THE dream world of humans is still not completely understood, but several stunning breakthroughs in neuroscience give us a more precise understanding of what happens to our brains when we sleep.
Sigmund Freud called dream interpretation the “royal road" to the unconscious, and his book The Interpretation of Dreams, published in 1899, was one of the building blocks of modern psychoanalytic theory. Freud believed dreams were a gateway into the workings of the unconscious mind and a form of wish fulfilment during sleep (and being Freud, he said these arose from our sexual urges).
His theories have since been countered by scientific research that suggests dreams are more likely to be about processing waking thoughts and, therefore, a reflection of the conscious mind rather than the unconscious.
How brainwaves work
Professor Mark Solms is the director of neuropsychology at the Neuroscience Institute of the University of Cape Town and Groote Schuur Hospital. He is also a trained psychologist. He has been studying dreaming for 30 years and is famous for having discovered the brain mechanisms of dreaming.
“Beyond psychoanalysis and perhaps even within psychoanalysis, today, there is not much consensus about dreams," he says. “There's no consensus regarding the theoretical question of why we dream, but if you look at the dreaming brain, which we can do with PET imaging, you can see what is happening in the brain while you're dreaming. And we know that the prefrontal cortex is deactivated in dreaming sleep, while the limbic system is hyperactivated."
The prefrontal cortex is the part of the brain that operates slowly, logically and precisely, while the limbic system works fast and is dominated by emotion and impulse.
“We used to think that dreams happen during REM [rapid eye movement] sleep and that, therefore, the brain mechanisms for generating REM sleep are the mechanisms for generating dreams. We now know this is incorrect," says Solms.
“It is now definitively proven that dreams occur pretty frequently outside of REM sleep. About a quarter of our dreams occur outside of the REM phase of sleep. It's not accurate to portray the brain mechanisms of REM as the same thing as the brain mechanisms of dreaming; they co-occur and correlate, but they're not the same."
Andrew Huberman is a professor of neurobiology and ophthalmology at Stanford Medicine. He explains that sleep physiology explains how and why we dream.
“Regardless of how long we sleep, sleep is generally broken into 90-minute cycles. Early in the night, these comprise of slow-wave sleep and less REM sleep. As these cycles progress through the night, we have more and more REM sleep. And this will be regardless of whether your sleep is broken through waking up or having to go to the bathroom.
“REM sleep and non-REM sleep have distinctly different roles in learning and unlearning different types of information," he says.
“Slow-wave sleep is characterised by a particular pattern of brain activity in which the brain is metabolically active with these big sweeping waves of neural activity. Studies show that learning and detail learning occur in slow-wave sleep at the beginning of the night. [And that] this sleep phase is essential for laying down knowledge in our neural circuits. For instance, in certain sports, any coordinated movement like playing the piano or learning synchronised dance movements. Or the spelling of words, and also the recovery from exercise.
“While you have periods of REM sleep throughout the night, you have more and more of it as you move towards morning.
“REM sleep was discovered in the 50s when researchers observed that people's eyes were moving under their closed eyelids … very erratically in all different directions. There are a couple of things happening. In this phase, in contrast to slow-wave sleep, the neurotransmitter serotonin is essentially absent. Serotonin creates feelings of bliss, wellbeing and calmness. In addition, norepinephrine, the neurotransmitter involved in movement and alertness, is absent. It's one of the only times epinephrine is at zero activity within our systems."
This has several implications for the sorts of dreaming that occur during REM sleep. First, during REM sleep we experience a kind of paralysis called atonia. We also experience what we are dreaming about as a kind of hallucination. So, in REM, our eyes move while the rest of our body is paralysed — and we hallucinate. Epinephrine is also the chemical signature of fear and anxiety released by our adrenal glands when we experience something frightening. Adrenaline and epinephrine are equivalent molecules, but as we now know, they are absent from our bodies in this phase.
“So, we are hallucinating and having these outrageous experiences in our minds, but the chemical associated with fear, panic and anxiety is not available," says Huberman. “That turns out to be very important as it allows us to experience both replays of things that did occur and elaborate contortions of things that didn't happen, without fear or anxiety.
“And that … is very important for adjusting our emotional relationship to challenging things that happened while we were awake. Those challenging things can sometimes be social, or just having been working very hard, or being worried about an upcoming event. Sometimes, people, for instance, report dreams where they find themselves late to an exam, naked in public, or in some situation that would be troubling. And that almost certainly occurs during REM sleep. So we have this incredible period of sleep in which our experience of emotionally laden events is disassociated — chemically blocked — from the actual emotion."
Dreaming is learning
Professor Ken Paller, director of the cognitive neuroscience programme at Northwestern University, says dreaming is essential for consolidating knowledge.
“We know that when humans learn information, it doesn't necessarily stick immediately. And we know that you have to rehearse information. [There is] a prolonged process we call consolidation, where the information we learned integrates with other things we know. We have evidence from multiple sources that happens during slow-wave sleep because evidence shows that slow waves make efficient communication between different brain regions possible. And when you consolidate memories during slow-wave sleep, you wake up without knowing that you were doing that."
Harvard psychologist and world-renowned dream researcher Deirdre Barrett says dreaming has a function beyond the biological and physiological.
“I have no trouble with the neurological types who say that dreaming is determined because of some biological need, but I think there are layers here. We spend so much time in states where our brains make looser associations and can hallucinate neat visual imagery … and we use that to enhance creativity around visual-spatial things to help us think outside the box when we're stuck in our waking thoughts. Dreams may provide insights that our waking minds may be unable to access due to our everyday rational thinking."
During the Covid-19 pandemic, Barrett collected 9,000 dreams from 3,700 people, analysing them and highlighting the significance of dreams in her research.
“Dreams are essentially a form of thinking in a different brain state, with different prefrontal and visual cortex activation levels. Dreaming occurs across all stages of sleep, but the most interesting vocalisations happen during REM sleep, where people can say many sentences, tell jokes, laugh, and even respond meaningfully."
In her book The Committee of Sleep, she describes how dreams have played a role in inspiring artists and inventors, leading to the creation of beautiful works of art and practical tools. Dreams provide visual-spatial insights that go beyond regular imagination.
So what about vivid nightmares? Huberman says they probably occur during slow-wave sleep because the lack of norepinephrine during REM sleep makes it unlikely that you can experience intense, fearful memories.
“Maybe you were experiencing something troubling in the daytime and repeating that experience in your sleep. Epinephrine is unavailable; therefore, the brain circuits associated with fear and anxiety are shut off, and you can process those events without those emotions. Those dreams tend to be vivid and have a lot of detail. But what can happen is that suddenly, you wake up, and there's a surge of adrenaline or epinephrine and those emotions can now be felt and connected to that experience."
Knowing that we process emotions during REM sleep explains why we experience a particular emotional state when we have too little of it, says Huberman.
“The lack of REM sleep tends to make people emotionally irritable; it tends to make us feel as if the little things are the big things. It’s very clear from laboratory studies where people have been deprived selectively of REM sleep that our emotionality tends to get a little bit unhinged without enough of it."
During REM sleep, we integrate “general themes of things and locations and how they fit together”; he calls this “meaning”.
“During the day, we're experiencing all sorts of things. Meaning is how we individually piece together the relevance of one thing to the next. REM sleep is where we establish the emotional load but where we also start discarding all the irrelevant meanings. And if you think about emotionality, a lot of over-emotionality, or catastrophising, is about seeing problems everywhere. REM sleep has this amazing capacity to eliminate the meanings that don't matter.
“The point of being emotionally stable, reasonable, rational human beings is about the capacity to eliminate certain connections between things. So REM sleep seems to be where we uncouple the potential for emotionality between various experiences. [And because it happens without] the chemical epinephrine that triggers anxiety or fear, REM sleep almost certainly plays a vital role in uncoupling emotion from experiences. It is a form of self-induced therapy that we go into each night."
An influential 20th-century psychoanalyst, Erich Fromm, said: “Both dreams and myths are important communications from ourselves to ourselves. If we do not understand the language in which they are written, we miss a great deal of what we know and tell ourselves in those hours when we are not busy manipulating the outside world."
The research and findings of modern neuroscience are not as far from the world of psychology as once thought.
As Solms says, “the idea that dreams have meaning is not at odds with the latest scientific findings regarding brainwave activity during sleep.[We now know that] dreams are a motivated state, not just random firings of neurons in your brain while you're sleeping. It's what your brain does about your needs while sleeping. Dreams are not senseless absurdities. They have meaning in terms of your life."
♦ VWB ♦
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