14．One of the most important recent medical breakthroughs has been the impact of gut flora（肠道菌群）on overall health．This dynamic mix of bacteria in the digestive tract（消化道）may affect everything from obesity to asthma（哮喘）．
The Gut-Mood Link
Anyone who's ever experienced"butterflies"in his or her stomach knows that the gut and the brain are connected．But until recently，scientists hadn't realized that the trillions of bacteria in our digestive tract may be driving the relationship．
One recent experiment suggests that you can control calm．Canadian researchers gave healthy mice a mixture of antibiotics，which change the makeup of GI-tract（胃肠道）bacteria．Over two weeks，some animals became more anxious and some less，depending on which drugs they received．
In another study，when gut bacteria from calm mice were transferred to anxious mice，the jittery（紧张的）creatures seemed less nervous．
UCLA professor Kirsten Tillisch，doctor of medicine，recently had healthy women eat a yogurt rich in certain types of"good"probiotic（益生菌的）bacteria．Two'Control groups ate yogurt without such bacteria or ate nothing．Brain scans of the probiotic-yogurt eaters indicated changes in regions that could be associated with a less-anxious response in fearful or stressful situations compared with the control groups．
Scientists are even exploring whether gut microbes（微生物）might treat some brain disorders．
A new study in Cell found that mice with features of autism（自ICJ症）given a type of bacteria in healthy human GI tracts exhibited less autism-like behavior．In a recent case report，a Boston ps} chiatrist says a course of certain probiotics and antibiotics helped relieve a patient's compulsive disorder．
-We tend to focus on how your mood affects your body from the top down，not the bottom up，"says Dr．Tillisch．"Now we know that the gut affects how your brain responds to the environment-it's a remarkable change in thinking．"
How Bacteria Talk to the Brain
Scientists aren't sure how gut flora affect brain chemistry．One theory is that the bacteria access pathways along the nerve，the main highway in the nervous system that links the brain to the gut．
Another is that the bacteria influence the immune system，releasing chemicals that affect conditions like depression．Finally，researchers believe that bacteria produce or affect the metabolism（新陈代'i） of chemicals，which change brain function．
Dr．Tillisch told me that patients always ask which probiotics will lift their mood．Her answer：
"We don't know yet，but we hope to one day．"In the future，patients might receive probiotics or transplant（移植） in which bacteria from the gut of a healthy person are transferred to the gut of a sic'：one-to prevent or treat mental health issues．But these approaches are years away from primary time．Until then，a diet rich in fruit and veggies helps cultivate（培养）better-balanced microbes than a typical Western diet high in animal and processed products．Avoiding unnecessary antibiotics，particularly in early childhood，may also establish healthier gut bacteria．
63．According to the passage，gut bacteria might help us in many ways EXCEPTD．
A．lightening our mood
B．treating autism
C．relieving depression
D．transplanting gut flora
64．The missing sentence"Everyday foods may also affect the composition of gut bacteria，and in turn，brain chemistry．"could be put beforeC•
A．Paragraph 2 B．Paragraph 3 C．Paragraph 4 D．Paragraph 5
65．Which of the following can be the best subtitle for the last paragraph？A
A．Cultivating a Happier Gut B．Growing Bacteria in the Future
C．Balancing Microbes and Diet D．Living a Happy Healthy Life．
分析 本文属于说明文阅读，作者通过这篇文章向我们介绍了肠道菌可以帮助改善我们的情绪，减轻压力，并且对我们的健康有益，同时介绍了应该如何培养健康 的肠道菌群．
解答 63．D 细节拉筋题：根据文章的二三四段In another study，when gut bacteria from calm mice were transferred to anxious mice，the jittery（紧张的）creatures seemed less nervous．可知肠道菌群可以改善我们的情绪，减轻压力；第五段A new study in Cell found that mice with features of autism 可知肠道菌群可以治疗自闭症，而D选项在文中没有提及，故选D．
64．C 推理判断题：根据第三段scientists hadn't realized that the trillions of bacteria in our digestive tract may be driving the relationship．可知接下来要介绍的是食物和肠道以及大脑化学物质的关系，因此这句话应该放在第四段之前，故选C．
65．A 段落大意题：根据最后一段的内容：a diet rich in fruit and veggies helps cultivate（培养）better-balanced microbes than a typical Western diet high in animal and processed products．可知本段向我们介绍的是应该如何培养更健康的肠道菌群，故选A．
点评 考查学生的细节理解和推理判断能力．做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确选择．在做推理判断题时不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
