What is consciousness? - Michael S. A. Graziano

譯者: Lilian Chiu 審譯者: Helen Chang

Here are two images of a house.

這是一間房子的兩張圖片。

There’s one obvious difference,

有一個非常明顯的不同點，

but to this patient, P.S.,

但對這位病人 P.S. 來說，

they looked completely identical.

它們一模一樣。

P.S. had suffered a stroke that damaged the right side of her brain,

P.S. 中風過，造成 她的大腦右邊受損，

leaving her unaware of everything on her left side.

讓她無法意識到左側的東西。

But though she could discern no difference between the houses,

但，雖然她無法分辨出 兩間房子的差別，

when researchers asked her which she would prefer to live in,

當研究者問她想要 住在哪一間房子中時，

she chose the house that wasn’t burning—

她會選擇沒有在燃燒的那一間——

not once, but again and again.

不只一次，每次她都這樣選擇。

P.S.’s brain was still processing information

P.S. 的大腦在處理的資訊，

from her whole field of vision.

仍然是來自她完整 視線範圍的資訊。

She could see both images

她能夠看見兩張圖片，

and tell the difference between them,

並區別出它們的差別，

she just didn’t know it.

只是她自己不知道而已。

If someone threw a ball at her left side,

如果有人從她的左側向她 丟一顆球，她可能會閃開。

she might duck.

But she wouldn’t have any awareness of the ball,

但她不會意識到有球飛過來，

or any idea why she ducked.

也不會知道她自己為什麼要閃躲。

P.S.’s condition,

P.S. 的狀況就是半空間忽略症，

known as hemispatial neglect,

reveals an important distinction between the brain’s processing of information

這種狀況說明了 「大腦對資訊的處理」

以及「我們對於那處理的體驗」 有很大的差別。

and our experience of that processing.

That experience is what we call consciousness.

這種體驗就是我們所謂的意識。

We are conscious of both the external world and our internal selves—

我們對於外在世界 和內在自我都有意識——

we are aware of an image

我們意識到圖片的方式，

in much the same way we are aware of ourselves looking at an image,

和我們意識到我們正在 看著圖片的方式差不多，

or our inner thoughts and emotions.

或我們意識到自己 內在思想和情緒的方式。

But where does consciousness come from?

但，意識是從哪裡來的？

Scientists, theologians, and philosophers

科學家、神學家，和哲學家

have been trying to get to the bottom of this question for centuries—

數世紀來都一直在嘗試 探究這個問題——

without reaching any consensus.

卻沒有達成任何共識。

One recent theory is that

有一個近期的理論認為意識是

consciousness is the brain’s imperfect picture of its own activity.

大腦對於其自身活動的 不完美寫照。

To understand this theory,

若要了解這個理論，

it helps to have a clear idea

可以先弄清楚

of one important way the brain processes information from our senses.

大腦怎麼處理來自感官的資訊。

Based on sensory input,

大腦會根據感官 輸入的資訊來建立模型，

it builds models,

which are continuously updating, simplified descriptions

這個模型會不斷更新，

將世界上各種事、 物的描述給簡化。

of objects and events in the world.

Everything we know is based on these models.

我們所知的一切都是 以這些模型為基礎。

They never capture every detail of the things they describe,

這些模型並未包含 其所描述之目標事物的所有細節，

just enough for the brain to determine appropriate responses.

只要足夠讓大腦判斷 做出什麼反應才適當就夠了。

For instance, one model built deep into the visual system

比如，在視覺系統深處 有一個內建的模型，

codes white light as brightness without color.

它會將白光編碼為 「沒有顏色的明亮」。

In reality,

在現實中，

white light includes wavelengths

白光包含我們能夠看見的

that correspond to all the different colors we can see.

各種顏色所對應的波長。

Our perception of white light is wrong and oversimplified,

我們對於白光的感知 是錯誤的，且過度簡化。

but good enough for us to function.

但這樣的感知就夠我們運作了。

Likewise, the brain’s model of the physical body

同樣的，大腦針對 實際身體建立的模型

keeps track of the configuration of our limbs,

會持續追蹤肢體的配置結構，

but not of individual cells or even muscles,

但不會細到包含每個個別細胞 或甚至肌肉的狀況，

because that level of information isn’t needed to plan movement.

因為規劃動作 用不到這麼細的資訊。

If it didn’t have the model keeping track of the body’s size, shape,

如果大腦沒有一個模型 來追蹤身體的大小、形狀，

and how it is moving at any moment,

及身體時時刻刻的動作，

we would quickly injure ourselves.

那我們可能很快就會讓自己受傷。

The brain also needs models of itself.

大腦也需要針對自己做模型。

For example,

比如，大腦有能力

the brain has the ability to pay attention to specific objects and events.

去注意任何特定的事物。

It also controls that focus,

它也能控制那焦點，

shifting it from one thing to another,

根據我們的需求，將焦點 從一樣事物移轉至另一樣，

internal and external,

according to our needs.

不論內在或外在。

Without the ability to direct our focus,

若我們沒有移動焦點的能力，

we wouldn’t be able to assess threats, finish a meal, or function at all.

就無法評估威脅、無法吃完一餐， 或甚至完全無法運作了。

To control focus effectively,

為了有效控制焦點，

the brain has to construct a model of its own attention.

大腦針對它自己的注意力 建立了一個模型。

With 86 billion neurons constantly interacting with each other,

在八百六十億個神經元 不斷地彼此互動的情況下，

there’s no way the brain’s model of its own information processing

大腦處理資料的模型不可能建得

can be perfectly self-descriptive.

有著完完整整描述的細節。

But like the model of the body,

但，就如同身體模型，

or our conception of white light,

或我們對於白光的概念，

it doesn’t have to be.

並不需要太多細節。

Our certainty that we have a metaphysical, subjective experience

我們很肯定自己具有 形而上學、主觀的體驗，

may come from one of the brain’s models,

這肯定性可能就來自 大腦的模型之一，

a cut-corner description of what it means to process information

這個模型簡便地描述了用專注、

深刻的方式來處理資訊的意義。

in a focused and deep manner.

Scientists have already begun trying to figure out

科學家已經開始試圖探究

how the brain creates that self model.

大腦如何創造出那個自我模型。

MRI studies are a promising avenue for pinpointing the networks involved.

MRI 研究是個很理想的方式， 可以精確找出它牽涉到哪些網路。

These studies compare patterns of neural activation

這些研究比較了神經啟動的模式

when someone is and isn’t conscious of a sensory stimulus, like an image.

在一個人有或沒有意識到感官刺激 （如一張圖片）時有什麼差別。

The results show that the areas needed for visual processing

結果顯示，不論受試者 是否有意識到圖片，

are activated whether or not the participant is aware of the image,

視覺處理要用到的區域都會啟動，

but a whole additional network lights up

但只有在他們有意識到 自己看見圖片時，

only when they are conscious of seeing the image.

整個額外的網路才會亮起來。

Patients with hemispatial neglect, like P.S.,

像 P.S. 這種半空間忽略症的病人

typically have damage to one particular part of this network.

通常是這個網路的特定部位受損。

More extensive damage to the network can sometimes lead to a vegetative state,

若這個網路受損更嚴重， 有時會造成植物狀態，

with no sign of consciousness.

沒有任何意識的跡象。

Evidence like this brings us closer to understanding

像這樣的證據讓我們多了解了一點

how consciousness is built into the brain,

意識如何被建置在大腦中，

but there’s still much more to learn.

但我們還有非常多要學的。比如，

For instance,

the way neurons in the networks related to consciousness

在意識相關的網路中的神經元

compute specific pieces of information

如何計算特定的資訊

is outside the scope of our current technology.

就超出了我們目前科技 能理解的範圍。

As we approach questions of consciousness with science,

當我們用科學來探究 意識的問題時，

we’ll open new lines of inquiry into human identity.

我們也會開啟一連串 關於人類身分的疑問。