Phantoms in the Brain: Probing the Mysteries of the Human Mind by V. S. Ramachandran, Sandra Blakeslee
Authors: V. S. Ramachandran, Sandra Blakeslee
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paralyzed, say, from a stroke. Why do people lose the use of an arm after a stroke? When a blood vessel supplying the brain gets clogged, the fibers that extend from the front part of the brain down to the spinal cord are deprived of oxygen and sustain damage, leaving the arm paralyzed. But in the early stages of a stroke, the brain swells, temporarily causing some nerves to die off but leaving others simply stunned and
"off−line," so to speak. During this time, when the arm is nonfunctional, the brain receives visual feedback:
"Nope, the arm is not moving." After the swelling subsides, it's possible that the patient's brain is stuck with a form of learned paralysis. Could the mirror contraption be used to overcome at least that component of the paralysis that is due to learning? (Obviously there is nothing one can do with mirrors to restore paralysis caused by actual destruction of fibers.)
But before we could implement this kind of novel therapy for stroke patients, we needed to ensure that the effect is more than a mere temporary illusion of movement in the phantom. (Recall that when Philip closed his eyes, the sense of movement in his phantom disappeared. )
What if the patient were to practice with the box in order to receive continuous visual feedback for several days? Is it conceivable that the brain would "unlearn" its perception of damage and that movements would be permanently restored?
I went back the next day and asked Philip, "Are you willing to take this device home and practice with it?"
"Sure," said Philip. "I'd love to take it home. I find it very exciting that I can move my arm again, even if only momentarily."
So Philip took the mirror home. A week later I telephoned him. "What's happening?"
"Oh, it's fun, doctor. I use it for ten minutes every day. I put my hand inside, wave it around and see how it feels. My girlfriend and I play with it. It's very enjoyable. But when I close my eyes, it still doesn't work. And if I don't use the mirror, it doesn't work. I know you want my phantom to start moving again, but without the mirror it doesn't."
Three more weeks passed until one day Philip called me, very excited and agitated. "Doctor," he exclaimed,
"it's gone!"
"What's gone?" (I thought maybe he had lost the mirror box.)
"My phantom is gone."
"What are you talking about?"
"You know, my phantom arm, which I had for ten years. It doesn't exist anymore. All I have is my phantom fingers and palm dangling from my shoulder!"
My immediate reaction was, Oh, no! I have apparently permanently altered a person's body image using a mirror. How would this affect his mental state and well−being? "Philip—does it bother you?"
"No no no no no no," he said. "On the contrary. You know the excruciating pain I always had in my elbow?
The pain that tortured me several times a week? Well, now I don't have an elbow and I don't have that pain anymore. But I still have my fingers dangling from my shoulder and they still hurt." He paused, apparently to let this sink in. "Unfortunately," he added, "your mirror box doesn't work anymore because my fingers are up too high. Can you change the design to eliminate my fingers?" Philip seemed to think I was some kind of 40
magician.
I wasn't sure I could help Philip with his request, but I realized that this was probably the first example in medical history of a successful "amputation" of a phantom limb! The experiment suggests that when Philip's right parietal lobe was presented with conflicting signals—visual feedback telling him that his arm is moving again while his muscles are
telling him the arm is not there—his mind resorted to a form of denial. The only way his beleaguered brain could deal with this bizarre sensory conflict was to say, "To hell with it, there is no arm!" And as a huge bonus, Philip lost the associated pain in his phantom elbow as well, for it may be impossible to experience a disembodied pain in a nonexistent phantom. It's not clear why his
"off−line," so to speak. During this time, when the arm is nonfunctional, the brain receives visual feedback:
"Nope, the arm is not moving." After the swelling subsides, it's possible that the patient's brain is stuck with a form of learned paralysis. Could the mirror contraption be used to overcome at least that component of the paralysis that is due to learning? (Obviously there is nothing one can do with mirrors to restore paralysis caused by actual destruction of fibers.)
But before we could implement this kind of novel therapy for stroke patients, we needed to ensure that the effect is more than a mere temporary illusion of movement in the phantom. (Recall that when Philip closed his eyes, the sense of movement in his phantom disappeared. )
What if the patient were to practice with the box in order to receive continuous visual feedback for several days? Is it conceivable that the brain would "unlearn" its perception of damage and that movements would be permanently restored?
I went back the next day and asked Philip, "Are you willing to take this device home and practice with it?"
"Sure," said Philip. "I'd love to take it home. I find it very exciting that I can move my arm again, even if only momentarily."
So Philip took the mirror home. A week later I telephoned him. "What's happening?"
"Oh, it's fun, doctor. I use it for ten minutes every day. I put my hand inside, wave it around and see how it feels. My girlfriend and I play with it. It's very enjoyable. But when I close my eyes, it still doesn't work. And if I don't use the mirror, it doesn't work. I know you want my phantom to start moving again, but without the mirror it doesn't."
Three more weeks passed until one day Philip called me, very excited and agitated. "Doctor," he exclaimed,
"it's gone!"
"What's gone?" (I thought maybe he had lost the mirror box.)
"My phantom is gone."
"What are you talking about?"
"You know, my phantom arm, which I had for ten years. It doesn't exist anymore. All I have is my phantom fingers and palm dangling from my shoulder!"
My immediate reaction was, Oh, no! I have apparently permanently altered a person's body image using a mirror. How would this affect his mental state and well−being? "Philip—does it bother you?"
"No no no no no no," he said. "On the contrary. You know the excruciating pain I always had in my elbow?
The pain that tortured me several times a week? Well, now I don't have an elbow and I don't have that pain anymore. But I still have my fingers dangling from my shoulder and they still hurt." He paused, apparently to let this sink in. "Unfortunately," he added, "your mirror box doesn't work anymore because my fingers are up too high. Can you change the design to eliminate my fingers?" Philip seemed to think I was some kind of 40
magician.
I wasn't sure I could help Philip with his request, but I realized that this was probably the first example in medical history of a successful "amputation" of a phantom limb! The experiment suggests that when Philip's right parietal lobe was presented with conflicting signals—visual feedback telling him that his arm is moving again while his muscles are
telling him the arm is not there—his mind resorted to a form of denial. The only way his beleaguered brain could deal with this bizarre sensory conflict was to say, "To hell with it, there is no arm!" And as a huge bonus, Philip lost the associated pain in his phantom elbow as well, for it may be impossible to experience a disembodied pain in a nonexistent phantom. It's not clear why his
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