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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 clearly tell the two groups of rats from each other in the test
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Whenever people go and live in another country they have new experiences and new feelings. They experience culture shock. Many people have a(n) 【C1】______about culture shock they think that it"s just a feeling of sadness and homesickness when a person is in a new country. But this isn"t really true. Culture shock is a completely natural【C2】______. and everybody goes【C3】______it in a new culture. There are four stages, or steps, in culture shock. When people first arrive in a new country they"re usually excited and【C4】______Everything is interesting. They notice that a lot of things are【C5】______their own culture and this surprises them and makes them happy. This is Stage One In Stage Two people notice how different the new culture is from their own culture. They become confused It seems difficult to do even very simple things. They feel【C6】______They spend a lot of time【C7】______or with other people from their own country. They think "My problems are all because I"m living in this country" Then in Stage Three they begin to understand the new culture better They begin to like some new customs. They【C8】______some people in the new country. They"re【C9】______comfortable and relaxed. In Stage Four they feel very comfortable. They have good friends in the new culture. They understand the new customs. Some customs are similar to their culture and some are different but that"s OK. They can【C10】______it. 【C3】
Whenever people go and live in another country they have new experiences and new feelings. They experience culture shock. Many people have a(n) 【C1】______about culture shock they think that it"s just a feeling of sadness and homesickness when a person is in a new country. But this isn"t really true. Culture shock is a completely natural【C2】______. and everybody goes【C3】______it in a new culture. There are four stages, or steps, in culture shock. When people first arrive in a new country they"re usually excited and【C4】______Everything is interesting. They notice that a lot of things are【C5】______their own culture and this surprises them and makes them happy. This is Stage One In Stage Two people notice how different the new culture is from their own culture. They become confused It seems difficult to do even very simple things. They feel【C6】______They spend a lot of time【C7】______or with other people from their own country. They think "My problems are all because I"m living in this country" Then in Stage Three they begin to understand the new culture better They begin to like some new customs. They【C8】______some people in the new country. They"re【C9】______comfortable and relaxed. In Stage Four they feel very comfortable. They have good friends in the new culture. They understand the new customs. Some customs are similar to their culture and some are different but that"s OK. They can【C10】______it. 【C2】
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. Not until recently did scientists find out that ______.
Patients can recall what they hear while under general anesthetic even if they don"t wake up, concludes a new study. Several studies over the past three decades have reported that people can retain conscious or subconscious memories of thoughts that happened while they were being operated on. But failure by other researchers to confirm such findings has led skeptics to speculate that the patients who remembered these events might briefly have regained consciousness in the course of operations. Gitta Lubke, Peter Sebel and colleagues at Emory University in Atlanta measured the depth of anesthesia using bispectral analysis, a technique which measures changes in brainwave pattern in the frontal lobes moment by moment during surgery. "Before this study researchers only took an average measurement over the whole operation," says Lubke. Lubke studied 96 trauma patients undergoing emergency surgery. Many of whom were too seriously injured to tolerance full anesthesia. During surgery each patient wore headphones through which a series of 16 words was repeated for 3 minutes each. At the same time bisecteal analysis recorded the depth of anesthesia. After the operation Lubke tested the patients by showing them the first three letters of a word such as "limit", and asking them to complete. Patients who had had a word starting with these letters played during surgery — "limit", for example — chose that word an average of 11 per cent more often than patients who had been played a different word list. None of the patients had any conscious memory of hearing the word lists. Unconscious priming was strongest for words played when patients were most lightly anaesthetized. But it was statistically significant even when patients were fully anaesthetized when the word was played. This finding which will be published in the journal Anesthesiology could mean that operating theatre staff should be more discreet. "What they say during surgery may distress patient afterwards," says Philip Merikle, a psychologist at the University of Waterloo, Ontario. What we can infer from the finding______.
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