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）
A: Brazilian jiu-jitsu, known as “BJJ,” has become more and more popular. Even Hollywood stars like Halle Berry and Tom Hardy are obsessed with it. B: Some Asian stars, such as Taiwanese actor Eddie Peng and South Korean actor Lee Joon-gi, have also practiced this martial art. A: BJJ is not just a martial art, but also a combat sport. B: I’ve always wanted to try it, but I’m worried about getting injured. A: Diana Wang, a US doctor of physical therapy, is holding a BJJ seminar at PMA Brazilian Jiu-jitsu in Taipei Friday night. Let’s go check out how we
Picture a 45-foot-long animal with a 5-foot-long skull and 3-foot-long arms. It may not seem strange until you realize that a human with those proportions would be 6 feet tall with 5-inch arms. Although the Tyrannosaurus rex went extinct 65 million years ago, the mystery of its unusual body __1__ has fascinated scientists for over a century. Barnum Brown, the paleontologist who first discovered T. rex fossils, initially found it hard to believe that the tiny arms belonged to such a __2__ creature. One of his colleagues speculated that the short forelimbs might have been used to hold the
A: Actually, Brazilian jiu-jitsu is particularly good for small people like you. B: Really? How so? A: According to Diana Wang, a US doctor of physical therapy, the BJJ’s purpose is to help smaller, weaker people defend themselves by using various techniques, such as leverage. B: That sounds interesting. What time does Dr Wang’s BJJ seminar begin tonight? A: The event is scheduled for 7:30pm at PMA Brazilian Jiu-jitsu in Taipei. Admission is free, but donations are welcome. A: 其實你的個子比較小，很適合練巴西柔術呢。 B: 真的嗎？為什麼？ A: 據美國理療醫師王幼瑞博士說，巴西柔術的概念是讓弱小的人，也能利用槓桿作用等技巧防身。 B: 真有趣，王醫師的巴柔研討會幾點開始？ A: 今晚7點半在「台北巴柔運動館」，免費入場自由樂捐唷！ （By Eddy Chang, Taipei Times／台北時報張迪）
Dogs’ noses are incredibly keen. They can even detect changes in cortisol levels in human sweat and breath. Known as the “stress hormone,” cortisol increases when humans are under pressure. Recent research indicates that the smell of human stress can influence a dog’s behavior and emotions. In the study, human volunteers were exposed to the stressful tasks of preparing and delivering a speech on the spot and then solving math problems. __1__ Researchers collected sweat and breath samples from the volunteers on pieces of cloth during both their stressful and restful states. Meanwhile, other researchers worked with 18
RSS