首页
登录
职称英语
Of 100 billion nerve cells in the human brain, how many form after birth? Fo
Of 100 billion nerve cells in the human brain, how many form after birth? Fo
游客
2024-04-21
6
管理
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. [br] What was the problem with Gould’s research result according to Rakic?
选项
A、It was glue that Gould found.
B、The new nerve cells exist in other parts of brains.
C、The work has technical problems.
D、Gould mistook the old cells as the new ones.
答案
C
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3564593.html
相关试题推荐
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
Internetadvertisingisbooming.Theindustryhasgonefrom$9.6billionin
Internetadvertisingisbooming.Theindustryhasgonefrom$9.6billionin
Internetadvertisingisbooming.Theindustryhasgonefrom$9.6billionin
Internetadvertisingisbooming.Theindustryhasgonefrom$9.6billionin
Internetadvertisingisbooming.Theindustryhasgonefrom$9.6billionin
Internetadvertisingisbooming.Theindustryhasgonefrom$9.6billionin
Anewreportsaysnearlyfour-billionpeoplehavemajortoothdecay,orcavi
Anewreportsaysnearlyfour-billionpeoplehavemajortoothdecay,orcavi
Anewreportsaysnearlyfour-billionpeoplehavemajortoothdecay,orcavi
随机试题
Mostpeopleconsiderbacteriadangerous.Afterall,thesemicroorganismscau
Thispartistotestyourabilitytodopracticalwriting.arerequiredtowr
患者男性,46岁,车祸致伤。查体:呼唤睁眼,不能正确回答问题,刺痛定位该病例GC
若红外热像仪的精度是2%或2℃,则目标在50℃时热像仪精度允许的温度范围是()(
13.《安规》要求,发布“倒闸操作”指令的全过程(包括对方复诵指令)和听取指令的
(2017年11月)年薪制的特点包括()A.适用范围比较特定 B.支付周
蒿芩清胆汤配伍陈皮、枳壳的用意是A.宽胸畅膈 B.清化痰热 C.宣畅气机
权证的杠杆作用表现为认股权证的市场价格要比其可认购股票市场价格上涨或下跌的速度
关于因果关系的认定,下列哪些选项是错误的?A.甲在5楼阳台发现乙从10楼掉下来,
在进行绩效评价中克服晕轮效应的核心是()。A.采取非系统的考核方法 B.从
最新回复
(
0
)