New neurons stop growing in a key region of the brain’s ’memory center』 as early as 13 years old, according to a controversial new study.
一項有爭議的新研究顯示，早在人類13歲時，大腦「記憶中心」一個關鍵區域的新神經細胞就停止生長了。
Scientists looking at brain tissue samples found no evidence of new nerve cell growth in the dentate gyryus, a part of the hippocampus vital to memory formation, after the age of 13.
研究腦組織樣本的科學家沒有發現人類在13歲後齒狀回中有新神經細胞生長的證據。齒狀回是海馬區的一個部分。海馬區對於記憶的形成至關重要。
The discovery contradicts previous findings suggesting that hippocampal neurons replenish themselves throughout adulthood, as they do in many other mammals.
該結論同先前的發現相左。以往研究顯示，人類大腦海馬區的神經元在整個成年時期都會不斷自我補充，就像很多其他哺乳動物一樣。
The newly found pattern seems to be a hallmark of big complex brains.
這種新發現似乎顯示了複雜大腦的特徵。
New hippocampus neuron development also dwindled over time in macaque monkeys, the scientists found. And hippocampus regeneration was thought to be lacking in big-brained dolphins, porpoises and whales.
科學家發現，在獼猴身上，新海馬神經元生長也會隨時間減弱。科學家認為，在有著大型腦的海豚和鯨中間，也缺少海馬神經元再生的情況。
Writing in the journal Nature, the authors led by Dr Arturo Alvarez-Buylia, from the University of California at San Francisco, concluded: 』Neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans.
該研究由加利福尼亞大學舊金山分校的阿圖羅?阿爾瓦雷斯-拜利亞博士領導，發表在英國《自然》周刊上。他總結道，「在成年人中，齒狀回中的神經元再生不會繼續，或極其稀少。」
The early decline in hippocampal neurogenesis raises questions about how the function of the dentate gyrus differs between humans and other species in which adult hippocampal neurogenesis is preserved.』
「海馬區神經再生的早期衰退提出了人類和其他物種之間齒狀回功能如何不同的問題。其他物種在成年期仍可再生海馬神經元。」
The scientists used marker antibodies to 』flag up』 neural precursor cells and immature neurons in 59 human brain tissue samples.
科學家們使用標記抗體來「指示」59個人類腦組織樣本中的神經前體細胞和不成熟神經元。
The post-mortem and post-surgery samples spanned all life stages from the foetus to older adulthood.
這些死後和手術後獲得的樣本橫跨從胎兒到老年的所有生命階段。
The number of developing neurons in the dentate gyrus reduced with age and the oldest sample in which any were found was from a 13-year-old. No young neurons were detected in samples from people aged 18 to 77.
在齒狀回中，生長中的神經元數量會隨年齡增長而減少。包含生長中神經元的最老樣本來自一個13歲的人。從18到77歲的人的腦樣本中沒有發現年輕的神經元。
The scientists added: 』Interestingly, a lack of neurogenesis in the hippocampus has been suggested for aquatic mammals (dolphins, porpoises and whales), species known for their large brains, longevity and complex behaviour.』
科學家還說：「有趣的是，水棲哺乳動物(海豚和鯨)的海馬體也缺乏神經元再生現象。這些物種以大規模的腦、長壽和複雜行為而聞名。」
Previous studies may have wrongly reported the detection of immature hippocampal neurons because the marker proteins used to disclose them do not work the same way in humans and animals, said the researchers.
研究人員說，過去的研究可能錯誤報導了不成熟海馬神經元的發現，因為用於指示它們的標記蛋白質在人類和動物身上以不同方式工作。
In an accompanying News & Views commentary, Dr Jason Snyder from the University of British Columbia, Canada, wrote: 』These findings are in stark contrast to the prevailing view that human hippocampal neurogenesis extends throughout adult life.』
加拿大英屬哥倫比亞大學的傑森斯奈德博士在一篇相關的新聞與觀察評論中寫道：「這些發現與人們普遍認為的人類海馬神經發生貫穿成年期的觀點形成了鮮明的對比。」