Crashing Through (29 page)

We also recognize this object as an elephant—despite its decidedly noncanonical view. How do we recognize something from a noncanonical view? After all, the picture above presents a very different two-dimensional form; it has a very different shape. Why don’t we see it as a different object from the one shown in the first photo?

It is thought that a primary reason we can identify an object from its various noncanonical views is because we already understand its depth from its canonical view. Once the brain understands an object’s depth—its robust and three-dimensional form—it can make the inference about how that object would look from different angles.

That ability is critical because most of the objects we encounter in our daily routines are not conveniently positioned for us at their canonical angles. And even if they were, their shapes would change the moment they moved or we moved. Our ability to see in three dimensions allows us to understand objects from virtually any viewpoint. If a person could see only in two dimensions, he would need to learn to recognize not just the objects in the world but myriad different views of each of those objects—an impossible task.

There are many other factors involved in recognizing objects, but without depth perception the rest are moot. Object recognition, like much of depth perception, develops later in the infant and can take years to perfect.

Motion

Infants perceive motion as early as two weeks after birth. By the time they’re ten or twelve weeks old they can smoothly follow moving objects. They seem able to do this almost instinctively, without much need for experimentation or interaction with the world. It seems that motion is simply there to be perceived, and making sense of motion is a relatively easy task that seems to be nearly complete by six months of age.

Color

Infants have considerable color vision by the age of about two months. Development of color vision seems merely to depend on seeing color in the world, and doesn’t require the baby to interact with the world. Color, like motion, seems simply to be there to be seen.

This understanding of the various parts of vision raises a critical question: Is there a difference between the things May perceives well (motion and color) and the things he perceives poorly (faces, depth, and objects)?

It definitely looks as if there is.

Motion and Color:

•
don’t require a complicated knowledge of the world to be perceived.

•
Infants understand motion and color within the first few months of life.

Faces, Depth, and Objects:

•
are more complex.
They are often characterized by tiny and subtle variations, cues, and clues that change frequently and are often dependent on context.

•
require a massive and complicated knowledge of the world to be perceived.

This knowledge is derived in early childhood from constant interaction and experimentation with the world and its objects. It takes infants several months to understand faces and depth and to recognize objects.

The differences between the two categories are stark and fundamental. They also seem to suggest that the broken parts of May’s vision can be fixed—maybe even made perfect.

Remember that knowledge and vision are highly related. If May can’t perceive faces, depth, and objects, that might be because he forgot or otherwise lost the knowledge of how to do it. That makes intuitive sense. Perceiving faces, depth, and objects are among themost complicated tasks the visual system must learn—just the kind of complex knowledge we know that brains forget all the time. (Few of us, for example, remember those lengthy algebra formulas from school.) It makes equal sense that he’d retain the knowledge of how to perceive motion and color; they are among the simplest tasks for the visual system—just the kind of basic things that brains seem to remember forever. (Most of us, for example, remember basic arithmetic for life.)

This sounds very hopeful for May. If he forgot or otherwise lost the knowledge of how to see faces, depth, and objects, then surely he can relearn it. Who better than May to undertake some challenging learning?

But Fine wasn’t sure he could learn it. To understand why, we must know a bit about neurons—the cells that calculate and contain all the knowledge we have—and how they work in the brain.

The human brain contains approximately 100 billion neurons. Neurons are a particular type of nerve cell designed to process and transmit electrical impulses. Some of these neurons transmit signals from the world outside, bringing signals to the brain from the eyes, ears, fingers, and even the stomach wall (“Oof—I ate too much”). But the majority of neurons receive, modify, and pass along signals from other neurons. Each neuron forms thousands of connections with other neurons, meaning that the number of possible combinations between them is greater than the number of elementary particles in the universe. It is thought that the brains of higher primates, and their network of neurons, are the most complex structures in the universe.

Particular connections between neurons are what give rise to particular sensations, perceptions, feelings, thoughts, memories—everything a person experiences, remembers, and feels. When a person perceives a banana, it is the result of electrical impulses traveling first from the eye to the brain, and then through a very particular network of neurons that have been formed to recognize and react to bananas. These “banana neurons,” as we might call them, are created and strengthened by our experience with bananas. Neurons and connections for recognizing Uncle Joe are created and strengthened by experience with Uncle Joe. Forming particular neural networks is what we call learning. We form particular neural networks to represent everything we experience in the world, including faces, depth, objects, motion, and color.

To learn something as staggeringly complex as vision—with all its subtleties, shadows, cues, clues, priors, exceptions, contexts, and confusions—a person needs massive amounts of neurons available and ready for that purpose. But who owns a supply like that?

Young children do.

Consider the enormous learning of which young children are capable. Compared with adults, for example, they learn language at a staggering rate. Such learning is made possible in the very young child by huge stores of available neurons that are awaiting assignment. In fact, children have an
overabundance
of available neurons for learning; those that don’t get used actually die as the baby becomes a small child.

Adults, however, don’t have that kind of ready supply of neurons available for learning. Nor, it seems, do adult neurons form connections with other neurons as quickly and easily as do young-child neurons. That’s why adults simply can’t learn like children do.

A powerful example of this is language learning. An adult who learns a language will never be as fluent as a person who learned that language in childhood. In most cases, a native speaker can tell the difference between another native speaker and an expert later learner. A linguist can tell in every case.

Another example can be seen in cases of early brain damage. Frighteningly large chunks of brain are often removed from small children because of tumors or epilepsy—sometimes almost half the brain. That kind of brain loss in an adult would cause a severe handicap; the person might never walk or speak properly again. But in small children the brain can reorganize to make the best use of the remaining neurons (remember, there are 100 billion of them). Often, after a few years these children show no signs that a large part of their brain is missing.

This all seemed to be bad news for May. If he was to relearn the complex parts of vision he forgot or lost during his forty-three years of blindness, he would need the massive supply of neurons that children possess to do that kind of learning.

Maybe May still had his supply. After all, he possessed those neurons when he went blind, at age three, while he was still learning. Shouldn’t his supply still be available for learning faces, depth, and objects? Shouldn’t he be able to pick up where he left off?

Fine was skeptical that May’s face, depth, and object neurons were still available for those tasks. She had serious questions about whether he could resume his learning at all.

She knew from recent research that when certain neurons lose their input, they change what they represent in the world. If they can’t do the job they were meant to do, they get up from their current jobs and go to represent something else. A neuron’s ability to change its representation is known as its plasticity. Plasticity was one of Fine’s particular areas of interest.

What determines if a neuron, deprived of its input, goes on to do something else? What determines its plasticity when its signals stop arriving—as happens to some vision neurons when a person goes blind?

It turns out that when neurons lose their input they are more likely to change what they represent if:

•
they are deprived of input during childhood—especially early childhood

•
there’s a demand from another part of the brain for their services

•
they represent complex tasks

Some of May’s vision neurons—namely, those that process faces, depth, and objects—fell into all three categories, making them prime contenders to have gone off to represent something else.

Other of May’s vision neurons—namely, those that process motion and color—seemed to satisfy only the first two categories, making them far less likely to have gone off to represent something else. The third category was key.

If that’s what happened, Fine thought, it boded badly for May. It suggested that the neurons and networks he used as a child to perceive faces, depth, and objects had gone to do something else, perhaps to read braille or to aid in echolocation or to help him recall telephone numbers he couldn’t write down. They were plastic enough when he was blinded to learn other useful skills, but they would not do that again; they would not come back to do vision now that he was an adult. Brains, for complicated evolutionary reasons, are not built to make many new neural connections in adulthood. If that was the case with May, it was likely he would never perceive faces, depth, or objects normally because he, like all adults, no longer had the available neural networks to learn them.

Still, Fine was not certain that this was the case. After all, no one had done the studies—almost all research on the effects of visual deprivation had been carried out on animals, like cats and mice, that are very different from humans. So this idea was purely speculative. She stayed up late into the nights, turning May’s case over in her head, contemplating it, hypothesizing about it, testing it against all that science knew about vision and neurology. Textbooks provided no answers. The case histories gave no insights. There were no other subjects in the world like May. It was a full-blown mystery with particulars unlike any a scientist had ever tried to tackle. How was anyone to know whether May’s vision neurons had irreversibly reassigned themselves?

There was, Fine thought, one way to know for sure.

She called May and asked if he’d be game for a new test, one that was very unusual and very new. It was one, she said, that some people would never consider.

CHAPTER
FIFTEEN

On the telephone with May, Fine explained the deep connection between knowledge and vision. She described the magnitude of the knowledge required to see properly, and how much of vision was subtle, complex, dependent on context, based on tiny clues and rules of thumb. She related how vision slowly developed during early childhood, when the brain was capable of such massive learning, and how this huge amount of unconscious knowledge is imposed on the visual scene instantaneously and unconsciously—an astonishing feat of computing power. She told May that he’d once had this knowledge but must have forgotten or otherwise lost it after his accident. She said that without that knowledge a person couldn’t see normally no matter how good his eyes.

For six months May’s vision had been a mystery to him. Now it began to make sense. If a person couldn’t bring this massive bank of knowledge to a visual scene, it stood to reason that he would bring whatever knowledge he could. That’s why he yearned to touch everything. That’s why he strained for context, leaned so heavily on color, motion, and his other senses. It was all to bring whatever knowledge he could to the raw data streaming into his eye.

“That must be why it’s exhausting,” May said. “I’m doing it all consciously. I’ve got to think about it. You don’t.”

“Precisely,” Fine said.

“And that’s why it feels overwhelming.”

“Absolutely. By the time you’re finished thinking through one visual image, others have jumped into the scene, each of which demands the same conscious, deliberate deciphering. I can imagine that would feel overwhelming.”

Fine said that she suspected that to May vision felt like speaking a second language, a deliberate process similar to conjugating verbs, recalling vocabulary, working out tenses, and then assembling the parts into a whole.

“That’s just how it feels,” May said. “Imagine doing that every waking moment of every day.”

Fine didn’t need a crystal ball to know May’s next question.

“Okay, I forgot how to see. How do I learn to do it again now?”

She explained to him about neurons and plasticity—about how some neurons, when deprived of input, will go off to do other jobs while others seem perfectly happy to remain at their original posts. She told him that it was distinctly possible that the neurons he needed to perceive faces, depth, and objects—the ones he needed for so much of normal vision—might have gone away for good.

May sat in wonder at the simplicity of Fine’s explanation. This single idea—that his brain might be wired for some parts of vision but not others—explained his world. It was why stairs looked like lines but he could catch a ball on the run. It was why he couldn’t recognize his children’s faces but could perfectly sort the laundry. It was why he could navigate his way around a cluttered room but could not find his shoes in that same room.

“Can I get those vision neurons back?” he asked.

“If they’re gone, then we don’t think so,” Fine said. “It’s like when you build a new house. Say you want to move the master bedroom from upstairs to downstairs. If it’s early in construction—in the house’s early childhood, so to speak—it’s not a big deal to move the bedroom. But if the house is an adult already, it’s too late—the bedroom is there to stay. That seems to be how plasticity works with certain neurons. They can shift early in a person’s life, but shifting late is much rarer.”

May’s throat tightened. He understood the implications of Fine’s explanation. If his vision neurons had permanently changed their representations, he would never improve; vision would always be a nonstop process of heavy cognitive lifting and information overflow.

“Does that mean I can’t get better?” he asked.

For a moment Fine was silent.

“I’m not sure,” she said. “We don’t know if the parts of your brain that once perceived faces, depth, and objects are still wired to do those things. But there’s a fairly new technology that can go a long way to telling us what’s happening in your brain.”

Fine told him about a special type of brain scan known as functional magnetic resonance imaging, or fMRI. An fMRI scan could look at specific areas of the brain and detect whether those areas were responding to specific stimuli. It could do that because active areas of the brain use oxygen, giving them slightly different magnetic properties than inactive areas. The fMRI could detect those differences.

Fine explained the process: She and some fMRI specialists would slide May into a large scanner, one that filled the better part of a room. While he was inside, they would show him pictures of faces. If the parts of his brain responsible for processing faces showed activity when presented with images of faces, then Fine would know that May still had the neurons and networks necessary to process faces. If they did not respond, she would know that his brain simply did not work for faces anymore. She would do the same with objects, simple forms, and motion. That would give the scientists the best chance to understand what was happening in May’s brain. That would give them the best answer to whether May could learn to see again.

“What are the chances that the neurons I need are still there?” May asked.

“I don’t know,” Fine said. “No one’s done a case like this before; it’s totally unique. I wouldn’t bet ten dollars on it either way.”

“But there’s a chance they’re still there?”

“There’s a chance. And that would prove you’ve got something to work with.”

“When do we start?” May asked.

“Well, I should tell you that these scanners can be claustrophobic. They can be quite noisy. You’re put inside them and asked not to move at all. Some people aren’t comfortable—”

“When do we start?” May asked.

May’s fMRI scan was scheduled for late September at Stanford University. He had two weeks to wait. He spent much of the time searching for new Sendero investors, and began to apply for federal development grants. His GPS-Talk product still performed beautifully, but May knew that the government agencies he hoped would buy it for clients still couldn’t get their arms around paying several thousand dollars for a device that guided the blind from the heavens when they could pay twenty-five dollars for a cane that guided them from the ground. More and more, he believed that his company’s survival depended on securing a new influx of investment or a major grant to allow him to shrink the product’s form factor and reduce its price. Time was growing short.

Flush with a new understanding of his vision, May dialed his friend Bashin and invited him to a steak dinner in Sacramento.

“I know how things work,” May said. “Dr. Fine explained it all to me.”

“Forget steak,” Bashin said. “We need a place where we can really talk. I know a Thai restaurant where they let you sit all night—they forget you’re even there.”

“What day should we do it, Bryan?”

“The question isn’t what day, Mike. The question is, do we meet tonight at six-thirty or seven o’clock?”

May loved the boy in Bashin’s voice. After months of questions, thrills, struggles, and uncertainties, Bashin still conceived of May’s new vision as an adventure.

“Let’s make it six,” May said.

Over pad thai and imported beer, May recounted Dr. Fine’s explanation for his vision. To a man of science like Bashin, the information was thrillingly cutting-edge. He asked strings of questions, most of which May found he could answer, a testament to the clarity of Fine’s exposition.

As the restaurant emptied and the ice in their glasses melted, the men’s conversation took a different turn.

“It’s fascinating,” Bashin said. “Dr. Fine says that a lot of what people see is based on their assumptions and expectations about the world, right?”

“Yes, that’s how I understand it.”

“Don’t you think that’s true in the emotional sense, too? How much of a person, I mean of their heart and soul, do we see or don’t see because we have certain assumptions about them? Or how much beauty are we missing in things like this spoon or, say, the old wood on a park bench because we don’t assume we’ll see beauty in them?”

“That’s true,” May said. “You know, Ione talked a lot about how the brain imposes knowledge in order to see. But I think there might also be beauty in not imposing knowledge—”

“In being open to everything—”

“Yes, in being open to everything, in being open to every possible interpretation. In ways, there’s something liberating about my vision, in the sense that so much of what I see can be anything. It’s fascinating to think that an object, or even a person, can be anything. It means that almost anything can be beautiful.”

Bashin and May talked deeper into the night. Each was fascinated by Fine’s characterization of depth perception as an interpretation of the world, an intuitive leap by the brain. What other things in the world, they wondered, seemed ironclad but were merely interpretations? They laughed as they entertained possibilities both silly and serious.

Near closing time, a waiter blew out the candle on their table and took their water glasses. The men rose and reached for their wallets.

“You know,” May said, “Ione told me about a famous study from the 1960s. I think you’d find it interesting.”

He described the experiment in which two kittens were raised in the dark except for short periods during the day when they were placed in connected baskets and the lights were turned on. One kitten was allowed to put its paws through holes in the basket so it could reach the ground and move both baskets along. The other kitten had no holes in its basket and could only watch. Visually, their experiences were identical. At the end of the experiment, the active kitten had normal vision. The passive kitten was functionally blind.

“That’s remarkable,” Bashin said.

“It makes sense to me,” May said. “I think exploration is everything. I think that’s why I never grew up feeling like I couldn’t see.”

In late September, May squeezed into Fine’s rental car for the hundred-mile drive from his home to the neuroimaging center at Stanford University. When they arrived, they joined another postdoctoral researcher, Alex Wade, professor Brian Wandell, and graduate student Alyssa Brewer. Together, these scientists would use a colossal magnet to journey deep into May’s brain.

After exchanging pleasantries, Fine and her colleagues scurried to collect bite bars, stimulus equipment, swipe cards, and computer disks. And bawdy jokes. The jokes were part of the deal. May would be expected to remain in the scanner for long stretches, often with nothing to do. Reading him off-color jokes during downtimes was the least Fine could do to help him pass the time.

Wandell showed May to the scanning room, where he was read a lengthy disclaimer, asked if there were any bullets in his body (metal interferes with the machine’s magnetic fields), and told to remove his personal belongings. He was surprised to learn that he needn’t do anything inside the scanner except lie still, stay awake, and look at the images shown to him, which would be projected onto a mirror angled over his eye.

May peered at the scanner, a massive white rectangle that reached nearly to the ceiling and seemed to occupy most of the room. A patient would lie on a connected conveyor table that would slide him inside the machine through a narrow round bore at the scanner’s front end. Operators sat in a nearby control room. May had heard tales of scanner claustrophobia and panic.

“Can I touch it?” he asked Wandell.

“Sure, go ahead.”

May ran his hands over the bore’s opening, the attached projector, and the conveyor table. To the scientists, he appeared to exhale after this tactile exploration. To them, it appeared that touch had switched on his vision.

May lay down on the table and prepared for his trip inside. He was given headphones, through which he would hear instructions. A projector, a screen, and a mirror were clamped across his neck, making him look like an invading alien from a 1950s science fiction movie. Though he wasn’t told it at the time, the screen was nicknamed “the guillotine.” When he was finally ready to go, the scientists moved to the observation area.

“Wait a minute!” Fine called out. “Where are my dirty jokes?”

Brewer ran in clutching several pages of randy puns, limericks, and blonde jokes. Fine inspected the lot.

“No, no, no!” she said. “These are too funny! He’ll laugh too hard and move his head. Run back and find some that are only moderately funny. And hurry!”

The conveyor table began to move, and in a moment May was inside the scanner. Metal banged and magnets whirred—WAKACHUCK! WAKACHUCK! WAKACHUCK!—as Fine first showed May a series of movies showing stationary and moving dots. Next, she showed him a series of human faces—one per second for 20 seconds—followed by twenty seconds of blank screen. Then, she projected a panoply of images of everyday objects. After a lunch break, she showed him several different motion stimuli. All the while, the scientists watched May’s brain for changes in oxidization and recorded the results.

Two hours later, the scientists thanked May for his time and for the opportunity to do such pioneering work. They told him it would be several days before they finished the first look at the data. Fine drove May back to Davis and said she would call him with the results. He stopped for a moment before leaving her car.

“Can I ask a final question?” May said.

“Of course,” replied Fine.

“Do you have any leftover jokes I can take with me?”

The fMRI specialists went to work on May’s scans. The results were unmistakable. The areas of his brain responsible for motion lit up like a pinball machine in response to motion stimuli—they were as robust as those areas in the brain of a normally sighted person. But the areas of May’s brain responsible for processing faces showed no response to faces. The areas responsible for recognizing objects showed no response to objects. The areas responsible for perceiving simple form did respond—weakly—but they seemed strangely disorganized in a way the scientists had never seen before. Fine took a deep breath and got ready to call May with the news.