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
26
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 doctrine was overturned according to the 1980’s biologists?
选项
A、The human brain contains 100 billion nerve cells.
B、The nerve cells can be generated after birth.
C、The nerve cells can’t be generated after birth.
D、The human brain has a reservoir of stem cells.
答案
C
解析
细节题。本题可以定位到第一段第一、二句。本题是有关被推翻的生物学界长期认同的观点的。根据首段第三句But from 1980s,biologists overturned that doctrine,再根据that doctrine可以推断答案在首段前两句中。根据前两句的内容可知以前官方认为神经元细胞没有在出生后产生的,而1980年代的生物学家们的发现推翻了这个理论。故选C。
转载请注明原文地址:https://jikaoti.com/ti/t8qFFFFM
0
大学英语六级
相关试题推荐
Conservationistsmaybemiscalculatingthenumbersofthethreatenedanimalssuchaselephants,sayAfricanandAmericanresearc
Inthepasthundredyearsamillionpeoplehavediedinearthquakes,anothermillionhavebeenkilledby【B1】______andtornadoes
A、Todrinkmorewater.B、Tostretchhimselfbeforelearning.C、Tokeephisbodybalance.D、Towearformalclothes.A细节题。对话结尾女士提醒
Collegerankingsaredead!Longlivecollegerankings!Atameetingofthecountry’sleadingliberalartsschoolsthisweekinA
NegotiatingSkillsCanBeLearnedManagersnegotiatecontinuously,withsuperiors,subordinates,peersandclients.Research
A、ItaffectseconomicgrowthinAsia.B、Itleadstomorechildren’searlydeath.C、Itaffectspeople’smentalhealth.D、Itcontr
FromhumblebeginningsinagarageinMenloPark,Californiain1998,Googlehasgrownintoamultinationalcompanycarryingout
ThemainreasonweexploreMarsistodetermineiflifeeverexistedontheplanet.Wehavetriedforcenturies,startingwith【
TheCaseAgainstRetirementAh,retirement!Beforethe1950s,itwassomethingonlythewealthycouldaffordtodo.Everyone
随机试题
垂体性Cushing病与异位ACTH综合征缓慢发展型的鉴别,正确的是
A、砂仁、豆蔻、鱼腥草B、西洋参、西红花、人参C、车前子、葶苈子、海金沙D、姜汁、梨汁、蜂蜜E、阿胶、鳖甲胶、鹿角胶需要另煎的一组药物是
A.James染色B.维多利亚蓝染色C.丽春红S染色D.PTAH染色E.MSB染色纤维蛋白
企业在进行租赁或购买设备决策时,需要考虑的主要因素包括( )。
背景材料:某城市的公路改建项目,业主为了控制工程造价,与设计方详细研究了各种成本控制措施,要求通过成本管理的各种手段,不断促进降低施工项目成本,尽可能地以最低的成本达到设计要求。施工方在面对业主提出的要求后也采取了一系列措施,选择适宜的施工方案,
下列关于民事诉讼中陪审制度的说法正确的是()
在()上,传统人事管理方法单一,以人工为主处理数据,而现代人力资源管理,更强调使用电脑技术处理信息资料,及时准确地提供决策依据。
敏敏每次做完题总是会一遍又一遍地检查,她自己也知道没必要,但却没办法控制自己。这说明敏敏可能患有()。
已知数a=2×3×5,数6=3×5×7那么a与b的最大公因数是()。
Comparedwiththedevelopedcountries,someAfricancountriesareleftfarbehindintermsofpeople’slivingstandard.
最新回复
(
0
)