How do we safely study living brains? - John Borghi and Elizabeth Waters

翻译人员: Ye He 校对人员: Scarlett Ren

罂粟红，苹果香，云雀在歌唱， 都只发生在大脑中。——Oscar Wilde

As far as we know,

据我们目前所知， 在我们整个太阳系中，

there’s only one thing in our solar system sophisticated enough to study itself:

唯一一个复杂到能够研究 它自身的东西，就是我们的大脑。

the human brain.

But this self-investigation is incredibly challenging;

但是这个自我研究的过程非常困难。

a living brain is shielded by a thick skull,

大脑被保护在坚硬的颅骨里，

swaddled in layers of protective tissue,

被层层保护性组织包围住，

and made up of billions of tiny, connected cells.

而且由上亿个极小的 相互连接的细胞所组成。

That’s why it’s so difficult to isolate, observe, and understand diseases

这就是为何很难去解析，观察， 并了解像老年痴呆症

这种大脑疾病。

like Alzheimer’s.

So how do we study living brains without harming their owners?

那我们怎样才能在不伤害人体的情况下， 去研究一个活生生的大脑呢？

We can use a trio of techniques called EEG,

我们可以使用这三种技术： 脑电图（EEG)，

fMRI,

功能性磁共振成像 (fMRI)，

and PET.

以及正电子发射型 计算机断层显像 (PET) 。

Each measures something different and has its own strengths and weaknesses,

每一个技术测量不同的指标， 并且都有自己的长处与短处，

and we’ll look at each in turn.

我们会带你去逐一了解每项技术。

First is EEG, or electroencephalography,

首先是脑电图（EEG）， 英文全称为 electroencephalography，

which measures electrical activity in your brain.

它测量大脑内的电生理活动，

As brain cells communicate, they produce waves of electricity.

当脑细胞互动时， 它们会产生生物电波。

Electrodes placed on the skull pick up these waves,

这些电波能被放置于 头皮上的电极记录下来，

and differences in the signals detected between electrodes

不同电极之间记录到的信号差异

provide information about what’s happening.

可以提供脑内活动的信息。

This technique was invented almost 100 years ago,

这项技术在近 100 年前被发明出来，

and it’s still used to diagnose conditions like epilepsy and sleep disorders.

至今仍然被用来诊断 如癫痫和睡眠障碍等疾病。

It’s also used to investigate what areas of the brain are active

它还被用来测量当大脑 在学习或专注状态时，

during learning or paying attention.

哪个区域是活跃的。

EEG is non-invasive,

EEG 是无创的，

relatively inexpensive,

相对廉价，

and fast:

而且很快。

it can measure changes that occur in just milliseconds.

它能记录毫秒间发生的变化，

Unfortunately, it’s hard to determine

但是这种技术很难精确

exactly where any particular pattern originates.

定位任何活动模式的来源。

Electrical signals are generated constantly all over the brain

电信号在全脑不断地生成，

and they interact with each other to produce complex patterns.

并且交互生成复杂的模式。

Using more electrodes or sophisticated data-processing algorithms can help.

使用更多的电极或复杂的 数据处理算法能有所帮助。

But in the end, while EEG can tell you precisely when certain activity occurs,

但是到头来，EEG 虽能精确地 告诉你特定活动是何时发生的，

it can’t tell you precisely where.

却不能告诉你是在哪里发生的。

To do that, you’d need another technique,

为了解决这个问题，你需要另一种技术，

such as functional magnetic resonance imaging, or fMRI.

比如功能磁共振成像，简称 fMRI。

fMRI measures how quickly oxygen is consumed by brain cells.

fMRI 测量脑细胞消耗氧气的速度。

Active areas of the brain use oxygen more quickly.

活动的脑区消耗氧气更快，

So watching an fMRI scan while a person completes cognitive or behavioral tasks

所以当观察一个人在进行认知 或行为任务的 fMRI 扫描时，

can provide information about which regions of the brain might be involved.

能观察到大脑的哪个区域 可能参与了任务。

That allows us to study everything from how we see faces

这有助于我们研究很多问题， 从我们如何观察面孔

to how we understand what we’re feeling.

到我们如何理解我们当前的感受。

fMRI can pinpoint differences in brain activity to within a few millimeters,

fMRI 能探测到几毫米内 大脑活动的差异，

but it’s thousands of times slower than EEG.

但它比 EEG 慢了几千倍。

Using the two techniques together

将这两种技术结合，

can help show when, and where, neural activity is occurring.

有助于揭示神经活动 在何时及何地发生。

The third, even more precise, technique is called positron emission tomography

第三种，更加精确， 它是正电子放射断层成像技术（PET），

and it measures radioactive elements introduced into the brain.

能够测量进入脑内的放射性元素。

That sounds much scarier than it actually is;

它其实没有听起来那么可怕；

PET scans, like fMRI and EEG, are completely safe.

PET 扫描和 fMRI 及 EEG 一样完全安全。

During a PET scan, a small amount of radioactive material called a tracer

在 PET 扫描时，少量放射性 的物质，称为示踪剂，

is injected into the bloodstream,

被注射进血液中，

and doctors monitor its circulation through the brain.

然后医生监测它在脑内的循环。

By modifying the tracer to bind to specific molecules,

通过变化示踪剂来 结合特定的分子，

researchers can use PET to study the complex chemistry in our brains.

研究人员能用 PET 研究 脑内复杂的化学变化。

It’s useful for studying how drugs affect the brain

这有助于研究药物如何影响大脑，

and detecting diseases like Alzheimer’s.

以及检测疾病，如阿尔茨海默症。

But this technique has the lowest time resolution of all

但是这项技术的时间分辨率是最低的，

because it takes minutes for the tracer to circulate and changes to show up.

因为示踪剂需要数分钟 来循环，显示变化。

These techniques collectively help doctors and scientists

这些技术共同帮助医生和科学家

connect what happens in the brain with our behavior.

将脑活动与行为活动联系起来。

But they’re also limited by how much we still don't know.

但是它们仍受限于我们所未知的。

For example, let's say researchers are interested in studying how memory works.

举例来讲，研究人员想研究记忆 是如何工作的。

After asking 50 participants to memorize a series of images while in MRI scanners,

通过让 50 名被试者在进行 MRI 扫描时记忆一系列图片，

the researchers might analyze the results

研究者能分析这些实验结果，

and discover a number of active brain regions.

并且发现一系列激活的脑区。

Making a link between memory and specific parts of the brain

将记忆和特定脑区联系起来，

is an important step forward.

是一项重大的进步。

But future research would be necessary

但是在未来，我们仍需要研究

to better understand what’s happening in each region,

如何更好地理解每个脑区发生了什么，

how they work together,

它们是如何协同工作的，

and whether the activity is because of their involvement in memory

以及这些激活是否因为 它们参与了记忆活动，

or another process occurring simultaneously.

又或是参与了 另一个同时发生的活动。

More advanced imaging and analysis technology

更多先进的成像和分析技术

might one day provide more accurate results

在未来可能会提供更精确的结果，

and even distinguish

甚至能区分

the activity of individual neurons.

单个神经元的活动。

Until then, our brains will keep measuring, analyzing, and innovating

在那之前，我们的大脑 将继续测量，分析和创新

in pursuit of that quest to understand

为了能够理解

one of the most remarkable things we’ve ever encountered.

我们遇到的最非凡的事情之一。