A music teacher who appeared to have unusual vision problems went to his ophthalmologist, but the doctor could not help him. He referred the man to neurologist Oliver Sacks, in hopes that a brain specialist could succeed where an eye specialist could not.
Sacks saw the man and his wife during an office visit. The man, whom Sacks calls “Dr. P.,” acted strangely. He cocked his head to face Sacks with his ears, not his eyes. And when Dr. P. did turn his gaze toward Sacks, it flicked from place to place in an unnatural way. Sacks sensed that Dr. P. was checking out his features one at a time. When the visit was over, Dr. P. got ready to leave. He reached for his wife’s head and tried to lift it as if it were his hat. His wife reacted as if it happened all the time.
For the next visit, Sacks went to Dr. P.’s home. Sacks wore a rose in his jacket lapel, but Dr. P. could not fathom what it was. He described it as “a convoluted red form with a green attachment.” Only when Dr. P. smelled the rose did he realize what it was.
Like this subject, described in Sacks’s book The Man Who Mistook His Wife for a Hat, a man in England also developed a strange change in his brain’s visual processing system late in life. In 1988, the man, named John in the story related in The Tell-Tale Brain by Vilayanur S. Ramachandran, went into the hospital for an operation to remove his appendix. While there, the 60-year-old suffered a stroke that destroyed a part of his brain. When John’s wife walked into his room, he no longer recognized her face. Nor could he recognize anyone’s face, for that matter—not even his own. John told his doctor that he could see perfectly well. What he couldn’t do was recognize objects instantly. Shown a carrot, John said, “It’s a long thing with a tuft at the end—a paint brush?”
Both men had a form of visual agnosia, a disorder that keeps the brain from recognizing or understanding the visual signals it receives via the retinas. Patients with agnosia often can describe shape, color, texture, and other details of what they see but cannot put the whole picture together. Typically, the disorder arises from damage to the posterior occipital lobes, home of the visual cortex, and the temporal lobes. John’s particular case included prosopagnosia, the inability to recognize faces. People with the condition often develop coping strategies, such as John’s technique of recognizing his wife by her voice. Interestingly, Sacks discovered in middle age that he had some degree of prosopagnosia himself. He had great difficulty with faces, especially when seeing them out of context. He realized that, beginning as a child, he recognized people by individual characteristics—a pink dress, big eyebrows, a thatch of red hair, and so on.
For the vast majority of children and adults, visual perception works easily and unconsciously. You look upon the world, and it makes sense. But that’s because 30 visual areas of the cortex synchronize their work to process individual bits of visual data, provide feedback to one another, and assemble an image. Once light bounces off an object, enters the eye, and is focused on the retinas, it is broken into electrical impulses. These impulses—like dots and dashes of Morse code—fly to the visual cortex for sophisticated processing. It no longer makes sense to speak of whole “images” in the brain. Signals for shape, color, movement, and so on go through processing before the brain’s visual networks construct a comprehensible representation of the world in the “mind’s eye.” Failure anywhere along the line can cause trouble. You can have fully functioning eyes and still not see.
LOOK AGAINThe brain’s role in constructing meaning out of what you see is easily demonstrated by optical illusions.
Illusions can emerge from retinal processing of the visual primary colors of red, green, and blue in the eye’s cone cells, or deeper in the brain’s neural networks. Two good examples of illusions resulting from neural processing are the Necker cube and Ames room. The former takes its name from the Swiss crystallographer Louis Albert Necker, who was looking at a cubic crystal through a microscope in 1832, when the back and front sides of the cube seemed to spontaneously flip. Necker repeated the illusion by devising a simple drawing of a transparent wire-frame cube whose perspective shifted as he gazed upon it. The viewer’s brain imposes order on the cube by selecting one face to be the one closest to the eyes. However, in short order, the brain switches orientation, sending the previously foremost square face to the back side. The brain chooses one perspective or the other, and cannot hold both images in mind at the same time.
The Ames room, named for inventor Adelbert Ames, Jr., is a grossly distorted room of trapezoidal shape that, when viewed from one point directly front and center, appears to have normal right-angled walls, floor, and ceiling. One corner opposite the viewer is much farther away than the other, but clever manipulation of perspective makes the room seem rectangular with the far wall parallel to the room’s front. A person in the far corner seems tiny while another person in the near corner appears gigantic; walking from one corner to the other makes a person appear to grow or shrink. The illusion works because the brain insists that the room must be a three-dimensional rectangular shape, which it has been conditioned to expect.
Illusions can have a practical side, tricking the brain into improving performance.
Psychologist Jessica Witt of Purdue University, who won a gold medal at the World Games as part of an Ultimate Frisbee team, examines the phenomenon of altered perception among athletes—those moments when the basketball rim seems larger or smaller, or the tennis net seems to get higher or lower. She noted that softball and tennis players report that when they’re hitting well, their brains perceive the ball as larger than normal. Witt performed a study, published in 2012, to make a golf cup seem larger. She and co-authors Dennis R. Proffitt of the University of Virginia and Sally A. Linkenauger of the Max Planck Institute-Tübingen set up a golf hole on a ramp. A projector shone 11 small circles around the cup, creating the illusion of the cup appearing larger than its normal diameter of four and one-quarter inches. College students using the optically enhanced cup sank 10 percent more putts than those without the enhancement. Expanding on her research, Witt said visual distractions confuse the brain and make it harder for athletes to perform. Crazy fans wagging giant foam fingers under the basket may actually alter the performance of free-throw shooters.
BRAIN INSIGHT
Finding Waldo
The search for the cartoon figure involves a coordinated mental effort
You probably know Waldo. Tall, thin. Wears jeans, a red-and-white pullover, and a matching cap. Round eyeglasses. Gets lost in crowds. For years, neuroscientists were split on how the brain orchestrated the search for Waldo’s tiny cartoon image amid huge illustrations in the popular Where’s Waldo? children’s books of Martin Handford. Some said the brain’s visual system worked like a spotlight, moving from image to image, in a manner known as serial processing. Others said the visual system took in the entire illustration and then used its focusing abilities to pull Waldo’s colors and shapes out of the jumble, in a manner known as parallel processing.
Turns out, both sides had part of the answer, according to Robert Desimone, director of the McGovern Institute for Brain Research at MIT. He led a study tracking brain activity in macaque monkeys executing a Waldo-like search. His team found that neurons in the V4 region of the visual cortex synchronize their signals to direct attention toward colors and shapes being sought. Desimone likens it to a chorus rising above a noisy party. Individual neurons detect and fire, and then join together to force a shift in gaze toward the object sought.
SEEING THE WORLD ANEWEye specialists sometimes perform image-based therapy to treat the complex interactions of eyes, brain, and body. So-called vision therapy has been used for a variety of conditions, including weak or missing binocular vision (resulting from poor coordination between the nerves of the two eyes); amblyopia, or “lazy eye”; strabismus, or “crossed eyes”; and other deficiencies in how patients’ brains process visual sensations. Exercises may include viewing three-dimensional images to encourage the brain to process the dual eye signals that promote depth perception.
Children sometimes are misdiagnosed with disorders in their prefrontal cortex when instead they have difficulty processing visual data in the occipital lobe, such as seeing in only two dimensions or failing to maintain focus. Illusions and graphics used in vision therapy challenge the brain to make sense of a three-dimensional world, by adding depth and dimension, and encourage the growth of neural pathways to process new ways of seeing.
Versions of 3-D imaging systems have existed since the 19th century, when stereographs transported viewers to the pyramids, European capitals, and distant battlefields. A wood-and-glass stereograph viewer held a card, bearing two pictures side by side, that the viewer could examine through two lenses that resembled binoculars. The two pictures were taken at the same time by a special camera with lenses a few inches apart, approximating the distance between human eyes. This parallax view created the 3-D effect. Modern versions of the stereograph include polarized images, 3-D movies and glasses, and Magic Eye stereograms—those pictures that look like random collections of colored dots until, when stared at long enough, a 3-D picture emerges.
BRAIN INSIGHT
Mirror, Mirror
Your eyes can fool your brain
Derek Steen had his left arm amputated after shredding it in a motorcycle accident. Trouble was, he continued to feel the arm—a phenomenon called “phantom limb.” And the arm was in pain.
Steen’s condition occurred because his brain redrafted its body map after losing contact with arm nerve impulses. It misinterpreted signals from other body parts as originating in the missing limb, making it feel real.
In the mid-1990s, neuroscientist Vilayanur S. Ramachandran tricked Steen’s brain into taking away his pain by reacting as if the missing arm had been restored. Ramachandran constructed a simple mirror box, open at the top with a hole on the side for inserting Steen’s right arm. The box’s central mirror made it appear as if Steen had two healthy arms. Seeing his “left arm” let Steen access and fire the neurons for its movement. After three weeks of mirror box therapy, his pain went away. Mirror boxes have since been used to treat a variety of conditions.
The box underlines how the brain constructs reality out of feedback loops combining vision, other senses, body movements, and motor commands. The brain reacts to what it sees, even if what it sees is a lie.
DROWNING OUT DISTRACTIONSAttention allows the brain to consciously pick out salient sensory information and ignore the rest. At a cocktail party, selective attention lets you understand the conversation of someone sitting next to you by focusing on the sound of a voice and the motion of lips and face. Laboratory experiments have examined visual selective attention by having test subjects pick out words, letters, or pictures from similar images acting as background noise. The greater the similarity between the targeted image and the distractors, as between the letters O and Q, the greater difficulty the brain has in finding its prey. Research has also shown that the brain has greater difficulty as it ages in executing so-called conjunctive searches, which involve seeking two unrelated but linked visual characteristics. A simple search would target a chocolate-iced doughnut in a room full of vanilla-iced doughnuts. A conjunctive search would make the target a chocolate-iced doughnut in a room containing vanilla-iced doughnuts and chocolate-iced éclairs. That particular search requires comprehension of shape (round versus rectangular) and color (brown versus white).
One study found that young brains outperformed old brains in the conjunctive search for a red X in a field of green Xs and red Os. However, this age-related deficit decreases if the older brain has experience with the targeted object and distractors. For example, middle-age medical technicians performed as well as younger medical technicians when evaluating x-rays, a task that requires seeking particular information amid a host of distractors. Broader applications suggest themselves. You’ll improve your handling of loose change, including distinguishing one coin from another, if you practice. So too will you improve your sorting of buttons, stamps, or shoes. What you practice with your visual and prefrontal cortices, you improve.
When your brain “pays attention,” you choose where to pinpoint your focus. A related phenomenon called visual attention occurs below the level of consciousness. It happens as you drive, read, or interact with other people. When you’re behind the wheel of a car heading down the highway, for example, your brain automatically scans the environment looking for anything requiring a reaction. It could be anything from a dog running onto the pavement to a car entering the highway via an on-ramp and inching sideways toward you.
One measure of visual attention is the so-called attentional blink. It’s the time required for the brain to shift from one stimulus to another one. Research on attentional blinks has focused on video games and challenges as ways to improve visual attention for young and old.
A team at the University of Rochester has found that skilled players of action video games, the kind where the player typically has to react instantly to shoot a monster or enemy soldier, have a shorter attentional blink than people who don’t play video games or players who prefer slower simulation games. Some action-game players, including Shawn Green, one of the researchers, shift attention so rapidly that they lack a measurable attentional blink entirely.
Green found that action-game players can easily keep track of five objects at the same time on the video screen. Nongamers handle only three. Further investigation revealed that these differences are neither inborn nor a matter of people with various attentional blink levels self-selecting their preferred games. When nonplayers took up video gaming and practiced the high-action kind, they shortened their attentional blink.
Similar studies of people performing Internet searches—the manipulation of words in search engines to maximize returns—revealed that practicing search techniques increased activity in the frontal lobes, particularly in working and short-term memory, complex reasoning, and decision making.
BRAIN INSIGHT
Investigating Adderall Abuse
Some brain-altering drugs may be reaching more than their target audience
Each year, 21 million prescriptions for medication to treat attention-deficit disorder are filled for Americans ages 10 to 19. Yet some of these prescriptions are going to students without a legitimate need. Many students abuse such drugs because they help focus attention, particularly while studying for and taking tests. In 2012, the New York Times reported that, according to interviews with doctors and students at more than 15 prestigious schools, 15 to 40 percent of students take stimulants to help them study.
Adderall, an amphetamine that treats attention deficit/hyperactivity disorder, has become routinely abused, especially at highly competitive schools where excellent performance is a step toward admission to an elite college. A federal drug enforcement agency said Adderall abuse exists throughout the United States.
Abuse can alter mood or lead to other drugs. And, as it was designed to do, Adderall affects brain function by interfering with neurons’ ability to reabsorb dopamine from the synapses. Extended Adderall use lowers dopamine levels.
“Children have prefrontal cortexes that are not fully developed, and we’re changing the chemistry of the brain. That’s what these drugs do,” Paul L. Hokemeyer, a family therapist in Manhattan, told the Times.
Users apparently either don’t know potential risks, or choose to gamble long-term negatives for short-term gain.
Software and online companies have developed programs to increase visual attention as well as cognitive processing speed, memory, and executive function. Those are exactly the skills that make a good driver, so it makes sense that computer-based programs have sprung up to improve driving skills. These include DriveSharp by Posit Science of San Francisco, a visual memory system that aims to train a driver’s brain to think and react faster. The manufacturer claims that people who use the system three times a week reduce their crash risk and improve their reaction time. One of the Posit Science games, US 66 Road Tour, aims to improve the useful field of view to get drivers to hit their brakes in time to avoid an accident. Players must match cars on the screen with those that appeared previously. Then, they must continue that challenge while adding a new one: pinpointing a road sign when it appears. Cars and signs eventually appear for only a moment, making more demands on visual attention.
Insurance companies have shown interest in Posit Science and other companies’ brain-training software for drivers. One company, for example, invited 100,000 of its Pennsylvania customers to try Posit Science’s software. Only 8,000 accepted. The San Francisco Chronicle, which reported on the insurance company’s offer, raised a concern: Insurance companies might hold bad scores on a driver-improvement game against the players.
