Now she breathes deeper, yawns, her body trembles briefly. She sleeps. He continues with the story, without changing the rhythm or the volume or the cadence. The sound spreads like before and strikes his daughter’s eardrum, displacing hair cells and leading the ion current to activate the neurons of her auditory cortex. Everything is the same, but she is no longer creating the story in her mind. She no longer repeats the words in a whisper. Or does she? Where do the words we hear in our sleep go to?
Tristán Bekinschtein decided to take on this question, creating a simple, boring, routine experiment that was perfect for falling asleep. A reciting of words. A childhood game. It’s not the typical image we have of a laboratory experiment; in fact, it takes place in a bed where someone is listening to a soporific, repetitive voice: elephant, chair, table, squirrel, ostrich… Each time the name of an animal is heard, they must move their right hand; if it is a piece of furniture, their left. It is easy and hypnotic. Soon the responses come intermittently. Sometimes they are extremely slow and finally they disappear. The person’s breathing is deeper and the electroencephalogram shows a synchronous state, meaning that they are already asleep. The words continue, as if through inertia, like in the father’s story as he presumes that his daughter is listening in her sleep.
Through observing the mark left by voices in the transitions to sleep, Tristán discovered that in the sleeping brain these voices turn into words, and those words acquire meaning. What’s more, the brain continues playing the same game; the cerebral region that controls the right hand activates each time an animal is mentioned, and the region that controls the left hand activates each time a piece of furniture is mentioned, just as was established in the rules of the waking game.
Consciousness has an on/off switch. During sleep, in a coma state or under anaesthesia, the switch turns off and so does consciousness. Some cases are drastic, and consciousness turns off unambiguously. At other times, like in the transition to sleep, it fades out gradually and intermittently. When the switch is turned on, the cerebral activity associated with states of consciousness assumes different forms; we saw, for example, that the consciousness of very young children operates on a different time scale, and that schizophrenics are unable to recognize that they are the owners of the voices in their heads, creating a distortion of the narrative.
Nocturnal elephants
We can think of dreams as fertile ground for mental simulation that does not involve the body. This disconnection between the mind and the body is literal; when we dream there is an inhibition of the motor neurons through which the brain controls and governs the muscles, generating a brain chemistry that is very distinct from our waking one.
Normally there is a synchronicity between the return to a waking state–characterized by organized conscious thought–and cerebral contact with the body. But sometimes those two processes get out of synch and we wake up without having regained chemical contact with our bodies. This is called sleep paralysis and it is experienced by between 10 and 20 per cent of the population. It can be agonizing: complete paralysis with full lucidity. Yet after a few minutes it goes away on its own, and the brain is once again in contact with the body. And the opposite can also happen, when the brain does not disconnect from the muscles during sleep, and the dreamer will act out their dream.*
What does the brain do as we dream? The first thing we should know is that the brain does not turn off while we sleep. Actually, the brain never stops; if it shuts off, our life ends. When we are sleeping, the brain is carrying out sustained activity, both throughout the REM (rapid eye movement) phase during which we dream, and throughout slow wave sleep, which is deeper and typically without dreams.
The myth that the brain shuts off at night is tied to the idea that sleeping is a waste of time. We recognize the merits of our own and others’ lives through the achievements we make while awake–the jobs, friends, relationships–but there is no merit in being a good dreamer.*
Sleep is a reparative state, during which a cleaning programme is carried out, eliminating biological waste and residue from the cerebral metabolism. In effect, the brain, over the course of the night, takes out the rubbish. This relatively recent biological discovery is in line with the common, intuitive idea that sleep is the functional flipside of our waking lives and without it, besides being tired, we get sick.
Beyond this restorative role, key facets of the cognitive apparatus are set in motion while we are sleeping. For example, during one of the first phases of sleep–slow wave–memory is consolidated. So after a few hours of sleep or even a quick nap, we remember better what we’ve learned over the course of the day. And that is not only due to the rest we’ve had. In fact, it is largely due to an active process that goes on while we are sleeping. By taking a closer look through experiments on the cellular and molecular level, we now know that during this phase of sleep specific connections between neurons in the hippocampus and the cerebral cortex that store and stabilize memory are reinforced. These changes begin during diurnal experience and are consolidated during sleep. This mechanism is so precise that, during sleep, it can recap exactly some neuronal patterns activated during the day. This is a contemporary physiological version of one of Freud’s main ideas about sleep, the remains of the day. Those who are fans of naps could also argue that a long stretch of sleep at night is not necessary for this to be carried out. Short naps also function to consolidate memory.
During slow wave sleep, cerebral activity increases and decreases, forming repeating cycles over a period of little more than a second. In other words, the brain activity pulses oscillate in a clear, slow, defined rhythm. The more pronounced this oscillating wave of activity is, the more effective the memory consolidation. Can this oscillation be induced from outside the brain of the sleeper and thus improve their memory?
A person’s rhythm of cerebral activity during sleep can be measured with an electroencephalogram. Then the neuronal activity of the sleeper can be increased, by making them hear sounds that are synchronized to the rhythm of their brain.
This experiment, carried out by the German neuroscientist Jan Born, began during the day with a list of new words that had to be remembered. Born discovered that people who later, during the night, listened to tones synchronized with the rhythm of their own cerebral activity would remember many more words the next day than those people who were not stimulated or were stimulated in a non-synchronized way.
This means that we can improve the memory of learning begun while awake by manipulating, in a relatively simple way, a cerebral mechanism that consolidates learning during sleep. However, the fantasy of putting on headphones at night and waking up speaking a new language that we’ve never studied continues to be just a fantasy.*
The uroboros plot
Memory consolidation occurs during a phase known as slow wave, in which cerebral activity is monotonous and repetitive. But this is not the sole register of cerebral activity throughout sleep. In the REM phase, brain activity is much more complex and similar to activity while awake. In fact, during the REM period, the sleeper’s subjective experience becomes conscious in the form of dreams.
When someone wakes up in the middle of the REM cycle, they almost always have a vivid memory of the content of their dreams. However, this does not happen when we wake up in other phases of sleep. From the point of view of our subjective experience, consciousness during sleep is similar to waking consciousness. In dreams we can fly, talk to people who are no longer alive, walk through a garden of half-buried train carriages, and even obey traffic laws. Dream images are vivid and intense. But, strangely, we lose the notion that we are the authors of the stories told in our dreams. We experience what we dream as if it were a true description of reality and not a figment of our imaginations.
The main difference between dream and waking consciousness is control. During sleep, as in schizophrenia, we do not detect our authorship of that virtual world. The bizarre nature of dreams is such that the brain does not recogniz
e them for what they are: hallucinations.
While slow wave sleep is a state in which waking neuronal activity is repeated, during REM sleep more variable neuronal patterns are generated, with the ability to recombine pre-existing patterns of neural activity. Is this perhaps a metaphor for what happens on the cognitive plane? Is REM sleep a state conducive to creating new ideas and connecting elements of thought that were disconnected during the day? Are dreams a creative thought factory?
The history of human culture is filled with stories of revolutionary ideas originating from dreams. One of the most famous is that of August Kekulé, who discovered the structure of benzene, a ring of six carbon atoms. During a celebration of this great landmark in the history of chemistry, Kekulé revealed the secret behind his discovery. After failing miserably for years, the solution finally came to him as he dreamed of an uroboros, a serpent biting his own tail, making a ring shape. Something similar happened to Paul McCartney, who woke up in his bedroom on Wimpole Street with the melody to ‘Yesterday’ in his head. For days, McCartney searched in record stores and asked his friends for clues as to the origin of the melody, because he supposed that the dream had come from something he had listened to.
We can already anticipate the problem with these anecdotes: the conscious narrative is tinged with fiction. The same is true for memory, since we can recall with full conviction an episode that never happened. Even more extraordinary is that it is possible to implant a memory that a person then believes to be authentic. And invoking creativity during sleep can be a trick and a trap.
Perhaps with that hunch in mind, a chemist, John Wotiz, meticulously reconstructed the history of the discovery of the structure of benzene. And he found out that the French chemist Auguste Laurent, ten years before Kekulé’s dream, had already explained that benzene was a ring of carbon atoms. Wotiz’s thesis is that the invocation of the dream was part of Kekulé’s strategy to hide his intellectual theft. What Paul McCartney honestly feared–that his dream was the expression of information gathered while awake–was deliberately manipulated by Kekulé.
But beyond the possible intrigue, can creative thought be shown to derive from dreams in an objective way that is not contaminated by the inevitable human distortions? That is what our dream hero, Jan Born, set out to discover.
The key to the experiment was finding an objective and precise way to measure creativity. In order to do that, Born set out a problem that could be solved in a slow but effective way or an original and simple one, by changing the perspective of the approach. The participants worked on that problem for a long while. Then, some slept and others just rested. Later, they all went back to their problem-solving. And the simple but conclusive result was that the creative solution was much more likely to appear after sleeping on it. Which is to say that part of the creative process is expressed while we sleep.
Jan Born’s experiment shows us that sleep is an element in the creative process but not the only one. Despite a contemporary loss of prestige for drills and practice, the rote, ordered side of creativity is also important. Dreaming–like other forms of disordered thought–can help in the induction process of an original idea, but only after a firm base of great knowledge of the field in which we aspire to be creative has been established. We see this in the McCartney case; he had deep-rooted knowledge of the material and was later able to improvise in dreams. The same is true in Born’s experiment. Night-time is the space of a creative process only after a day of arduous, methodical work that lays the foundations for creativity in dreams.*
That is how, in short, the thought factory works at full efficiency during the night shift. Sleep is a very rich, heterogeneous state of mental activity that allows us to understand how consciousness works. There is a first phase in which consciousness fades, not haphazardly but towards a place of great synchronization that activates a memory consolidation process. Then there is a second phase that is physiologically similar to the waking state but generates a more disordered pattern of cerebral activity. During this process an ingredient of creative thought is expressed, gestating new combinations and possibilities. All of this is accompanied by an oneiric narrative that can combine terror, eroticism and confusion. A full dream state. But are we really dreaming as we sleep? Or is it just one of our brain’s many illusions?
Deciphering dreams
We have all had the experience of waking up thinking that we were only asleep for a few seconds, and actually hours have passed. Or the opposite, a few seconds of sleep sometimes seem to have lasted an eternity. As we sleep, time flows in an odd way. In fact, it’s possible that the dream itself was just the illusion of a story constructed as we woke up.
Today we are able to resolve this mystery by observing traces of thought in the brain in real time. Just as we can investigate the thought processes of vegetative patients and babies, and subliminal processing based on cerebral activity, we can use similar tools to decipher our thoughts during dreams.
One way of decoding thought based on cerebral activity is dividing the visual cortex into a grid, as if each cell were a pixel in the sensor of a digital camera. Based on that we can reconstruct what is in the mind in the form of images or videos. Using this technique, Jack Gallant was able to re-create a strikingly clear film, by observing only the brain activity of the person watching the film.
This allowed a Japanese scientist, Yukiyasu Kamitani, to develop a kind of oneiric planetarium. His team reconstructed the plot of dreams based on the cerebral activity of the dreamers. Once they were awake, it was proven that the conjectures they’d based on their patterns of cerebral activity coincided with what the participants said they had dreamed.
They were narratives of this type: ‘I dreamed I was in a bakery. I grabbed a baguette and went out on to the street, where there was someone taking a photo’; ‘I saw a large bronze statue on a small hill. Below it were homes, streets, and trees.’ Each one of these dream fragments was decoded on the basis of cerebral activity. In this demonstration the conceptual skeleton of dreams was deciphered, but not their visual qualities, their glimmering and their shadows. Reconstructing dreams in high definition and Technicolor is still being worked on in the experimental kitchen.
Daydreams
During sleep, the brain does not shut off but is actually in a highly active state, carrying out vital functions for a proper working of the cognitive apparatus. But it also happens that when we are working, driving, talking to someone or reading, our brain frequently unmoors from reality and creates its own thoughts. We often spend a large part of the day talking to ourselves. This is daydreaming, the expression of a state similar to dreams in form and content but while we are wide awake.
Daydreaming has a very clear neuronal correlate. While we are awake, the brain organizes itself into two functional networks that, to a certain extent, alternate. The first we are already familiar with: it includes the frontal cortex (which functions as the control tower), the parietal cortex (which establishes and links routines, controls space, the body and attention) and the thalamus (which functions as a traffic distribution centre). These nodes are the nucleus of a mode of active cerebral functioning that is focused and concentrated on a particular task.
When dreaming invades our waking state, this frontoparietal network deactivates and another group of brain structures takes control, near the plane that separates the two hemispheres. This network includes the medial temporal lobe, a structure linked to memory, which could be the fuel behind our daydreams. And also the posterior cingulate, which is highly connected to other regions of the brain and coordinates daydreaming just as the prefrontal cortex does when the focus is on the outer world. This system of brain regions is called the default mode network, a name which reflects how it was discovered.
When it became possible to explore human brain functioning in real time with functional magnetic resonance imaging (fMRI), the first studies compared cerebral activity while someone was doing something–a mental calculation, playing chess,
remembering words, talking, expressing emotion–with another state in which they were doing nothing. In the mid-nineties, Marcus Raichle discovered that when a person is doing these tasks some regions activate while others deactivate. With one important distinction, the brain regions that activate vary depending on the task, while the ones that deactivate are always the same. Raichle understood that this reflected two important principles: (1) there is no such thing as a state in which our brain does nothing, and (2) the state in which thought wanders at its own volition is coordinated by a precise system which Raichle called the default network.
The structure of the brain’s default network is almost diametrically opposed to the structure of the executive control network, reflecting certain antonymy between these two systems. The awake brain constantly alternates between a state with its focus on the outer world and another governed by daydreams.
Are daydreams just wasted time, some sort of cerebral distraction? Or maybe, like nocturnal dreams, they have a good reason for existing in the framework of our way of thinking, discovering and remembering.*
The way our thoughts sometimes drift as we read is fertile territory for the study of daydreaming. We have all had the experience of suddenly realizing we don’t have the faintest idea of what we’ve been reading over the last three pages. We were occupied with a parallel story that pushed the contents of our reading to the margins of our consciousness.
A careful recording of eye movements shows that during daydreams we continue to scan word by word as we read, and to slow down on the longer words. But at the same time, during that daydreaming, activity in the prefrontal cortex lessens and the default system activates, which makes the information from the text we’re reading fail to access the privileged gardens of consciousness. Which is why we go back with the sensation that we have to reread the entire lost fragment again, as if it were the first reading. But that is not the case. This new reading builds on the previous one, done amidst dreams.
The Secret Life of the Mind Page 14
