雅思阅读 063 — 'Super Agers' with Great Memory Have More Young Brain Cells

改编自 Scientific American / Nature（2026-02，Mariana Lenharo）。研究发表于 Nature。

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Adults whose brains still produce new neurons at a high rate seem to have better memory and cognitive function than those in whom this ability wanes, finds a study published in Nature. The authors examined brain samples from deceased donors ranging from young adults to "super agers" — people older than 80 with exceptional memory.

They found that young and old adults with healthy cognition generated neurons, a process called neurogenesis, at high levels for their age. The team estimated that the new neurons made up only a small fraction — roughly 0.01 per cent — of those in the hippocampus, a brain region essential for memory. By contrast, in people experiencing cognitive decline, including individuals with Alzheimer's disease, neurogenesis seemed to falter: the researchers spotted fewer developing, or immature, neurons in those brain samples.

Surprisingly, a group of "super agers" had an even higher number of immature neurons than did other healthy groups, and significantly more than those with Alzheimer's. However, the group sizes were small — each had ten or fewer individuals — so the findings were not all statistically significant.

Maura Boldrini Dupont, a neuroscientist and psychiatrist at Columbia University in New York City, says that the small size of the groups is a reason to take the results with a grain of salt.

Understanding the tools that the brain uses to generate neurons and maintain cognitive function in old age could help researchers to develop drugs that induce neurogenesis in people with cognitive decline, says co-author Orly Lazarov, a neuroscientist at the University of Illinois Chicago.

A long-standing controversy

The findings support the idea that people's brains continue to generate neurons even in adulthood. But that idea has not always been accepted.

In the early 1900s, the Spanish neuroscientist Santiago Ramón y Cajal suggested that the human brain could not form neurons after birth. Eventually, researchers found that neurogenesis did occur in childhood, but still thought that was the endpoint. "That's what they used to teach when I went to medical school," Dupont says.

In the past few decades, however, this dogma was challenged by new evidence supporting neurogenesis in the adult hippocampus, fuelling an ongoing debate in neurobiology.

Although researchers know that neurogenesis occurs in some adult animals, including mice and primates, they have not been able to agree on whether it happens in the brains of human adults. That is mainly because there are more tools for studying neurogenesis in animals than in humans. In mice, for instance, researchers can inject chemicals that trace the birth and development of neurons. This cannot be done in living people, and research on donated human brain samples has been limited.

One tool researchers have used to study neurogenesis in humans is protein markers. Antibodies can be used to detect certain proteins expressed by neural stem cells — which can turn into neurons — and immature neurons in donated brain samples. But critics argue that these proteins are not specific enough and could be expressed in other cell types, not just in neurogenesis.

So scientists have turned to single-cell RNA sequencing to find more specific genetic markers of neural stem cells and immature neurons in the human hippocampus.

New methods, new hope

Lazarov and her colleagues went a step further in their latest study. They not only used RNA sequencing to identify the genetic signatures of these cell types, but also uncovered their epigenetic signatures. Epigenetic markers are chemical modifications to DNA that control gene expression without altering the underlying sequence. The team used an assay that pinpoints parts of a cell's DNA that are primed for expression to determine these signatures. Dupont says that the assay is a strong point of the study.

Lazarov says the next step will be to understand the function of the neurons generated in the adult brain. "What we need is functional validation of these cells, to tell what they are doing in the human brain," she says, adding that this would require new imaging techniques sensitive enough to detect this activity in living people.

If the link between neurogenesis and memory holds up, the work could eventually lead to therapies that boost neuron production in patients with Alzheimer's and other forms of dementia.

Questions

Questions 1–5: TRUE / FALSE / NOT GIVEN

1. The study examined brain samples from living donors.
2. Neurogenesis refers to the brain's production of new neurons.
3. New neurons make up approximately half of all neurons in the hippocampus.
4. Super agers had more immature neurons than people with Alzheimer's disease.
5. The study's group sizes were large enough for strong statistical significance.

Questions 6–10: Choose the correct letter, A, B, C or D.

6. Santiago Ramón y Cajal argued that the human brain

   • A. produces neurons throughout life
   • B. cannot form neurons after birth
   • C. produces more neurons in childhood than in adulthood
   • D. loses neurons every year

7. Why has neurogenesis in adult humans been so hard to prove?

   • A. Human brains are much smaller than animal brains.
   • B. Tracing chemicals cannot be safely injected into living people.
   • C. Human neurons do not divide.
   • D. The hippocampus is too small to study.

8. A limitation of using protein markers to identify neurogenesis is that

   • A. proteins disappear too quickly
   • B. they are not specific enough to distinguish neurons from other cell types
   • C. antibodies cannot enter brain tissue
   • D. they only work in mice

9. The new study improved on previous methods by

   • A. using MRI scans on living patients
   • B. combining RNA sequencing with epigenetic signatures
   • C. studying live mice instead of human samples
   • D. injecting traceable chemicals into human volunteers

10. The ultimate practical goal of this research is to

    • A. prove that Ramón y Cajal was wrong
    • B. develop therapies that boost neuron production in dementia patients
    • C. map every neuron in the human brain
    • D. cure Alzheimer's disease within five years

Questions 11–13: Complete the sentences. Choose NO MORE THAN TWO WORDS.

11. The hippocampus is a brain region crucial for __________.
12. Epigenetic markers are chemical modifications to __________ that control gene expression.
13. Lazarov says the next step requires __________ validation of the new neurons' function.

Answers

1. FALSE (来自已故捐赠者)
2. TRUE
3. FALSE (只占 0.01%)
4. TRUE
5. FALSE (每组 ≤10 人，样本小)
6. B
7. B
8. B
9. B
10. B
11. memory
12. DNA
13. functional

Glossary

• neuron /ˈnjʊərɒn/ n. 神经元
• neurogenesis /ˌnjʊərəʊˈdʒenəsɪs/ n. 神经发生
• hippocampus /ˌhɪpəˈkæmpəs/ n. 海马体
• cognitive /ˈkɒɡnətɪv/ adj. 认知的
• epigenetic /ˌepɪdʒɪˈnetɪk/ adj. 表观遗传的
• assay /əˈseɪ/ n. 化验，测定
• dementia /dɪˈmenʃə/ n. 痴呆
• dogma /ˈdɒɡmə/ n. 教条
• primed /praɪmd/ adj. 准备就绪的