gre考试阅读真题解析(A)

　　Much of the research on hallucinogenic drugs such as LSD has focused on the neurotransmitter serotonin, a chemical that when released from a presynaptic serotonin-secreting neuron causes the transmission of a nerve impulse across a synapse to an adjacent postsynaptic, or target, neuron. There are two major reasons for this emphasis. First, it was discovered early on that many of the major hallucinogens have a molecular structure similar to that of serotonin. In addition, animal studies of brain neurochemistry following administration of hallucinogens invariably reported changes in serotonin levels.

　　Early investigators correctly reasoned that the structural similarity to the serotonin molecule might imply that LSDs effects are brought about by an action on the neurotransmission of serotonin in the brain. Unfortunately, the level of technical expertise in the field of brain research was such that this hypothesis had to be tested on peripheral tissue . Two different groups of scientists reported that LSD powerfully blockaded serotonins action. Their conclusions were quickly challenged, however. We now know that the action of a drug at one site in the body does not necessarily correspond to the drugs action at another site, especially when one site is in the brain and the other is not.

　　By the 1960s, technical advances permitted the direct testing of the hypothesis that LSD and related hallucinogens act by directly suppressing the activity of serotonin-secreting neurons themselvesthe so-called presynaptic hypothesis. Researchers reasoned that if the hallucinogenic drugs act by suppressing the activity of serotonin-secreting neurons, then drugs administered after these neurons had been destroyed should have no effect on behavior, because the system would already be maximally suppressed. Contrary to their expectations, neuron destruction enhanced the effect of LSD and related hallucinogens on behavior. Thus, hallucinogenic drugs apparently do not act directly on serotonin-secreting neurons.

　　However, these and other available data do support an alternative hypothesis that LSD and related drugs act directly at receptor sites on serotonin target neurons . The fact that LSD elicits serotonin syndromethat is, causes the same kinds of behaviors as does the administration of serotoninin animals whose brains are depleted of serotonin indicates that LSD acts directly on serotonin receptors, rather than indirectly through the release of stores of serotonin. The enhanced effect of LSD reported after serotonin depletion could be due to a proliferation of serotonin receptor sites on serotonin target neurons. This phenomenon often follows neuron destruction or neurotransmitter depletion; the increase in the number of receptor sites appears to be a compensatory response to decreased input. Significantly, this hypothesis is supported by data from a number of different laboratories.

　　17. According to the passage, which of the following is one of the primary factors that led researchers studying hallucinogenic drugs to focus on serotonin?

　　 The suppression of the activity of serotonin-secreting neurons by the administration of hallucinogens

　　 The observed similarities in the chemical structures of serotonin and hallucinogens

　　 The effects the administration of hallucinogens has on serotonin production in the human brain

　　 Serotonin-induced changes in the effects of hallucinogens on behavior

　　 Hallucinogen-induced changes in the effects of serotonin on behavior

　　18. It can be inferred that researchers abandoned the presynaptic hypothesis because

　　 a new and more attractive hypothesis was suggested

　　 no research was reported that supported the hypothesis

　　 research results provided evidence to counter the hypothesis

　　 the hypothesis was supported only by studies of animals and not by studies of human beings

　　 the level of technical expertise in the field of brain research did not permit adequate testing of the hypothesis

　　19. Which of the following best expresses the main idea of the passage?

　　 Research has suggested that the neurotransmitter serotonin is responsible for the effects of hallucinogenic drugs on the brain and on behavior.

　　 Researchers have spent an inadequate amount of time developing theories concerning the way in which the effects of hallucinogenic drugs occur.

　　 Research results strongly suggest that hallucinogenic drugs create their effects by acting on the serotonin receptor sites located on target neurons in the brain.

　　 Researchers have recently made valuable discoveries concerning the effects of depleting the amount of serotonin in the brain.

　　 Researchers have concluded that hallucinogenic drugs suppress the activity of serotonin-secreting neurons.

　　20. The research described in the passage is primarily concerned with answering which of the following questions?

　　 How can researchers control the effects that LSD has on behavior?

　　 How are animals reactions to LSD different from those of human beings?

　　 What triggers the effects that LSD has on human behavior?

　　 What technical advances would permit researchers to predict more accurately the effects of LSD on behavior?

　　 What relationship does the suppression of neuron activity have to the occurrence of serotonin syndrome?

　　21. Which of the following best defines serotonin syndrome as the term is used in the passage?

　　 The series of behaviors, usually associated with the administration of serotonin, that also occurs when LSD is administered to animals whose brains are depleted of serotonin

　　 The series of behaviors, usually associated with the administration of LSD, that also occurs when the amount of serotonin in the brain is reduced

　　 The maximal suppression of neuron activity that results from the destruction of serotonin-secreting neurons

　　 The release of stores of serotonin from serotonin-secreting neurons in the brain

　　 The proliferation of serotonin receptor sites that follows depletion of serotonin supplies in the brain

　　22. Which of the following best describes the organization of the argument that the author of the passage presents in the last two paragraphs?

　　 Two approaches to testing a hypothesis are described, and the greater merits of one approach are indicated.

　　 The assumptions underlying two hypotheses are outlined, and evidence for and against each hypothesis is discussed.

　　 A phenomenon is described, and hypotheses concerning its occurrence are considered and rejected.

　　 The reasoning behind a hypothesis is summarized, evidence supporting the hypothesis is presented, and research that counters the supporting evidence is described.

　　 A hypothesis is discussed, evidence undermining the hypothesis is revealed, and a further hypothesis based on the undermining evidence is explained.

　　23. The authors attitude toward early researchers reasoning concerning the implications of similarities in the structures of serotonin and LSD molecules can best be described as one of

　　 complete agreement

　　 reluctant support

　　 subtle condescension

　　 irreverent dismissal

　　 strong opposition

　　When literary periods are defined on the basis of mens writing, womens writing must be forcibly assimilated into an irrelevant grid: a Renaissance that is not a renaissance for women, a Romantic period in which women played very little part, a modernism with which women conflict. Simultaneously, the history of womens writing has been suppressed, leaving large, mysterious gaps in accounts of the development of various genres. Feminist criticism is beginning to correct this situation. Margaret Anne Doody, for example, suggests that during the period between the death of Richardson and the appearance of the novels of Scott and Austen, which has been regarded as a dead period, late-eighteenth-century women writers actually developed the paradigm for womens fiction of the nineteenth centurysomething hardly less than the paradigm of the nineteenth-century novel itself. Feminist critics have also pointed out that the twentieth-century writer Virginia Woolf belonged to a tradition other than modernism and that this tradition surfaces in her work precisely where criticism has hitherto found obscurities, evasions, implausibilities, and imperfections.

　　24. It can be inferred from the passage that the author views the division of literature into periods based on mens writing as an approach that

　　 makes distinctions among literary periods ambiguous

　　 is appropriate for evaluating only premodern literature

　　 was misunderstood until the advent of feminist criticism

　　 provides a valuable basis from which feminist criticism has evolved

　　 obscures womens contributions to literature

　　25. The passage suggests which of the following about Virginia Woolfs work?

　　I. Nonfeminist criticism of it has been flawed.

　　II. Critics have treated it as part of modernism.

　　III. It is based on the work of late-eighteenth-century women writers.

　　 I only

　　 II only

　　 I and II only

　　 II and III only

　　 I, II and III

　　26. The author quotes Doody most probably in order to illustrate

　　 a contribution that feminist criticism can make to literary criticism

　　 a modernist approach that conflicts with womens writing

　　 writing by a woman which had previously been ignored

　　 the hitherto overlooked significance of Scotts and Austens novels

　　 a standard system of defining literary periods

　　27. The passage provides information that answers which of the following questions?

　　 In what tradition do feminist critics usually place Virginia Woolf?

　　 What are the main themes of womens fiction of the nineteenth century?

　　 What events motivated the feminist reinterpretation of literary history?

　　 How has the period between Richardsons death and Scotts and Austens novels traditionally been regarded by critics?

　　 How was the development of the nineteenth-century novel affected by womens fiction in the same century?

答案：17-27：BCCCAEBECAD