespan, we will need to first summarize the key milestones or periods of the human life cycle from the cradle to the grave. Table 8.1 displays key characteristics of each of the major human life-cycle stages and sketches corresponding dream findings.

Sleep is a need, just like food, water, or oxygen. If we don’t get enough of it, we die. But right off the bat, we need to qualify this claim a bit. There are at least two forms of sleep documented in human beings: NREM (non–rapid eye movement) and REM sleep. While it is clear that we will, in fact, die without NREM, the case of REM is more complicated. Since this book is also an introduction to the science of dreams, it is worth digging into REM biology right at the start as well, as it is the form of sleep wherein we most often experience vivid dreams. Without REM, it seems, we will likely crumble mentally, but we may not die.

It is not possible to understand dreams unless we become familiar with the whole terrain of dreams. We have discussed ordinary run-of-the-mill dreams that are associated with both REM and NREM sleep states. But there is a very large variety of dream types reported by people. To build an adequate understanding of dreams and a testable theory of dreams, we therefore need to marshal all of the salient facts concerning dreams, and those facts must include the chracteristics of a wide variety of dream types. Scientists who study dreams agree that dreams vary substantially in terms of their content and formal phenomenologic features. For example, children’s dreams are very different from adult’s dreams, and men’s dreams differ substantially from women’s dreams. There are nightmares, “big” or emotionally significant dreams, lucid dreams, shared or mutual dreams, twin dreams (dreams reported by twins), “spiritual” dreams, precognitive or prophetic dreams, visitation dreams (where deceased loved ones appear in a dream), and many other types. Dreams also vary by historical period: Dreams of the ancient Greeks and Romans are different than dreams of people in the Rennaissance period of European history. Dreams also vary by culture: Dreams of people living in traditional socieities are very different from the dreams of modernized peoples. Similarly, dreams of people living in Islamic cultures differ from the dreams of people living in cultures where other religions predominate and so on. All of this should be pretty obvious, but dream variation is an understudied topic in the field of sleep and dream studies. While the variation in dream content and types has been documented, there is little discussion of the theoretical importance of that variation. The fundamental theoretical importance of dream variation, I will argue, is that it suggests that dream function is probably multiple. Dreams do not have only one function. No one theory can account for the huge variation in dream conent. The evident fact that there are multiple dream types is also consistent with the idea that dreams are products of the social brain and function, at least in part, to shape, alter, influence, or manipulate social relationships. Now that is NOT all that dreams do. It is likely that dreams transcend mundane social functions in multiple ways, but we simply do not know enough about these suprarational functions of dreams to comment upon them intelligently. I urge further research on so-called anomalous phenomena and dreams, but I focus here on the available empirical data we have on hand.