In Our Time - Pain

Episode Date: July 22, 1999

Melvyn Bragg and guests discuss pain; something of which everyone has an individual experience. What causes it, how do we cope with it, what mechanisms are involved, what is the traditional view of pain and how is that being challenged today? Do we experience pain in the same way and how is emotional pain different from physical pain? What can our experience of pain tell us about ourselves and human consciousness? Is each individual human experience unique or are there experiences we can say apply across all of human consciousness? Is science a blunt instrument for examining subjective experience?With Patrick Wall, Professor of Physiology at St Thomas’ Hospital, London and author of Pain: The Science of Suffering; Semir Zeki, Professor of Neurobiology at University College, London.

This BBC podcast is supported by ads outside the UK. 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 4. I hope you enjoy the program. Hello, I'm joined today by two neurologists, Patrick Wall and Semir Zeki, to look at pain and subjective experience.

What can our experience of pain tell us about ourselves and about human consciousness? Is each individual human experience unique or other experiences we say can apply across all of human consciousness. Patrick Wall is a world expert on the nature of pain and Professor of Physiology at St. Thomas's Hospital London. He's the co-originator with Ron Melsack of the influential gate control theory of pain,

a reversal of the idea that there's a straightforward relationship between pain and injury. His books include Defeating Pain, The Challenge of Pain, and a new book out this week called Simply Pain, The Science of Suffering. Later this year, he'll be awarded. awarded a Queen's Medal by the Royal Society. Professor Semeazeki is a renowned neurobiologist

and professor of neurobiology at University College London. In the 1970s, he pioneered the work on vision, which caused a revolution in our understanding of the brain by showing that the brain separated different aspects of vision, form, motion and colour. Since then, he's examined many different aspects of the brain relating to human consciousness and art. He's written about his discoveries in,

a vision of the brain, and he has a new book out in the autumn called Inner Vision, Art and the Brain. Patrick Wall, there's a classical theory of pain. Could you explain as simply as you can what that was and why and how your theory differs from it? So the classical theory goes certainly back to Descartes and is perhaps what people feel intuitively is what's going on inside them, is the idea that you've got a hardwired fixed system in you, something like a burglar alarm or a fire alarm, which is absolutely specialized in producing pain as a result of some stimulus.

Now, that turns out to be simply wrong. Pain is part of the spectrum of our sensations and it can appear and disappear, not with this reliability of a fire alarm, but depending on many circumstances, what the general situation is, what your attitude is, what the injury is. All of these have profound effects on how much pain you feel. So when you say it goes back to Descartes, can you just examine that a little more for us? Descartes, who was, of course, the great inventor of dualism,

proposed and has a spectacular diagram that shows someone with a foot in a flame, and leading from the foot is a representation of a nerve, which he knew about, leading straight from the foot to the brain and to what he believed was a common-sense center. that was sensation for Descartes, which was then inspected by something entirely different, the mind, so that you had a frontier there between a relatively mechanical process that produced a pure sensation, and the mind that decided whether or not to pay attention to it and adding all the decorations of feeling. Samia Zaki, do you find that explanation given by Patrick Orle, is that a call? with your analogous investigations into the brain?

I think a very similar picture was put forward in vision with the pure sensation of vision, as it was called, being elaborated by one area of the brain, and then another part of the brain interpreting that pure sensation. I think these were actually up to a point influenced by philosophical speculations. Probably would include Descartes among the philosophers. Can I ask you what is the purpose of pain,

and I hope you'll excuse me if I use a quote from yourself referring, which refers to yourself, you say, for instance, cancer pain is worse than useless. You're suffering yourself from cancer. So why do you say cancer pain is worse than useless? That will surprise a lot of people listening. And could you tell us what you think is the purpose of pain? To begin with, we are evolved animals and evolved challenged by certain historical problems in how to remain alive.

Now, unfortunately, cancer was not one of them, and so the origin of my statement there is that pain as a signal for the onset of cancer is terrible. It's hopeless. It's not an early warning for cancer. And then the pain of the cancer starts up and continues and continues and continues when you've got the message. Why keep it up? So I think this is a design fault in us, if you like, or that we simply were not involved to cope with cancer. It's often said that pain is all in the mind.

What's your reaction to that? I hate it. I hate it when doctors say that to patients. There was a recent survey of American amputees, both military and civil. 70% of them had had doctors say precisely that. There's nothing wrong with you. It's all in the mind. Now, that is a wicked thing to say.

Amongst other things, it simply shifts the responsibility from the doctor to the patient and says it's your fault. You're inventing this. Now, I don't know of any invention. I think I have once in my life seen a patient that I thought was genuinely symbolically inventing a pain. I think there are a large number of pains, many low back pains, which are very, very common, where the best of medical diagnosis cannot find anything wrong in the back.

Now, there's then a traditional pathology-driven medicine that says all pains, originate from damaged tissue. If I can't find some damaged tissue, then the person must be inventing this. I would say maybe the doctor's method of diagnosis isn't all that hot, and that is particularly because of the sort of work that is now appearing and that I've been involved in

where the source of the pain may have started in the periphery, but can be instability in the central nervous system itself. And that doesn't mean in the head. It means a breakdown of control in spinal cord and places like that. Stanley, how would you react to this all in the mind? Well, I think, Patrick, we're going too far. From your book, it is partly in the mind anyway. I mean, the influence of set and culture and previous experience of learning.

So it is partly in the mind. But I'm quite interested when you say to me that we are, dominated by the cortex, as indeed you're right we are. Would you experience much pain without the cortex? Can you just explain to this? I would like everybody to up the speed on this because it's really important for a lot of people.

Just can you briskly tell people how vital the cortex is? Well, the cortex is the most highly developed layer on top of the brain. It is the part of the nervous system which we're told gives us our higher faculties of learning, of intelligence,

of experiencing and so on. it is vastly expanded into the human brain. Indeed, the characteristic of the human brain is a huge, huge amount of cerebral cortex. I would agree with you, of course, that we have been rather dominated by the study of the cortex, but could you have someone experiencing pain without a cortex? Fine. So just to go over that again, of course I agree with you that pain is in the mind. My objection is dualistic doctors who are,

trying to essentially blame the patient for their pain and not say that this is something with a pathological medical cause. But now getting on to your question of the cortex, if you take vision as an example, it is sadly true that destruction of the back of the cortex really produces absolute total blindness, and that's it. and it's a justification for saying

at least these pathways are crucial for vision. No such pathway has been discovered for pain. And of course it's been looked for massively. Because of people with intractable pain, why not take out the piece of cortex which they are using in order to generate pain? It's been tried. And of course it's tried by accident,

injuries and strokes and so on. You do not get analgesis, and this is, you modify the pain, and this is one of the reasons for saying that deeper structures, thalamus, brainstem, midbrain and so on, are evidently sufficient, unfortunately, to produce an agonizing pain. But is it not true to say that every time people in pain have been imaged through within the scanner, there has been some cortical activity, although not in any given specific place, as it would be envisioned. Exactly. But one of the absolutely crucial events preceding feeling pain is to pay attention. Now, there are certainly images of attention-switching mechanisms in cortex.

I agree with you. Of course, cortex lights up in people in pain. and part of that and the most consistent part of that, I think, is to do with the attention mechanism. You have also said, but, injury may occur without pain and pain without injury. Could you develop, use examples from soldiers and so on? Injury without pain. And here I think it's fascinating that this not only occurs actually quite commonly in humans, but also in animals.

A famous example of that was Henbit broke a leg while running in the Derby and accelerated out of the pack and won the Derby on a broken leg. Of course, there are a mass of experiences of people being injured and not feeling pain at the time. Battlefield, sports fields are a very common source of this, actually everyday life. And the characteristic is that people are doing something which is dominating their attention. It may be scoring a goal or finishing the race.

These are not heroic non-pain complaining people. These are people who, under those circumstances, in those circumstances, didn't create pain. Let's talk about pain without injury, Patrick. Now, I've given one example, which is some 70, 80. percent of the acute low back pains, awful pains, huge number of people have experienced, the most intense diagnosis fails to find injury in the sense of damaged tissue. Now, that could be either we are not good enough at making a diagnosis of damaged tissue. Perhaps there is some damaged tissue, but we can't see it.

The alternative is that we have an unstable nervous system. which sometimes starts generating false signals. But we don't yet have good enough diagnostic tools to see if that's the case. This pain without injury, for quite a few people, there are a great deal of emotional pain, real pain, the loss of someone, someone that you loved very much, various forms of loss, and people experience this as pain. Now, how does that fit in?

I think we're really talking in analogies. say this is closest to being personally injured. And it is. So our nervous system is making an analogy with physical pain. That's right. But people do have broken hearts, don't they? And so how does, can you explain how this turns into that, as it were? I think we humans are clever people, but we are classifiers. And especially in our language, we want to say, what word do I have, the best expresses this and we put this in the class of pain. Pains associated with injury have many, many different classes. Why not extend that outside yourself and include other people? You know, there's also the injury happening many years before the pain sets in.

And a very good example which actually also tells us something about pain being in the mind is the pain which people who become blind often have many, not often, but sometimes have, many years after they have become blind, and they see colors. These colors are golden or purple usually, and they are extremely painful, but painful in a way that you and I have not experienced. And actually, they are almost driven to suicide. Now, the interesting thing about those patients, of whom I've seen about 5 or 6, is that they have always written to me, He's showered me with letters of gratitude. And I ask them, I have not done anything for you. I can't do anything for you. They say, but you have believed us.

Because all we've been told, this is in the mind. But the interesting thing is that this pain occurs many, many years after the blindness is set in. So that's another example of pain without injury. You're talking about that in the phantom limb in your book. So here really is an example of a phantom sensation. All of us have experienced a phantom, which is really, very educational. Go to the dentist, give a local anesthetic block, you have a numb lip, come out of the dentist. That lip isn't a hole in your face. There are no nerve impulses

coming from that lip at all, and yet you feel a swollen lip, an attraction getting lip, and you keep on poking it. That's a phantom lip. And what has happened is the brain has said to itself, I normally receive a... trickle of messages from the lip. I'm not getting the news. Pay attention. Something is curious there. Now, what happens then is that the brain says,

I'm still not getting the news. Maybe I should increase the gain. And the phantom becomes more and more intense. And these translations of the brain's reaction, which are quite mechanical and reasonably well-understand. in which excitability builds up, can build up to the stage where these cells simply start screaming by themselves, announcing this missing limb,

and then you have a painful phantom limb, which is an invention of the brain, a way in which it is attempting to restore normality so that you can say it's in the mind, doesn't help the patient at all. No, no, right. and doesn't lead to any possible therapy, because therapies are on their way,

where the signal which the brain recognizes as missing, perhaps you could replace it, so the brain said, okay, I'm getting the news, I won't make a phantom. Is a phantom painful, usually? Initially no, but then a high percentage of amputees have a pain.

which simply continues for the rest of their life. What does the placebo effect have in your thinking about pain? Here is a hugely important practical issue that someone in pain who believes and expects that they have been given a successful therapy response, although the actual drug has no physiological effect at all. And yet the response is great. What's that about?

Very powerful, very common. I think what the person has done is to themselves take or volunteer to take a therapy. And they have done something which they believe will abolish the pain, and it goes. That's what you call taking control of your pain. Yes, by a belief. But all this really suggests. It seems to me you're a good recruit to the cortical involvement in pain. We're going to motor planning.

You plan, of course, for all sorts of things, and many of them are not painful. Some of the motor planning that you must do to avoid pain, such as removing your finger from pain, is also the same motor planning that you use for other situations. So the brain must be able to distinguish very precisely between two motor plans which have common features, the withdrawal of the finger. but one of which is associated with pain, the other one is not.

Dear Samir, you must read the book. But I notice you lurched straight back to the cortex and neglecting this remarkable pathway, all of which is modifiable from the point of injury up to and including the cortex and down to the motor system. We talked about the placebo effect, people taking something which has no seems to have no intrinsic value

but there's great value for them and there's a culture effect too isn't it you use the example of Keeney and women in your book and we know about Christianity one of the things that Christianity said was basically learn to suffer in silence and our own English tradition gained a great deal

especially in war from the stiff upper lip which in war was extremely valuable indeed. Can you talk about culture and kind. Well, I make a big distinction between private suffering and public display. Obviously, public display is tremendously culture.

It's a method of communication. So the Labor Ward in Oslo is very different from the Labor Ward in Naples because of the social expectation. One is rather quiet. The other's rather noisy.

And people in Naples would be worried if they saw a quiet mother. So, but now the question is, what about the individual, is the private suffering? Is that really exempt from the culture in which they live? And the answer is surely no. So these placebos are themselves tremendously culture-bound. Placebos, in terms of medicine, especially injections, don't work on young children.

children. You have to have grown to learn that people in white coats with syringes are good and help you. At the age of five, you don't know that, and you don't have a placebo effect to that. You do have a placebo effect, and mummy will kiss it better. What do you say about this business of a culture behaving? I referred to Kenyan women chatting quite casually while their children were born as I learned in your book. A later investigation found out that they were suffering as much as every woman suffers when they have children, but they said the custom of our people is not to show it. What does that say to you about external objectives and subjective experience of pain?

There is no metric of pain because partly of these cultural influences, for example, if we were to take some other sensation, let us take a favorite example of mine, Calivision, you can actually specify the stimulus in considerable detail and you can get them to match. and so you know that you've got some kind of guides to what they are perceiving, but in pain there isn't that. And the fact that the thresholds can vary a great deal,

I cannot come and tell you, look, I feel intensity of pain X. Is that not right? Quite. To go to the cultural influence, to give another example in Vision, the Amazon Indians can apparently distinguish 200 different kinds of green, because they need to do that to distinguish various fruit. In a way, it's similar, is it not to your cultural influence? The absence of a metric for pain must be a tremendous problem.

Yes. Again, because the unpleasantness is built-in and dominating aspect of pain, which it isn't in terms of color, let us say. So that I don't think it's at all surprising that a sensation which is associated with an individual, imperative action to stop this, to get rid of it, to help, to cure, which is clearly not the case in Colovision, which can be looked at as a neutral event, dissected, analyzed, in which you could train people so they all do more or less the same thing like being able to read. That doesn't apply to pain. Now, I do agree with you that for the treatment of pain or for a person's attitude to their own pain, they do need.

to shift gears away from this sense of an automatic register that they are sitting inside their heads reading a dial on the wall that says pain. That's wrong. But the consequence you see, the practical consequence from what you tell us is that the doctor says, look, I have treated you for your pain and you're now getting to be a tiresome irritation. Go away. And this is not at all, of course, the patient's point of view who is actually generally suffering the pain. And part of the reason why the doctor says that is that he's got a different concept of pain. And you say that's quite wrong. Absolutely.

And particularly this action that you say, where you dismiss the patient because you don't believe them. That is absolutely unacceptable. How would you go about modifying this? If you were to be made the Secretary of State for Pain. He is the Secretary. He is the Secretary of State for Pain. Well, I certainly have no easy answers.

And the fascinating thing is that a very large number of therapies do work in some people, including placebo. And I think that needs exploration. And the first clue, which I believe I don't have an answer to, but needs intense study, is this question of attention. It is clear that whatever may be going on, some crucial step. occurs in which attention becomes riveted on this. Many of the treatments are in fact an attempt to shift attention. Shift attention from the pain. Exactly.

And their distraction, counter-stimulation, etc. But it doesn't work for everyone. No. And therefore, I think we need to be able to study much better this question of how to unlock attention other than the rather easy ways of learning distractions and even some things given rather pretentious names of

cognitive behavioral therapy which are really teaching people how to shift attention. Can you, if you're feeling pain in your shoulder, can you feel pain of the same intensity at the same time, for example, in your toe? Absolutely not. It's a basis of folk therapy that counter-stimulation works,

and it's an aspect of attention in every respect. You can only pay attention to one thing at a time. A lot of people would argue with that, but I think if you follow it through, it's true. And therefore, Pat, you're only conscious of one thing at a time. Exactly.

Do you think that pain is available to a solution through neurobiological methods? It will be found to rest in physical causes? Well, yes. And in terms of practical matters, I've already discussed that in terms of the phantom limb pain, which I think is due to a cascade of events starting with the amputation

or the cutting of nerves, which then sweeps forward. Those are understandable transfer of information of messages from one part of the nervous system to another, which is reacted by becoming hyper-excitable, we should be on the edge of being able to detect the message and put in a counter. What are Patrick's views on pain in this book, as it were, illuminating your area, which is much more to do with vision and culture and art. Did you find similarities of the way of approach? Oh, tremendous.

Tremendous similarities. I think that we are both in agreement on the fact that these are constructions of the brain, that we've been doing a disservice to our subject by carrying on with the separation of sensations from perception. And I agree with you also that in Vision 2, motor planning is a very, very intimate part of the seeing process. What you're essentially saying in a visual term that you cannot separate seeing from understanding.

Seeing is understanding. And that I agree with absolutely is. It's been very instructive to see how similar, in its basic organization, of a sensory system the brain is. Finally, Patrick, do you think that by addressing this in the way that you suggest, people will have their suffering alleviated if doctors take into account the new propositions,

the new discoveries you've made? That would be overstating it, but at an absolute minimum, pain is unpleasant, produces tension, produces anxiety, and prolonged anxiety produces depression, and particularly if you simply don't know what's going on. And I wrote this book in the hope that people would have some feeling of what is going on and feel less tense, less anxious about it.

Well, thank you very much, Patrick Wall and Sam Ezeki. The book we've been talking about is called Pain, The Signs of Suffering by Patrick Wall. This is the last in the present series. I'll be back after the summer break in September for a new series of In Our Time. Thank you for listening. We hope you've enjoyed this Radio 4 podcast. You can find hundreds of other programmes about history, science and philosophy at BBC.com.ukuk forward slash radio 4.