It'soneofourcommonbeliefsthatm-考网

It's one of our common beliefs that mice areafraid of cats.Scientists have long known that even if a mouse has never seena cat before,it is still able to detect chemical signals released from the catand run away in fear.This has always been thought to be something that ishard-wired into a mouse's brain.

But now Wendy Ingram,a graduate student at theUniversity of California,Berkeley,has challenged this common sense.She hasfound a way to"cure"mice of their inborn fear of cats by infectingthem with a parasite,reported the science journal Nature.

The parasite,called Toxoplasma gondii,might soundunfamiliar to you,but the shocking fact is that up to one-third of peoplearound the world are infected by it.This parasite can cause different diseasesamong humans,especially pregnant women--it is linked to blindness and thedeath of unborn babies.

However,the parasite's effects on mice are unique.Ingram and her team measured how mice reacted to a cat's urine before and afterit was infected by the parasite.They noted that normal mice stayed far awayfrom the urine while mice that were infected with the parasite walked freelyaround the test area.

But that's not all.The parasite was found to bemore powerful than originally thought--even after researchers cured the mice ofthe infection.They no longer reacted with fear to a cat's smell,which couldindicate that the infection has caused a permanent change in mice's brains.

Why does a parasite change a mouse's brain insteadof making it sick like it does to humans?The answer lies inevolution."It's exciting scary to know how a parasite can manipulate amouse's brain this way,"Ingram said.But she also finds it inspiring."Typically if you have a bacterial infection,you go to a doctor and takeantibiotics and the infection is cleared and you expect all the symptoms toalso go away."She said,but this study has proven that wrong."Thismay have huge implications for infectious disease medicine."

The experiment found that mice infected withtoxoplasma gondii_______.查看材料

A.stayed far away from cat's urine
B.moved around the area freely and fearlessly
C.became more sensitive to cat's smell
D.were more afraid of cats

查看答案纠错

答案： B

本题解析：

细节题。根据第四段中的“They noted that normal mice stayed far away from the urine whilemice that were infected with the parasite walked freely around the test area”可知，受到寄生虫感染的老鼠能够自由随意地在测试区域周围走动。故本题选B。