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  3. The Science of Anxiety All animals, especially the small kind, appear to feel anxiety. Humans have felt it since the days t

The Science of Anxiety All animals, especially the small kind, appear to feel anxiety. Humans have felt it since the days t

admin2009-04-23  44
问题                                     The Science of Anxiety
     All animals, especially the small kind, appear to feel anxiety. Humans have felt it since the days they shared the planet with saber-toothed tigers. But we live in a particularly anxious age. A recent study found that eight months after the September 11 event, nearly two-thirds of Americans think about the terror attacks at least several times a week. And it doesn’t take much for all the old fears to come rushing back. What was surprising about the recent drumbeat of terror warnings was how quickly it triggered the anxiety so many of us thought we had put behind us.
    This is one of the mysteries of anxiety. While it is a normal response to physical danger and can be a useful tool for focusing the mind when there’s a deadline looming-anxiety becomes a problem when it persists too long beyond the immediate threat. Sometimes there’s an obvious cause. Other times, we don’t know why we can’t stop worrying.
    Anxiety disorder—which is what health experts call any anxiety that persists to the point that it interferes with one’s life—is the most common mental illness in the US which in its various forms, afflicts 19 million  Americans.
    In recent years, researchers have made significant progress in nailing down the underlying science of anxiety. In just the past decade, they have come to appreciate that whatever the factors that trigger anxiety, it grows out of a response that is rooted in our brains. They have learned, among other things:
    -There is a genetic component to anxiety; some people seem to be born worriers.
    -Brain scans can reveal differences in the way patients who suffer from anxiety disorders respond to danger signals.
    -Due to a shortcut in our brain’s information-processing system, we can respond to threats before we become aware of them.
    -The root of an anxiety disorder may not be the threat that triggers it but a breakdown in the mechanism that keeps the anxiety response from careering out of control.
    Before we dig into the latest research, let’s define a few terms. Though we all have our own intuitive sense of what the words stress and fear mean, scientists use these words in very specific ways. For them, stress is an external stimulus that signals danger, often by causing pain. Fear is the short-term response such stresses produce in men, women or lab rats. Anxiety has a lot of the same symptoms as fear, but it’s a feeling that lingers long after the stress has lifted and the threat has passed.
    In general, science has a hard time pinning down emotions because they are by nature so slippery and subjective. Most people are as clueless about why they have certain feelings. But fear is the one aspect of anxiety that’s easy to recognize. Humans break out in a cold sweat. Heartbeats race, and blood pressure rises. That gives scientists something they can control and measure.
    Indeed, a lot of what researchers have learned about the biology of anxiety comes from scaring rats and then cutting them open. The researchers destroy small portions of the rats’ brains to see what effect that has on their reactions. By painstakingly matching the damaged areas with changes in behavior, scientists have, bit by bit, created a road map of fear as it travels through the rat’s brain.
    The journey begins when a rat feels the stress, in this case an electric shock. The rat’s senses immediately send a message to the central portion of its brain, where the stimulus activates two neural pathways. One of these pathways is a relatively long, circuitous route(迂回径路) through the cortex(脑皮层), where the brain does its most elaborate and accurate processing of information. The other route is a kind of emergency shortcut that quickly reaches a cluster of cells called the amygdale(扁桃体).
    What’s special about the amygdala is that it can quickly activate just about every system in the body to fight like the devil or run like crazy. It’s not designed to be accurate, just fast. If you have ever gone hiking and been startled by a snake that turned out to be a stick, you can thank your amygdala.
    But while the amygdala is busy telling the body what to do, it also fires up a nearby curved cluster of neurons called the hippocampus. The job of the hippocampus is to help the brain learn and form new memories. And not just any memories. The hippocampus allows a rat to remember where it was when it got shocked and what was going on around it at the time. Such contextual learning helps the rat avoid dangerous places in the future. It probably also helps it recognize what situations are likely to be relatively safe. This makes sense, in terms of survival. After all, it’s better to panic unnecessarily than to be too relaxed in the face of life-threatening danger.
    Discovering this basic neural circuitry(路线) turned out to be a key breakthrough in understanding anxiety. It showed that the anxiety response isn’t necessarily caused by an external threat; rather, it may be traced to a breakdown in the mechanism that signals the brain to stop responding. Just as a car can go out of control due to either a stuck accelerator or failed brakes, it’s not always clear which part of the brain is at fault. It may turn out that some anxiety disorders are caused by an overactive accelerator while others are caused by an underactive prefrontal cortex (call it the brake).
    Of course, what you would really like to know is whether any of the work done in rats applies to humans. Clearly researchers can’t go around performing brain surgery on the amygdales of living patients to see if it affects their anxiety levels. But the fascinating case of a woman known only by her research number, SM046, suggests that when it comes to fear, rats and humans really aren’t so different.
    Owing to an unusual brain disorder, SM046 has a defective amygdala. As a result, her behavior is abnormal in a very particular way. When scientists at the University of Iowa show SM046 pictures of a series of faces, she has no trouble picking out those that are happy, sad or angry. But if the face is displaying fear, she cannot recognize the feeling. She identifies it as a face expressing some intense emotion, but that is all. Her unusual condition strongly suggests that even in humans, fear takes hold in the amygdala.
    Eventually, researchers would like to learn what role our genes, as opposed to our environment, play in the development of anxiety. "It has been known for some time that these disorders run in families," says Kenneth Kendler, a psychiatric geneticist at Virginia Commonwealth University in Richmond, Va. "So the next logical question is the nature-nurture issue." In other words, are anxious people born that way, or do they become anxious as a result of their life experiences?
    Kendler and his colleagues approached the question by studying groups of identical twins, who share virtually all their genes, and fraternal twins, who share only some of them. What Kendler’s group found was that both  identical twins were somewhat more likely than both fraternal twins to suffer from generalized anxiety disorder, phobias(恐怖症) or panic attacks.
    The correlation isn’t 100%, however. "Most of the heritability is in the range of 30% to 40%," Kendler says. That’s a fairly moderate genetic impact, he notes" Your genes set your general vulnerability," he concludes. "You can be a low-vulnerable, intermediate-vulnerable or a high-vulnerable person.” But your upbringing and your experiences still have a major role to play. Someone with a low genetic vulnerability, for example, could easily develop a fear of flying after surviving a horrific plane crash.
    So, there are no guidebooks to tell you when it’s safe to venture out again. Our brains are even now in the process of rewiring themselves. How successfully we navigate this delicate transition will depend a lot on our genes, our environment and any future attacks.
选项 A、Y
B、N
C、NG
答案B
解析 定位到文章第二段第二句破折号后anxiety becomes a problem when it persists too long beyond the immediate threat(如果在受到威胁后焦虑时间过长，那焦虑就变成问题了)。所以，焦虑过久没有好处，也并不是所有的焦虑都对人有好处。题干与原文不符。
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