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大脑功能核磁共振成像的原理是什么? – 译学馆
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大脑功能核磁共振成像的原理是什么?

How do brain scans work? - John Borghi and Elizabeth Waters

据我们所知
As far as we know,
在太阳系中 只有一种东西
there’s only one thing in our solar system
足够复杂 可以进行自我研究
sophisticated enough to study itself:
那就是人类的大脑
the human brain.
但这种自我研究 非常具有挑战性
But this self-investigation is incredibly challenging;
活体大脑由厚厚的头盖骨保护
a living brain is shielded by a thick skull,
包裹在层层保护组织之中
swaddled in layers of protective tissue,
而且由数以亿计相连的微小细胞组成
and made up of billions of tiny, connected cells.
这就是很难去分开 观察
That’s why it’s so difficult to isolate, observe,
那么 我们应该怎样在不伤害人体的情况下 研究活体大脑呢?
So how do we study living brains without harming their owners?
我们可以利用一种三件套科技 即 脑电图扫描器 功能磁共震成像
We can use a trio of techniques called EEG, fMRI,
以及 正电子成像术
and PET.
每一种技术测量不同种类的东西且都有各自的优点和缺点
Each measures something differentand has its own strengths and weaknesses,
接下来我们将依次介绍它们
and we’ll look at each in turn.
首先是脑电图扫描器
First is EEG, or electroencephalography,
它测量大脑的脑电活动
which measures electricalactivity in your brain.
脑细胞之间相互交流时 会产生脑电波
As brain cells communicate,they produce waves of electricity.
位于头盖骨上的电极会接收这些电波
Electrodes placed on the skull pickup these waves,
以及在电极间检测到的信号的不同之处
and differences in the signals detectedbetween electrodes
提供 事物发生的信息
provide informationabout what’s happening.
这种技术发明于近100年以前
This technique was inventedalmost 100 years ago,
如今仍被用来诊断 类似癫痫 和睡眠紊乱的疾病
and it’s still used to diagnose conditions like epilepsy and sleep disorders.
也被用于
It’s also used to
研究大脑在学习和集中注意力时
investigate what areas of the brain are active
哪块区域是活跃的
during learning or paying attention.
脑电图扫描器无需侵入体内 价格相对便宜 而且速度快
EEG is non-invasive, relatively inexpensive, and fast:
它可以检测出 仅在毫秒间发生的变化
it can measure changes that occur in just milliseconds. Unfortunately,
不幸的是 很难去确定
it’s hard to determine
任何特定模式 确切的起源之处
exactly where any particularpattern originates.
整个大脑都在不断地产生电信号
Electrical signals are generatedconstantly all over the brain
电信号之间互相作用 产生复杂的模式
and they interact with each other toproduce complex patterns.
使用更多电极或复杂数据处理算法 会有所帮助
Using more electrodes or sophisticateddata-processing algorithms can help.
但是最终
But in the end,
虽然脑电图能告诉你 某一活动发生的准确时间
while EEG can tell you precisely when certain activity occurs,
但它不能告诉你确切位置
it can’t tell you precisely where.
要做到这点 你需要另一种技术
To do that, you’d need another technique,
比如 功能磁共震成像
such as functional magneticresonance imaging, or fMRI.
功能磁共震成像 检测 氧气是多快被脑细胞消耗掉的
fMRI measures how quickly oxygenis consumed by brain cells.
大脑的活动区域会更快地使用氧气
Active areas of the brain useoxygen more quickly.
在一个人完成认知或行为任务时
So watching an fMRI scan
观察功能磁共震成效扫描
while a person completes cognitive or behavioral tasks
能对于哪部分大脑参与其中 提供信息
can provide information about which regions of the brain might be involved.
这使我们可以研究一切事情从如何观察面孔
That allows us to study everything from how we see faces
到如何理解我们感受到的
to how we understand what we’re feeling.
功能磁共震成像可以在几毫米内精确找到
fMRI can pinpoint differences in brain activity to
脑活动的不同之处
within a few millimeters,
但是 它要比脑电图扫描器慢数千倍
but it’s thousands of times slower than EEG.
一起使用这两种技术能够帮助展示
Using the two techniques together can help show when,
神经活动正在进行的时间和位置
and where, neural activity is occurring.
第三种科技更精确 叫正电子成像术
The third, even more precise, techniqueis called positron emission tomography
它能测量被引入大脑的放射性元素
and it measures radioactive elementsintroduced into the brain.
听起来很可怕 但实际上并非如此
That sounds much scarierthan it actually is;
正电子成像术 就像功能磁共震成像和脑电图扫描器一样安全
PET scans, like fMRI and EEG,are completely safe.
在进行电子成像术时
During a PET scan,
一种叫做示踪剂的少量放射性物质
a small amount of radioactive material called a tracer
被注入血液中
is injected into the bloodstream,
医生会监控它在大脑中的流通情况
and doctors monitor its circulation through the brain.
通过调整示踪剂 将其与特定分子结合
By modifying the tracerto bind to specific molecules,
研究人员能够用正电子成像术来研究人脑中复杂的化学过程
researchers can use PET to study the complex chemistry in our brains.
这对于研究药物如何影响大脑
It’s useful for studying how drugs affect the brain
以及检测类似老年痴呆症的疾病 很有用
and detecting diseases like Alzheimer’s.
但是这种技术是所有解决方法中速度最慢的
But this technique hasthe lowest time resolution of all
因为示踪剂需要几分钟循环 产生变化后才能显示出来
because it takes minutes for the tracer to circulate and changes to show up.
这些技术能共同帮助医生与科研工作者
These techniques collectivelyhelp doctors and scientists
把脑中的活动与我们的行为联系起来
connect what happens in thebrain with our behavior.
但它们也有很多未知的局限性
But they’re also limitedby how much we still don’t know.
例如 研究人员对记忆如何工作的研究很感兴趣
For example, let’s say researchers are interested in studying how memory works.
50名参与者被要求在接受功能核磁共振成像扫描的时
After asking 50 participants to memorize a series
记住一系列图片
of images while in MRI scanners,
研究人员分析结果
the researchers might analyze the results
发现大量的活跃的大脑区域
and discover a numberof active brain regions.
在记忆和大脑特定部分之间制造一种联系
Making a link between memoryand specific parts of the brain
是很有意义的进步
is an important step forward.
但是未来研究可能有必要
But future research would be necessary to better
更好的了解每一个区域的活动
understand what’s happening in each region,
它们是如何一起运作的
how they work together,
以及是否这种活动是由于它们参与了记忆
and whether the activity is because of their involvement in memory
还是同时发生了另一过程
or another process occurring simultaneously.
更先进的成像和分析技术
More advanced imaging and analysis technology
可能会在将来提供更精确的结果
might one day provide more accurate results
甚至能区分个体神经元的活动
and even distinguish the activity of individual neurons.
直到那时 我们的大脑会不断地测量 分析与创新
Until then, our brains willkeep measuring, analyzing, and innovating
以求懂得我们所遇到的
in pursuit of that quest to understand one
最了不起的事情之一
of the most remarkable things we’ve ever encountered.

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视频概述

功能核磁共振成像 脑电图扫描器 以及 正电子成像术 的作用以及原理

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视频来源

https://www.youtube.com/watch?v=B10pc0Kizsc

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