Here are two images of a house. There’s one obvious difference, but to this patient, P.S., they looked completely identical.
這是一間房子的兩張圖片。 有一個非常明顯的不同點, 但對這位病人 P.S. 來說, 它們一模一樣。
P.S. had suffered a stroke that damaged the right side of her brain, leaving her unaware of everything on her left side. But though she could discern no difference between the houses, when researchers asked her which she would prefer to live in, she chose the house that wasn’t burning— not once, but again and again.
P.S. 中風過,造成 她的大腦右邊受損, 讓她無法意識到左側的東西。 但,雖然她無法分辨出 兩間房子的差別, 當研究者問她想要 住在哪一間房子中時, 她會選擇沒有在燃燒的那一間—— 不只一次,每次她都這樣選擇。
P.S.’s brain was still processing information from her whole field of vision. She could see both images and tell the difference between them, she just didn’t know it. If someone threw a ball at her left side, she might duck. But she wouldn’t have any awareness of the ball, or any idea why she ducked.
P.S. 的大腦在處理的資訊, 仍然是來自她完整 視線範圍的資訊。 她能夠看見兩張圖片, 並區別出它們的差別, 只是她自己不知道而已。 如果有人從她的左側向她 丟一顆球,她可能會閃開。 但她不會意識到有球飛過來, 也不會知道她自己為什麼要閃躲。 P.S. 的狀況就是半空間忽略症,
P.S.’s condition, known as hemispatial neglect, reveals an important distinction between the brain’s processing of information and our experience of that processing. That experience is what we call consciousness. We are conscious of both the external world and our internal selves— we are aware of an image in much the same way we are aware of ourselves looking at an image, or our inner thoughts and emotions. But where does consciousness come from? Scientists, theologians, and philosophers have been trying to get to the bottom of this question for centuries— without reaching any consensus.
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。 這種體驗就是我們所謂的意識。 我們對於外在世界 和內在自我都有意識—— 我們意識到圖片的方式, 和我們意識到我們正在 看著圖片的方式差不多, 或我們意識到自己 內在思想和情緒的方式。 但,意識是從哪裡來的? 科學家、神學家,和哲學家 數世紀來都一直在嘗試 探究這個問題—— 卻沒有達成任何共識。
One recent theory is that consciousness is the brain’s imperfect picture of its own activity.
有一個近期的理論認為意識是 大腦對於其自身活動的 不完美寫照。
To understand this theory, it helps to have a clear idea of one important way the brain processes information from our senses. Based on sensory input, it builds models, which are continuously updating, simplified descriptions of objects and events in the world. Everything we know is based on these models. They never capture every detail of the things they describe, just enough for the brain to determine appropriate responses. For instance, one model built deep into the visual system codes white light as brightness without color. In reality, white light includes wavelengths that correspond to all the different colors we can see. Our perception of white light is wrong and oversimplified, but good enough for us to function. Likewise, the brain’s model of the physical body keeps track of the configuration of our limbs, but not of individual cells or even muscles, because that level of information isn’t needed to plan movement. If it didn’t have the model keeping track of the body’s size, shape, and how it is moving at any moment, we would quickly injure ourselves.
若要了解這個理論, 可以先弄清楚 大腦怎麼處理來自感官的資訊。 大腦會根據感官 輸入的資訊來建立模型, 這個模型會不斷更新, 將世界上各種事、 物的描述給簡化。 我們所知的一切都是 以這些模型為基礎。 這些模型並未包含 其所描述之目標事物的所有細節, 只要足夠讓大腦判斷 做出什麼反應才適當就夠了。 比如,在視覺系統深處 有一個內建的模型, 它會將白光編碼為 「沒有顏色的明亮」。 在現實中, 白光包含我們能夠看見的 各種顏色所對應的波長。 我們對於白光的感知 是錯誤的,且過度簡化。 但這樣的感知就夠我們運作了。 同樣的,大腦針對 實際身體建立的模型 會持續追蹤肢體的配置結構, 但不會細到包含每個個別細胞 或甚至肌肉的狀況, 因為規劃動作 用不到這麼細的資訊。 如果大腦沒有一個模型 來追蹤身體的大小、形狀, 及身體時時刻刻的動作, 那我們可能很快就會讓自己受傷。
The brain also needs models of itself. For example, the brain has the ability to pay attention to specific objects and events. It also controls that focus, shifting it from one thing to another, internal and external, according to our needs. Without the ability to direct our focus, we wouldn’t be able to assess threats, finish a meal, or function at all. To control focus effectively, the brain has to construct a model of its own attention. With 86 billion neurons constantly interacting with each other, there’s no way the brain’s model of its own information processing can be perfectly self-descriptive. But like the model of the body, or our conception of white light, it doesn’t have to be. Our certainty that we have a metaphysical, subjective experience may come from one of the brain’s models, a cut-corner description of what it means to process information in a focused and deep manner.
大腦也需要針對自己做模型。 比如,大腦有能力 去注意任何特定的事物。 它也能控制那焦點, 根據我們的需求,將焦點 從一樣事物移轉至另一樣, 不論內在或外在。 若我們沒有移動焦點的能力, 就無法評估威脅、無法吃完一餐, 或甚至完全無法運作了。 為了有效控制焦點, 大腦針對它自己的注意力 建立了一個模型。 在八百六十億個神經元 不斷地彼此互動的情況下, 大腦處理資料的模型不可能建得 有著完完整整描述的細節。 但,就如同身體模型, 或我們對於白光的概念, 並不需要太多細節。 我們很肯定自己具有 形而上學、主觀的體驗, 這肯定性可能就來自 大腦的模型之一, 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。
Scientists have already begun trying to figure out how the brain creates that self model. MRI studies are a promising avenue for pinpointing the networks involved. These studies compare patterns of neural activation when someone is and isn’t conscious of a sensory stimulus, like an image. The results show that the areas needed for visual processing are activated whether or not the participant is aware of the image, but a whole additional network lights up only when they are conscious of seeing the image. Patients with hemispatial neglect, like P.S., typically have damage to one particular part of this network. More extensive damage to the network can sometimes lead to a vegetative state, with no sign of consciousness.
科學家已經開始試圖探究 大腦如何創造出那個自我模型。 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。 這些研究比較了神經啟動的模式 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。 結果顯示,不論受試者 是否有意識到圖片, 視覺處理要用到的區域都會啟動, 但只有在他們有意識到 自己看見圖片時, 整個額外的網路才會亮起來。 像 P.S. 這種半空間忽略症的病人 通常是這個網路的特定部位受損。 若這個網路受損更嚴重, 有時會造成植物狀態, 沒有任何意識的跡象。
Evidence like this brings us closer to understanding how consciousness is built into the brain, but there’s still much more to learn. For instance, the way neurons in the networks related to consciousness compute specific pieces of information is outside the scope of our current technology. As we approach questions of consciousness with science, we’ll open new lines of inquiry into human identity.
像這樣的證據讓我們多了解了一點 意識如何被建置在大腦中, 但我們還有非常多要學的。比如, 在意識相關的網路中的神經元 如何計算特定的資訊 就超出了我們目前科技 能理解的範圍。 當我們用科學來探究 意識的問題時, 我們也會開啟一連串 關於人類身分的疑問。