题目内容：
根据下面资料，回答题 Before a big exam, a sound night' s sleep will do you better than poring over textbooks. That, at least, is thefolk wisdom. And science, in the form of behavioral psychology, supports that wisdom. But such behavioral studiescannot distinguish between two competing theories of why sleep is good for the memory. One says that sleep is whenpermanent memories form. The other says that they are actually formed during the day, but then "edited" at night,to flush away what is superfluous.
to tell the difference, it is necessary to look into the brain of a sleeping person, and that is hard. But after adecade of painstaking work, a team led by Pierre Maquet at Liege University in Belgium has managed to do it. Theparticular stage of sleep in which the Belgian group is interested is rapid eye movement (REM) sleep, when brainand body are active, heart rate and blood pressure increase, the eyes move back and forth behind the eyelids as ifwatching a movie, and bralnwave traces resemble those of wakefulness. It is during this period of sleep that peopleare most likely to relive events of the previous day in dreams.
Dr. Maquet used an electronic device called PET to study the brains of people as they practiced a task duringthe day, and as they slept during the following night. The task required them to press a button as fast as possible, inresponse to a light coming on in one of six positions. As they learnt how to do this, their response times got faster.What they did not know was that the appearance of the lights sometimes followed a pattern--what is referred to as "artificial grammar". Yet the reductions in response time showed that they learnt faster when the pattern was presentthan when there was not.
What is more, those with more to learn ( i. e. the "grammar", as well as the mechanical task of pushing thebutton) have more active brains. The "editing" theory would not predict that, since the number of irrelevant stimuliwould be the same in each case. And to eliminate any doubts that the experimental subjects were learning as opposedto unlearning, their response times when they woke up were even quicker than when they went to sleep.
The team, therefore, concluded that the nerve connections involved in memory are reinforced through reactiva-tion during REM sleep, particularly if the brain detects an inherent structure in the material being learnt. So now, onthe eve of that crucial test, maths students can sleep soundly in the knowledge that what they will remember the nextday are the basic rules of algebra and not the incoherent talk from the radio next door.
Researchers in behavioral psychology are divided with regard to __ A．how dreams are modified in their courses
B．the difference between sleep and wakefulness
C．why sleep is of great benefit to memory
D．the functions of a good night' s sleep
参考答案：
答案解析：