首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Of 100 billion nerve cells in the human brain, how many form after birth? For years, the official answer was "zero". Scientists
Of 100 billion nerve cells in the human brain, how many form after birth? For years, the official answer was "zero". Scientists
admin
2013-11-22
137
问题
Of 100 billion nerve cells in the human brain, how many form after birth? For years, the official answer was "zero". Scientists thought people were born with all the neurons they’d ever have. But from 1980s, biologists overturned that doctrine, finding a reservoir of stem cells that became fresh neurons in two parts of the brains of adult birds, monkeys and humans. Those discoveries were stunning, but the next seemed to top them all. In 1999, psychologist Elizabeth Gould reported large numbers of new nerve cells in a third of the monkey brain, hinting that the same part in humans — the neocortex, which lets us reason and remember — was regenerating, too. If she was right, scientists would have to revise almost all their ideas about human memory, and doctors might someday find a way to treat Alzheimer’s patients by simply turning on the neural-construction equipment.
The birth of new nerve cells, or "neurogenesis", is now confirmed in the original two parts of human brain, the hippocampus and olfactory bulb. But for the neocortex, the no-neurons theory lives — and it’s just gotten major boost.
Until December, Gould’s study stood alone and unverified. Two neuroscientists have repeated her work in Science, but not her results. Where Gould saw new nerve cells in the neocortex, Rakic and Kormack see only glial cells, the "glue" that supports neurons. But they do spot new nerve cells in the other two areas. In a January review in Nature Neuroscience, Rakic charges Gould’s work with technical problems. Focusing on what appeared to be 100 new neurons, Rakic and Kornack found that every one was merely a new glial cell hiding behind an old neuron. Gould has a cross-sectioned image from her own study that she says shows one cell marked as new — and it’s clearly a neuron. But Rakic has an answer for that, too. The method that identified the cells as "new" finds DNA synthesis, which can happen in cells that aren’t actually dividing. Rakic says Gould’s tests were too sensitive, tagging "new" neurons that weren’t. Gould responses that Rakic’s methods just weren’t sensitive enough. But even she can’t explain why that might be.
Rakic’s study squares with the idea that memory comes not from new nerve cells but from chemicals in the spaces between old ones.
Gould’s team are circulating response to Rakic and Kornack and recreating two studies side by side to see if small differences in methods are to blame. Others are also redoing the tests; a Japanese team’s unpublished results echoes Rakic’s, while another team’s support Gould’s.
Meanwhile work on less controversial new neurons marches forward. Neuroscientist Fred Gage, who’s just wrapped up a study of the function of new hippocampus nerve cells, says that’s as it should be. Still, until more studies confirm Rakic and Kornack, he’ll keep a close eye on the neocortex debate.
What does Gould’s team do in response to Rakic and Kornack?
选项
A、They ask a Japanese team to repeat their experiment.
B、They redo the tests.
C、They ask other teams to support them.
D、They recreate two studies side by side to see if small differences in methods are to blame.
答案
D
解析
细节题。本题可以定位到第五段第一句。本题是有关Gould小组对Rakic and Komack的质疑所作出的应对的。根据第五段首句Gould’s team are circulating response to Rakic and Komack…Gould的研究小组同时开展两个实验,以辨明是否问题出在方法上的细微差别上,其目的不仅仅是检查结论,选项B错误。其它研究组重复他们的实验,但Gould的研究组并没有请人来重复实验,更没有请求其它研究组的支持。所以选项A,选项C错误。故选项D正确。
转载请注明原文地址:https://kaotiyun.com/show/k217777K
0
大学英语六级
相关试题推荐
A、0.13B、0.16C、0.14D、0.15D细节题。原文关于科威特石油储备量的句子是:ithasapproximatelyfifteenpercentoftheworld’sknownpetroleumreserves.(
A、Byforcingthemfarming.B、Byaffectingthequalityofsoils.C、Byaddingchemicalsandpollutingthewaterways.D、Byaffectin
A、Todrinkmorewater.B、Tostretchhimselfbeforelearning.C、Tokeephisbodybalance.D、Towearformalclothes.A细节题。对话结尾女士提醒
A、Veryimpolite.B、Notcustomary.C、Veryurgent.D、Notnecessary.C推理判断题。原文中涉及早上电话的部分为Ifyoutelephonehimearlyintheday,whil
DoSomethingYou’veprobablyheardthecommonrefrain,"Childrenaretheleadersoftomorrow."Oneorganizationrefutestha
Twelveyearsago,asafirst-yearlanguage-artsteacheratamiddleschoolinHouston,Ihad50minutesadaywitheachofmycl
A、Tomakehermoreawareofherfinancialability.B、Tosavemoneybeforethetransactionfeesrise.C、Toteachherhowtoearn
A、ItaffectseconomicgrowthinAsia.B、Itleadstomorechildren’searlydeath.C、Itaffectspeople’smentalhealth.D、Itcontr
A、ApoorBritishman.B、ArichAmerican.C、ArichBritishman.D、ApoorAmerican.B由对话中男士提到的theAmericanbillionaire,HowardHugh
A、Creatingspeciallanguage.B、Sellingavarietyofproducts.C、Providingacomfortableenvironment.D、Openingstoresinbusyar
随机试题
设计机床电路时应根据工艺要求先设计________电路,并加入必要保护。
头部外伤后,腰穿发现脑脊液呈血性,揭示临床诊断是
下列属于施工安全技术交底基本要求的有( )。
商业银行内部控制要与商业银行的经营规模、业务范围、竞争状况和风险水平相适应,并随着情况的变化及时加以调整,遵循的是内部控制的()。
某运输企业扩大生产规模,有甲乙两个方案可供选择,基准收益率为7%,两个方案相关数据资料如下表所示。如将残值作为负的费用处理,两个对比方案的效果费用比分别为()。
A类不合格的可接收质量限AQL值应()B类不合格的AQL值。
课程目标的制定既要依据对学生和社会的研究,又要依据对()。
治安管理处罚的适用对象是()。
学习对于()相当于()对于写字楼
(演示文稿题)张老师正在准备有关儿童孤独症的培训课件,按照下列要求帮助张老师组织资料、完成该课件的制作:将第11张幻灯片中的文本内容转换为“表层次结构”SmartArt图形。适当更改其文字方向、颜色和样式;为SmartArt图形添加动画效果,令Smar
最新回复
(
0
)