Scientists are providing a fuller understanding of the essential role that sleep plays in brain health, identifying an abrupt transition at about 2.4 years of age when its primary purpose shifts from brain building to maintenance and repair.
Researchers on Sept. 18 said they conducted a statistical analysis on data from more than 60 sleep studies. They looked at sleep time, duration of rapid eye movement (REM) sleep, brain size and body size, and devised a mathematical model for how sleep changes during development.
There are basically two types of sleep, each tied to specific brain waves and neuronal activity. REM, with the eyes moving quickly from side to side behind closed eyelids, is deep sleep with vivid dreams. Non-REM sleep is largely dreamless.
Photo: Reuters 照片：路透
During REM sleep, the brain forms new neural connections by building and strengthening synapses — the junctions between nerve cells, or neurons — that enable them to communicate, reinforcing learning and consolidating memories. During sleep, the brain also repairs the modicum of daily neurological damage it typically experiences to genes and proteins within neurons as well as clearing out byproducts that build up.
At about 2.4 years of age, the findings showed, sleep’s primary function changed from building and cutting connections during REM sleep to neural repair during both REM and non-REM sleep. “It was shocking to us that this transition was like a switch and so sharp,” said Van Savage, a UCLA professor of ecology and evolutionary biology and of computational medicine who is a senior author of the research published in the journal Science Advances.
REM sleep declines with age. Newborns, who can sleep about 16 hours daily, spend about 50 percent of their sleeping time in REM, but there is a pronounced drop-off at around 2.4 years. It drops to about 25 percent by age 10 and to about 10 percent to 15 percent around age 50. “Sleep is required across the animal kingdom and is nearly as ubiquitous as eating and breathing,” Van Savage said. “I’d say it is a pillar of human health.”(Reuters)
科學家近日提出更完整的理論，進一步闡釋睡眠對大腦健康扮演不可或缺的角色。科學家確認，兒童大腦約在二歲五個月時會發生突然的轉變。此時，睡眠的首要目的從大腦發育轉變成維護與修復。
研究人員於九月十八日指出，他們對超過六十個睡眠研究提供的資料進行統計學分析。他們觀察睡眠時間、快速動眼期的持續長度、大腦和身體尺寸，並且設計出一套數學模型，研究睡眠在成長過程中會如何發生變化。
基本上，睡眠分成兩種類型，各自和特定的腦波與神經元活動密切相關。在快速動眼期，眼球會在緊閉的眼皮後方快速左右移動，進入深層睡眠，此時做的夢也特別清晰。非快速動眼期則大多是無夢的。
在快速動眼期睡眠中，大腦藉由建立以及強化「突觸」──也就是神經細胞（或稱神經元）的相接處──形成新的神經連結，讓它們得以互相交流，藉此加深學習並且鞏固記憶。在睡眠期間，大腦也會修復平日受到的少量神經系統損傷──通常發生於基因和神經元裡面的蛋白質──同時清除累積的副產物。
研究顯示，在大約二歲五個月左右，睡眠的首要功能會發生改變，從快速動眼期睡眠中持續建立並且切斷連結，轉變成在快速動眼期以及非快速動眼期這兩個睡眠期間進行神經修復。這份研究近日發表於期刊《科學進展》，其資深作者范‧薩維奇指出：「我們很訝異，這個轉變就像是切換開關一樣，非常突然。」范‧薩維奇是美國加州大學洛杉磯分校生態學和演化生物學教授，同時也是計算醫學教授。
快速動眼期睡眠會隨著年紀增長而減少。新生兒一天可以睡到十六個小時，其中大約一半的睡眠時間都花在快速動眼期。然而，大概到兩歲五個月的時候，快速動眼期就會顯著降低。到了十歲，快速動眼期約佔睡眠時間的百分之二十五；到五十歲時，快速動眼期更衰退到睡眠時間的百分之十到十五左右。「睡眠在整個動物界都是必要的活動，就跟進食和呼吸一樣無所不在。」范‧薩維奇表示：「我會說，睡眠是人類健康的支柱。」（台北時報章厚明譯）
The Dutch introduced the Indian mango (Mangifera indica) to Taiwan in the 17th century. It is a green-skinned mango with thick fibers that get stuck in the teeth, but it boasts a rich aroma and a unique taste. In 1954, Taiwan’s Council of Agriculture introduced several mango cultivars from Florida, USA, including the Irwin, Haden, and Keitt varieties. After seven years of testing and domestication, the Irwin variety was chosen for promotion. Years later, the sample saplings started to bear fruit. These mangoes were large, with thin, vibrant red peels and golden pulp. The Irwin mangoes were mouth-wateringly sweet and
As the priest Antonius Hambroek stood in the dim chamber of Fort Zeelandia, his eldest daughter clung to him, her voice trembling. “Father, don’t go. They’ll kill you, and what will become of Mother and my sisters?” Outside, the sounds of Koxinga’s relentless canon siege boomed through the fortress. The defenders were on the brink of collapse. Starvation gnawed at their resolve, and the air carried the acrid stench of spent gunpowder and rotting flesh. Dutch reinforcements from Batavia had failed to arrive, leaving the garrison isolated and hopeless. Hambroek’s face was calm, though sorrow weighed heavily on his
對話 Dialogue 清清：今天中午我要多吃一點，不然晚上可能會吃不飽。 Qīngqing: Jīntiān zhōngwǔ wǒ yào duō chī yìdiǎn, bùrán wǎnshàng kěnéng huì chībùbǎo. 華華：怎麼了？為什麼會吃不飽？ Huáhua: Zěnmele? Wèishénme huì chībùbǎo? 清清：今天大年初七，是「人日節」，傳統上結了婚的女兒要回家給父母送長壽麵，而且最好是素的，我姐姐會回來，只吃素麵，我應該很快就餓了。 Qīngqing: Jīntiān Dànián chūqī, shì “Rénrì jié,” chuántǒng shàng jiéle hūn de nǚ’ér yào huíjiā gěi fùmǔ sòng chángshòumiàn, érqiě zuìhǎo shì sù de, wǒ jiějie huì huílái, zhǐ chī sùmiàn, wǒ yīnggāi hěn kuài jiù èle. 華華：我還是第一次聽說有「人日節」呢！這是怎麼來的啊？ Huáhua: Wǒ háishì dì yī cì tīngshuō yǒu “Rénrì jié” ne! Zhè shì zěnme lái de a? 清清：老一輩的人說，女媧是在第七天造出了「人」，所以今天可說是我們每個人的「生日」呢！生日快樂！ Qīngqing: Lǎoyíbèi de rén shuō, Nǚwā shì zài dì qī tiān zào chūle “rén,” suǒyǐ jīntiān kěshuōshì wǒmen měi ge rén de “shēngrì” ne! Shēngrì kuàilè! 華華：你也是啊！欸？那前六天女媧都做了什麼呢？ Huáhua: Nǐ yěshì a! Éi? Nà
As we bundle up in thick coats to stay warm during the winter, there is a population that has already adapted to extremely low temperatures. These people live in the remote city of Yakutsk, the coldest city on Earth. Yakutsk is situated in the heart of Siberia, which is the capital of the Sakha Republic in Russia. This historic mining city began to flourish in the 19th century following the discovery of gold deposits. Given its construction on permafrost, the average temperature in the city remains below 0°C for over half the year, with winter temperatures dropping to an astonishing -50°C.
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