シャドーイング練習: What happens when you remove the hippocampus? - Sam Kean - YouTubeで英語スピーキングを学ぶ
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On September 1, 1953, William Scoville used a hand crank and a cheap drill saw to bore into a young man's skull,
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cutting away vital pieces of his brain and sucking them out through a metal tube.
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But this wasn't a scene from a horror film or a gruesome police report.
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Dr. Scoville was one of the most renowned neurosurgeons of his time,
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The young man was Henry Malayason,
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the famous patient known as H.M.,
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whose case provided amazing insights into how our brains work.
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As a boy, Henry had cracked his skull in an accident and soon began having seizures,
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blacking out, and losing control of bodily functions.
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After enduring years of frequent episodes and even dropping out of high school,
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the desperate young man had turned to Dr. Scoville,
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a daredevil known for risky surgeries.
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Partial lobotomies had been used for decades to treat mental patients,
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based on the notion that mental functions were strictly localized to corresponding brain areas.
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Having successfully used them to reduce seizures in psychotics,
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Scoville decided to remove H.M.'s hippocampus,
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a part of the limbic system that was associated with emotion,
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but whose function was unknown.
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At first glance, the operation had succeeded.
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H.M.'s seizures virtually disappeared, with no change in personality,
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and his IQ even improved.
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But there was one problem.
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His memory was shot.
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Besides losing most of his memories from the previous decade, H.M was unable to form new ones,
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forgetting what day it was,
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repeating comments, and even eating multiple meals in a row.
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When Scoville informed another expert,
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Wilder Penfield, of the results,
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he sent a PhD student named Brenda Milner to study HM at his parents' home,
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where he now spent his days doing odd chores and watching classic movies for the first time,
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over and over.
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What she discovered through a series of tests and interviews didn't just contribute greatly to the study of memory.
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It redefined what memory even meant.
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One of Milner's findings shed light on the obvious fact that although H.M couldn't form new memories,
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he still retained information long enough from moment to moment to finish a sentence or find the bathroom.
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When Milner gave him a random number,
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he managed to remember it for 15 minutes by repeating it to himself constantly.
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But only five minutes later,
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he forgot the test had even taken place.
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Neuroscientists had thought of memory as monolithic,
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all of it essentially the same,
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and stored throughout the brain.
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Milner's results were not only the first clue for the now familiar distinction between short-term and long-term memory,
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but showed that each uses different brain regions.
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We now know that memory formation involves several steps.
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After immediate sensory data is temporarily transcribed by neurons in the cortex,
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it travels to the hippocampus,
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where special proteins work to strengthen the cortical-synaptic connections.
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If the experience was strong enough,
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or we recall it periodically in the first few days,
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the hippocampus then transfers the memory back to the cortex for permanent storage.
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HM's mind could form the initial impressions,
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but without a hippocampus to perform this memory consolidation,
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they eroded like messages scrawled in sand.
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But this was not the only memory distinction Milner found.
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In a now-famous experiment,
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she asked H.M to trace a third star in the narrow space between the outlines of two concentric ones,
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while he could only see his paper and pencil through a mirror.
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Like anyone else performing such an awkward task for the first time, he did horribly.
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But surprisingly, he improved over repeated trials,
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even though he had no memory of previous attempts.
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His unconscious motor centers remembered remembered what the conscious mind had forgotten.
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What Milner had discovered was that the declarative memory of names,
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dates, and facts is different from the procedural memory of riding a bicycle or signing your name.
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And we now know that procedural memory relies more on the basal ganglia and cerebellum,
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structures that were intact in H.M.'s brain.
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This distinction between knowing that and knowing how has underpinned all memory research since.
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H.M died at the age of 82 after a mostly peaceful life in a nursing home.
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Over the years, he had been examined by more than 100 neuroscientists,
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making his the most studied mind in history.
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Upon his death, his brain was preserved and scanned before being cut into over 2,000 individual slices
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and photographed to form a digital map down to the level of individual neurons,
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all in a live broadcast watched by 400,000 people.
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Though H.M spent most of his life forgetting things,
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he and his contributions to our understanding of memory will be remembered for generations to come.
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Thank you.
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このレッスンについて
このレッスンでは、英語学習者が記憶に関する興味深い科学的発見を学びながら、英語をシャドーイング練習します。サム・キーンのビデオを通じて、海馬がどのように機能し、記憶形成においてどのような役割を果たしているのかを探ります。また、H.M.と呼ばれる患者のケーススタディを通じて、記憶が短期と長期にどのように分かれるのかについての理解を深めます。この内容は、英語スピーキング練習においても非常に有益です。
重要な語彙とフレーズ
- 海馬 (hippocampus) - 記憶形成に関わる脳の部分。
- 記憶形成 (memory formation) - 情報が記憶として保存される過程。
- 短期記憶 (short-term memory) - 短期間で保持される記憶。
- 長期記憶 (long-term memory) - 長期間にわたり保持される記憶。
- 動作記憶 (procedural memory) - 自転車に乗ることやサインを書くようなスキルを覚える記憶。
- 意識的 (conscious) - 自覚している状態。
- 無意識的 (unconscious) - 自覚していない状態。
練習のコツ
このビデオの速度でシャドーイングを行うためのアドバイスとして、まずはゆっくりとしたトーンでの再生を検討してください。自分のペースで始めることができるので、YouTubeで英語学習を使って、繰り返し視聴することがおすすめです。特に重要なフレーズを繰り返し口に出すことで、英語シャドーイングの効果を最大化できます。
最初は、全部を正確に再現しようとするのではなく、キーワードやフレーズを意識しながら行いましょう。例えば、「海馬」というフレーズが出てきた時は、その意味を考えながらスピーキング練習を行ってみてください。また、shadow speechの練習をすることで、リスニング能力も同時に向上させることができます。このようにして、自然な英語のフローを身につけましょう。
最後に、言葉だけでなく、その背後にある意味やメッセージを理解することで、英語スピーキング練習がより効果的になります。独自の体験を交えながら、繰り返し練習して、取り入れた知識を自分のものにしていってください。
シャドーイングとは？英語上達に効果的な理由
シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。