Phantoms in the Brain: Probing the Mysteries of the Human Mind (25 page)

In the first experiment, I tested the idea that the patient is simply monitoring motor signals that are being sent to the arm. Larry Cooper is an intelligent fifty−six−year−old denial patient who had suffered a stroke one week before I went to visit him in the hospital. He lay under a blue and purple quilt his wife had brought to the room, with his arms flopped outside the covers—one paralyzed, one normal. We chatted for ten minutes and then I left the room, only to return five minutes later. "Mr. Cooper!" I exclaimed, approaching his bed.

"Why did you just now move your left arm?" Both arms were dead still, in the same position as when I had left the room. I've tried this on normal people and the usual response is utter bewilderment. "What do you mean? I wasn't doing anything with my left arm" or "I don't understand; did I move my left arm?" Mr. Cooper looked at me calmly and said, "I was gesticulating to make a point!" When I repeated the experiment the next day, he said, "It hurts, so I moved it to relieve the pain."

Since there is no possibility that Mr. Cooper could have sent a motor command to his left arm at the exact moment I questioned him, the result suggests that denial stems not merely from a sensory motor deficit. On the contrary, his whole system of beliefs about himself is so profoundly deranged that there's apparently no limit to what he will do to protect these beliefs. Instead of acting befuddled, as a normal person might, he happily goes along with my deception because it makes perfect sense to him, given his worldview.

The second experiment was almost diabolical. What would happen, I wondered, if one were temporarily to

"paralyze" the right arm of a denial patient whose left arm, of course, really is paralyzed. Would the denial now encompass his right arm as well? The neglect theory makes a very specific prediction—because he only neglects the left side of his body and not the right side, he should notice that the right arm isn't moving and say, "That's very odd, doctor; my arm isn't moving." (My theory, on the other hand, makes the opposite prediction: He should be insensitive to this "anomaly" since the discrepancy detector in his right hemisphere is damaged.)

To "paralyze" a denial patient's right arm, I devised a new version of the virtual reality box we had used in our phantom limb experiments. Again, it was a simple cardboard box with holes and mirrors, but they were positioned very differently. Our first subject was Betty Ward, a seventy−one−year−old retired schoolteacher who was mentally alert and happy to cooperate in the experiment. When Betty was comfortably seated, I asked her to put a long gray glove on her right hand (her good one) and insert it through a hole in front of the box. I then asked her to lean forward and peek into the box through a hole in the top to look at her gloved hand.

Next, I started a metronome and asked Betty to move her hand up and down in time with the ticking sounds.

"Can you see your hand moving, Betty?"

"Yes, sure," she said. "It's got the right rhythm."

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Then I asked Betty to close her eyes. Without her knowledge, a mirror in the box flipped into position and an undergraduate stooge, who was hiding under the table, slipped his gray gloved hand into the box from a hole in the back. I asked Betty to open her eyes and look back into the box. She thought she was looking at her own right hand again, but,

because of the mirror, she actually saw the student's hand. Previously I had told the stooge to keep his hand absolutely still.

"Okay, Betty. Keep looking. I'm going to start the metronome again and I want you to move your hand in time with it."

Tick, tock, tick, tock. Betty moved her hand but what she saw in the box was a perfectly still hand, a

"paralyzed" hand. Now when you do this experiment with normal people, they jump out of their seat: "Hey, what's going on here?" Never in their wildest dreams would they imagine that an undergraduate was hiding under the table.

"Betty, what do you see?"

"Why, I see my right hand moving up and down, just like before," she replied.8

This suggests to me that Betty's denial crossed over to the right side of her body—the normal side with no neglect—for why else would she say that she could see a motionless hand in motion? This simple experiment demolishes the neglect theory of anosognosia and also gives us a clue for understanding what really causes the syndrome. What is damaged in these patients is the manner in which the brain deals with a discrepancy in sensory inputs concerning the body image; it's not critical whether the discrepancy arises from the left or right side of the body.

What we observed in Betty and in the other patients we've discussed so far supports the idea that the left hemisphere is a conformist, largely indifferent to discrepancies, whereas the right hemisphere is the opposite: highly sensitive to perturbation. But our experiments only provide circumstantial evidence for this theory. We needed direct proof.

Even a decade ago, an idea of this kind would have been impossible to test, but the advent of modern imaging techniques such as functional magnetic resonance (fMR) and positron emission tomography (PET) has tremendously accelerated the pace of research by allowing us to watch the living brain in action. Very recently, Ray Dolan, Chris Frith and their colleagues at the Queen Square Neurological Hospital for Neurological Diseases in London performed a beautiful experiment using the virtual reality box that we had used on our phantom limb patients. (Recall this is simply a vertical mirror propped in a box, perpendicular to the person's chest.) Each person inserted his left arm into the box and looked into the left side of the mirror at the reflection of his left arm so that it was optically superimposed on the felt location of his right arm. He was then asked to move both hands synchronously up and down, so that there was no discrepancy between the visual appearance of his moving right hand (actually the reflection of his left) and the kinesthetic movement sensations—from joints and muscles—emerging from his right hand. But if he now moved the two hands out of sync—as when doing the dog paddle—then there was a profound discrepancy between what the right hand appeared to be doing visually and what it
felt
it was doing. By doing a PET scan during this procedure, Dr.

Frith was able to locate the center in the brain that monitors discrepancies; it is a small region of the right hemisphere that receives information from the right parietal lobe. Dr. Frith then did a second PET scan with the subject looking into the right side of the mirror at the reflection of his right hand (and moving his left hand out of sync) so the discrepancy in his body image now appeared to come from his
left
side rather than the right. Imagine my delight when I heard from Dr. Frith that once again the right hemisphere "lit up" in the 101

scanner. It didn't seem to matter which side of the body the discrepancy arose from—right or left—it always activated the right hemisphere. This is welcome proof that my "speculative" ideas on hemispheric specialization are on the right track.

When I conduct clinical Grand Rounds—presenting a denial patient to medical students—one of the most common questions I am asked is "Do the patients only deny paralysis of body parts or do they deny other disabilities as well? If the patient stubbed her toe, would she deny the pain and swelling in that toe? Do they deny that they are seriously ill? If they suddenly had a migraine attack would they deny it?" Many neurologists have explored this in their patients, and the usual answer is that they don't deny other problems—like my patient Grace who, when I offered her candy if she could tie shoelaces, shot back at me,

"You know I'm diabetic, doctor. I can't eat candy!"9

Almost all the patients I have tested are well aware of the fact that they've had a stroke and none of them suffers from what you might call "global denial." Yet there are gradations in their belief systems—and accompanying denials—that correlate with the location of their brain lesions. When the injury is confined to the right parietal lobe, confabulations and denials tend to be confined to body image. But when the damage occurs closer to the front of the right hemisphere (a part called the ventromedial frontal lobe), the denial is broader, more varied and oddly self−protective. I remember an especially striking example of this— a patient named Bill who came to see me six months after he had been diagnosed with a malignant brain tumor. The tumor had been growing

rapidly and compressing his right frontal lobe, until it was eventually excised by the neurosurgeon.

Unfortunately, by then it had already spread and Bill was told that he probably had less than a year to live.

Now, Bill was a highly educated man and ought to have grasped the gravity of his situation, yet he seemed nonchalant about it and kept drawing my attention to a little blister on his cheek instead. He bitterly complained that the other doctors hadn't done anything about the blister and asked whether I could help him get rid of it. When I would return to the topic of the brain tumor, he avoided talking about it, saying things like "Well, you know how these doctors sometimes incorrectly diagnose things." So here was an intelligent person flatly contradicting the evidence provided by his physicians and glibly playing down the fact that he had terminal brain cancer. To avoid being hounded by a free−floating anxiety, he adopted the convenient strategy of attributing it to
something
tangible—and the blister was the most convenient target. Indeed, his obsession with the blister is what Freud would call a displacement mechanism—a disguised attempt to deflect his own attention from his impending death. Curiously, it is sometimes easier to deflect than to deny.10

The most extreme delusion I've ever heard of is one described by Oliver Sacks, about a man who kept falling out of bed at night. Each time he crashed to the floor, the ward staff would hoist him back up, only to hear a resounding thud a few moments later. After this happened several times, Dr. Sacks asked the man why he kept toppling out of bed. He looked frightened. "Doctor," he said, "these medical students have been putting a cadaver's arm in my bed and I've been trying to get rid of it all night!" Not admitting ownership of his paralyzed limb, the man was dragged to the floor each time he tried to push it away.

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The experiments we discussed earlier suggest that a denial patient is not just trying to save face; the denial is anchored deep in her psyche.11 But does this imply that the information about her paralysis is locked away somewhere—repressed? Or does it imply that the information doesn't exist anywhere in her brain? The latter view seems unlikely. If the knowledge doesn't exist, why does the patient say things like "I tied my shoelaces with
both my hands'''
or "I can't wait to get back to two−fisted beer drinking"? And why evasive remarks like

"I'm not ambidextrous"? Comments like these imply that "somebody" in there 102

knows she is paralyzed, but that the information is not available to the conscious mind. If so, is there some way to access that forbidden knowledge?

To find out, we took advantage of an ingenious experiment performed in 1987 by an Italian neurologist, Eduardo Bisiach, on a patient with neglect and denial. Bisiach took a syringe filled with ice−cold water and irrigated the patient's left ear canal—a procedure that tests vestibular nerve function. Within a few seconds the patient's eyes started to move vigorously in a process called nystagmus. The cold water sets up a convection current in the ear canals, thereby fooling the brain into thinking the head is moving and into making involuntary correctional eye movements that we call nystagmus. When Bisiach then asked the denial patient whether she could use her arms, she calmly replied that she had no use of her left arm! Amazingly, the cold water irrigation of the left ear had brought about a complete (though temporary) remission from the ano−sognosia.

When I read about this experiment, I jumped out of my seat. Here was a neurological syndrome produced by a right parietal lesion that had been reversed by the simple act of squirting water into the ear. Why hadn't this amazing experiment made headlines in
The New York Times?
Indeed, I discovered that most of my professional colleagues had not even heard of the experiment. I therefore decided to try the same procedure on the next patient I saw with anosognosia.

This turned out to be Mrs. Macken, an elderly woman who three weeks earlier had suffered a right parietal stroke that resulted in left side paralysis. My purpose was not only to confirm Bisiach's observation but also to ask questions specifically to test her memory—something that hadn't been done systematically. If the patient suddenly started admitting that she was paralyzed, what would she say about her earlier denials? Would she deny her denials? If she admitted them, how would she account for them? Could she possibly tell us
why
she had been denying them, or is that an absurd question?

I had been seeing Mrs. Macken every three or four days for two weeks, and each time we had gone through the same rigmarole.

"Mrs. Macken, can you walk?"

"Yes, I can walk."

"Can you use both arms?"

"Yes."

"Are they equally strong?"

"Yes."

"Can you move your left hand?"

"Yes."

"Can you move your right hand?"

"Yes."

"Are they equally strong?"

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"Yes."

After going through the questions, I filled a syringe with ice−cold water and squirted it into her ear canal. As expected, her eyes started moving in the characteristic way. After about a minute, I began to question her.

"How are you feeling, Mrs. Macken?"

"Well, my ear hurts. It's cold."

"Anything else? What about your arms? Can you move your arms?"

"Sure," she said.

"Can you walk?"

"Yes, I can walk."

"Can you use both your arms? Are they equally strong?"

"Yes, they are equally strong."

I wondered what these Italian scientists were talking about. But as I was driving home, I realized that I had squirted the water into the wrong ear! (Cold water in the left ear or warm water in the right ear causes the eyes to drift repetitively to the left and jump to the right. And the opposite is true. It's one of those things that many physicians get confused about, or at least I do. So I had inadvertently done the control experiment first!) The next day we repeated the experiment on the other ear.