فصل 9

فصل: چرا می‌خوابیم / فصل 9

فصل 9

توضیح مختصر

  • زمان مطالعه 0 دقیقه
  • سطح خیلی سخت

دانلود اپلیکیشن «زیبوک»

این فصل را می‌توانید به بهترین شکل و با امکانات عالی در اپلیکیشن «زیبوک» بخوانید

دانلود اپلیکیشن «زیبوک»

فایل صوتی

دانلود فایل صوتی

متن انگلیسی فصل

PART 3

How and Why We Dream

CHAPTER 9

Routinely Psychotic

REM-Sleep Dreaming

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—something 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 immediate psychological treatment. Yet for reasons that are only now becoming clear, the brain state called REM sleep and the mental experience that goes along with it, dreaming, are normal biological and psychological processes, and truly essential ones, as we shall learn.

REM sleep is not the only time during sleep when we dream. Indeed, if you use a liberal definition of dreaming as any mental activity reported upon awakening from sleep, such as “I was thinking about rain,” then you technically dream in all stages of sleep. If I wake you from the deepest stage of NREM sleep, there is a 0 to 20 percent chance you will report some type of bland thought like this. As you are falling asleep or exiting sleep, the dream-like experiences you have tend to be visually or movement based. But dreams as most of us think of them—those hallucinogenic, motoric, emotional, and bizarre experiences with a rich narrative—come from REM sleep, and many sleep researchers limit their definition of true dreaming to that which occurs in REM sleep. As a result, this chapter will mainly focus on REM sleep and the dreams that emerge from this state. We will, however, still explore dreaming at these other moments of sleep, as those dreams, too, offer important insights into the process itself.

YOUR BRAIN ON DREAMS

In the 1950s and 1960s, recordings using electrodes placed on the scalp gave scientists a general sense of the type of brainwave activity underpinning REM sleep. But we had to wait until the advent of brain-imaging machines in the early 2000s before we could reconstruct glorious, three-dimensional visualizations of brain activity during REM sleep. It was worth the wait.

Among other breakthroughs, the method and the results undermined the postulates of Sigmund Freud and his nonscientific theory of dreams as wish fulfillment, which had dominated psychiatry and psychology for an entire century. There were important virtues of Freud’s theory, and we will discuss them below. But there were deep and systemic flaws that led to a rejection of the theory by modern-day science. Our more informed, neuroscientific view of REM sleep has since given rise to scientifically testable theories of how it is that we dream (e.g., logical/illogical, visual/non-visual, emotional/non-emotional) and what it is that we dream about (e.g., experiences from our recent waking lives/de novo experiences), and even gives the chance to nibble away at surely the most fascinating question in all of sleep science—and arguably science writ large—why it is that we dream, that is, the function(s) of REM-sleep dreaming.

To appreciate the advance that brain scanners made to our understanding of REM sleep and dreaming beyond simple EEG recordings, we can return to our sports stadium analogy from chapter 3. Dangling a microphone over the stadium can measure the summed activity of the entire crowd. But it is geographically nonspecific in this regard. You cannot determine whether one segment of the crowd in the stadium is chanting loudly while the segment directly next door is relatively less vocal, or even completely silent.

The same nonspecificity is true when measuring brain activity with an electrode placed on the scalp. However, magnetic resonance imaging (MRI) scans do not suffer this same spatial smearing effect in quantifying brain activity. MRI scanners effectively carve up the stadium (the brain) into thousands of small, discreet boxes, rather like individual pixels on a screen, and then measure the local activity of the crowd (brain cells) within that specific pixel, distinct from other pixels in other parts of the stadium. Furthermore, MRI scanners map this activity in three dimensions, covering all levels of the stadium brain—lower, middle, upper.

By placing individuals inside brain scanning machines, I and many other scientists have been able to observe the startling changes in brain activity that occur when people enter into REM sleep and begin dreaming. For the first time, we could see how even the very deepest structures previously hidden from view came alive as REM sleep and dreaming got under way.

During dreamless, deep NREM sleep, overall metabolic activity shows a modest decrease relative to that measured from an individual while they are resting but awake. However, something very different happens as the individual transitions into REM sleep and begins to dream. Numerous parts of the brain “light up” on the MRI scan as REM sleep takes hold, indicating a sharp increase in underlying activity. In fact, there are four main clusters of the brain that spike in activity when someone starts dreaming in REM sleep: (1) the visuospatial regions at the back of the brain, which enable complex visual perception; (2) the motor cortex, which instigates movement; (3) the hippocampus and surrounding regions that we have spoken about before, which support your autobiographical memory; and (4) the deep emotional centers of the brain—the amygdala and the cingulate cortex, a ribbon of tissue that sits above the amygdala and lines the inner surface of your brain—both of which help generate and process emotions. Indeed, these emotional regions of the brain are up to 30 percent more active in REM sleep compared to when we are awake!

Since REM sleep is associated with the active, conscious experience of dreaming, it was perhaps predictable that REM sleep would involve a similarly enthusiastic pattern of increased brain activity. What came as a surprise, however, was a pronounced deactivation of other brain regions—specifically, circumscribed regions of the far left and right sides of the prefrontal cortex. To find this area, take your hands and place them at the side corners of the front of your head, about two inches above the corners of your eyes (think of the crowd’s universal hand placement when a player just misses scoring a goal during overtime in a World Cup soccer game). These are the regions that became icy blue color scheme blobs on the brain scans, informing us that these neural territories had become markedly suppressed in activity during the otherwise highly active state of REM sleep.

Discussed in chapter 7, the prefrontal cortex acts like the CEO of the brain. This region, especially the left and right sides, manages rational thought and logical decision-making, sending “top-down” instructions to your more primitive deep-brain centers, such as those instigating emotions. And it is this CEO region of your brain, which otherwise maintains your cognitive capacity for ordered, logical thought, that is temporarily ousted each time you enter into the dreaming state of REM sleep.

REM sleep can therefore be considered as a state characterized by strong activation in visual, motor, emotional, and autobiographical memory regions of the brain, yet a relative deactivation in regions that control rational thought. Finally, thanks to MRI, we had our first scientifically grounded, whole-brain visualization of the brain in REM sleep. Coarse and rudimentary as the method was, we entered a new era of understanding the why and the how of REM-sleep dreaming, without relying on idiosyncratic rules or opaque explanations of past dream theories, such as Freud’s.

We could make simple, scientific predictions that could be falsified or supported. For example, after having measured the pattern of brain activity of an individual in REM sleep, we could wake them up and obtain a dream report. But even without that dream report, we should be able to read the brain scans and accurately predict the nature of that person’s dream before they report it to us. If there was minimal motor activity, but a lot of visual and emotional brain activity, then the particular dream should have little movement but be filled with visual objects and scenes and contain strong emotions—and vice versa. We have conducted just such an experiment, and the findings were so: we could predict with confidence the form of someone’s dream—would it be visual, would it be motoric, would it be awash with emotion, would it be completely irrational and bizarre?—before the dreamers themselves reported their dream experience to the research assistant.

As revolutionary as it was to predict the general form of someone’s dream (emotional, visual, motoric, etc.), it left a more fundamental question unanswered: Can we predict the content of someone’s dream—that is, can we predict what an individual is dreaming about (e.g., a car, a woman, food), rather than just the nature of the dream (e.g., is it visual)?

In 2013, a research team in Japan, led by Dr. Yukiyasu Kamitani at the Advanced Telecommunications Research Institute International in Kyoto, found an ingenious way to address the question. They essentially cracked the code of an individual’s dream for the very first time and, in doing so, led us to an ethically uncomfortable place.

Individuals in the experiment consented to the study—an important fact, as we shall see. The results remain preliminary, since they were obtained in just three individuals. But they were highly significant. Also, the researchers focused on the short dreams we all frequently have just at the moment when we are falling asleep, rather than the dreams of REM sleep, though the method will soon be applied to REM sleep.

The scientists placed each participant into an MRI scanner numerous times over the course of several days. Every time the participant fell asleep, the researchers would wait for a short while as they recorded the brain activity, and then wake the person up and obtain a dream report. Then they would let the person fall back to sleep, and repeat the procedure. The researchers continued to do this until they had gathered hundreds of dream reports and corresponding snapshots of brain activity from their participants. An example of one of the dream reports was: “I saw a big bronze statue . . . on a small hill, and below the hill there were houses, streets, and trees.”

Kamitani and his team then distilled all of the dream reports down into twenty core content categories that were most frequent in the dreams of these individuals, such as books, cars, furniture, computers, men, women, and food. To obtain some kind of ground truth of what participants’ brain activity looked like when they actually perceived these types of visual images while awake, the researchers selected real photographs that represented each category (relevant pictures of cars, men, women, furniture, etc.). Participants were then placed back inside the MRI scanner and shown these images while awake as the researchers measured their brain activity again. Then, using these patterns of waking brain activity as a truth template of sorts, Kamitani went pattern-matching in the sea of sleeping brain activity. The concept is somewhat like DNA matching at a crime scene: the forensics team obtains a sample of the victim’s DNA that they use as a template, then go in search of a specific match from among the myriad possible samples.

The scientists were able to predict with significant accuracy the content of participants’ dreams at any one moment in time using just the MRI scans, operating completely blind to the dream reports of the participants. Using the template data from the MRI images, they could tell if you were dreaming of a man or a woman, a dog or a bed, flowers or a knife. They were, in effect, mind reading, or should I say, dream reading. The scientists had turned the MRI machine into a very expensive version of the beautiful handmade dream-catchers that some Native American cultures will hang above their beds in the hopes of ensnaring the dream—and they had succeeded.

The method is far from perfect. It cannot currently determine exactly what man, woman, or car the dreamer is seeing. For example, a recent dream of my own shamelessly featured a stunning 1960s vintage Aston Martin DB4, though you’d never be able to determine that degree of specificity from MRI scans, should I have been a participant in the experiment. You would simply know that I was dreaming of a car rather than, say, a computer or piece of furniture, but not which car it was. Nevertheless, it is a remarkable advance that will only improve to the point of scientists having the clear ability to decode and visualize dreams. We can now begin to learn more about the construction of dreams, and that knowledge may help disorders of the mind in which dreams are deeply problematic, such as trauma nightmares in PTSD patients.

As an individual, rather than a scientist, I must admit to having some vague unease with the idea. Once, our dreams were our own. We got to decide whether or not to share them with others and, if we did, which parts to include and which parts to withhold. Participants in these studies always give their consent. But will the method someday reach beyond science and into the philosophical and ethical realm? There may well be a time in the not-too-distant future where we can accurately “read out” and thus take ownership of a process that few people have volitional control over—the dream.I When this finally happens, and I’m sure it will, do we hold the dreamer responsible for what they dream? Is it fair to judge what it is they are dreaming, since they were not the conscious architect of their dream? But if they were not, then who is? It is a perplexing and uncomfortable issue to face.

THE MEANING AND CONTENT OF DREAMS

MRI studies helped scientists better understand the nature of dreaming, and allowed low-level decoding of dreams. Results of these brain scanning experiments have also led to a prediction about one of the oldest questions in all of humanity, and certainly of sleep: Where do dreams come from?

Before the new science of dreaming, and before Freud’s unsystematic treatment of the topic, dreams came from all manner of sources. The ancient Egyptians believed dreams were sent down from the gods on high. The Greeks shared a similar contention, regarding dreams as visitations from the gods, offering information divine. Aristotle, however, was a notable exception in this regard. Three of the seven topics in his Parva Naturalia (Short Treatises on Nature) addressed the state of slumber: De Somno et Vigilia (On Sleep), De Insomniis (On Dreams), and De Divinatione per Somnum (On Divination in Sleep). Levelheaded as always, Aristotle dismissed the idea of dreams as being heavenly directed, and instead he cleaved strongly to the more self-experienced belief that dreams have their origins in recent waking events.

But it was actually Freud who, in my opinion, made the most remarkable scientific contribution to the field of dream research, one that I feel modern-day neuroscience does not give him sufficient credit for. In his seminal book The Interpretation of Dreams (1899), Freud situated the dream unquestionably within the brain (that is, the mind, as there is arguably no ontological difference between the two) of an individual. That may seem obvious now, even inconsequential, but at the time it was anything but, especially considering the aforementioned past. Freud had single-handedly wrested dreams from the ownership of celestial beings, and from the anatomically unclear location of the soul. In doing so, Freud made dreams a clear domain of what would become neuroscience—that is, the terra firma of the brain. True and inspired was his proposal that dreams emerge from the brain, as it implied that answers could only be found by way of a systematic interrogation of the brain. We must thank Freud for this paradigmatic shift in thinking.

Yet Freud was 50 percent right and 100 percent wrong. Things quickly went downhill from this point, as the theory plunged into a quagmire of unprovability. Simply put, Freud believed that dreams came from unconscious wishes that had not been fulfilled. According to his theory, repressed desires, which he termed the “latent content,” were so powerful and shocking that if they appeared in the dream undisguised, they would wake the dreamer up. To protect the dreamer and his sleep, Freud believed there was a censor, or a filter, within the mind. Repressed wishes would pass through the censor and emerge disguised on the other side. The camouflaged wishes and desires, which Freud described as the “manifest content,” would therefore be unrecognizable to the dreamer, carrying no risk of jolting the sleeping individual awake.

Freud believed that he understood how the censor worked and that, as a result, he could decrypt the disguised dream (manifest content) and reverse-engineer it to reveal the true meaning (latent content, rather like email encryption wherein the message is cloaked with a code). Without the decryption key, the content of the email cannot be read. Freud felt that he had discovered the decryption key to everyone’s dreams, and for many of his affluent Viennese patients, he offered the paid service of removing this disguise and revealing to them the original message content of their dreams.

The problem, however, was the lack of any clear predictions from Freud’s theory. Scientists could not design an experiment that would test any tenets of his theory in order to help support or falsify it. It was Freud’s genius, and his simultaneous downfall. Science could never prove him wrong, which is why Freud continues to cast a long shadow on dream research to this day. But by the very same token, we could never prove the theory right. A theory that cannot be discerned true or false in this way will always be abandoned by science, and that is precisely what happened to Freud and his psychoanalytic practices.

As a concrete example, consider the scientific method of carbon dating, used to determine the age of an organic object like a fossil. To validate the method, scientists would have the same fossil analyzed by several different carbon-dating machines that operated on the same underlying principle. If the method was scientifically robust, these independent machines should all return the same value of the fossil’s age. If they do not, the method must be flawed, as the data is inaccurate and cannot be replicated.

The method of carbon dating was shown by this process to be legitimate. Not so for the Freudian psychoanalytic method of dream interpretation. Researchers have had different Freudian psychoanalysts interpret the same dream of an individual. If the method was scientifically reliable, with clear structured rules and metrics that the therapists could apply, then their respective interpretations of this dream should be the same—or at least have some degree of similarity in the extracted meaning they return. Instead, the psychoanalysts all gave remarkably different interpretations of this same dream, without any statistically significant similarity between them. There was no consistency. You cannot place a “QC”—quality control—sticker on Freudian psychoanalysis.

A cynical criticism of the Freudian psychoanalytic method is therefore one of “the disease of generic-ness.” Rather like horoscopes, the interpretations offered are generalizable, seemingly providing an explanatory fit to any and all things. For example, before describing the criticisms of Freudian theory in my university lectures, I often do the following with my students as a (perhaps cruel) demonstration. I start by asking anyone in the lecture auditorium if they would be willing to share a dream that I will interpret pro bono, on the spot. A few hands will go up. I point to one of the respondents and ask them their name—let’s call this one Kyle. I ask Kyle to tell me his dream. He says:

I was running through an underground parking lot trying to find my car. I don’t know why I was running, but I felt like I really needed to get to my car. I found the car, um, but it wasn’t actually the car I owned but I thought it was my car in the dream. I tried to start the car, but each time I turned the key, nothing happened. Then my cell phone went off loudly and I woke up.

In response, I look intensely and knowingly at Kyle, having been nodding my head throughout his description. I pause, and then say, “I know exactly what your dream is about, Kyle.” Amazed, he (and the rest of the lecture hall) awaits, my answer as though time has ground to a halt. After another long pause, I confidently enunciate the following: “Your dream, Kyle, is about time, and more specifically, about not having enough time to do the things you really want to do in life.” A wave of recognition, almost relief, washes over Kyle’s face, and the rest of the class appear equally convinced.

Then I come clean. “Kyle—I have a confession. No matter what dream anyone ever tells me, I always give them that very same generic response, and it always seems to fit.” Thankfully, Kyle is a good sport and takes this with no ill grace, laughing with the rest of the class. I apologize once again to him. The exercise, however, importantly reveals the dangers of generic interpretations that feel very personal and uniquely individual, yet scientifically hold no specificity whatsoever.

I want to be clear, as this all seems dismissive. I am in no way suggesting that reviewing your dreams yourself, or sharing them with someone else, is a waste of time. On the contrary, I think it is a very helpful thing to do, as dreams do have a function, as we will read about in the next chapter. Indeed, journaling your waking thoughts, feelings, and concerns has a proven mental health benefit, and the same appears true of your dreams. A meaningful, psychologically healthy life is an examined one, as Socrates so often declared. Nevertheless, the psychoanalytic method built on Freudian theory is nonscientific and holds no repeatable, reliable, or systematic power for decoding dreams. This, people must be made aware of.

In actual fact, Freud knew of this limitation. He had the prophetic sensibility to recognize that a day of scientific reckoning would come. The sentiment is neatly encapsulated in his own words when discussing the origin of dreams in The Interpretation of Dreams, where he states: “deeper research will one day trace the path further and discover an organic basis for the mental event.” He knew that an organic (brain) explanation would ultimately reveal the truth of dreams—a truth that his theory lacked.

Indeed, four years before he descended into a nonscientific, psychoanalytic theory of dreaming in 1895, Freud initially tried to construct a scientifically informed, neurobiological explanation of the mind in a work called the Project for a Scientific Psychology. In it are beautiful drawings of neural circuits with connecting synapses that Freud mapped out, trying to understand the workings of the mind while awake and asleep. Unfortunately, the field of neuroscience was still in its infancy at the time. Science was simply not up to the task of deconstructing dreams, and so unscientific postulates such as Freud’s were inevitable. We should not blame him for that, but we should also not accept an unscientific explanation of dreams because of that.

Brain scanning methods have offered the first inklings of just this organic truth about the source of dreams. Since autobiographical memory regions of the brain, including the hippocampus, are so active during REM sleep, we should expect dreaming to contain elements of the individual’s recent experience and perhaps give clues as to the meaning, if any, of dreams: something that Freud elegantly described as “day residue.” It was a clear-cut, testable prediction, which my longtime friend and colleague Robert Stickgold at Harvard University elegantly proved was, in fact, utterly untrue . . . with an important caveat.

Stickgold designed an experiment that would determine the extent to which dreams were a precise replay of our recent waking autobiographical experiences. For two weeks straight, he had twenty-nine healthy young adults keep a detailed log of daytime activities, the events they were engaged in (going to work, meeting specific friends, meals they ate, sports they played, etc.), and their current emotional concerns. In addition, he had them keep dream journals, asking them to write down any recalled dreams that they had when they woke up each morning. He then had external judges systematically compare the reports of the participants’ waking activities with their dream reports, focusing on the degree of similarity of well-defined features, such as locations, actions, objects, characters, themes, and emotions.

Of a total of 299 dream reports that Stickgold collected from these individuals across the fourteen days, a clear rerun of prior waking life events—day residue—was found in just 1 to 2 percent. Dreams are not, therefore, a wholesale replay of our waking lives. We do not simply rewind the video of the day’s recorded experience and relive it at night, projected on the big screen of our cortex. If there is such a thing as “day residue,” there are but a few drops of the stuff in our otherwise arid dreams.

But Stickgold did find a strong and predictive daytime signal in the static of nighttime dream reports: emotions. Between 35 and 55 percent of emotional themes and concerns that participants were having while they were awake during the day powerfully and unambiguously resurfaced in the dreams they were having at night. The commonalities were just as clear to the participants themselves, who gave similarly confident judgments when asked to compare their own dream reports with their waking reports.

If there is a red-thread narrative that runs from our waking lives into our dreaming lives, it is that of emotional concerns. Counter to Freudian assumptions, Stickgold had shown that there is no censor, no veil, no disguise. Dream sources are transparent—clear enough for anyone to identify and recognize without the need for an interpreter.

DO DREAMS HAVE A FUNCTION?

Through a combination of brain activity measures and rigorous experimental testing, we have finally begun to develop a scientific understanding of human dreams: their form, content, and the waking source(s). There is, however, something missing here. None of the studies that I have described so far proves that dreams have any function. REM sleep, from which principal dreams emerge, certainly has many functions, as we have discussed and will continue to discuss. But do dreams themselves, above and beyond REM sleep, actually do anything for us? As a matter of scientific fact, yes, they do.

مشارکت کنندگان در این صفحه

تا کنون فردی در بازسازی این صفحه مشارکت نداشته است.

🖊 شما نیز می‌توانید برای مشارکت در ترجمه‌ی این صفحه یا اصلاح متن انگلیسی، به این لینک مراجعه بفرمایید.