Plasticity is a very broad notion and to explain how plasticity helps us to understand certain aspects of brain function I’m going to briefly discuss with you some clinical examples.
To begin, however, I would like to illustrate how the ways in which a normal individual perceives, understands and remembers the world can become radically altered. In his book “Touching the Rock”, John Hull, an Australian living in England, described how after he became blind in middle age he lost the ability to visualize those with whom he had daily contact, such as members of his family or friends and acquaintances he met after he lost his sight. People he no longer met he could still visualize – until the moment he encountered them once again. He also described how, while he was still living in England, in the period following his loss of sight he was still able to visualize Australia. One day he and his family paid a visit to his former homeland and as soon as he arrived on Australian soil he lost the ability to visualize the country where he had grown up. This is an example of how memory is constantly updated: when he has contact with people or places he used to know visually, his recollections become transformed into a non-visual form. He can only retain visual recollections of people and places with whom and with which he has not had contact since he lost his sight. Memory, then, is dynamic; it is not the matching of a past image with the present, but a process that incorporates past and present into something that is neither the past nor the immediate present, but both in a new form that is our conscious awareness.
To accomplish this task the brain has what we call “maps” and the images, the recollections, our perceptions are the consequence of correlations among these maps. Tor example, the surface of the skin has at least 30 mappings in the brain; one map might have to do with pressure on the skin, another map might have to do with the feeling of heat and cold, another map might have something to do with itching and so on. So there are all kinds of different maps; these are dynamic maps; these maps ‘communicate’ with each oher and with other forms of sensory information. Visual, auditory, tactile information is constantly being correlated.
But these maps – that are also correlated with an internalized, dynamic ‘body schema’ – can become misaligned, damaged, through disease or accident. Take autism, for example, In a recently described case a young Indian boy was unable to stop moving. “I exist only when I move.” In other words, only when he can create a ‘body schema’ through movement is he able to think and perceive the world around.The body schema he creates through movement uses many mappings. The brain needs a body schema to make sense of sensory input, and to help create perceptions and thoughts through correlations of the mapped sensory input. The brain needs the body schema; it is using it as a frame of reference. I’m talking about is an abstract body schema, or image that is inside the brain, that we’re not necessarily actually conscious of. In any event, this autistic child has to constantly move, and I think that one can say that it’s almost characteristic of autism that they lose or they don’t have normal body images. Now there’s another striking characteristic of autism, which relates to something that’s already been brought up here, and that’s synesthesia. It is often seen in autism. The Russian neurologist, Alexandre Luria wrote a little book about the case of a man who had a perfect memory. His perfect memory was pathological; in fact couldn’t do anything apart from performing in freak shows. He also had synesthesia; one sensory modality gets in the way of the other – when he is looking at a house, the sound of a foghorn with block out his view of the house. Synesthesia is an enormous handicap. Well, autistic children have a very peculiar relationship to vision, sound, touch, and so on, if they’re busy watching something and you suddenly start talking to them, they lose what they’re watching. Or if they’re listening to something and you try to attract their visual attention, they lose what they’re listening to. This autistic child that I was just talking about actually says, “You people who are normal are lucky. You can listen and touch things, see things, all at the same time. I have to readjust each time I change the modality.”
Now again, to get back to this mapping story, this is a sign that there’s something wrong with the interconnections between the maps; they’re not in synch; the information is not being correlated. We don’t really understand this process; in a way we are talking figuratively right now, but what is clear is there’s a breakdown in terms of how sensory information in different mappings is integrated. So it’s not as if you can separate yourself from one modality and just talk about another modality. A good example is human speech – language. It’s not as if you can suddenly think without language; it’s there all the time, it’s part of the structure of our knowledge. And even if you think you’re looking silently, without any kind of linguistic backing, it’s part of the process. So it’s illusory to think that these different modalities actually separate themselves out.
Okay, let me turn from autism to now another example of a clinical syndrome. Sorry I have to do these so rapidly. The next case I’d like to describe is the Alien Limb Phenomenon and again it’s related to memory problems – and to the body schema or body image. What happens in some cases of brain damage, usually transient phenomenon lasting a few months, is the patient denies, for example, that his paralyzed arm is his. Not only does the patient reject the arm or the leg, but he has no recollection of ever having used it. So, all his memories are reworked around someone who never had the arm or leg that has become paralyzed. Oliver Sack wrote a famous book in which he notes how his walks along the river before he had developed a paralyzed leg become completely ‘forgotten’ – unimaginable – after his leg becomes paralyzed. So, notice how when the internalized body schema or image is damaged, perception and memory become abnormal. It’s not as if memory is independent of perception or is independent of thought in general; they’re all part of the whole system.
In the case of the alienated arm we can recover normal memory and perception by putting cold water into the inner ear; this causes the liquid in the vestibular canals to start moving, changing the brain’s internalized body schema or image. The patient will then suddenly see his paralyzed arm. And if you say to him “2 minutes ago you told me that wasn’t your arm,” he will say, “I never say such a thing.” And then, when the cold water wears off a few hours later, and you ask him to point to his paralyzed arm he will say, “that’s not arm.” And you say, “Well 2 minutes ago you were saying that was your paralyzed arm.” And once again they’ll say they never said any such thing.
Hence we have in the case of autism and the alien limb a breakdown of the body image; and with the breakdown of the body image, memory and perception are profoundly altered. Body image is essential as a frame of reference for the brain. If you want to see how essential it is, even in normal individuals, all one has to do is put one in an extrasensory deprivation tank. If you have no light, and you’re put in a bath of water that is practically the same temperature as your body, within about half an hour you’ll start hallucinating, and you will be incapable of carrying on a coherent conversation. If you’re not in contact with the outside world, you can’t function. Language too depends on the other. There was no such thing an individual developing language all alone.
Let me know turn to an example, which I think might have been discussed in an earlier symposium organized by Warren on the Phantom Limb. This will contrast with the two cases that I just described – Autism and the Alien Limb. Now what happens in a Phantom Limb, is we have a “normal brain.” There is no neurological damage. If you lose, let’s say a hand or an arm, the brain will compensate for that loss by creating a ‘phantom’. Why? Because in fact you need a normal internalized body image for the brain to function normally. It may be that children who have been born without an arm or leg also develop phantoms. And, they didn’t lose a limb; it’s almost as if it’s an innate part of the brain structure to create a normal body image. In any event, in the case of a loss of an arm or a leg or whatever, that loss is compensated for by the creation of a phantom. You have the feeling that there is something there, that there is something attached to the upper arm. The point is that brain needs a more or less normal body image to function normally. And people with phantom limbs more or less function normally. Ok what’s bizarre about that is that I know full well if I have a phantom limb that it’s a phantom. I know it’s not there. I feel it and yet I know it doesn’t actually exist. The consequence of this is an incoherence the brain mappings – and this inchoherence gives rise to enormous pain.
Pain…what do we mean by pain? Pain is not in the body; it’s obviously invented by the brain. Physicians used all kinds of treatments to rid patients of phantom limb pain; they tried to cut nerves, use anesthetics and so on. Nothing worked. Now there have been a number of spectacular examples of how the pain has been eliminated. V.S. Ramachandran in California used a mirror in a box that covered the phantom limb. The patient watched the reflection or his normal hand in the mirror. He moved his good hand and the reflected image of his hand (covering the phantom) gave him the illusion his phantom hand was real. The phantom pain disappeared. Another version of this treatment was done in France using a video of the normal hand instead of a mirror reflection of the hand. And about 2/3 of the patients are “cured” by this and actually the French have a very interesting explanation of this. The point is that what seems to be happening is the visual system is so powerful, even though the patient’s brain knows full it is being fooled by looking at a video or looking in a mirror, it is so overwhelmed by the visual system, that the brain re-sets the mappings creating, from the brain’s point of view a coherence, and hence eliminating the pain. So, to show you how much pain is just an invention of the brain. The visual system of the brain is so powerful that it can “redo” the body mappings, and as a consequence it can eliminate the pain.
Let me close this rapid tour of neurology with one other case, first reported in 1923 by a French neurologist, J. Capgras. It is the story of a woman who one day went to the police to report that she was surrounded by a bunch of impostors. Her husband was a fake husband, he looked like her husband, but she wasn’t fooled; her children, too were imposters. They had all been substituted for; she suspected her real husband and real children had been kidnapped. Her own identity, too, had been stolen. She had been born extremely rich, her real name was Rio de Branco, Someone had stolen her real identity, her real name at birth and ever since then she had been hanging out with imposters. She was put in an asylum.There too she complained that everyone around her was fake, and they were all stealing her identity; she let them get away with it. A lot of criminals were coming and stealing things from her, pretending they were her. Similar cases have been described since Capgras. In one reported case a young man told his father, ” Don’t think you’re kidding me, you’re not my father.” And then he called up his father and warned him there was an someone impersonating him. His father – whose voice he recognized – tried to convince him that the person he had seen was really he himself, but to no avail.
Here’s a case of the visual system in fact fooling us. Why? Now, the main problem, Capgras claimed, is a loss of an emotional reaction. That is, if I see somebody I know well I’m going to have an emotional reaction to them, and if I have no capability of reacting emotionally, they’re going to appear strange to me. Capgras says they are familiar but they’re strange; they don’t look right. Today neurologists repeat this story about emotions as if it is all there is to the Capgras syndrom. If you go back to the original case you will find other problemst that are very interesting. Capgras’ patient explains why she thinks her husband is an impostor. She says, “It’s all in the details. His mustache changes from day to day. His earlobes change from day to day. The cut of his hair changes from day to day.” One of the characteristics of patients with the Capgras syndrome is that they have bad facial recognition. They look at the details. It is characteristics, by the way, of autism as well. If you take a photograph of a face and turn it upside-down, normal people cannot recognize the face. Autists have no trouble recognizing the face. They focus in on the details, so it doesn’t matter if the photo is upside down. They have no gestalt of the overall face. And apparently, a similar thing is happening in Capgras. The Capgras patient focuses on details; and because he or she is focusing in on details, he or she notices that the details are constantly changing (mustache, hair etc.), and indeed he thinks he is looking at an impostor.
Finally, notice how these neurological problems are all interrelated. They are concerned with body schema, in other words, body image or embodiment. What happens in Capgras? Well, what happens in Capgras’ original description, the woman is constantly taking notes on her body. One of the complaints is that her body is constantly changing. Every time she’s writing it down she says, “I don’t even know if I am who I am. I have to constantly ask people who I am.” There’s really a loss of identity. And, “the only way I can have any idea what’s happening to me is I write it down. But you know, when I write it down I see everyday it’s changing, which means they are manipulating my body. They’re doing something to me.”
To sum up this mini course, let me say the brain creates what we see, hear and imagine. It is not a sponge. One important constraint on the inventions (creations) or the brain is the body schema, or body image. And one of the consequences of the breakdown of the normal body image is abnormal perception and memory; and you actually get a breakdown of any kind of logic, it’s not as if they all don’t go together. Consequently, given these constraints, we should recognize the enormous fragility of memory, perception and thought in general.