CHAPTER FIVE

THE DREAMING MIND

For all the virtue and value that people throughout history have accorded to dreams, and all the abundance of philosophical perspectives that scholars have held about them, what exactly occurs in the mind when we’re dreaming was terra incognita for millennia. Still, there had been somewhat of a consensus that as animated as oneiric visions can be, that when we are sleeping and dreaming, the mind is downregulated and relatively asleep. That all changed in 1953, when a groundbreaking paper was published in the journal Science that would forever transform our understanding. In this article, entitled “Regularly Occurring Periods of Eye Motility, and Concomitant Phenomena, During Sleep,” the authors, Eugene Aserinsky and Nathaniel Kleitman, reported on the discovery of rapid eye movement (REM) sleep that they had uncovered during research that transpired in the previous two years.

The experiments — which then research assistant Aserinsky conducted in Kleitman’s sleep lab at the University of Chicago — and their subsequent reporting laid the groundwork for future seminal sleep and dream discoveries. These expounded on how REM sleep — which we now know accounts for about 25 percent of the total time adults spend sleeping — is the period believed to be when the most vivid dreams occur. They also discovered that, in addition to the occurrence of the rapid eye movements under closed lids, which became the hallmark of this period, other physiological shifts transpire in REM, such as increased heart and respiratory rates. And, strikingly, it was also then shown that while we may be sleeping during REM, the brain is actually not, with brain waves looking relatively similar to those present during waking. The seemingly anomalous occurrence of an awake mind with a sleeping body inspired French neuroscientist Michel Jouvet to coin “paradoxical sleep” as an alternative term for REM.

REM vs. JEM

If you think that rapid eye movement and REM aren’t the most poetic of names for the period of sleep in which the most poetic of events — vivid dreams — occur, it could have been worse. Eugene Aserinsky has shared that REM wasn’t his original choice; owing to the abrupt movements that he noticed the eyes making during this period, he first thought to call it jerky-eye movement sleep (JEM).

Sleep and Dream Stages

Since the discovery of REM, sleep was recategorized into having two main periods: that which features rapid eye movements, and that which does not. The former, of course, is known as REM sleep. The latter is known by a term that reflects not so much what it is, but what it isn’t: it is known as non-REM (or NREM) sleep. NREM sleep begins when we first fall asleep and features three distinct parts, known as stage 1, stage 2, and stage 3. REM sleep begins after these have initially appeared, and is sometimes referred to as stage 4 sleep. Here are some more details on the features of each.

NREM SLEEP

Stage 1

This is the transitional state of drowsiness we enter when we first begin to fall asleep. It’s a state of consciousness during which we can easily be awakened. High-frequency, low-amplitude beta waves in the brain, which are generally associated with engagement in mental activities, begin to be replaced by theta waves. We experience a slight decrease in muscle tone, and our response to external stimuli begins to shift.

Stage 2

During this stage, our body temperature decreases, as does our heart rate. Stage 2 is characterized by the appearance of brain wave forms known as sleep spindles and K complexes. There is further reduction in both muscle activity and conscious awareness of the environment. Stages 1 and 2 are considered light sleep.

Stage 3

Once divided into two different stages, this period of slow-wave sleep (SWS) is now considered as one. This is the time at which the deepest sleep occurs, and when it’s the most difficult to awaken people from sleep. During SWS, our brain activity features a concentration of slow-speed delta waves. Our eyes are not moving, and there is continued reduction in muscle tone and responsiveness. This restorative stage of sleep is our time to get deep rest. It’s also the period when growth hormone release increases, and our immune system becomes replenished. Sleepwalking, bedwetting, and night terrors occur in this phase.

A Powerful Trio

While Eugene Aserinsky and Nathaniel Kleitman are noted as co-authors of the famous Science article detailing the finding of REM, it was actually Aserinsky’s work that formed the foundation of this discovery. With his persistent and innovative approach to research, he actually had one of his initial sleep-study breakthroughs when observing rapid eye movements during slumber in a most unusual, and familial, laboratory subject: his eight-year-old son Armond. Kleitman is considered the father of modern sleep research, establishing the first lab to study the workings of sleep at the University of Chicago. His contributions to the field are nothing short of monumental. In addition to co-authoring the now famous REM sleep-discovery study, he also wrote the influential 1939 book Sleep and Wakefulness; as we saw in chapter 2, it was in there that he coined the term sleep hygiene. After Aserinsky’s initial discoveries, he was assisted by then-medical student William Dement, who had a strong interest in further understanding how REM was related to dreaming. Dement went on to not only make significant research advances, but also to author the seminal book The Promise of Sleep, as well as establish the first sleep clinic at Stanford University.

REM SLEEP

Stage 4

While this is the fourth stage of sleeping, it’s not usually referred to as stage 4, but just as REM. It’s the period that’s come to be most associated with dreams. And while researchers have discovered that dreams do occur in other sleep stages, something that they didn’t realize until recently, it’s still thought that it’s in REM that we experience the most vivid of our oneiric visions.

SLEEP STAGE CYCLING

In addition to there being different stages of sleep, what’s interesting is that there’s a repeating rhythm to their occurrence. It’s not that there’s a single trajectory from stage 1 through REM that goes throughout the whole night. Rather, this four-stage cycle, through NREM and REM, usually lasts about 90 minutes (although it can be as long as 120 minutes) and repeats itself throughout our slumber. As such, if you get 8 hours of sleep, you’re likely experiencing four or five full REM cycles, and consequently about four or five periods replete with vivid dream potential.

However, sleep stage cycling is even more nuanced than that, in a way that has significant repercussions for dreaming. As the subsequent 90-minute cycles occur, the time that each sleep stage occupies shifts. For example, in the beginning of the night, deep and restful sleep (stage 3 SWS) takes up a big portion of each cycle. Yet, as the night turns to morning, its allocated time reduces, and more sleep is taken up by REM. This means that for some not-yet-identified reason, as we get closer to transporting ourselves back to waking, we spend a concentrated time in this stage in which graphic and memorable dreams occur. So, if you sleep 8 hours, and approximately one-quarter of your sleep is REM, then you’ll have 2 hours each night in which you can have dreams that may be dynamic, animated, and evocative. Looked at another way, on average, one-twelfth of our day yields to us the potential to have powerful oneiric visions.

The Ebbs and Flows of NREM and REM

During sleep, our body maintains the integrity of its neural networks, which is vital for brain function, including emotional memory consolidation. During NREM, aspects of faulty neural networks are broken down, while their connections are re-strengthened during REM. While it’s still not fully clear why this occurs as it does, this NREM/REM deconstruct-to-reconstruct partnership may underlie why the amount spent in each of these stages varies throughout the night.

The Physiology of a Dreaming Brain

The dreaming brain is so fascinating and unique that many researchers contend that there are actually three primary brain states, or ways in which it fashions itself: the awake brain, the sleeping brain, and the dreaming brain. As previously discussed, there are similarities in brain wave activity between the dreaming REM state and the awake state. In addition, through EEG (electroencephalogram) testing, research has found that when an activity is undertaken while awake and while dreaming, the brain reveals a similar activation pattern. However, there are some notable differences between the dreaming REM brain and what is occurring while we’re awake. The unique ways in which they express themselves may very well help us understand more about why oneiric visions appear as they do.

During REM, the brain area known as the prefrontal cortex (PFC) is downregulated. Given that it governs what’s considered to be executive function, it controls such things as critical thinking, judgment, and self-control, all of which are tamped down during dreaming. The PFC is also thought to be involved in metacognition, the knowledge that you know that you have knowledge, the witness part of you that knows that you are thinking. When all of these functions aren’t operating as they usually do in the waking state, we may then feel a more fluid sense of self that is able to expand beyond the boundaries of what’s deemed acceptable and realistic, a quality we associate with our dreams. Plus, without metacognition, we can be experiencing something bizarre while lacking the rational judgment to denote that it’s actually bizarre, a classic attribute of dreams. We don’t know we are thinking, and invariably we then don’t know we are dreaming. That is, unless we are lucid dreaming, a state in which the PFC is not as passive as it is in regular dreaming, which may be why it’s an experience filled with the awareness that you are actually dreaming. (You can find more information on lucid dreams in chapter 9.)

Other parts of the brain, though, exhibit an upregulation during REM dreaming. These include the limbic system, the seat of our emotional mind. Additionally, the part of our brain related to visual awareness is energized. This may help explain why dreams can have such a strong feeling tone, as well as why they are so graphic and pictorial. Additionally, certain brain chemicals appear in differing levels when we are dreaming compared to when we are awake. This includes the neurotransmitter norepinephrine, which is at a reduced level when we’re dreaming; since one of its functions is to help shuttle short-term memories into long-term ones, this may be one of the reasons that it’s so difficult to recall our dreams. (For more on dream recall, see chapter 12.)

Another hallmark of the REM stage is that most people (except those with REM disorders) experience muscle paralysis during it. Known as muscle atonia, it’s thought to be a mechanism to protect us, so that we don’t act out our dreams and potentially incur harm. What’s also fascinating about the dreaming brain is that the images and feelings that it brings forth come not from processing the external world; after all, when we are sleeping, our eyes are closed and our senses aren’t processing at the same level as when we are awake. Rather, it seems that most of the ingredients that the dreaming mind uses to create each unique oneiric journey come from within, from the deep recesses of the landscape of our consciousness.

Factors That Impact REM Dreams

There are some physiological factors that may actually deter vivid dreams from occurring as they usually do, owing to their ability to disturb our sleep architecture (the structural organization of our sleep) and cause REM disruption. This may manifest in either reducing our ability to have highly activated and memorable dreams, or in shifting sleep cycles in such a way that we have exceptionally animated dreams early in the morning. Disturbing regular REM cycles may have negative impacts upon our memory and emotional equilibrium in ways that have yet to be fully illuminated.

ALCOHOL

While alcohol may lull some people to sleep, it disrupts sleep architecture. It reduces the amount of REM we undergo during the first half of the night. But, in the body’s natural attempt to maintain balance, it later creates what’s known as REM rebound, in which we have lengthened periods of REM in the second half of sleep. This may account for people reporting more vivid dreams after having a few drinks. Yet, for others, this reduces their REM dream time by causing more frequent arousals while the body is working to eliminate the alcohol.

ANTICHOLERGENIC DRUGS

Anticholergenic drugs — those that function by blocking the action of the neurotransmitter acetylcholine — also reduce REM sleep. Numerous drugs have anticholergenic properties, including some used to treat overactive bladders, Parkinson’s disease, allergies, and other conditions. That research has suggested that long-term use of anticholergenics may be linked to an increased risk of dementia has some researchers wondering even more about the role of REM in maintaining brain health.

ANTIDEPRESSANTS

Many antidepressant medications suppress REM sleep. These include those in the three major classes of such drugs: the monoamine oxidase inhibitors (MAOI), the tricyclic antidepressants (TCA), and the selective serotonin-reuptake inhibitors (SSRI).

CANNABIS

Preliminary research suggests that cannabis, as well as tetrahydrocannabinol (THC) edibles, reduces REM sleep. While cannabinoids (CBD) have been researched for their potential benefit in treating a condition called REM sleep behavior disorder, the effects of CBD on sleep stages and dreams are not fully known.

REM Sleep Behavior Disorder

Typically during REM sleep, our eyes are shut and our muscles tone is inactivated. This feels like nature’s safeguard, so that we won’t be stirred to act out the actions that animate our dreams. However, not everyone is so lucky. There’s a condition called REM sleep behavior disorder (RBD) in which muscles don’t disengage and sleep paralysis doesn’t occur. This leads to dreamers often acting out their dreams both vocally and in movements that could be quite animated, and possibly dangerous. RBD occurs more frequently in those with narcolepsy, and many people who have Parkinson’s disease and Lewy body dementia have RBD preceding their diagnosis. As such, it is thought to be a possible predictive factor for these conditions, although not everyone who has the condition will develop those neurodegenerative diseases. It is more common in the elderly than in younger people. While its causes are not fully understood, RBD may be related to damage in the part of the brain that controls muscle atonia (the loss of tone and strength) that naturally occurs during REM sleep. While usually chronic, there are some cases in which it is more acute, brought on by shifts in certain factors, including alcohol or drug withdrawal. For those with RBD, modifying their bedroom environment to minimize injury is a first-line strategy. There are some medications used to help mitigate the condition, with newer research suggesting that high-dose melatonin supplements may also be of benefit. Those with RBD should seek guidance from a trained health-care practitioner.

INSOMNIA

If you have the type of insomnia that has you waking up in the early morning hours, unable to fully go back to sleep, you may miss out on the extended REM sleep periods that occur during this time. Given these are when vivid dreams are likely to happen, this form of insomnia may not only rob you of your sleep, but also of the ability to have quite memorable dreams.

SLEEP APNEA

Non-treated sleep apnea occurs in both NREM and REM sleep, yet has been found to be more prevalent during the latter. This may be due to the reduction of muscle tone that is a characteristic of this sleep stage. Among its other consequences, the interrupted breathing that is a hallmark of non-treated sleep apnea may cause awakenings that fragment REM sleep periods.