题目内容
For many years, people believed that the brain, like the body, rested during sleep. After all, we are rendered unconscious by sleep. Perhaps, it was thought, the brain just needs to stop thinking for a few hours every day. Wrong. During sleep, our brain -- the organ that directs us to sleep -- is itself extraordinarily active. And much of that activity helps the brain to learn, to remember and to make connections. It wasn’t so long ago that the regretful joke in research circles was that everyone knew sleep had something to do with memory -- except for the people who study sleep and the people who study memory. Then, in 1994, Israeli researchers reported that the average performance for a group of people on a memory test improved when the test was repeated after a break of many hours -- during which some subjects slept and others did not. In 2000, a Harvard team demonstrated that this improvement occurred only during sleep. There are several different types of memory -- including declarative (fact-based information), episodic (events from your life) and procedural (how to do something) -- and researchers have designed ways to test each of them. In almost every case, whether the test involves remembering pairs of words, tapping numbered keys in a certain order or figuring out the rules in a weather- prediction game, "sleeping on it" after first learning the task improves performance. It’s as if our brains squeeze in some extra practice time while we’re asleep. This isn’t to say that we can’t form memories when we’re awake. If someone tells you his name, you don’t need to fall asleep to remember it. But sleep will make it more likely that you do. Sleep-deprivation experiments have shown that a tired brain has a difficult time capturing memories of all sorts. Interestingly, sleep deprivation is more likely to cause us to forget information associated with positive emotion than information linked to negative emotion. This could explain, at least in part, why sleep deprivation can trigger depression in some people: memories stained with negative emotions are more likely than positive ones to "stick" in the sleep-deprived brain. Sleep also seems to be the time when the brain’s two memory systems -- the hippocampus (海马体) and the neocortex (新皮质) -- "talk" with one other. Experiences that become memories are laid down first in the hippocampus, eliminating whatever is underneath. If a memory is to be retained, it must be shipped from the hippocampus to a place where it will endure -- the neocortex, the wrinkled outer layer of the brain where higher thinking takes place. Unlike the hippocampus, the neocortex is a master at weaving the old with the new. And partly because it keeps incoming information at bay, sleep is the best time for the "undistracted" hippocampus to shuttle memories to the neocortex, and for the neocortex to link them to related memories. What do we know about the brain from the first paragraph
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Questions 19 to 22 are based on the conversation you have just heard.
患者因失眠睡前服用苯巴比妥钠100mg，第二天上午呈现宿醉现象，这属于
The curse of jet lag has struck most international travelers at one time or another -- and anyone lucky enough to have avoided it will surely have suffered the equally unpleasant sleep-deprivation involved in an early-morning start. Nor, as shift workers know too, is it possible to escape by going to bed earlier the previous evening, and thus putting sleep in the bank. Sleepiness is controlled by the body’s internal biological clock, so an earlier bedtime just means several wakeful hours staring in frustration at a darkened ceiling. For years, some travelers and shift workers have sworn by melatonin (褪黑素). This is a hormone that regulates the biological clock. It is made in the brain by a structure called the pineal gland (松果体), as darkness sets in after sunset. Light is the one that keeps the biological clock in the same pace with solar time. The clock then tells the brain when to go to sleep. The theory of those who use melatonin is that an external dose of it can reset the clock, and thus cause the "go to sleep" signal to be sent at a more convenient moment~ Melatonin can also increase sleepiness during the day, when the pineal gland is not producing it. This has resulted in a growing, and often unregulated, market in melatonin-supplement tablets. The pharmaceutical industry’s response to this seems to be: "If you can’t beat them, join them." A paper in this week’s Lancet, by Shantha Rajaratnam of the Harvard Medical School and his colleagues, reports two trials, funded by drug companies, of tasimelteon, a substance that binds to the same receptors in the brain as melatonin does, and which it is expected will have a similar effect. In the course of these trials, more than 400 people had their bedtimes brought forward by five hours in controlled conditions. Half an hour before lights out, a quarter of them were given common drug, while the remaining three-quarters were given varying doses of tasimelteon. Dr. Rajaratnam and his colleagues report that the new drug let people fall asleep faster at the unnaturally early time, and also allowed them to sleep longer than those given the common one. When will melatonin be made in the brain according to the passage
An epidemic of swine flu (猪流感) has recently developed in Mexico and the United States, says the CDC. Swine flu has killed many people, and the outbreak has features that suggest it could become a global pandemic (瘟疫). A pandemic is an epidemic that spreads around the whole world. Pandemics also often cause more severe disease than epidemics. Flu is a disease caused by the influenza virus. Humans, pigs, birds and other animals all can be infected by influenza viruses. Typically, influenza viruses can infect only one species, so the influenza viruses of humans are different from those of pigs and birds. However, sometimes a virus can infect more than one species. For examples, pigs sometimes can be infected not only with pig influenza viruses, but also with human and bird influenza viruses. Then these viruses can come up to one another secretly and swap (交换) genes, creating new viruses that have a mix of genes -- from human, pig, and bird viruses. That is what has happened with this new swine flu virus. Sometimes this swapping of genes allows a virus that was originally able to infect only pigs or only birds to also infect humans. When that happens, we refer to the illness as "swine flu" or "bird flu". This current virus could actually be called "swine/bird flu", since it has some genes from pig flu viruses and other genes from bird flu viruses. Most viruses that cause swine flu or bird flu are very hard to pass from one human to another: they don’t cause epidemics. Sometimes, however, further changes in genes create a virus that can spread rapidly among humans, and can produce a more severe illness. One reason this illness is more severe is that the virus is so new. The regular flu that comes each year is caused by a regular human influenza virus that often has similarities to the viruses that have caused the flu in years past, so people have some degree of immunity to the latest virus. The unusual swine flu or bird flu viruses that develop the ability for person-to-person spread are so different that people have little or no immunity to them. The worst global pandemic in modem times was the influenza pandemic of 1918 to 1919. It affected about a third of the human race, and killed at least 40 million people in less than a year -- more than those who have been killed by AIDS in three decades. The world economy went into a deep recession. The average length of life dropped for 10 years. Unfortunately, the new swine flu virus can be transmitted between humans. It is not clear yet how easily it is transmitted, nor how it is transmitted. Almost surely it is transmitted by sneezing and coughing, and by skin-to-skin contact with an infected person. According to the passage, a pandemic ______.
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