Synopsis
An accessible resource to the structure and chemistry of the brain explains how its systems shape our perceptions, feelings, and behaviors while outlining his theory of the dynamic interaction between the four major brain systems. 40,000 first printing.
Extrait
1
DEVELOPMENT
She was doing it again. That young woman who periodically showed up dressed in a Western shirt and kerchief was standing in front of the automatic sliding doors at the Safeway supermarket. She'd look intently straight ahead, take five abrupt steps toward the doors, and try to restrain herself from walking through until they had fully opened. Sometimes she couldn't stop herself and nearly slammed right into the glass. Other times she'd wait long enough and then lunge through. Regardless, she'd back out and do it again. And again. Regular shoppers at the Phoenix, Arizona, store would hesitate beside her, then scurry past, eyeing her while trying not to stare. Once inside they'd shake their heads and make the usual comments: "Must be insane." They didn't know that Temple Grandin would go on to earn a doctorate in animal sciences and become an internationally recognized expert in animal handling. Or that she was autistic.
Temple had a normal birth, but by the time she was six months old she'd stiffen at her mother's touch and claw to free herself from her mother's hug. Soon she could not stand the feeling of other skin touching hers. A ringing telephone and a car driving by her house while a conversation was going on inside caused such severe confusion and hurt in the toddler's ears that she would tantrum, hitting whoever was within reach.
When she was three the doctors said that Temple had "brain damage." Her parents hired a stern governess, who structured the child's day around physical exercise and repetitive play such as "marching band." Occasionally the routine allowed Temple to focus on what she was doing, even speak. She taught herself to escape the stimuli around her, which caused pain in her overly sensitive nervous system, by daydreaming in pictures of places far away. By the time she reached high school she had made great progress. She could handle some of the academic subjects, and sometimes she could control her hypersensitive reactions to the chaos around her, primarily by shutting down to reduce the constant anxiety and fear. This made the other kids regard her as cold and aloof. She grew agonizingly lonely and would often tantrum or engage in pranks to combat her feelings of rejection. The school expelled her.
When she was sixteen Temple's parents sent her to an aunt's cattle ranch in Arizona. The rigid daily schedule of physical work helped her focus. She became fixated on the cattle chute, a large machine with two big metal plates that would squeeze a cow's sides. The high pressure apparently relaxed the animals, calming them enough for a vet to examine them. She visualized a squeeze machine for herself to give her the tactile stimulation she craved but couldn't get from human contact because the stimulation from physical closeness to another person was too intense, like a tidal wave engulfing her.
By this time Temple and her doctors had realized that she had a photographic memory. She was an autistic savant. When she returned to a special school for gifted children with emotional difficulties--the only school option left--her advisors allowed her to build a human squeeze machine. The project got her hooked on learning mechanical engineering and mathematics and on problem-solving, and she excelled at them all. She built a prototype, and would climb into it and use a lever to control the degree and duration of the pressure on her body. Afterward, she would feel relieved, more empathic, and more in touch with feelings of love and caring, even more tolerant of human touch. She started controlled experiments with the device and became skilled in research and lab techniques--which provided the impetus to apply to college.
Temple's state of hyperarousal and her inability to manage environmental stimuli impaired her ability to cope with the normal surroundings of her family or peers. The repetitive exercises as a child, the squeeze machine, and her academic successes gradually gave her the ability to control her offending behavior. Yet by her late twenties she still had had no success in creating social relationships. She was in a constant state of stage fright. She would get so anxious about approaching someone that she would literally race up and knock the person over, unable to restrain her muscles as she got emotionally energized. If she did manage to stop in time she would stand collar to collar, talking three inches from the person's face, an instant turnoff.
Then Temple put it all together. Walking up to someone in a socially acceptable way was the same as approaching the automatic doors at the supermarket. Both had to be done at the same relaxed pace. So she started showing up at the Safeway. She practiced approaching the doors for hours on end, until the process became automatic. The exercise helped. She found that she could approach people properly if she visualized herself approaching the doors. The doors were like a physical map; they provided a concrete visual picture of an abstract idea about approaching social interactions carefully.
Temple used another rehearsal technique to learn how to negotiate with people, a stressful interaction that usually sent her reeling. She read the New York Times's accounts of the Camp David peace talks conducted by President Jimmy Carter with Egypt's Anwar Sadat and Israel's Menachem Begin. She read every word and memorized them at once; being a savant came in handy. She played the conversations over and over again in her brain, like watching an internal videotape, and used them to guide her own conduct when negotiating with real people.
Today Temple Grandin, at fifty-one, leads a fulfilling professional and social life. It is twenty-five years since her training in front of the Safeway doors, and she has learned to pay attention to certain stimuli while ignoring others so that she does not become overly aroused. She also takes low doses of an antidepressant drug that alleviates her pent-up discomfort even better than the squeeze machine.
Temple resorted to a host of unusual practices to rewire her faulty brain circuits in order to control her conduct. She developed the circuits that enabled her to approach the supermarket doors, and then used these newly trained circuits to help position herself with relation to other people. She mastered each technique with practice, made it automatic, and then applied the newly imprinted pattern to other cognitive skills. Temple developed in adulthood the brain circuits her physical childhood development did not provide.
The brain is not a computer that simply executes genetically predetermined programs. Nor is it a passive gray cabbage, victim to the environmental influences that bear upon it. Genes and environment interact to continually change the brain, from the time we are conceived until the moment we die. And we, the owners--to the extent that our genes allow it--can actively shape the way our brains develop throughout the course of our lives. There is a great ongoing debate between different schools of neuroscientists as to whether the brain is merely a "ready-to-respond-to-environment" machine, an idea championed by a group who identify themselves as "connectionists," and those who would say that the brain is genetically made up of "ready-to-access" modules that the environment merely stimulates. However, the majority of neuroscientists see a hybrid, where the broad outlines of the brain's development are under genetic control, while the fine-tuning is up to the interaction of brain and environment.
Certainly, much of the course of our brains' development is determined while we are fetuses and young children. But as we will see, there are many other factors that can alter the process--in pregnancy, childhood, adulthood, and old age. A father's smile, exercise before the workday, a game of chess in the retirement home--everything affects development, and development is a lifelong process.
We are not prisoners of our genes or our environment. Poverty, alienation, drugs, hormonal imbalances, and depression don't dictate failure. Wealth, acceptance, vegetables, and exercise don't guarantee success. Our own free will may be the strongest force directing the development of our brains, and therefore our lives. As Temple's experience shows, the adult brain is both plastic and resilient, and always eager to learn. Experiences, thoughts, actions, and emotions actually change the structure of our brains. By viewing the brain as a muscle that can be weakened or strengthened, we can exercise our ability to determine who we become. Indeed, once we understand how the brain develops, we can train our brains for health, vibrancy, and longevity. Barring a physical illness, there's no reason that we can't stay actively engaged into our nineties.
Research on the brain's development has been fast and furious in this decade. The subject has become so popular that in the last few years it has rated a cover story in Time (three times), Newsweek (twice), and Life, as well as in other major magazines. New imaging technologies and scores of studies are providing enormous insight into ways to help the brain develop in babies, children, and adults, even in fetuses in the womb. Of course, there is also the chance here for misdirection.
The research has even prompted political action at the highest levels of government. In April 1997, Hillary Clinton hosted an all-day White House scientific conference, an unusual event, on new findings indicating that a child's acquiring language, thinking, and emotional skills is an active process that may be largely finished before age three. This premise is in stark contrast to the common wisdom of only a few years ago: that infants are largely passive beings who are somewhat unaware of their surroundings or who simply record everything in the environment without editing it. If infants are in fact editing and processing environmental stimuli, it behooves us to make these stimuli such good ones that they can move through them quickly and on to other learning.
The problem here is that such notoriety can cause sweeping action that may run ahead of sound clinical trials and testing of new hypotheses. Based on research that is not fully confirmed, panelists at the White House conference urged the adoption of federal programs to increase wages and training for day-care workers, improve parenting education, broaden training of pediatricians, and expand prenatal health-care coverage.
The best example of running ahead of research involves the "proof" that exposing infants to classical music enhances their brain development. Several recent studies indicate that this is so, yet others do not, and replication of the positive studies is not yet conclusive. Nonetheless, Georgia governor Zell Miller added $105,000 to his 1998 state budget proposal so that a cassette or compact disk of classical music could be included with the bag of free goodies that hospitals send home with each of the 100,000 babies born in the state each year. Miller's proposal, and his press conference about it, made national headlines. "No one questions that listening to music at a very early age affects the spatial, temporal reasoning that underlies math and engineering, and even chess," he said. "Having that infant listen to soothing music helps those trillions of brain connections to develop."
While the governor's awareness of brain research was commendable, his action might have been premature. The worry is not that it may waste the state's money. As Sandra Trehaub, a professor of psychology at the University of Toronto who studies infants' perception of music, said in response, "If we really think you can swallow a pill, buy a record or book, or have any one experience that will be the thing that gets you into Harvard or Princeton, then that's an illusion." John Breuer, president of the McDonnell Foundation, a funding organization for biomedical and behavioral research as it affects education, warns that though there may be great advantages to early education programs, neuroscience does not provide reasons for it yet. The link is just beginning to become clear. And as Michael Gazzaniga, a noted neuroscientist at Dartmouth, cautions, we are in danger of being overdone with "politically correct pseudoscience babble" when we allow our enthusiasm to outstrip facts.
Hillary Clinton realized herself that the White House conference could lead to premature and irresponsible decision-making and that the enthusiasm it catalyzed had to be tempered. Appearing on ABC's Good Morning America a week later, she admitted that the hyperfocus on properly stimulating babies "does ratchet up the guilt" about what parents ought and ought not to do.
That is why we will take a careful look at research findings throughout this book, and particularly in this chapter. There is much we can learn about how to improve the development of our brains and those of our children. But we have to keep a trained eye out to distinguish research that can be applied to our daily lives from that which is, for now, simply interesting.
A JUNGLE OF NEURONS
The human brain is responsible for the painting of Van Gogh, the creation of democracy, the design of the atomic bomb, psychosis, and the memory of one's first vacation and of the way that hot dog tasted. How does this organ encompass such diversity?
The brain is not a neatly organized system. It is often compared to an overgrown jungle of 100 billion nerve cells, or neurons, which begin as round cell bodies that grow processes called axons and dendrites. Each nerve cell has one axon and as many as 100,000 dendrites. Dendrites are the main way by which neurons get information (learn); and axons are the main way by which neurons pass on information to (teach) other neurons. The neuron and its thousands of neighbors send out roots and branches--the axons and dendrites--in all directions, which intertwine to form an interconnected tangle with 100 trillion constantly changing connections. There are more possible ways to connect the brain's neurons than there are atoms in the universe. The connections guide our bodies and behaviors, even as every thought and action we take physically modifies their patterns.
This description of the developing brain was heresy until recently. For decades scientists maintained that once its physical connections were completed during childhood, the brain was hard-wired. The tiny neurons and their interconnections were fixed; any neuron or link could die, but none could grow stronger, reorganize, or regenerate. Today, these axioms have been amended and enhanced. Thanks to sharp imaging technology and brilliant clinical research, we now have proof that development is a continuous, unending process. Axons and dendrites, and their connections, can be modified up to a point, strengthened, and perhaps even regrown.
Temple Grandin's achievement demonstrates that the brain has great plasticity. But what was actually going on, physically, inside her head? We get a strong clue from Michael Merzenich at the University of California, San Francisco.
Merzenich implanted electrodes in the brains of six adult squirrel monkeys, in the region that coordinates the movement of their fingers. Using computer imaging, he created a map of the neurons that fired when the monkeys manipulated objects with their hands. He then placed four food cups of decreasing diameter outside each of their cages. He put a single banana-flavored food pellet in the widest cup. The monkeys would reach through the bars and work their fingers into the cups until each was able to grasp its pellet and eat it. They practiced dozens of times for several days.
Once they had mastered the widest cup, Merzenich put the food pell...
Les informations fournies dans la section « A propos du livre » peuvent faire référence à une autre édition de ce titre.
