In Our Time - Dreams

Episode Date: March 4, 2004

Melvyn Bragg and guests discuss the interpretation of dreams. Over a hundred years ago, Sigmund Freud declared confidently, “The interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind”. He was writing in his famous volume, The Interpretation of Dreams and his ideas made a huge impact on the century that was to follow. However, despite the cultural influence of his work, there is still no agreement in neuroscience as to the function or mechanism of dreaming; this is partly because for much of the century the prevailing wisdom was that there was no meaning to dreams at all.What is the mental circuitry that creates our dreams? If they have no meaning, why do we dream them? And why is the tide turning with neuroscientists starting to find reasons to take dreams seriously again?With Professor V S Ramachandran, Director of the Center for Brain and Cognition at the University of California, San Diego; Mark Solms, Professor of Neuropsychology at the University of Cape Town; Martin Conway, Professor of Psychology at the University of Durham.

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or wherever you get your pods. Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uk, forward slash radio four. I hope you enjoy the program. Hello, over 100 years ago, Sigmund Freud declared confidently, quote,

The interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind, unquote. He was writing in The Interpretation of Dreams, and his ideas made a huge impact on the century that was to follow. However, despite the cultural influence of his work, there's still no agreement in neuroscience as to the function or mechanism of dreaming. This is partly because, for much of the century, despite Freud, the prevailing neuroscientific wisdom was that there was no meaning to dreams at all. What is the mental circuitry that creates our dreams? If they have no meaning, why do we dream them?

And is the tight turning with neuroscientists starting to find reasons to take dreams seriously again? With me to discuss the neuroscience of dreams is Mark Solmes, Professor of Neuropsychology, at the University of Cape Town. Martin Conway, Professor of Psychology at Durham University, and last year's re-letcher, Professor V.S. Ramachandran from the University of California, San Diego, who's here to launch the Winchester Festival of Art and the Mind tomorrow. In the 20th century, to rather amplify what I said in that introduction,

Professor Ramachandran, what did neurologists in the last century think about dreams? Well, in a way, it's very embarrassing because dreams are such an important part of our mental life. They're so extremely vivid and in many ways enrich our mental lives. And yet we know nothing about them and what causes them, what's going on in the brain. And therefore, in thinking about this, it seems to me that if you take the broad view, there are at least three possibilities. One view is dreams are just noise, just froth. There is some kind of random activity in the brain even when you're asleep for some other reason.

and maybe there's no purpose, no biological purpose, and dreams are a manifestation of that, and you just stream together images at random, and there's no point trying to analyze them. That was a prevailing view. The second view is that maybe the neural mechanisms in the brain that generate the dream have some biological function, such as consolidation of memories

or some of the type of housekeeping, and dreams are the surface manifestation of that activity, but the dreams themselves don't have any meaning. And the third extreme view, of course, is a Freudian view, that know that dreams are in fact are the royal road to the unconscious, and they themselves may have an evolutionary function. And I think it's embarrassing that after 100 years of research on dreams, both physiological and waking people up during dreams, we still don't really know which of those three possibilities is correct. The research concentrated recently from the middle of the century on what is called REM, rapid eye movement sleep. This was first defined in the mid-50s by the American physiologist Claytman and Demand. Can you tell us what they observed and why REM became so important?

Well, I think it was very exciting because to find any obvious physiological, biological correlate of some mental phenomena like dreams was exciting at that time. And when they noticed that the eyes were rapidly moving, and this happened in bursts at specific periods during the sleep cycle. and they wondered, they were curious, what would happen if you woke up somebody during those periods, and it turned out that most of the time they were dreaming. And this led to the view that maybe REM sleeps are, REM periods are synonymous with dreaming. This suggested that, in fact, to me at least, it suggests that, you know,

you don't have something in biology unless it has a function, evolutionary function. We don't know whether dreams have a function, but at least the periods when you're dreaming, something is going on very interesting in the brain. which may have a function. What is generating this REM, this rapid eye movement sleep zone, these moments when the eyes are active, these little bursts through sleep, what's activated them as far as neurologists are concerned? Well, they're mainly ascending influences from the brain stem.

This is the stalk on which the brain sits, and there's influences ascending from the ponds up to innervating vast regions of the cortex, but some regions more than other regions. And it used to be thought they were randomly active, parts of the cortex. And maybe the brain or the person then strings together these random kaleidoscopic images into some quasi-meaningful sequences, as you do when you're watching, say, MTV or any random sequence. Mark Psalms, why was he thought the dreams were a product?

We can unpick a lot of been said there. Why was you thought the dreams were a product of REM sleep, that you almost you had these perturbations in your sleep at 90-minute intervals or something like that. And it was then that the dreams came. Those two were totally synonymous. Why was that thought to be the case? Well, it was a reasonable hypothesis to begin with. When those American physiologists that you mentioned first observed this startling state of heightened activation during sleep, they called it paradoxical sleep

before the term REM sleep caught on. And that referred to the paradox that you're asleep and yet in a heightened, at least from a neurophysiological point of view, in an activated aroused state. So you're aroused in all sorts of ways. You breathe more heavily, you become agitated, the erogenous zones are excited.

You're in a heightened state, although your muscle, you're semi-paralyzed at sleep. So there's this strange juxtaposition going on. Yes, muscle turn drops, but there are dramatic changes in brain activity as measured on EEG, brain activity looks almost like waking brain activity during these REM phases. Then there are changes in respiration, changes in heart rate, changes as you mentioned in one's genitals too, genital engorgement. So from a physiological point of view, you appear to be aroused.

And the natural assumption, I think, was, well, we have something similar happening in our mental experience. during sleep, there's another paradox which is that mentally, although you're asleep, you have these moments, these periods when you're in consciously a very active state. I was just going to say that the assumption was therefore that these two things might be one

and the same. And on testing that hypothesis by waking people up during REM versus non-REM sleep, that's indeed what they found, that the dreams occurred during the REM. So that led to the understandable conflation of these two things,

given the evidence that was available then, it looked as if they were indeed one and the same. You don't believe that dreams and REM sleep, R-E-M-R-E-M-R-A-M-Movement sleep, are synonymous. You don't believe that that conjunction is helpful or accurate anymore. Indeed, it's not helpful. It's not accurate. It's not helpful. It's positively misleading.

When Rama mentioned earlier, how embarrassing it is, that after all of this time, we still don't know what the function of dreaming is, I think that that's largely due to the conflation of dreams with REM sleep. People who wanted to test hypotheses about what the function of dreaming is did it by manipulating REM sleep variables. Dreams do not occur exclusively during REM sleep. Although when you wake somebody up during REM, you have approximately 80% chance of getting them to report a dream to you.

If you wake people up during non-REM sleep, you have a 10% chance. Can I co-grossom? Yeah, go ahead. Martin, so what were they saying most of them in the 20th century? Before we move on further as to whether they have any meanings or what can you gain, I've used the word dreams as noise and dreams as froth. So what were neurologists, what conclusions, if any, Ramos, embarrassing that didn't come to many conclusions at all,

but what were they gathering about this? very important subject that everybody knows about people, talk about, has an impact on everybody listening and in that. What were the neurologists adding to this? I think the fact of the matter is that following Freud's great work, the interpretation of dreams, basically nothing of theoretical interest happened on the dreaming front, really until present time. And what I think has become why that knowledge to be is a re-evaluation of Freud and his thinking. That's not to say, that Freud's ideas are accepted without a reservation or 100%.

But it's clear that he, probably alone, had the best theoretical ideas on the function and nature dreams. But first of all, why was he so heavily challenged? Can you just explain why he was so... Well, this is interesting. Because a lot of people still have it in that culture that there was quite a lot in Freud. He was getting...

But by scientists, he was considered a nebulous subject. He was very dismissed. People didn't go into a dream, as it were, research, because they thought, well, there's nothing there really. So why was it so heavily challenged? I think it's very interesting actually. I think there's a whole kind of philosophy of knowledge that we need to understand here to understand the lack of acceptance of Freud's ideas.

I mean, essential to Freud's thinking is that human cognition is motivated. There are purposes, there are goals, all of it has meaning. But the prevailing view, I think, at the turn of the 20th century, beginning of the 20th century, was a move more into a much, more mechanistic kind of thinking about the brain and about the mind. And that type of thinking was a thinking that eschewed ideas and motivation. It was a type of thinking that wanted to put forward mechanisms and processes, but didn't do so in a way in which they were motivated. So we could have, for example, and Freud himself contributed this a very good description of reading, for example.

But why would you read something in the first place? Was a question that was left and answered. So we could have a good description of the brain areas, we have a good idea of the cognitive processes and mechanisms lying behind reading, but there's no model of why you would read in the first place. And that is

clearly a major gap in our thinking about the human mind. And it's a gap that Freud attempted to fill, I think. Well, I think there's also another very important reason and this also tells you something about the history of ideas and the way people think. And that is, Freud, attempted to, even though he was a genius in many ways, he attempted to substitute intuition for

experiments. And this is one reason that scientists, neuroscientists and other scientists, in fact, psychologists were reluctant to accept his ideas because he would say, here is a plausible scenario, maybe dreams of this, maybe it has to do with wish fulfillment. It seems intuitively likely that it has something to do with wish fulfillment because you often do this in your dreams. And that was unfortunately not well received by scientists, or fortunately was not well received by scientists. And that explains why, even after 100 years, people are not receptive to Freudian ideas.

But that doesn't mean he's wrong. It just means that we need more experimental work on dreams. For example, a simple phenomenon like what's called assimilation. And that is, we all have the experience if somebody throws water on you when you're in a REM episode, and then you wake up. And you have this vivid impression of having been in a rain, in a storm, rainstorm.

and the duration seems like for several hours you were in the rainstorm and then you woke up. So you have simulated this physical event into your dreams called incorporation. And the question is, why does this happen? That's a simple example of an experiment that's been done on dreams. And there are dozens of experiments that could be done on dreams that haven't been done. And here, Dr. Soames have started doing things like that, and there's more that needs to be done. Let's get back to the mechanism of it, though, for a moment.

Mark Psalms, can you just say where you think dreams are generated from them? Well, this goes back to the question of why Freud's thought was, Freud's theories about dreaming were so roundly rejected in the 20th century. It's because when REM sleep was discovered, there are things about REM sleep itself, which are incompatible with Freud's theory, just in terms of its own phenomenology, for example, that it happens automatically every 90 minutes.

nothing to do with your childhood, nothing to do with your relationship with your parents. You're going to have REM sleep every 90 minutes, and during REM sleep you're going to dream. When it was discovered what part of the brain generates this state, REM sleep, that is, it became more, Freud's theory became all the more implausible. Because REM sleep is generated by a small group of neurons,

a set of three groups of neurons, in the pontine brainstem. That is sort of the second lowest level of the brain. You go from spinal cord to medulla oblongata and then to pons. It's reptilian in its phylogeny. It's an ancient, ancient structure. It's got nothing. Well, I like that.

It's not attractive to... It's not attractive to a Mardin of Freudian dream theory because there's nothing about that part of the brain that could possibly generate the mental gymnastics that Freud thought were causal in the generation of dreams. This is a basic little switch in the ponds. It switches REM sleep on and it switches REM sleep off. And the only contribution that that level of the brain makes to mental life is it generates consciousness, a level of awareness, a background sort of quantitative.

The lights are on. but the content, the internal workings of the mind, have nothing to do with that part of the brain. Can you tell us your view, can you give us your view of how dreams are generated? Yes, it speaks directly to this issue. We now have large numbers of patients in whom dreaming has stopped completely due to circumscribed damage to very particular brain structures. Broadly speaking, there are two structures,

of them is in the parietal lobes, which is a sort of spatial cognitive area and crucial for generating mental imagery and the like. Therefore, no great surprise that if there should be damage there, you wouldn't be able to generate that class of mental imagery we call dreams. Far more interesting is the second group. They have damage in the white matter of the ventrameasial quadrant of the frontal lobes. Now, that's a bit of a mouthful, but basically it's just behind the eyes, above the nose, behind the nose, the eyes on both sides of the brain. Terribly interesting is the fact that that very same part of the brain used to be targeted by the old psychosurgeons when they did the prefrontal leukotomies.

They severed those very same fibres deliberately in order to prevent hallucinations and delusions in psychotic patients. And the operation indeed was able to control those symptoms. And no surprise if you think about what hallucinations and delusions have in common with dreams, it's in the essence of dreams, that there are states of hallucination and delusion. And damage to that part of the brain leads to a cessation of dreaming, and simultaneously REM sleep is preserved. This is one of the strongest bits of evidence for the dissociation of dreaming from REM sleep. If you have damage to the part of the brain that generates REM sleep,

you carry on dreaming. If you have damage to this part of the brain, you no longer dream, but REM sleep continues. And the heart of the brain, you know, the heart of the brain, of the problem that we're discussing now is what is the function of dreams? Why do we dream? What is the essential causal mechanism of dreams too? So I think we need to ask ourselves, what does this part of the brain do?

Because clearly it's absolutely crucial to everything that dreaming is about. And what it does is motivational. It's a motivational structure. It's a structure which neurobiologists call it the seeking system or the wanting system or the reward system. It has everything to do with what drives us to do what we do to remember what we remember and so on.

So let's take that on. We've got a motivation. So we're coming back to Freud in a way. Well, we're all known or no, no. So can you just take that on? I think it's important to ask, starting from scratch, starting from first principles, what might the functions of dreaming be? And one can speculate on this.

One possibility is that during wakefulness, you're encountering a bewildering array of sensory inputs, and you're trying to weave a coherent scheme, a story about yourself, your place in the scheme of things, about the events in your daily life, there's a sense of narrative, a sense of being a person in a narrative. And to do this, you can't accumulate everything you encounter, and you have to do a little bit of censorship, you have to brush things under the carpet, to impose coherence and continuity to your life. There are unpleasant memories which are disturbing to your self-esteem, disturbing to your ego.

So here I sound very Freudian, but what may be going on is you may be doing some kind of function such as organizing these memories and, you know, creating a coherent perspective, trying out scenarios which would be too disturbing to try out in ordinary wakefulness. There is no evidence for this because people have done the right experiments, and it's hard to say how you test it. Very Martin, would you like to take one, what Mark said as well? Well, the function of dreams, basically. Motivational aspects of dreams. Yeah. From my perspective, I think that dreams and memories have actually quite a close relationship. And if you think about remembering, remembering is an act in which you turn attention inwards towards mental representations which are created from your long-term memory. You downgrade or attenuate attention to the external world.

So remembering is an act that kind of hijacks cognitive processing and focuses it inwards. Dreams are perhaps the paramount case of attention being focused inwards because you're asleep and there's nowhere else for attention to focus, basically. And I think what's going on here is that if we think about our motivations and our goals, we don't really have much in the way of conscious insight into them. We could say why are we all here today and we can all give various answers to that. But there wouldn't be that satisfactory in accounting a kind of causal way for why we're here. Now it might be that goals, as they're implemented in the human brain, are processes which we can't have access to. We can experience their endpoints. We can perhaps aid their beginning.

But once they're running, they're like programs that you can't easily alter. And it might be that dreams are somehow some aspect of processing that's related to these goals, which otherwise aren't really open to attention and consciousness. And maybe, I mean, it's all very nebulous, and we just don't know enough about dreams to be able to give, a profoundly definitive answer. As soon as you sort of get away from the neurology, you're back in the sort of foothills of Freud, aren't you? Well, not entirely.

How does, I mean, can we, well, in a sense, can I just come to this, what might seem rather an irrelevant point? If mammals do, if we know that mammals dream, all mammals dream, how does that square, what has been said by, like, how does that square what these two have been saying, which is very much to do the individual personality, the individual's autobiography, and so and so, but that's one thing.

Second thing, if dreams are so important to us, why don't we dream and we're awake? And this is a third thing, but I'll come back to that later. Well, first of all, some of my best non-human friends are mammals. But the truth is we don't know whether mammals dream or not. We cannot know about the subjective experience of non-human mammals. But they have the REM effect, don't that? That's the point, you see.

Again, we keep on falling into that error. We assume because they have REM, they're dreaming. And that simply isn't a sustainable view anymore. So, I mean, as I say, I'm happy to think that my little puppies and so on are dreaming, it's a lovely idea, but we just cannot know for sure. All that we know is that they have REM sleep. Rem sleep activates instinctual circuitry. If we go back to the neurology, as you said earlier, you know, let's try and stick to the neurological evidence that we have, and we do have quite a bit. During REM sleep, the brain is activated in a very specific pattern. There are certain structures,

which are strikingly deactivated. For example, the lateral convexity of the frontal lobes. The part of the brain that has most to do with our normal, rational, goal-oriented behavior, our self-reflection, our insight, the insights that Martin was referring to earlier are, as it were, offline during REM sleep, which is when most dreams occur. By stark contrast, the instinctual parts of the brain, the circuitry that underpins our... are most basic urges and basic behavioral stereotypes that go with those urges, you know, like fight or flight responses, sexual behaviors and the like, attraction to things that taste nice and repulsion from things that don't and so on.

Those parts of the brain are very active during REM sleep, which is when most of our dreams occur, including this motivational circuit that I mentioned earlier. It's strikingly active. Now, if you stimulate that circuit in any mammal, including a human, what you get is the equivalent, depending on the species, of foraging behavior. Cocaine, by the way, for the listeners you want to know what happens when you stimulate that structure, cocaine stimulates it more than anything. It makes you very active, interested, interactive, positively disposed, expecting something good from the environment, and you go out there and you seek it, you look for it. Now imagine during sleep those circuits are activated. This is when most dreams occur. And if those circuits are damaged, you can't dream.

Can I come into it another way there on me here? We've talked about Martin was talking about memory, so this is to both of you there. As far as I can understand from general reading, sleeps are very ill-remembered, part of remembrance. So if they have this, why is that? Why do we remember them so poorly? Well, this hearts back to the question of, again, what the functions of dreaming might be and why you dream only when you're asleep and why you don't remember them very vividly when you're awake.

All of that's pointing to the fact that if this bizarre imagery were to surface during wakefulness, it would lead to instability and mental instability and chaos. So you're allowed to try out these bizarre scenarios in the quote-unquote semi-conscious state, when you're paralyzed completely. There are messages going down into the spinal cord making you completely quadriplegic when you're dreaming and when you're asleep. So you have a system here

where you can do an internal virtual reality simulation of various scenarios without having to pay the penalty actually trying it out in the real world. If you're dreaming that you're flying and actually went out and started flapping your arms, you'd be dead. So it's a way of preventing you

from actually enacting those bizarre scenarios at the same time allowing you to try it out in your head. So this is a very speculative idea and it's quite close to the sort of thing that Freud had in mind. But the main problem is it's not easy to think of ways to test it. This is what we're all struggling with. Can I just add a bit to that and build on something Melvin just said, which is the idea

that we don't dream when at times when we're not asleep, but we do. I mean, I think a lot of our mental life is about dreaming, daydreaming. I'm taking a two and a half hour train journey home shortly and I'll be sitting on that train and daydreaming. It's a total different quality though. you don't have the emotional charge. Well, I just want to raise that question about whether it is of a totally different quality. I mean, I think when you fall into a fairly intense daydream,

I think it has qualities that are really rather similar to night dreams. And perhaps these executive processes, which Mark was alluding to, and he was talking about the deactivation of the frontal lobes during sleep, maybe one of their functions when they're active, is to stop us daydreaming, is to keep us focused on what we're doing, not to fall into some wishful fantasy about the way that we'd like the world to be. rather to concentrate on writing that paper and making your contribution. And so I think there is a tension there.

And I think these frontal circuits are kind of in a tension with more primitive drive circuits and trying to coordinate them into coherent activation, which I think is what Roma was saying as well. But there does seem to me as an observer to the three of you that there still has to be a leap between what you've been saying, Mark, about the circuitries and the neurons. And then you say, well, and then when you say, start to talk more generally and more in ways that people listening are more used to hearing.

You say this is an abilus, we can't prove we don't know anything about this. The qualifications entering instantly. There seems to be quite a gap there still. I think it's because you're having a programme on a topic that is very much in flux in neuroscience. We've only recently discovered conclusively that dreaming and REM sleep are two separate things. So now we're able to do the appropriate experiments on the appropriate things. If we want to find out what the function of dreams is, then we don't look at REM sleep. We look at dreaming proper. And we have a clinical population that enables us to test any hypothesis about the function of dreams

because we have a group of people not small. It's fairly common. Patients with damage to specific brain structures can no longer dream. So anything that we want to attribute to dreaming as being the functional contribution that dreams make to mental life should be missing, at least reduced in these patients. and there you test any hypothesis. But do you think that from these patients you are going to arrive at conclusions not dissimilar from those arrived at by Freud or in the same umbrella description?

I think as far as Freud's concerned, what we can say at this point in this evolving field is, first of all, Freud's theory is far more plausible than we thought it was. It doesn't mean we've proven it to be correct, but it's much more compatible with what we do know about the brain mechanisms of dreaming than we thought. there are a number of alternative interpretations that can be put on the data that we've got so far but I think that the one thing the simplest thing we can say which I hope my colleagues would agree with me about is that during dreaming sleep the basic emotional motivational instinctual circuitry of the brain is far more active than the reflective cognitive rational part of the brain

And this goes a long way already to explaining some of the most obvious phenomenal features of dream experience. We're getting towards you on now, but all sorts of theories being thrown at now. The dreams are a form of, as a private expression of mental disorder that is contained and controlled. As it worked, to use an old-fashioned word, you can go insane in safety in your dream. Is that just another theory? Do you have any? I think that there's a lot of truth in that. I think it's not that you can, it's that you do.

What we understand of the neurochemistry of dreams and the neuroanatomy of dreams has striking overlaps with what we know of the neurochemistry and anatomy of schizophrenia of schizophrenia and anatomy of schizophrenia of psychotic, positive psychotic symptoms like hallucinations and delusions. They share a lot. Thank you all very much. Indeed. Next week we'll be talking about the Gnors, so thanks for listening. We hope you've enjoyed this Radio 4 podcast.

You can find hundreds of other programs about history, science and philosophy at BBC.com.com.uk forward slash radio four.