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
2023-12-27
35
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] Which of the following can be used as the title of the passage?
选项
A、Study of Human Brains
B、Imaging Techniques
C、Contribution of Israeli Researchers
D、Fine-tuning Imaging of Brain Activity
答案
D
解析
主旨题型可用排除法:选项A不对,因本文谈的不只是对人脑的研究;选项B不全面,因本文中The Imaging Techniques指的只有PET和M.R.I.两种成像技术,而本文谈的是利用成像技术来研究大脑的活动;选项C不对,因本文虽提到但并没将重点放在介绍以色列科学家的贡献上;而通读全文发现本文是谈通过成像技术等对大脑活动进行研究,因此D为答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3311106.html
相关试题推荐
Acitythatactsmorelikealivingorganismissaidtobeasmartcity.[br][
Acitythatactsmorelikealivingorganismissaidtobeasmartcity.[br][
Acitythatactsmorelikealivingorganismissaidtobeasmartcity.[br][
Acitythatactsmorelikealivingorganismissaidtobeasmartcity.[br][
Acitythatactsmorelikealivingorganismissaidtobeasmartcity.[br][
Acitythatactsmorelikealivingorganismissaidtobeasmartcity.[br][
Rockclimbingisanactivityinwhichparticipantsclimbup,downoracross
Rockclimbingisanactivityinwhichparticipantsclimbup,downoracross
Rockclimbingisanactivityinwhichparticipantsclimbup,downoracross
Rockclimbingisanactivityinwhichparticipantsclimbup,downoracross
随机试题
[originaltext]There,YaleUniversityprofessorsagreedinapaneldiscussio
Oneofthemostfamousandmosttalked-aboutactressestocomeoutofHollyw
我国海上运输货物保险包括()。A.平安险 B.附加险 C.海洋运输散装桐
(2011年)甲企业计划投资购买一台价值35万元的设备,预计使用寿命5年,按年限
从商业银行的经营情况看,对公存款业务主要的风险点有()。A.业务不合规 B
西方启发式教育思想的渊源是{}。
下表为改革开放以来,某省注册医院数量发展情况表,根据下表,请问该省注册医院数量年
男性,45岁,患Crohn病10年,发现有杵状指(趾)、关节炎等许多表现,其中有
下列列明的各类措施中,属于《海关法》赋予海关可以采取的强制措施的有()。A
仅糖异生需要的A、磷酸果糖激酶-2 B、3-磷酸甘油醛脱氢酶 C、丙酮酸激酶
最新回复
(
0
)