While the phantom limbs of some people can move, either voluntarily or involuntarily, those of others cannot; they are "paralyzed." This can be the result of what Ramachandran calls "learned paralysis." In such cases, the brain, having become used to receiving no signals from, say, an actual arm paralyzed after an accident, continues after amputation to register the new phantom arm as paralyzed. Ramachandran wondered: If the brain can learn paralysis, can it unlearn it? He answered this question with a mirror.
The first person to explore this new world was Philip Martinez. In 1984 Philip was hurled off his motorcycle, going at 45 miles an hour down the San Diego freeway. He skidded across the median, landed at the foot of a concrete bridge and, getting up in a daze, he had the presence of mind to check himself for injuries. A helmet and leather jacket prevented the worst, but Philip's left arm had been severely torn near his shoulder. Like Dr. Pons's monkeys, he had a brachial avulsion—the nerves supplying his arm had been yanked off the spinal column. His left arm was completely paralyzed and lay lifeless in a sling for one year. Finally, doctors advised amputation. The arm was just getting in the way and would never regain function.
Ten years later, Philip walked into my office. Now in his mid-30s, he collects a disability benefit and has made a rather impressive reputation for himself as a pool player known among his friends as the "one-armed bandit."
Philip had heard about my experiments with phantom limbs in local press reports. He was desperate. "Dr. Ramachandran," he said, "I'm hoping you can help me." He glanced down at his missing arm. "I lost it ten years ago. But ever since I've had a terrible pain in my phantom elbow, wrist, and fingers." Interviewing him further, I discovered that during the decade, Philip had never been able to move his phantom arm. It was always fixed in an awkward position. Was Philip suffering from learned paralysis? If so, could we use our virtual reality box to resurrect the phantom visually and restore movements?
I asked Philip to place his right hand on the right side of the mirror in the box and imagine that his left hand (the phantom) was on the left side. "I want you to move your right and left arms simultaneously," I instructed.
"Oh, I can't do that," said Philip. "I can move my right arm but my left arm is frozen. Every morning when I get up, I try to move my phantom because it's in this funny position and I feel that moving it might help relieve the pain. But," he said, looking down at his invisible arm, "I have never been able to generate a flicker of movement in it."
"Okay, Philip, but try anyway."
Philip rotated his body, shifting his shoulder, to "insert" his lifeless phantom into the box. Then he put his right hand on the other side of the mirror and attempted to make synchronous movements. As he gazed into the mirror, he gasped and then cried out, "Oh, my God! Oh, my God, doctor! This is unbelievable. It's mind-boggling." He was jumping up and down like a kid. "My left arm is plugged in again. It's as if I'm in the past. All these memories from so many years ago are flooding back into my mind. I can move my arm again. I can feel my elbow moving, my wrist moving. It's all moving again.
After he calmed down a little I said, "Okay, Philip, now close your eyes."
"Oh, my," he said, clearly disappointed. "It's frozen again. I feel my right hand moving, but there's no movement in the phantom."
"Open your eyes."
"Oh, yes. Now it's moving again."
It was as though Philip had some temporary inhibition or block of the neural circuits that would ordinarily move the phantom and the visual feedback had overcome this block. More amazing still, these bodily sensations of the arm's movements were revived instantly, even though they had never been felt in the preceding ten years!