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Scientists used to believe adult brains did not grow any new neurons, but it has emerged that new neurons can sprout in the brains of adult rats, birds and even humans. Understanding the process could be important, for finding ways to treat diseases such as Alzheimer"s in which neurons are destroyed. Most neurons sprouting in adulthood seem to be in the hippocampus, a structure involved in learning and memory. But they rarely survive more than a few weeks. "We thought they were possibly dying because they were deprived of some sort of input," says Elizabeth Gould, a neuroscientist at Princeton. Because of the location, Gould and her colleagues suspect that learning itself might bolster the new neurons" survival, and that only tasks involving the hippocampus would do the trick. To test this, they injected adult male rats with a substance that labeled newborn neurons so that they could be tracked. Later, they gave some of the rats standard tasks. One involved using visual and spatial cues, such as posters on a well, to learn to find a platform hidden under murky water. In another, the rats learnt to associate a noise with a tiny shock half a second later. Both these tasks use the hippocampus — if this structure is damaged, rats can"t do them. Meanwhile, the researchers gave other rats similar tasks that did not require the hippocampus finding a platform that was easily visible in water, for instance. Other members of the control group simply paddled in a tub of water or listened to noises. The team reported in Nature Neuroscience that the animals given the tasks that activate the hippocampus kept twice as many of their new neurons alive as the others. "Learning opportunities increase the number of neurons," says Gould. But Fred Gage and his colleagues at the Salk Institute for Biological Studies in La Jolla, California, dispute this. In the same issue of Nature Neuroscience, they reported that similar water maze experiments on mice did not help new neurons survive. Gould thinks the difference arose because the groups labeled new neurons at different times. She gave the animals tasks two weeks after the neurons were labeled. When the new cells would normally be dying, she thinks the Salk group put their mice to work too early for new neurons to benefit. "By the time the cells were degenerating, the animals were not learning anything." she says. Which of the following can be the best title for the passage
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It seems intuitive that going to a specialist physician will result in more thorough and up-to-date care for whatever ails you. In fact many studies support this idea — but health-care researchers caution that they may not tell the whole story. The first question is whose patients are sicker Specialists tend to treat more complicated forms of disease but generalists — family physicians and general practitioners — are more likely to treat patients with several coexisting diseases. A second question is what counts as the most valuable treatment Specialists are more familiar with standards of care for the diseases they treat regularly, says Harlan M. Krumholz of Yale University. On the other hand, a generalist may do a better job of coordinating a patient"s care and keeping an eye on a person"s overall health, says Martin T. Domohoe of the Oregon Health Sciences University in Portland. To further complicate comparisons many generalists will consult with specialists on complicated cases but medical records do not always show that, says Carolyn Clancy of the Agency for Health Care Policy and Research in Rockville, Md. That said stroke patients treated by neurologists are more likely to survive than stroke patients treated by generalists. Among about 38,000 stroke sufferers nationwide, 16.1% of those treated by a neurologists died within 3 months compared with 25.3 percent of those treated by family physicians. Several studies have shown that people with heart disease fare better when they are treated by cardiologists, says S. Nash of the Mount Sinai Medical Center in New York. But it"s hard to figure out exactly why. "Physician specialty, in addition to being a measure of formal training in the field, is also a proxy for clinical experience." he says, "It"s very difficult to separate out the overlapping concepts. One, that practice makes perfect; two, the effect of the educational and time investments in a clinical problem the physician is simply interested in; and three, the issue of formal training." Differences between specialist care and generalist care, however. Pale in comparison with the finding that both specialists and generalists often fail to put the latest knowledge into practice, contend both Donohoe and Clancy. A report by the US General Accounting Office documented that heart attack survivors who saw cardiologists regularly were more likely to take cholesterol-lowering drugs and beta blockers which reduce heart rate and blood pressure than those who received care from a generalist. Even so, these life-prolonging drugs were not prescribed to many patients who appeared to be eligible for them, implying that both generalists and specialists could do better. "Maybe we are focusing too much energy on the differences between generalist and specialist care," says Donohoe. Perhaps, he adds, "We should focus more intently on improving the quality of communication between generalists and specialists and on developing and promoting practice guidelines that might have a much bigger effect on the overall health of Americans." According to the passage, the better treatment of stroke and heart disease on the part of specialists______.
Children are spending an increasing amount of time using computers. Computers are now found in most classrooms, and in the majority of homes, almost always with internet access. However, many studies of children"s use of computers show that there are possible negative effects. This essay will explain the possible negative effects of computer use on children, focusing on the effects on family and peer relationships and the increased tendency towards violent behavior. Computer use may negatively affect social relationship between children and their parents. Because children spend so much time on computers, they often know more about advanced computer use than their parents. According to Subrahmanvam and his colleagues(2001)this often leads to a role reversal, where the child becomes a teacher to the parent. In other words, it is often the case a highly computer technology. This can lead to a reduction in parental authority. Moreover, with the anonymity of online communication, computer users do not know if they are talking to a child or an adult, so all users are treated equally(Subrahmanyam et al, 2001). Children may then expect the same equality in real life, further contributing to a breakdown in the parent-children relationship(Subrahmanyam et al, 2001). Children"s peer relationships can also be negatively affected by extensive computer use. Since computers are more likely to be used in isolation by children, they spend little time integrating with their peers(Shields & Behrman, 2001). As a result, children may not develop the social skills they need, or be able to maintain friendships in the real world(Subrahmanyam et al, 2001). With the very extended computer use, this isolation from the real world can lead to loneliness and even depression(Shields & Behrman, 2001). A disturbing possible effect of computer use on children is the link between computer games and violence. Current research has already documented a strong link between violent films and television and aggressive behavior in children, so it is reasonable to believe that a similar link will be found between violent behavior in children and violence in computer games(Subrahmanyam et al, 2001). However, as Shields Behrman(2001)points out, it is important to note that although the games may affect all children, children who prefer violent games could be most affected. In conclusion, using a computer. particularly for extended periods, may affect the parent-children relationship in families. It could also result in children not learning the social skills they need to interact with peers and maintain friendships. Moreover, it seems likely that playing violent computer games is linked to violence in children. Although the research is not conclusive, it appears that extended use of computers could have a negative effect on children"s social development. From the very beginning, the author is trying to draw our attention to______.
Here"s yet another to lose weight. Heavier people are more likely to be killed or seriously injured in car accidents than lighter people. That could mean car designers will have to build in new safety features to compensate for the extra hazards facing overweight passengers. In the US, car manufacturers have already had to redesign air bags so they inflate to lower pressures making them less of a danger to smaller women and children. But no one yet knows what it is that puts overweight passengers at extra risk. A study carried out in Seattle, Washington, looked at more than 26,000 people who had been involved in car crashes, and found that heavier people were at far more risk. People weighing between 100 and 119 kilograms are almost two-and-a-half times as likely to die in a crash as people weighing less than 60 kilograms. And importantly, the same trend held up when the researchers looked at body mass index(BMI)— a measure that takes height as well as weight into account. Someone 1.8 meters tall weighing 126 kilograms would have a BMI of 39, but so would a person 1.5 meters tall weighing 88 kilograms. People are said to be obese if their BMI is 30 or over. The study found that people with a BMI of 35 to 39 are over twice as likely to die in a crash compared with people with BMIs of about 20. It"s not just total weight, but obesity that"s dangerous. While they do not yet know why this is the case, the evidence is worth pursuing, says Charles Mock, a surgeon and epidemiologist at the Harborview Injury Prevention and Research Center in Seattle, who led the research team. He thinks one answer may be for safety authorities to use — heavier crash-test dummies when certifying cars are safe to drive. Crash tests normally use dummies that represent standard-sized males weighing about 78 kilograms. Recently, smaller crash-test dummies have also been used to represent children inside crashing cars. But larger and heavier dummies aren"t used, the US National Highway Traffic Safety Administration in Washington, D.C. told New Scientist. The reasons for the higher injury and death rates are far from clear. Mock speculates that car interiors might not be suitably designed for heavy people. Or obese people, with health problems such as high blood pressure or diabetes, could be finding it tougher to recover from injury. Which of the following questions is closely related to the passage
Here"s yet another to lose weight. Heavier people are more likely to be killed or seriously injured in car accidents than lighter people. That could mean car designers will have to build in new safety features to compensate for the extra hazards facing overweight passengers. In the US, car manufacturers have already had to redesign air bags so they inflate to lower pressures making them less of a danger to smaller women and children. But no one yet knows what it is that puts overweight passengers at extra risk. A study carried out in Seattle, Washington, looked at more than 26,000 people who had been involved in car crashes, and found that heavier people were at far more risk. People weighing between 100 and 119 kilograms are almost two-and-a-half times as likely to die in a crash as people weighing less than 60 kilograms. And importantly, the same trend held up when the researchers looked at body mass index(BMI)— a measure that takes height as well as weight into account. Someone 1.8 meters tall weighing 126 kilograms would have a BMI of 39, but so would a person 1.5 meters tall weighing 88 kilograms. People are said to be obese if their BMI is 30 or over. The study found that people with a BMI of 35 to 39 are over twice as likely to die in a crash compared with people with BMIs of about 20. It"s not just total weight, but obesity that"s dangerous. While they do not yet know why this is the case, the evidence is worth pursuing, says Charles Mock, a surgeon and epidemiologist at the Harborview Injury Prevention and Research Center in Seattle, who led the research team. He thinks one answer may be for safety authorities to use — heavier crash-test dummies when certifying cars are safe to drive. Crash tests normally use dummies that represent standard-sized males weighing about 78 kilograms. Recently, smaller crash-test dummies have also been used to represent children inside crashing cars. But larger and heavier dummies aren"t used, the US National Highway Traffic Safety Administration in Washington, D.C. told New Scientist. The reasons for the higher injury and death rates are far from clear. Mock speculates that car interiors might not be suitably designed for heavy people. Or obese people, with health problems such as high blood pressure or diabetes, could be finding it tougher to recover from injury. While exploring the reason for the higher injury and death rates, Mock would most probably say that______.
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