MATTHEW WALKER
In an exclusive essay, neuroscientist and sleep expert Matthew Walker explores the mystery of sleep and dreams
Last night, you became flagrantly psychotic. It will happen again tonight. Before you reject this diagnosis, allow me to offer five justifying reasons.
First, when you were dreaming last night, you started to see things that were not there—you were hallucinating. Second, you believed things that could not possibly be true—you were delusional. Third, you became confused about time, place, and person—you were disoriented. Fourth, you had extreme swings in your emotions—some- thing psychiatrists call being affectively labile. Fifth (and how delightful!), you woke up this morning and forgot most, if not all, of this bizarre dream experience—you were suffering from amnesia. If you were to experience any of these symptoms while awake, you’d be seeking psychological treatment. Yet for reasons that are only now becoming clear, the brain state called rapid eye movement (REM) sleep, and the mental experience that goes along with it, dreaming, are normal biological and psychological processes, and truly essential ones.
Having cast off the non-scientific theory of Sigmund Freud, neuroscience research has since demonstrated that dreaming is not just a byproduct of REM sleep, but serves critical functions for our wellbeing. Can we even take conscious control over our dreams? Scientific evidence suggests the answer is indeed, yes. That fact alone leads to the possibility of self-selecting what experiences (and benefits) we harness from our nocturnal fantasias each and every night?
Creative Inspiration
We often hear stories of people who’ve had remarkable dream-inspired creativity. Think of Paul McCartney’s story of how his hit song, “Yesterday,” came to him in a dream. Keith Richards had a similar dream experience that gifted to him the iconic opening guitar chords of the song, Satisfaction. Or take Mendeleev’s the dream-derived construction of the table of the periodic elements.
It’s been shown that deep non-REM sleep strengthens individual memories. But recent work in my sleep centre, and work of other scientists, has now shown that REM-sleep dreaming is when those memories can be fused and blended together in abstract and highly novel ways. During the dreaming state, your brain will cogitate vast swaths of acquired knowledge and then extract what overarching rules and commonalties, creating a mindset that can help us divine solutions to previously impenetrable problems.
How do we know dreaming and not just sleep is important to this process? In one study, we tested this by waking up participants during the night—during both non-REM sleep and dreaming sleep—and gave them very short tests: solving anagram puzzles, where you try to unscramble letters to form a word [i.e. OSEOG = GOOSE]. We monitored the participants during sleep, woke up them up at different points of the night to perform the test. When woken during non-REM sleep, they were not particularly creative—they could solve very few puzzles. But, when we woke up participants during REM sleep, they were able to solve 15-35 percent more puzzles than when they were awake. Not only that, participants woken while dreaming reported that the solution just “popped” into their heads, as if it were effortless.
In another study, I and my colleagues taught participants a series of relational facts—such as, A>B, B>C, C>D, and so on—and tested their understanding by asking them questions, for example: Is B>D or not? Afterwards, we compared their performance on this test before and after a full night’s sleep, and also after they’d had a 60-90-minute nap that included REM sleep. Those who’d slept or had a long nap performed much better on this test than when they were awake, as if they’d put together disparate pieces of a jigsaw puzzle in their sleep.
Peace at last: neuroscientist and sleep expert Matthew Walker
Some may consider this trivial, but it is one of the key operations differentiating your brain from your computer. It also underlies the difference between knowledge (retention of individual facts) and wisdom (knowing what they all mean when you fit them together). The latter seems to be the work of REM-sleep dreaming.
Dreaming improves creative problem solving, too. In one study, participants learned to navigate a virtual maze, with the goal of finding an exit as quickly as possible. They did this using trial and error, aided by the placement of unique objects at certain locations in the maze, such as a football or a Christmas tree. After this learning session, the research participants were split into two groups, with half taking a subsequent afternoon nap, while the other half watched a video for 90 minutes. Nappers were occasionally awoken to ask about the content of their dreams. At equivalent times, those watching a video were also asked about thoughts going through their minds. Afterwards, all participants went back into the virtual maze again.
Those individuals who napped were significantly better at it than those who didn’t, as expected. But, the nappers who reported dreaming about the maze were 10 times better at the task than those who napped and didn’t dream about the maze. Interestingly, when looking at the content of these dreams, it was clear that the participants didn’t dream a precise replay of the learning experience while awake. Instead, they were cherry picking salient fragments of the learning experience and attempting to place them within the catalog of preexisting knowledge.
Therefore, sleep was not the engine of creativity. Rather, it was dreaming of salient features of the experience that enhanced problem solving. Little wonder, then, that you have never been told to “stay awake on a problem.” Instead, you are instructed to “sleep on it.” Interestingly, this phrase, or something close to it, exists in most languages (from French “dormir sur un problem,” to Swahili “kulala juu ya tatizo”), indicating that the problem-solving benefit of dream sleep is universal, common across the globe.
Overnight therapy
It’s said that time heals all wounds; but research suggests that time spent in dream sleep is what heals. REM sleep, and dreams themselves, appears to take the painful sting out of difficult, even traumatic, episodes experienced during the day. In this way, dreaming provides a form of emotional first aid, offering psychological resolution when you awake each morning.
REM sleep is the only time when our brain shuts off the anxiety-triggering molecule noradrenaline (the body’s equivalent of which is adrenaline). At the same time, emotional and memory related centers of the brain are reactivated as we dream. This means that emotional memory reactivation is occurring in a brain free of a key stress-related neurochemical, which allows us to re-process painful and even traumatic memories in a safer, calmer neural environment.
Supporting evidence comes from one study in my sleep center in young adult participants watched a set of emotion-inducing images while inside an MRI scanner. Twelve hours later, they were shown the same emotional images; but for half the participants, the twelve hours were in the same day, while for the other half the twelve hours were separated by an evening of sleep—a full hours.
Those who slept in between the two sessions reported a significant decrease in how emotional they felt in response to seeing those images again. Their MRI scans agreed—there was a palliative decrease in reactivity in the amygdala—the emotional center of the brain that can create painful feelings. In addition, there was a reengagement of the rational prefrontal cortex of the brain after sleep that provides a dampening brake on emotional reactivity. In contrast, those who remained awake across the day showed no such dissolving of emotional reactivity over time.
This evidence itself doesn’t say anything about the role of dream sleep. But, we had recorded the sleep of each participant during the intervening night between the two test sessions. We discovered that a specific kind of electrical brain activity that reflects a drop in stress-related chemistry during the dream state determined the success of overnight therapy from one individual to the next.
These studies, and those of many others, led to the suggestion that dream sleep has the potential to help people recover from especially difficult traumatic experiences, since the emotional content of dreams is paired with a decrease in brain noradrenaline.
Support for this idea came from research by the psychiatrist, Murray Raskind. He studied war veterans with post-traumatic stress disorder (PTSD), who often suffer debilitating nightmares. When given the drug Prazosin—a medication that lowers blood pressure and also acts as a blocker of the brain stress chemical, noradrenaline— the soldiers had more REM sleep, fewer nightmares and while awake, fewer PTSD symptoms, than those given a placebo. Newer studies suggest this effect can be shown in children and adolescents with nightmares, as well; though the research on this is still in its infancy.
Scientific evidence therefore fits the prophetic wisdom of Charlotte Brontë’s, who stated that “a ruffled mind makes a restless pillow”. Said more optimistically, the best bridge between despair and hope is a good night of sleep.
Controlling your dreams
Lucid dreaming occurs at the moment when you become aware that you are dreaming. However, the term is more colloquially used to describe gaining volitional control of what an individual is dreaming, and the ability to manipulate that experience, such as deciding to fly, or perhaps even the functions of it, such as problem solving.
The concept of lucid dreaming was once considered a sham. Scientists debated its very existence. You can understand the skepticism. First, the assertion of conscious control over a normally non-volitional process injects a heavy dose of ludicrous into the already preposterous experience we call dreaming. Second, how can you objectively prove a subjective claim, especially when the individual is fast asleep during the act?
Several years ago, a truly ingenious experiment removed all such doubt. Scientists placed lucid dreamers inside an MRI scanner. While awake, these participants first clench their left and then right hand, over and over. Researches took snapshots of brain activity, allowing them to define the precise brain areas controlling each hand of each individual.
The participants were allowed to fall asleep in the MRI scanner, entering REM sleep where they could dream. During REM sleep, however, all voluntary muscles are paralyzed, preventing the dreamer from acting out ongoing mental experience. Yet the muscles that control the eyes are spared from this paralysis, and give this stage of sleep its frenetic name. Lucid dreamers were able to take advantage of this ocular freedom, communicating with the researchers through eye movements.
Pre-defined eye movements would therefore inform the researchers of the nature of the lucid dream (e.g., the participant made three deliberate leftward eye movements when they gained lucid dream control, two rightward eye movements before clenching their right hand, etc.). Non-lucid dreamers find it difficult to believe that such deliberate eye movements are possible while someone is asleep, but watch a lucid dreamer do it a number of times, and it is impossible to deny.
When participants signaled the beginning of the lucid dream state, the scientists began taking MRI pictures of brain activity. Soon after, the sleeping participants signaled their intent to dream about moving their left hand, then their right hand, alternating over and over again, just as they did when awake. Their hands were not physically moving—they could not, due to the REM-sleep paralysis. But they were moving in the dream.
At least, that was the subjective claim from the participants upon awakening. The results of the MRI scans objectively proved they were not lying. The same regions of the brain that were active during physical right and left voluntary hand movements observed while the individuals were awake similarly lit up in corresponding ways during times when the lucid participants signaled that they were clenching their hands while dreaming!
There could be no question. Scientists had gained objective, brain-based proof that lucid dreamers can control when and what they dream while they are dreaming. Other studies using similar eye-movement communication designs have further shown that individuals can deliberately bring themselves to timed orgasm during lucid dreaming, an outcome that, especially in males, can be objectively verified using physical measures by (brave) scientists.
It remains unclear whether lucid dreaming is beneficial or detrimental, since well over 80 percent of the general public are not natural lucid dreamers. If gaining voluntary dream control were so useful, surely Mother Nature would have imbued the masses with such a skill.
However, this argument makes the erroneous assumption—that we have stopped evolving. Is it possible that lucid dreamers represent the next iteration in Homo sapiens evolution? Will these individuals be preferentially selected for in the future on the basis of this unusual dreaming ability—one that may allow them to turn the creative problem-solving spotlight of dreaming on the waking challenges faced by themselves or the human race, and advantageously harness its power more deliberately?
Before trying to answer these lofty, even preposterous, questions, could I suggest we first take a night to sleep on it.
Matthew Walker is a Professor of Psychology and Neuroscience at the University of California, Berkeley and the director of the university’s Center for Human Sleep Science.
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