What happens when you remove the hippocampus? - Sam Kean

切除海馬體會有什麼後果呢? – 山姆‧基恩

譯者: Ya Hui Hung 審譯者: Adrienne Lin

On September 1st, 1953,

在 1953 年 9 月 1 日

William Scoville used a hand crank and a cheap drill saw

to bore into a young man's skull, cutting away vital pieces of his brain

鑽入一個少年的頭顱 切去部份大腦關鍵區域

and sucking them out through a metal tube.

並以金屬管吸出

But this wasn't a scene from a horror film or a gruesome police report.

這不是恐怖片片段 或可怕的警察報告

Dr. Scoville was one of the most renowned neurosurgeons of his time,

科維爾是當代最著名的 神經外科醫生之一

and the young man was Henry Molaison, the famous patient known as "H.M.",

而那少年是亨利‧莫萊森 被稱為 H.M. 的名病患

whose case provided amazing insights into how our brains work.

他的病例提供了 卓絕的大腦運作見解

As a boy, Henry had cracked his skull in an accident

小時候，亨利的頭骨因意外破裂

and soon began having seizures, blacking out and losing control of bodily functions.

不久後開始抽搐、昏厥、身體機能失控

After enduring years of frequent episodes, and even dropping out of high school,

經歷了數年頻繁的發作 甚至在高中時輟學

the desperate young man had turned to Dr. Scoville,

絕望的少年求治於斯柯維爾醫生

a daredevil known for risky surgeries.

因高風險手術而聞名的膽大醫生

Partial lobotomies had been used for decades to treat mental patients

以局部腦葉手術 治療精神病患已有幾十年

based on the notion that mental functions were strictly localized

基於經神功能是局限於

to corresponding brain areas.

相應腦區的想法

Having successfully used them to reduce seizures in psychotics,

這手術成功的降低了 精神病患的抽搐

Scoville decided to remove H.M.'s hippocampus,

斯科威爾決定切除 H.M. 的海馬體

a part of the limbic system that was associated with emotion

這是與情緒有關的 大腦邊緣系統的一部份

but whose function was unknown.

但其功能未知

At first glance, the operation had succeeded.

起初，手術看似成功了

H.M.'s seizures virtually disappeared, with no change in personality,

H.M. 的抽搐幾乎消失了 且沒性格改變

and his IQ even improved.

他的智商甚至提高了

But there was one problem: His memory was shot.

但有一問題 他的記憶喪失

Besides losing most of his memories from the previous decade,

除了幾乎完全喪失 他前十年的記憶

H.M. was unable to form new ones, forgetting what day it was,

H.M. 無法建立新的， 忘了日期、

repeating comments, and even eating multiple meals in a row.

重複論談、 甚至連續吃了多餐

When Scoville informed another expert, Wilder Penfield, of the results,

當斯科威爾將結果告知另一專家 懷爾德‧潘費德 (Wilder Penfield)

he sent a Ph.D student named Brenda Milner to study H.M. at his parents' home,

他請博士生布朗黛‧密爾納 (Brenda Milner) 到 H.M. 父母的家研究 H.M.

where he now spent his days doing odd chores,

H.M. 現在的生活是做些雜活

and watching classic movies for the first time, over and over.

重複看經典影片

What she discovered through a series of tests and interviews

從一系列的測試和面談

didn't just contribute greatly to the study of memory.

密爾納的發現 不單對記憶研究有貢獻

It redefined what memory even meant.

而重新定義了對記憶的認知

One of Milner's findings shed light on the obvious fact

蜜爾納的發現 揭示了一項明顯事實

that although H.M. couldn't form new memories, he still retained information

雖然 H.M. 無法建立新記憶 他能保留訊息的時間

long enough from moment to moment to finish a sentence or find the bathroom.

足夠他完成一個句子 或找到廁所

When Milner gave him a random number,

當密爾納給他一個隨機數

he managed to remember it for fifteen minutes

他能以不斷的重複

by repeating it to himself constantly.

記住這數字 15 分鐘

But only five minutes later, he forgot the test had even taken place.

但僅 5 分鐘後 他就忘了被測試過

Neuroscientists had though of memory as monolithic,

神經科學家原以為記憶是單石性的

all of it essentially the same and stored throughout the brain.

全本質相同， 儲存於整個大腦

Milner's results were not only the first clue for the now familiar distinction

蜜爾納的研究結果 並不是如今

between short-term and long-term memory,

短期和長期記憶之間 區別的第一線索

but show that each uses different brain regions.

但顯示它們儲存於不同腦區域

We now know that memory formation involves several steps.

如今我們知道 記憶的形成有幾個步驟

After immediate sensory data is temporarily transcribed by neurons in the cortex,

感覺訊息暫時在 大腦皮質神經元轉錄後

it travels to the hippocampus,

轉至海馬體

where special proteins work to strengthen the cortical synaptic connections.

那有特殊蛋白質 加強皮質突觸連接

If the experience was strong enough,

如果是夠強烈的經歷

or we recall it periodically in the first few days,

或在經歷後幾天間斷回憶

the hippocampus then transfers the memory back to the cortex for permanent storage.

海馬體則將記憶 轉回皮質做長期儲存

H.M.'s mind could form the initial impressions,

H.M. 的腦裡能形成初步印象

but without a hippocampus to perform this memory consolidation,

但沒海馬體執行記憶內存

they eroded, like messages scrawled in sand.

記憶受侵蝕，猶如寫在沙上的訊息

But this was not the only memory distinction Milner found.

但密爾納發現記憶區別不只如此

In a now famous experiment, she asked H.M. to trace a third star

在一個現在著名的實驗中， 她請 H.M.

in the narrow space between the outlines of two concentric ones

在兩個同心的星星 輪廓之間狹小空間中

while he could only see his paper and pencil through a mirror.

看著鏡子描繪出第三個星星

Like anyone else performing such an awkward task for the first time,

就如其他人， 首次做這有難度的作業

he did horribly.

他做得很糟

But surprisingly, he improved over repeated trials,

但出乎意料的， 在反覆試驗後，他進步了

even though he had no memory of previous attempts.

雖然他並無先前嘗試的記憶

His unconscious motor centers remembered what the conscious mind had forgotten.

他無意識的運動中樞記得 被有意識神志遺忘的

What Milner had discovered was that the declarative memory of names, dates and facts

蜜爾納所發現的是 姓名、日期、事實等陳述性記憶

is different from the procedural memory of riding a bicycle or signing your name.

有別於如何騎腳踏車、 簽名等的程序性記憶

And we now know that procedural memory

現今我們知道程序性記憶

relies more on the basal ganglia and cerebellum,

大都依賴基底核與小腦

structures that were intact in H.M.'s brain.

這些結構在 H.M. 腦中是完整的

This distinction between "knowing that" and "knowing how"

從此「知道」和「知道如何」的區別

has underpinned all memory research since.

成為記憶研究的根本

H.M. died at the age of 82 after a mostly peaceful life in a nursing home.

H.M. 的人生大都平靜的 在養老院度過，享年 82 歲

Over the years, he had been examined by more than 100 neuroscientists,

多年來， 他被超過 100 名神經學家研究過

making his the most studied mind in history.

是歷史上經歷最廣泛研究的大腦

Upon his death, his brain was preserved and scanned

他死後， 在有 40 萬人觀看的現場直播中

他的大腦被保存、掃描、

before being cut into over 2000 individual slices

切成了 2,000 多個切片

and photographed to form a digital map down to the level of individual neurons,

拍攝成有單神經元解析度的電子腦地圖

all in a live broadcast watched by 400,000 people.

Though H.M. spent most of his life forgetting things,

雖然 H.M. 的一生幾乎是在遺忘中度過

he and his contributions to our understanding of memory

但他對理解記憶的貢獻

will be remembered for generations to come.

將會永世的被記住