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

譯者: Chen Chi-An 審譯者: Helen Chang

As far as we know,

據我們了解，

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

太陽系中有個東西非常精密，

精密到要自我研究：

the human brain.

人類的大腦。

But this self-investigation is incredibly challenging;

但這自我探索的挑戰性非常高：

a living brain is shielded by a thick skull,

活體大腦被很厚的顱骨保護著，

swaddled in layers of protective tissue,

有數層保護組織包裹著，

and made up of billions of tiny, connected cells.

且大腦由數億細小、 互相連接的細胞所組成

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

因此，我們很難分離、 觀察並瞭解疾病

like Alzheimer’s.

如阿茲海默症。

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

那我們要如何研究活體大腦 而不傷害它的主人呢？

We can use a trio of techniques called EEG,

我們能用三種技術， 分別叫 EEG、

fMRI,

fMRI

and PET.

及 PET 。

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

它們測量的東西不同， 且各有優缺點，

and we’ll look at each in turn.

我們一項一項看。

First is EEG, or electroencephalography,

首先是 EEG ，又稱「腦電圖」，

which measures electrical activity in your brain.

它偵測大腦的電訊號。

As brain cells communicate, they produce waves of electricity.

腦細胞傳送訊息時會製造電波，

Electrodes placed on the skull pick up these waves,

由放在顱骨上的電極接收；

and differences in the signals detected between electrodes

電極接收到不同的訊號，

provide information about what’s happening.

能提供資訊，看發生什麼事了。

This technique was invented almost 100 years ago,

這項技術近百年前就發明了，

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

至今仍被使用在鑑別診斷上， 如癲癇和睡眠障礙；

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

它也被用在偵測大腦哪些區域

during learning or paying attention.

在學習或專注時是活化的。

EEG is non-invasive,

EEG 沒有侵入性、

relatively inexpensive,

相對便宜

and fast:

且能迅速反應：

it can measure changes that occur in just milliseconds.

它能偵測毫秒間的變化。

Unfortunately, it’s hard to determine

然而不幸的是，

它很難精準定位 特定波型特徵的來源。

exactly where any particular pattern originates.

Electrical signals are generated constantly all over the brain

電訊號一直在大腦中產生，

and they interact with each other to produce complex patterns.

而大腦用此方式傳遞訊息， 製造出複雜的波型特徵。

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

用更多電極，或建立複雜函數 來解讀檔案有幫助，

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

但最後，僅管 EEG 能告訴你 特定活動何時產生，

it can’t tell you precisely where.

卻無法精確說出在哪產生。

To do that, you’d need another technique,

為此，你需要另一個技術，

such as functional magnetic resonance imaging, or fMRI.

例如「功能性磁振造影」， 又稱 fMRI 。

fMRI measures how quickly oxygen is consumed by brain cells.

fMRI 偵測腦細胞 消耗氧氣的速率，

Active areas of the brain use oxygen more quickly.

大腦活化區域耗氧速度較快，

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

因此當某人完成認知 或行為上的任務時，

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

fMRI 可以提供大腦哪些部分 參與任務的資訊。

That allows us to study everything from how we see faces

這使我們能研究所有事情， 從如何觀察人臉

to how we understand what we’re feeling.

到如何理解自己的感受。

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

fMRI 能定位腦部活動， 其精準度在數毫米間，

but it’s thousands of times slower than EEG.

但時間比 EEG 慢數千倍。

Using the two techniques together

同時使用這兩個技術

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

能幫助我們了解，神經活動 開始的時間和位置。

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

第三個技術則更精確，叫做 「正子發射斷層掃描（ PET ）」，

and it measures radioactive elements introduced into the brain.

它能測量事先注入 大腦的放射性物質，

That sounds much scarier than it actually is;

這聽起來比實際上來得可怕，

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

然 PET 跟 fMRI 和 EEG 一樣 完全安全。

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

在 PET 掃描期間，少量 放射線物質稱作示蹤劑

is injected into the bloodstream,

會被注入血液，

and doctors monitor its circulation through the brain.

然後醫師會偵測血流到大腦。

By modifying the tracer to bind to specific molecules,

透過修改示蹤劑來結合特定分子，

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

研究者可以用 PET 來研究 腦部複雜的化學分子。

It’s useful for studying how drugs affect the brain

在研究藥物如何影響大腦

and detecting diseases like Alzheimer’s.

及偵測疾病如阿茲海默症上，這很有用。

But this technique has the lowest time resolution of all

但這技術所花時間最久，

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

因為要數分鐘，示蹤劑才會 流到腦部，變化才會顯現。

These techniques collectively help doctors and scientists

這些科技共同幫助醫師和科學家了解，

connect what happens in the brain with our behavior.

行為和大腦發生的事 如何連結起來，

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

但它們也受到我們知識有限的限制，

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

例如，研究者想知道記憶如何運作，

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

使用 fMRI ，在問過五十個 受試者記下一系列的圖片後，

the researchers might analyze the results

研究者可以分析結果，

and discover a number of active brain regions.

並發現一些腦部活化區域，

Making a link between memory and specific parts of the brain

發現記憶和腦部特定區域相關

is an important step forward.

是重要的一步，

But future research would be necessary

但未來的研究需要

to better understand what’s happening in each region,

更理解每個區域發生什麼事、

how they work together,

它們如何協同工作

and whether the activity is because of their involvement in memory

及這些活化訊號，

是因為參與記憶過程，

or another process occurring simultaneously.

還是其他同時發生的過程。

More advanced imaging and analysis technology

更先進的影像及分析技術

might one day provide more accurate results

有天或許能提供更準確的結果，

and even distinguish

或甚至區分個別神經元的活動。

the activity of individual neurons.

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

在那之前，我們的大腦會 繼續測量、分析和創新，

in pursuit of that quest to understand

為追求完全理解

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

人們遇過最精彩的東西之一。