雅思阅读 162: When the Two Halves of the Brain Went Their Separate Ways（当大脑两半分道扬镳）

改编自 Brain / PNAS（Gazzaniga & Sperry, split-brain research）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://academic.oup.com/brain/article/140/7/2051/3892700

Reading Passage

A. For most of medical history, the human brain was imagined as a single, cooperating whole — a committee that always spoke with one voice. That assumption was overturned not by a machine but by a handful of patients. In the 1940s and 1950s, surgeons facing severe, untreatable epilepsy tried a radical operation. To stop seizures leaping from one side of the brain to the other, they cut the thick cable of nerve fibres — the corpus callosum — that connects the left and right hemispheres. The operation worked: patients had far fewer and milder attacks, and, remarkably, they seemed ordinary. Their intelligence was unchanged, their personalities intact, their everyday conversation normal. No one watching them over dinner would guess anything had happened. They worked, drove, argued and lived like everyone else. But when a pair of researchers, Roger Sperry and his student Michael Gazzaniga, began to test these patients with carefully designed experiments in the 1960s, the normal surface peeled away to reveal something stranger: a brain in which information shown to one side could be kept, in a sense, from the other.

B. To understand what the tests showed, you must know how the eyes and the brain are wired. Everything you see to the right of where you are looking is routed to the left hemisphere, and everything to the left is routed to the right. The left hemisphere, in most people, is also the one that controls speech. A healthy brain instantly shares the result across the corpus callosum, so the two sides always agree. In a split-brain patient, that sharing line is cut. When the researchers flashed the word "KEY" briefly to the patient's left visual field — that is, into the right hemisphere, which cannot speak — something revealing happened. Asked what he had seen, the patient said, plainly, "Nothing." His speaking left hemisphere had no idea what the right one had glimpsed. Yet when the same patient reached his left hand — which, controlled by the right hemisphere, had seen the word — into a bag and felt among hidden objects, that hand pulled out a key. The right hemisphere knew; the left, talking hemisphere did not, and cheerfully invented a story to explain why the hand was doing what it was doing.

C. These demonstrations upended a century of assumptions about how the mind is put together. Each hemisphere, it turned out, was not a vague half of a single organ but a system with its own abilities. The left side dominated language, logic and the quick, explanatory narrative we weave about our own behaviour. The right side excelled at spatial tasks — drawing a shape, arranging blocks, recognising faces — and could understand some simple language but could not easily speak. The classic picture that emerged is not that one side is "logical" and the other "creative", as popular self-help books later exaggerated it, but that the two halves genuinely specialise, and that the vast connecting cable exists precisely so their specialities can be fused into one seamless experience. In an intact brain you never notice the division because the cable is constantly updating both sides; only in patients with a cut cable does the division become visible. Sperry was awarded the Nobel Prize in Physiology or Medicine in 1981 for this work, shared with two other researchers.

D. The most unsettling interpretation — and the one that caught the public imagination — was that a split-brain patient might, in some sense, harbour two streams of consciousness, each confined to its own half. The early experiments did seem to show just that: a hand could reach for an object the talking mouth denied seeing. Yet later, more careful work tempered the dramatic reading. The patients themselves reported feeling completely normal, never describing a battle of wills or a second voice inside the skull. The disconnected right hemisphere, capable of a left hand selecting a key, was far less capable than a full, independent mind; it could not, for example, handle the kind of reasoning a normal adult takes for granted. The right hemisphere's skills were real but partial, and the unity of the patient's experienced self, when asked directly, never fractured. What the surgery produced, researchers concluded, was not two people inside one head but one person whose brain, lacking the bridge between sides, failed only in narrow, testable ways — and only when information was deliberately confined to one visual field.

E. Half a century on, the split-brain patients remain a gold mine, precisely because they offered something no scanner could: a natural experiment in which the connecting cable is, by necessity, absent. Modern imaging has confirmed and extended their lessons, showing that the corpus callosum transfers information between hemispheres in fractions of a second, and that the specialities first glimpsed in a handful of people are real but subtly graded rather than absolute. The popular myth of the "left-brained" and "right-brained" personality — the engineer versus the artist — has been repeatedly debunked, because no one actually lives in one half; we all use both, connected by a cable we never know we have. The deeper legacy is more philosophical than clinical. The experiments reminded us that the seamless, single "I" each of us feels is an achievement of integration, not a given. Underneath the unity lies a team of specialists, quietly talking across a bridge of fibres — and it takes a cut cable to show how much we depend on the conversation. The patients themselves, over decades of patient cooperation, became some of the most studied people in the history of neuroscience, their generosity turning a rare surgical outcome into one of the clearest windows ever opened onto the ordinary, unbroken mind.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. Why surgeons severed the bridge between hemispheres ii. The classic experiment that exposed the hidden division iii. Each hemisphere has its own special strengths iv. The popular myth that two people live in one head v. Why the split-brain patients felt completely abnormal vi. A gold mine for modern neuroscience — and a humbling lesson vii. The Nobel Prize awarded for brain surgery itself

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why did surgeons cut the corpus callosum? A. To improve patients' memory. B. To stop epileptic seizures spreading between hemispheres. C. To cure blindness. D. To make patients more creative.

6. In the classic experiment, why did the patient say "Nothing" after "KEY" was shown to the left visual field? A. He was lying to confuse the researchers. B. The speaking left hemisphere had not received the information. C. His eyes were closed. D. The word was in a foreign language.

7. What did the left hand do while the patient denied seeing anything? A. It refused to move. B. It pulled a key out of a bag by touch. C. It wrote the word "KEY". D. It pointed at the researcher.

8. How did later work temper the dramatic "two consciousnesses" claim? A. Patients reported feeling normal and the right hemisphere's abilities were partial. B. It proved each patient had two separate voices. C. It showed the surgery caused amnesia. D. It found the left hemisphere was purely artistic.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. After surgery, the patients' intelligence and personality appeared unchanged.
10. The left hemisphere is usually the one controlling speech.
11. Roger Sperry won the Nobel Prize in 1981 for split-brain research.
12. Split-brain patients consistently reported feeling two separate selves inside their heads.
13. Modern imaging has shown that the corpus callosum takes several minutes to transfer information.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Information shown to the left visual field is routed to the (14) __________ hemisphere, which in most people cannot speak but can guide the left hand to pull out a (15) __________.

答案与解析

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