Phantoms in the Brain: Probing the Mysteries of the Human Mind (22 page)

Is there some trick you could use to make the patient accept the left side of the world and start noticing that her arm was not moving? What would happen if you put a mirror on the patient's right side at right angles to her shoulder? (If she were sitting in a phone booth, this would

correspond to the right wall of the booth.) If she now looks in the mirror, she will see the
reflection
of everything on her left side, including people, events and objects, as well as her own left arm. But since the reflection itself is on the right—in her nonneglected field—would she suddenly start paying attention to these things? Would she realize that these people, events and objects were on her left even though the reflection of them is on the right? If it worked, a trick of this kind would be nothing short of a miracle. Efforts to treat neglect have frustrated patients and physicians alike ever since the condition was first clinically described more than sixty years ago.

I telephoned Sam and asked whether his mother, Ellen, might be interested in trying out the mirror idea. It might help Ellen recover more quickly and it was easy enough to try.

The manner in which the brain deals with mirror reflections has long fascinated psychologists, philosophers and magicians alike. Many a child has asked the question "Why does a mirror reverse things left to right but not reverse them upside down? How does the mirror 'know' which way it should reverse?"—a question that most parents find embarrassingly difficult to answer. The correct answer to this question comes from the physicist Richard Feynman (as quoted by Richard Gregory, who has written a delightful book on this topic).6

Normal adults rarely confuse a mirror reflection for a real object. When you spot a car fast approaching you in your rearview mirror, you don't jam on your brakes. You accelerate forward even though it appears that the image of the car is approaching rapidly from the front. Likewise, if a burglar opened the door behind you as you were shaving in the bathroom, you'd spin around to confront him—not attack the reflection in the mirror.

Some part of your brain must be making the needed correction: The real object is behind me even though the image is in front of me.7

But like Alice in Wonderland, patients like Ellen and Steve seem to inhabit a strange no−man's−land between illusion and reality—a "warped world," as Steve called it, and there is no easy way to predict how they will react to a mirror. Even though all of us, neglect patients and normal people alike, are familiar with mirrors and take them for granted, there is something inherently surrealistic about mirror images. The optics are simple enough, but no one has any inkling of what brain mechanisms are activated when we look at a mirror reflection, of what brain processes are involved in our special ability to comprehend the paradoxical juxtaposition of a real object and its optical "twin." Given the right parietal lobe's important role in dealing with spatial relationships and "holistic" aspects of vision, would a neglect patient have special problems dealing with mirror reflections?

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When Ellen came to my lab, I first conducted a series of simple clinical tests to confirm the diagnosis of hemineglect. She flunked every one of them. First, I asked her to sit on a chair facing me and to look at my nose. I then took a pen, held it up to her right ear and began to move it slowly, in a sweeping arc, all the way to her left ear. I asked Ellen to follow the pen with her eyes, and she did so with no trouble until I reached her nose. At that point her eyes began to wander off, and soon she was looking at me, having "lost sight of" the pen near her nose. Paradoxically, a person who is really blind in her left visual field wouldn't display this behavior. If anything, she would try to move her eyes ahead of the pen in an effort to compensate for her blindness.

Next, I showed Ellen a horizontal line drawn on a sheet of paper and asked her to bisect it with a vertical mark. Ellen pursed her lips, took the pen and confidently placed a mark to the far right of the line because for her only half a line existed—the right half—and she was presumably marking the center of that half.8

When I asked her to draw a clock, Ellen made a full circle instead of just a half circle. This is a fairly common response because circle drawing is a highly overlearned motor response and the stroke did not compromise it.

But when it came time for Ellen to fill in the numbers, she stopped, stared hard at the circle and then proceeded to write the numbers 1 to 12, cramped entirely on the right side of the circle!

Finally, I took a sheet of paper, put it in front of Ellen and asked her to draw a flower.

"What kind of flower?" she said.

"Any kind. Just an ordinary flower."

Again, Ellen paused, as if the task were difficult, and finally drew another circle. So far so good. Then she painstakingly drew a series of little petals—it was a daisy—all scrunched on the right side of the flower (Figure 6.1).

"That's fine, Ellen," I said. "Now I want you to do something different. I want you to close your eyes and draw a flower."

Ellen's inability to draw the left half of objects was to be expected, since she ignores the left when her eyes are open. But what would happen with them closed? Would the mental representation of a flower—the daisy in her mind's eye—be a whole flower or just half of one? In other words, how deep does the neglect reverberate into her brain?

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I asked her to describe her eyeglasses, lipstick and clothing while looking straight into the mirror. She did so with no trouble. On receiving a cue, one of my students standing on Ellen's left side held out a pen so that it was well within the reach of her good right hand but entirely within the neglected left visual field. (This turned out to be about eight inches below and to the left of her nose.) Ellen could see my student's arm as well as the pen clearly in the mirror, as there was no intent to deceive her about the presence of a mirror.

"Do you see the pen?"

"Yes."

"Okay, please reach out and grab it and write your name on this pad of paper I've placed in your lap."

Imagine my astonishment when Ellen lifted her right hand and without hesitation went straight for the mirror and began banging on it repeatedly. She literally clawed at it for about twenty seconds and said, obviously frustrated, "It's not in my reach."

When I repeated the same process ten minutes later, she said, "It's behind the mirror," and reached around and began groping with my belt buckle.

A little later she even tried peeking over the edge of the mirror to look for the pen.

So Ellen was behaving as though the reflection were a real object that she could reach out and grab. In my fifteen−year career, I'd never seen anything like this—a perfectly intelligent, levelheaded adult making the absurd blunder of thinking that an object was actually inside the mirror.

We wanted to make sure that Ellen's behavior did not arise from some clumsiness of her arm movements or a failure to understand what mirrors

are. So we simply tried placing the mirror at arm's length in front of her, just like a bathroom mirror at home.

This time the pen appeared just behind and above her right shoulder (but just outside her visual field). She saw it in the mirror and her hand went straight back behind her to grab it. So her failure in the earlier task could not be explained by claiming that she was disoriented, clumsy or confused as a result of her stroke.

We decided to give a name to Ellen's condition—"mirror agnosia" or "the looking glass syndrome" in honor of Lewis Carroll. Indeed, Lewis Carroll is known to have suffered from migraine attacks caused by arterial spasms. If they affected his right parietal lobe, he may have suffered momentary confusion with mirrors that might not only have inspired him to write
Through the Looking Glass
but may help explain his general obsession with mirrors, mirror writing and left−right reversal. One wonders whether Leonardo da Vinci's preoccupation with left−right reversed writing had a similar origin.

The looking glass syndrome was intriguing to watch, but it was also frustrating because I had initially hoped for the exact opposite reaction— that the mirror would make Ellen more aware of the left side of the world and help with rehabilitation.

The next step was to find out how widespread this syndrome is. Do all neglect patients behave like Ellen? In testing another twenty patients, I found that many had the same kind of mirror agnosia. They would reach into the mirror for the pen or a piece of candy when it was held in the neglected field. They knew perfectly well they were looking into a mirror and yet they made the same mistake as Ellen.

Not all of the patients made this error, however. Some of them initially looked perplexed, but upon seeing the reflection of the pen or candy in the mirror, they chuckled, and—with a conspiratorial air—reached correctly 89

for the object on the left just as you or I might. One patient even turned his head to the left—something he was ordinarily reluctant to do—and beamed triumphandy as he snatched the reward. These few patients were clearly paying attention to objects they had previously ignored, raising a fascinating therapeutic possibility.

Will repeated exposure to the mirror help some people overcome neglect, gradually becoming more aware of the left side of the world?9 We are hoping to try this someday in the clinic.

Therapy aside, the scientist in me is equally intrigued by mirror agnosia—the patient's
failure
to reach correctly for the real object. Even my two−year−old son, when shown candy only visible in the mirror, gig−

gled, turned around and snatched the sweet. Yet the much older and wiser Ellen could not do this.

I can think of at least two interpretations of why she might lack this ability. First, it's possible that the syndrome is caused by her neglect. It's as though the patient was saying to herself, unconsciously, "Since the reflection is in the mirror, the object must be on my left. But the left does not exist on my planet—therefore, the object must be inside the mirror." However absurd this interpretation may seem to us with our intact brains, it's the only one that would make any sense to Ellen, given her "reality."

Second, the looking glass syndrome may not be a direct consequence of neglect, even though it is usually accompanied by neglect. We know that when the right parietal lobe is damaged, patients have all kinds of difficulties with spatial tasks, and the looking glass syndrome may simply be an especially florid manifestation of such deficits. Responding correctly to a mirror image requires you simultaneously to hold in your mind the reflection as well as the object that is producing it and then perform the required mental gymnastics to locate correctly the object that produced the reflection. This very subtle ability may be compromised by lesions in the right parietal lobe, given the important role of that structure in dealing with spatial attributes of the world. If so, mirror agnosia might provide a new bedside test for detecting right parietal lesions.10 In an age of escalating costs of brain imaging, any simple new test would be a useful addition to the neurologist's diagnostic kit.

The strangest aspect of the looking glass syndrome, however, is listening to patients' reactions.

"Doctor, why can't I reach the pen?"

"The darn mirror is in the way."

"The pen is inside the mirror and I can't reach it!"

"Ellen, I want you to grab the real object, not the reflection. Where is the real object?" She replied, "The real object is out there behind the mirror, doctor."

It's astonishing that the mere confrontation with a mirror flips these patients into the twilight zone so that they are unable—or reluctant— to draw the simple logical inference that since the reflection is on the right, the object producing it must be on the left. It's as though for these patients even the laws of optics have changed, at least for this small corner of their universe. We ordinarily think of our intellect and "high−level"

knowledge—such as laws concerning geometrical optics—as being im−

mune to the vagaries of sensory input. But these patients teach us that this is not always true. Indeed, for them it's the other way around. Not only is their sensory world warped, but their knowledge base is twisted to accommodate the strange new world they inhabit.11 Their attention deficits seem to permeate their whole outlook, rendering them unable to tell whether a mirror reflection is a real object or not, even though they can carry on normal conversations on other topics—politics, sports or chess—just as well as you or I. Asking these patients what is the "true location" of the object they see in the mirror is like asking a normal person 90

what is north of the North Pole. Or whether an irrational number (like the square root of 2 or Z with a never−ending string of decimals)
really
exists or not. This raises profound philosophical questions about how sure we can be that our own grasp on reality is all that secure. An alien four−dimensional creature watching us from his four−dimensional world might regard our behavior to be just as perverse, inept and absurdly comical as we regard the bumblings of neglect patients trapped in their strange looking−glass world.