Question

The scientists observed that the more junk food the rats ate, the more they wanted to eat – a behavior very similar to that of rats addicted(上了瘾的) to heroin, a dangerous drug. Johnson said the experiment shows that the brain chemistry of obesity(肥胖) and drug addiction may be quite similar.
In their experiment, Johnson and his team studied the “pleasure center” of rats’ brains. The pleasure center is a complicated network of nerve cells. If the animal exercises or eats, the cells reward the animal by releasing chemicals into the body that make it feel good. And when the body feels good, the animal – or person – will want to do the behavior again.
For the experiment, Johnson fed foods like cheesecake to one group of rats. Food like this is high in calories and fat. Another group of rats got a regular diet. The rats that ate junk food started to eat more and more.
“They’re taking in twice the amount of calories as the control rats,” says Paul Kenny, one of Johnson’s colleagues.
Kenny and Johnson wanted to know what was going on in the brains of these rats. They first designed a way to deliver a small electrical charge to the rats’ brains. This electrical charge would stimulate the pleasure centers to release pleasure-causing chemicals. The rats could control how much stimulation – and how much pleasure – they received by running on a wheel. The more the rat ran, the more pleasure it received.
The rats that had been eating junk food started running more and more. This behavior suggested that the junk-food-eating rats needed more brain stimulation to feel good compared with rats on a normal diet. In other words, their pleasure centers were becoming less sensitive and the junk food didn’t make them feel good unless they ate more and more.
Experiments like this one could help scientists understand how chemicals in the brain contribute to obesity. With that information, they may be able to help people avoid obesity in the first place.
(Note: Answer the questions or complete the statements in NO MORE THAN TEN WORDS.)
小题1: The scientists suggested it was actually ___________________ that made the rats feel good.
小题2: How did the scientist know what was happening in the brains of the junk-food-eating rats?
小题3:What was the purpose of the experiment mentioned in the article?

Answer 1

小题1:chemicals in the brain
小题2: By delivering a small electrical charge to the rats’ brains.
小题3:To understand how chemicals in the brain contribute to obesity.

试题分析：本文主要叙述的是一项研究，研究人脑中的化学物质是如何控制我们的行为的，尤其是如何控制我们的肥胖的。
小题1:chemicals in the brain
细节题。根据第二段2,3行If the animal exercises or eats, the cells reward the animal by releasing chemicals into the body that make it feel good.可知正是老鼠释放的化学物质让它感觉很好。
小题2: By delivering a small electrical charge to the rats’ brains.
细节题。根据文章第五段2,3行They first designed a way to deliver a small electrical charge to the rats’ brains. This electrical charge would stimulate the pleasure centers to release pleasure-causing chemicals.可知他们向老鼠的大脑里投放了一定数量的化学物质。以此来研究具体的反应。
小题3: To understand how chemicals in the brain contribute to obesity.
推理题。根据文章主体段第一段最后2行Johnson said the experiment shows that the brain chemistry of obesity(肥胖) and drug addiction may be quite similar.可知这个研究的目的在于理解头脑中的化学物质是如何导致我们的肥胖的。