雅思阅读 103: The Brain Listens Under Anesthesia

Adapted from 'The brain processes overheard words under anesthesia, but it may not remember them', Scientific American, May 2026.

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Under general anesthesia, the conscious mind shuts off, or so we have long thought. But a new study suggests the anesthetized brain still picks up sounds, words and even conversations. The participants did not remember them afterward, however.

Scientists discovered that the hippocampus, a deep-brain structure involved in memory and spatial navigation, continues to listen, learn and predict the meaning of words while a person is completely anesthetized. The hippocampus, over millions of years of evolution, became so specialized in taking information in and parsing it into a useful structure that it does this without awareness, explains Sameer Sheth of Baylor College of Medicine, co-senior author of the study published in Nature.

The researchers recruited seven people scheduled for anterior temporal lobectomy, surgery to treat severe epilepsy. While patients were under general anesthesia, surgeons inserted thin probes called Neuropixels into their hippocampus, allowing scientists to eavesdrop on hundreds of individual neurons at once.

The team played audio in the operating room. Some patients heard repetitive tones interrupted by unexpected frequencies, while others heard the Moth Radio Hour podcast. In the tone task, individual neurons discriminated between standard and unexpected tones, and this recognition emerged over time. The unconscious brain was learning to tell the tones apart during the 10-minute playback.

In the podcast experiment, hippocampal neurons encoded specific semantic and grammatical features of spoken words. Some fired for nouns; others fired more for verbs. Neurons seemed to recognize that words such as cat were semantically close to dog but distant from pen. Most fascinating, neurons made real-time predictions of what the next word would be.

Overall, language processing in the anesthetized hippocampus worked much like it does in an awake brain. But the patients reported no conscious recollection of the sounds. The team notes results were obtained with propofol, a common intravenous anesthetic, and that it is too early to generalize to other anesthetics or states such as sleep.

Questions 1-5

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

1. What did the study find about the anesthetized brain? A. It shuts off completely B. It still processes words and sounds C. It dreams vividly D. It stops all activity
2. How many patients participated? A. 7 B. 70 C. 700 D. 7,000
3. What are Neuropixels? A. A type of anesthesia B. Thin probes that record neuron activity C. A podcast D. A brain scan machine
4. In the podcast experiment, neurons fired differently for A. loud vs quiet sounds B. nouns vs verbs C. male vs female voices D. music vs speech
5. What did patients remember afterward? A. Every word B. The podcast story C. No conscious recollection D. The first five minutes

Questions 6-10

Do the following statements agree with the information? Write TRUE, FALSE or NOT GIVEN.

6. The hippocampus continues to work under anesthesia.
7. The study was published in Science.
8. Neurons predicted upcoming words in real time.
9. All anesthetics produce the same effect.
10. The patients were undergoing epilepsy surgery.

Questions 11-13

Complete the summary. Choose ONE WORD ONLY.

Under anesthesia, the hippocampus continues to 11 words. Neurons could distinguish nouns from 12 and made predictions about the next 13. Patients had no conscious memory.

Answers

1. B 2. A 3. B 4. B 5. C
2. TRUE 7. FALSE 8. TRUE 9. FALSE 10. TRUE
3. process 12. verbs 13. word

Key Vocabulary

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