首页
登录
职称英语
Scientists studying the activity of the living brain with widely used new im
Scientists studying the activity of the living brain with widely used new im
游客
2025-01-23
30
管理
问题
Scientists studying the activity of the living brain with widely used new imaging techniques have been missing some of the earliest steps in brain activity because those changes are subtle and are masked by reactions that happen seconds later, Israeli scientists say.
The imaging techniques — positron emission tomography scanning and magnetic resonance imaging, known as PET and functional M. R. I. scans — are used prominently in studies of brain activity. The most active brain areas appear to light up on the scans as specific tasks are performed. The two techniques do not measure nerve-cell activity directly; they measure the extra flow of blood that surges to the most active brain areas.
Researchers at the Weizmann Institute of Science in Rehovot, Israel, have monitored these changes in blood flow in anesthetized cats by removing parts of the skull and observing how the nerve cells in activated regions fuel their activities by rapidly removing oxygen from nearby red blood cells.
This rapid uptake of oxygen, made evident by visible changes in the color of the red cells, proves that early oxygen transfer gives these neurons the energy to do their work, the researchers said.
They also found that subtle changes in blood flow began significantly earlier than was detected by PET and functional M. R. I. scans, which lack sufficient resolution and do not form their images quickly enough to follow such rapid changes. Dr. Amiram Grinvald published the findings in the Journal Science.
"The initial event is very localized and will be missed if you don’t look for it soon enough and use the highest possible resolution," Dr. Grinvald said. "Now people are beginning to use our results with other imaging methods."
Working on the exposed brain lets researchers follow electrical activity and the accompanying blood flow in greater detail than is possible by using indirect imaging methods that track neural activity through the skull. However, opportunities for open-skull studies of humans are limited to some kinds of neurosurgery, and researchers must mostly rely on PET and functional M. R. I. images for studies linking behavior with specific brain activity.
By directly observing exposed cat brains and in similar work with a few human cases, Dr. Grinvald and his associates have been able to observe the first evidence of electrical activity and other changes in brain cells after a light has been seen or a limb moved.
The newest research showed that it took three seconds or more after an event for the flow of blood to increase to an area of the brain dealing with a stimulus. That is the blood-flow increase usually pictured in brain-function studies with PET or functional M. R. I techniques, the Israeli researchers said. However, the initial reaction observed in the Weizmann research by directly imaging the exposed brain — the direct transfer of oxygen from blood cells to neurons — occurred in the first-tenth of a second and was lost to conventional imaging, they said.
The later increase in blood flow to the area, Dr. Grinvald said, was obviously an attempt by the body to supply more oxygen for brain activity. But the increase in blood was so abundant that it covered an area much larger than the region directly involved in the activity being studied, masking some of the subtle changes, he said.
The body’s reaction, the researchers said in the paper, was like "watering the entire garden for the sake of one thirsty flower."
Dr. Kamil Ugurbil, said that the Israeli research provided clues that allowed the use of functional M. R. I. scans to picture earlier events in the activity of brain cells.
"Dr. Grinvald’s observations are very important, and they have significant implications for functional imaging with high resolution," Dr. Ugurbil said in an interview. "We have actually been able to look at the early changes with magnetic resonance imaging, but you need to use higher magnetic fields to see them clearly because they are small effects."
By timing their images more carefully and by using stronger magnetic fields than normal, he said, researchers have used Dr. Grinvald’s findings to study early neuronal responses to stimuli at smaller, more specific sites in the brain. [br] According to the passage, which of the following statements is true?
选项
A、The imaging techniques not only measure nerve-cell activity but also the extra flow of blood that surges to the most active brain areas.
B、The imaging techniques do not measure nerve-cell activity directly, but measure the flow of blood that surges to the most active brain areas.
C、The imaging techniques measure the extra flow of blood that surges to the most active brain areas.
D、The imaging techniques measure all the activities of the living brain.
答案
C
解析
是非题型见第二段最后一句:这两种(成像)技术并不直接测量神经细胞的活动,它们测量的是涌到大脑最活跃部分的血液的额外流量。因此答案为C。
转载请注明原文地址:https://tihaiku.com/zcyy/3925659.html
相关试题推荐
Allthestudentsintheclasstookpartintheactivityorganizedbytheclassb
Elderpeople_________alargeproportionofthoselivinginpoverty.A、consistB、i
Fromthehealthpointofviewwearelivinginamarvelousage.Weareimmun
Fromthehealthpointofviewwearelivinginamarvelousage.Weareimmun
Fromthehealthpointofviewwearelivinginamarvelousage.Weareimmun
Fromthehealthpointofviewwearelivinginamarvelousage.Weareimmun
Fromthehealthpointofviewwearelivinginamarvelousage.Weareimmun
Fromthehealthpointofviewwearelivinginamarvelousage.Weareimmun
Manyofthescientistsandengineersarejudged______howgreattheirachievemen
Allthestudentsintheclasstookpartintheactivityorganizedbytheclassb
随机试题
A.incomeB.polarizationC.transformationsD.oldE.changesF.worse
[originaltext]W:Dr.Thomas?ThisisKeetBradleyfromthedailynews.I’dlike
Sherodethebicycle(caution)______astheroadwasicy.cautiously句意:因为路面有冰,所以她小
CollegeStudents’Booklist1.这是一所大学里学生所购书籍的变化2.你对于学生选择书籍类别变化的评论3.哪
自流入排水管内的污、废水是在非满流情况下排除,其上部未充满水流的空间的作用如下,
()指在美术活动中形成创新意识,运用创意思维和创造方法。A.绘画创作 B.
根据实际经验,停车视距一般是会车视距的( )倍。A.0.5 B.1 C.2
分子内含有吡咯结构、具有开环的二羟基戊酸侧链的全合成的HMG-CoA还原酶抑制药
治疗冻伤(疮)的药物与患者教育内容A.未形成溃疡:轻轻按摩或温水湿敷,外涂敷紫云
项目部经过集思广益后通过本项目部的安全管理目标,由( )确认后予以发布。A.项目
最新回复
(
0
)