On September 1st, 1953, 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 and sucking them out through a metal tube. But this wasn't a scene from a horror film or a gruesome police report. Dr. Scoville was one of the most renowned neurosurgeons of his time, and the young man was Henry Molaison, the famous patient known as "H.M.", whose case provided amazing insights into how our brains work. As a boy, Henry had cracked his skull in an accident and soon began having seizures, blacking out and losing control of bodily functions. After enduring years of frequent episodes, and even dropping out of high school, the desperate young man had turned to Dr. Scoville, a daredevil known for risky surgeries. Partial lobotomies had been used for decades to treat mental patients based on the notion that mental functions were strictly localized to corresponding brain areas. Having successfully used them to reduce seizures in psychotics, Scoville decided to remove H.M.'s hippocampus, a part of the limbic system that was associated with emotion but whose function was unknown. At first glance, the operation had succeeded. H.M.'s seizures virtually disappeared, with no change in personality, and his IQ even improved. But there was one problem: His memory was shot. Besides losing most of his memories from the previous decade, H.M. was unable to form new ones, forgetting what day it was, repeating comments, and even eating multiple meals in a row. When Scoville informed another expert, Wilder Penfield, of the results, he sent a Ph.D student named Brenda Milner to study H.M. at his parents' home, where he now spent his days doing odd chores, and watching classic movies for the first time, over and over. What she discovered through a series of tests and interviews didn't just contribute greatly to the study of memory. It redefined what memory even meant. One of Milner's findings shed light on the obvious fact that although H.M. couldn't form new memories, he still retained information long enough from moment to moment to finish a sentence or find the bathroom. When Milner gave him a random number, he managed to remember it for fifteen minutes by repeating it to himself constantly. But only five minutes later, he forgot the test had even taken place. Neuroscientists had though of memory as monolithic, all of it essentially the same and stored throughout the brain. Milner's results were not only the first clue for the now familiar distinction between short-term and long-term memory, but show that each uses different brain regions. We now know that memory formation involves several steps. After immediate sensory data is temporarily transcribed by neurons in the cortex, it travels to the hippocampus, where special proteins work to strengthen the cortical synaptic connections. If the experience was strong enough, or we recall it periodically in the first few days, the hippocampus then transfers the memory back to the cortex for permanent storage. H.M.'s mind could form the initial impressions, but without a hippocampus to perform this memory consolidation, they eroded, like messages scrawled in sand. But this was not the only memory distinction Milner found. In a now famous experiment, she asked H.M. to trace a third star in the narrow space between the outlines of two concentric ones while he could only see his paper and pencil through a mirror. Like anyone else performing such an awkward task for the first time, he did horribly. But surprisingly, he improved over repeated trials, even though he had no memory of previous attempts. His unconscious motor centers remembered what the conscious mind had forgotten. What Milner had discovered was that the declarative memory of names, dates and facts is different from the procedural memory of riding a bicycle or signing your name. And we now know that procedural memory relies more on the basal ganglia and cerebellum, structures that were intact in H.M.'s brain. This distinction between "knowing that" and "knowing how" has underpinned all memory research since. H.M. died at the age of 82 after a mostly peaceful life in a nursing home. Over the years, he had been examined by more than 100 neuroscientists, making his the most studied mind in history. Upon his death, his brain was preserved and scanned before being cut into over 2000 individual slices and photographed to form a digital map down to the level of individual neurons, all in a live broadcast watched by 400,000 people. Though H.M. spent most of his life forgetting things, he and his contributions to our understanding of memory will be remembered for generations to come.
在 1953 年 9 月 1 日 威廉·斯科維爾 (William Scoville) 以手動曲柄、便宜的鋸鑽 鑽入一個少年的頭顱 切去部份大腦關鍵區域 並以金屬管吸出 這不是恐怖片片段 或可怕的警察報告 科維爾是當代最著名的 神經外科醫生之一 而那少年是亨利‧莫萊森 被稱為 H.M. 的名病患 他的病例提供了 卓絕的大腦運作見解 小時候,亨利的頭骨因意外破裂 不久後開始抽搐、昏厥、身體機能失控 經歷了數年頻繁的發作 甚至在高中時輟學 絕望的少年求治於斯柯維爾醫生 因高風險手術而聞名的膽大醫生 以局部腦葉手術 治療精神病患已有幾十年 基於經神功能是局限於 相應腦區的想法 這手術成功的降低了 精神病患的抽搐 斯科威爾決定切除 H.M. 的海馬體 這是與情緒有關的 大腦邊緣系統的一部份 但其功能未知 起初,手術看似成功了 H.M. 的抽搐幾乎消失了 且沒性格改變 他的智商甚至提高了 但有一問題 他的記憶喪失 除了幾乎完全喪失 他前十年的記憶 H.M. 無法建立新的, 忘了日期、 重複論談、 甚至連續吃了多餐 當斯科威爾將結果告知另一專家 懷爾德‧潘費德 (Wilder Penfield) 他請博士生布朗黛‧密爾納 (Brenda Milner) 到 H.M. 父母的家研究 H.M. H.M. 現在的生活是做些雜活 重複看經典影片 從一系列的測試和面談 密爾納的發現 不單對記憶研究有貢獻 而重新定義了對記憶的認知 蜜爾納的發現 揭示了一項明顯事實 雖然 H.M. 無法建立新記憶 他能保留訊息的時間 足夠他完成一個句子 或找到廁所 當密爾納給他一個隨機數 他能以不斷的重複 記住這數字 15 分鐘 但僅 5 分鐘後 他就忘了被測試過 神經科學家原以為記憶是單石性的 全本質相同, 儲存於整個大腦 蜜爾納的研究結果 並不是如今 短期和長期記憶之間 區別的第一線索 但顯示它們儲存於不同腦區域 如今我們知道 記憶的形成有幾個步驟 感覺訊息暫時在 大腦皮質神經元轉錄後 轉至海馬體 那有特殊蛋白質 加強皮質突觸連接 如果是夠強烈的經歷 或在經歷後幾天間斷回憶 海馬體則將記憶 轉回皮質做長期儲存 H.M. 的腦裡能形成初步印象 但沒海馬體執行記憶內存 記憶受侵蝕,猶如寫在沙上的訊息 但密爾納發現記憶區別不只如此 在一個現在著名的實驗中, 她請 H.M. 在兩個同心的星星 輪廓之間狹小空間中 看著鏡子描繪出第三個星星 就如其他人, 首次做這有難度的作業 他做得很糟 但出乎意料的, 在反覆試驗後,他進步了 雖然他並無先前嘗試的記憶 他無意識的運動中樞記得 被有意識神志遺忘的 蜜爾納所發現的是 姓名、日期、事實等陳述性記憶 有別於如何騎腳踏車、 簽名等的程序性記憶 現今我們知道程序性記憶 大都依賴基底核與小腦 這些結構在 H.M. 腦中是完整的 從此「知道」和「知道如何」的區別 成為記憶研究的根本 H.M. 的人生大都平靜的 在養老院度過,享年 82 歲 多年來, 他被超過 100 名神經學家研究過 是歷史上經歷最廣泛研究的大腦 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、 切成了 2,000 多個切片 拍攝成有單神經元解析度的電子腦地圖 雖然 H.M. 的一生幾乎是在遺忘中度過 但他對理解記憶的貢獻 將會永世的被記住