VOA慢速英语2020--科学家现在质疑大脑成像方法

Scientists Now Question Brain Imaging Methods

Brain scans offer us a rare sight: A look into the mind and its mysteries. They promise answers to many questions. How do we feel pain? How do we know a face? How do we move our body?

But can brain scans really answer these questions? Many scientists are now rethinking the value of brain scan research and whether its findings are true.

Brain scan studies have been criticized for several things. Criticisms include using too few subjects and incorrectly reading results.

Researchers have also come to understand that a person's brain scan results can be different from day to day, even when all the conditions stay the same. Now they admit that brain scan findings are limited. Some are studying these limitations. Others are using different methods to study the brain.

Earlier this year, Annchen Knodt, a researcher at Duke University in North Carolina, and her team published the latest paper on this topic. It questioned the usefulness of common brain scan projects. The team looked at 60 studies of the past 10 years -- including Knodt's own studies.

Watching brains ‘light up'

The research being re-examined uses a technique called functional¹ magnetic resonance² imaging, or fMRI. Using large magnets, fMRI scans find where oxygenated blood goes when someone does an activity, such as learning new words. This gives scientists a way to measure brain activity.

Researchers first began using this technology in the early 1990s. At the time, it seemed to open a window into the human brain.

Earlier imaging methods involved examining brain activity through small devices -- called electrodes -- placed on the skull³.

Another technique involved injecting radioactive material into the blood. By comparison, fMRI seemed faster and easier And the images were of higher quality.

Scientists started writing many papers about fMRI's ability to show brain activity. Reporters wrote many stories about these studies. The public wanted more.

But as years passed, troubling signs about some of the findings began to appear.

"It is a very powerful thing to show a picture of the brain," said Damian Stanley, a brain scientist at Adelphi University in New York State. However, such a powerful tool, he said, can lead to abuse and bad science. Stanley told the Associated Press that some scientists made their research seem more important than it actually was.

Another Duke brain scientist, Anita Disney, told the AP, "In the end, we probably jumped on the fMRI bandwagon a little too fast." In other words, the scientific community began supporting the technique very quickly, perhaps too quickly. But now, she said, the problems with fMRI are a concern to many scientists.

With doubts growing, many laboratories have become more careful about which imaging methods are used in brain research. And when studying the brain, there is a lot to look at. The average brain has about 177,000 kilometers of nerve fibers⁵.

Yale University researcher Joy Hirsch wants to understand "the social brain." She studies what happens in the brain when people talk, touch, or make eye contact with each other. So, she does not use fMRI. It can only be used on one person at a time and that person must stay perfectly⁶ still inside a large scanner.

Instead, Hirsch uses another method. Laser lights hit a fiber⁴ optic cable attached to a person's head and then finds blood flow. This method lets her subjects move freely during scanning. It also permits her to study real-life socializing among several people.

Duke's Anita Disney also does not use fMRI very often. She explained that it is not accurate enough to study brain chemistry.

But not everyone is walking away from fMRI.

Some doctors depend on the method to map a patient's brain before an operation. And fMRI has proven useful for studying diseases such as schizophrenia and Alzheimer's.

Latest method for studying the brain

Now, there is a new imaging method. It is called optogenetics. This method uses light to activate⁷ neurons. It may be brain science's latest method of studying the brain. But some scientists say it is too early to know whether they will use it as a tool.

Disney noted⁸ that when a new method comes out "it is actually really difficult to get people to do the basic work of understanding its limitations."

Words in This Story

scan – n. the act or process of using a special machine to see the inside of something (such as a part of the body) scan – v. to examine especially systematically⁹ with a sensing device (as a photometer or a beam of radiation)

subject – n. a person or thing that is being dealt with in a particular way

jump on a bandwagon - idiom to join an activity that has become very popular or to change your opinion to one that has become very popular so that you can share in its success

neuroscientist – n. one who studies the scientific study of nerves and especially of how nerves affect learning and behavior

nerve fiber – n. any of the processes (such as axons or dendrites) of a neuron

fiber optic cable – n. technical : the use of thin threads of glass or plastic to carry very large amounts of information in the form of light signals

activate – v. to cause (a device) to start working

basic – adj. the simplest and most important parts of something (such as a subject of study)

1 functional   

adj.为实用而设计的，具备功能的，起作用的

参考例句：

• The telephone was out of order,but is functional now.电话刚才坏了，但现在可以用了。
• The furniture is not fancy,just functional.这些家具不是摆着好看的，只是为了实用。

2 resonance   

n.洪亮；共鸣；共振

参考例句：

• Playing the piano sets up resonance in those glass ornaments.一弹钢琴那些玻璃饰物就会产生共振。
• The areas under the two resonance envelopes are unequal.两个共振峰下面的面积是不相等的。

3 skull   

n.头骨；颅骨

参考例句：

• The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
• He fell out of the window and cracked his skull.他从窗子摔了出去，跌裂了颅骨。

4 fiber   

n.纤维，纤维质

参考例句：

• The basic structural unit of yarn is the fiber.纤维是纱的基本结构单元。
• The material must be free of fiber clumps.这种材料必须无纤维块。

5 fibers   

光纤( fiber的名词复数 )； （织物的）质地； 纤维，纤维物质

参考例句：

• Thesolution of collagen-PVA was wet spined with the sodium sulfate as coagulant and collagen-PVA composite fibers were prepared. 在此基础上，以硫酸钠为凝固剂，对胶原-PVA共混溶液进行湿法纺丝，制备了胶原-PVA复合纤维。
• Sympathetic fibers are distributed to all regions of the heart. 交感神经纤维分布于心脏的所有部分。

6 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

7 activate   

vt.使活动起来，使开始起作用

参考例句：

• We must activate the youth to study.我们要激励青年去学习。
• These push buttons can activate the elevator.这些按钮能启动电梯。

8 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

9 systematically   

adv.有系统地

参考例句：

• This government has systematically run down public services since it took office.这一屆政府自上台以来系统地削减了公共服务。
• The rainforest is being systematically destroyed.雨林正被系统地毀灭。