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Dreams, memory, creativity, psychosis, evolutionary survival: It's all connected, at least in the mind of Sue Llewellyn, a researcher at the University of Manchester. Llewellyn is a professor of humanities, which makes her something of an outsider in the realm of sleep-and-memory research. But her grand theory, of sorts, hinges on a notion currently seeing a scientific renaissance: We need to dream to remember. During REM sleep, our minds make sense of seemingly unrelated experiences, Llewellyn argues, thereby sparking a-ha moments that are integral to creative insights. Now, the evidence is moving to her side. One recent study similarly suggested that suppressing the brain activity underlying REM sleep impedes memory formation. We spoke to Llewellyn about her work on REM recall, madness and genius, states of "dedifferentiated" consciousness, and how it all fits together.  

How did you find yourself studying dreams and consciousness?

I’ve always been interested in states of mind and am particularly interested in REM dreaming in the context of scientific discoveries. Nowadays, there’s a fair amount of consensus that sleep is important for memory, but what does that mean for subjective dreaming experience? This is a big generalization, but many [scientists] are only interested in what they call memory reactivation — meaning that what happens today, the brain replays that memory tonight, which happens in slow-wave sleep. But, REM sleep has been problematic in the scientific community because, except for in disorders like PTSD, REM sleep does not replay a whole memory. It appears to replay elements or fragments of memories and integrate them together. So why does that happen and what does it mean for memory processes?

For a long time, others have argued that dreaming is a form of madness and madness is a form of dreaming, but my thing isn’t that REM sleep is a delusional state of madness; it’s that it's a functional state that allows you to see non-obvious patterns between events.

And, as you may know, there’s a fair amount of evidence, and a sort of common-sense notion in the popular consciousness, that psychopathologies [mental disorders] of various kinds and creativity are linked. The idea of geniuses being close to madness, and this sort of thing. Research has shown that people who are very creative also score higher on standardized tests as well as show characteristics of mental disorders. One way of thinking about creativity and mental disorders is that they could both be consequences of states of dedifferentiation, i.e., being in a hybrid state between being awake and REM dreaming.

Could you explain the evolutionary purpose of REM, as you see it? 

In my head, an evolutionary explanation for REM sleep could be that, if your daily survival is uncertain because of predators and competition for food, something that would enhance survival would be a system to help you see "similarity and difference": A berry looks very different from a cow, but both things are food. And a lion looks different from hyena, but both are predators. And REM sleep might be that system, through [enabling] what science calls remote associations. A lot of theory that has shown that REM sleep is good for making non-obvious associations. I could say to you now, “What is the similarity between these words: falling, actor and dust?” (The answer is star.) You'd be more likely to get the answer right if I woke you up during sleep.

woman dreaming city

Here's an example of similarity and difference in a dream, where the association isn't semantic; it's based on experience. Say, [I dream] I'm walking along a street that seems normal, but then at the end of the street, there’s a house. And at first I’m thinking is that this house is covered in a piece of cloth, but then as I get closer, I can see it's covered in sand, and then I feel really scared and the dream wakes me up. Well, in my experience, what links sand, cloth and house? Death. But of course you won’t know that, because you’re not me. In an evolutionary sense, it's good to be able to link together experiences that have some sort of death or threat element to them. That’s not to say that all dreams are like that. Many dreams would be linked by a joyful experience, archetypically finding food or a mate.

So that may have driven REM sleep and the subjective experience of REM dreaming as a mode of linking things that have non-obvious link between them. Whereas in wake, people are much more attuned to logical relationships.

So, then, per your theory, what's the impact of dedifferentiation — getting stuck between REM and wake — on mental functioning?

The basic idea about dedifferentiation is that, when there's a lack of reciprocity between different neurotransmitter systems, a person gets "stuck," to use your word, in neither a dreaming nor waking state of mind. There are transitory types of the "stuck state" that have been linked to creativity. During lucid dreaming, for instance, neurotransmitters present when you are awake increase, so you get a lot of control over the dream action. But it's transitory — you would enter the situation and quickly go back to REM sleep or you’d wake up. Also, there's daydreaming. In the scientific community, they call it the Default Mode Network, and it's acquired a hell of a lot of interest in the past few years. And it's a normal phenomenon.

And creative types are more susceptible to falling into these betwixt states?

Right, my thinking is that creative minds are more likely to enter this zone where they might get stuck. The type of creativity that I and other people are arguing is linked to psychopathologies is what's called "creative insight," which leads to a-ha or eureka moments, and often comes from making non-obvious associations between things. 

So that would mean someone in a slightly dedifferentiated state should be a more creative person because you have access to that state-of-mind that archetypically belongs to REM sleep, which allows you to make associations that other less-creative people wouldn’t be able to make. There’s a whole series of anecdotes about people who wake from the dream state and have an a-ha moment. There was the guy who discovered the chemical structure of benzine, Robert Louis Stevenson, Paul McCartney.  

Anyway, the general thing is that creative people, like the "absent-minded professor," are dedifferentiated to some extent between REM and wake.

But, there are downsides to greater dedifferentiation.

In terms of dedifferentiation, you need to have boundaries between states of consciousness for them to function more or less normally. Perhaps paradoxically, a small degree of dedifferentiation may be beneficial, but a large degree would be quite catastrophic. If the "stuckness" arises spontaneously and fairly persistently, it can start to move from being a transitory phenomenon, as exemplified in daydreaming, to a more progressive and enduring one. And the dangerous thing is when the brain can’t get out of it. 

So a system that helps you see similarity and difference would help you survive. And REM sleep might be that system, through [enabling] what science calls remote associations.

If it progresses, then you will spend more time in loose-associational-type thinking, like what's known as "flight of ideas." If you suddenly started saying, “Oh that’s great, which reminds me of such and such, which is associated with so and so," well If I were a psychiatrist, which I’m not, I would think, hey, flight of ideas. This person is borderline psychotic. To some extent, this flight of ideas is a good thing because it generates the type of remote associational thinking that underlies creative insight, but if it goes too far, then it seeps into psychosis. 

How does dedifferentiation affect sleep — this is where memory comes in, right?

Yes, the other side of the equation would be that, because of the reciprocity between neurotransmitter systems, the wake state would start to intrude on sleep, and REM. And that’s precisely what happens in lucid dreaming, but at some point the intrusion will interfere with your ability to consolidate memories. And in psychopathology, it’s been known for a long time that [mental disorders and psychosis] have a big impact on memory.

What you need for normal memory functioning is to experience all these different stages of consciousness over 24 hours. So, you need to be awake to have sensory experiences. You can be daydreaming some of the time, but not the whole time because you’ve got to do work. Then, during slow-wave sleep, memories of those experiences are strengthened — science calls that consolidation — but also reorganized. And I would say that what's happening in REM is that your brain is able to spot these non-obvious associations between things.

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You mentioned that your theory is testable. How would you test it?

Many studies link creativity with psychopathology and psychopathology with sleep disturbances. Recent work indicates that abnormal sleep and psychopathologies share a common cause. This common cause may be de-differentiation. Work on ADHD, for example, shows that the wake, REM sleep and NREM sleep cycle is labile or de-differentiated. Also, during task performance in wake, the brain patterns of young people with ADHD closely resemble those of healthy humans during REM sleep, [and] this finding may signal de-differentiation. These are just preliminary results in ADHD. To test the theory properly, similar experiments would need to be done across other mental disorders.

A lot of what you've said about REM reminds me of Freud's concept of free association — would you relate it to your dedifferentiation theory?

Yes, well I think that, if you relate a dream to someone else, then free association is one way to get at memory sources. A friend of mine had this lovely dream about a butterfly made out of paper that at the same time was a kite, because in dreams it can be ambiguous as to what things are. So we talked about it over email, and she recalled that the butterfly had two prominent red spots on it, and I asked what they might be related to, and she came up with reasons and identified [relevant] memories. So that’s a sort of free association, but Freud, interestingly, didn’t think that it was linked to memory processes. He thought that free association, or what science now calls loose or remote or non-obvious associations, had to do with disguise and wish fulfillment. 

So how does your work jibe with other research on dream-wake states, memory and schizophrenia?

It’s nothing new to say that schizophrenia may be linked to the intrusion of the dreaming state into wake, but people think that because they assume dreaming is a delusional state, where you have no grasp on reality. Their supposition is that if this delusional state of mind starts to intrude on the wake state, you’ll be in trouble, basically. For a long time, Allan Hobson [a psychiatrist and dream researcher] and others argued that dreaming is a form of madness and madness is a form of dreaming, but my thing isn’t that REM sleep is a delusional state of madness; but that it’s a functional state that allows you to see non-obvious patterns between events. So that’s one difference.

You need to have boundaries between states of consciousness for them to function more or less normally.

The other difference is that people have not thought about the impact of dedifferentiation on the dreaming state. As I mentioned before, it’s important for there to be these different states during sleep because they all have different functions. I think it’s fair to say that there is no consensus in the scientific community about what the impact of REM dreaming is on memory. And a lot of scientists, to make a big generalization, are not interested in REM dreaming. They’re just like, “Okay, it’s subjective. Science can’t go there."