人類更愛晃著睡

Rocking babies to sleep—to both quiet the wails of youth and preserve the sanity of young parents—has been commonplace dating back to prehistory.Similarly,rhythmic motions like the muted clank of a train ride coax many of us adults into an instant slumber—but why?

搖晃嬰兒入睡——既能讓年輕人的哭聲安靜下來，又能讓年輕父母保持清醒——在史前時代就已經(jīng)司空見慣了。同樣，有節(jié)奏的動作，比如火車上發(fā)出的無聲的隆隆聲，會誘使我們許多成年人立即進(jìn)入睡眠狀態(tài)——但這是為什么呢?

Two new studies published today in Current Biology suggest our brains are evolutionarily programmed to respond to rocking.The research shows in both humans and mice,rocking to sleep may have significant health benefits such as better quality of sleep and even improved long-term memory formation.

今天發(fā)表在《當(dāng)代生物學(xué)》(Current Biology)雜志上的兩項新研究表明，從進(jìn)化的角度來看，我們的大腦天生就會對搖擺做出反應(yīng)。研究表明，無論是對人類還是小鼠，搖晃著入睡都可能對健康有顯著的好處，比如睡眠質(zhì)量更好，甚至可以改善長期記憶的形成。

In the first study the authors used electroencephalography(EEG)recordings to analyze the brain responses of 18 young healthy adults who spent three nights in a sleep lab.The first night was intended to acclimate them to their new sleep environment;the second they spent in a slowly rocking bed;the third—one week later—in a stationary bed.

在第一項研究中，作者使用腦電圖(EEG)記錄分析了18名年輕健康成年人在睡眠實驗室中度過三個晚上后的大腦反應(yīng)。第一晚的目的是讓他們適應(yīng)新的睡眠環(huán)境;第二次他們在一張慢慢搖動的床上度過;第三個，一個星期后，躺在一張固定的床上。

Even in people who were already good sleepers,rocking shortened the time it took for subjects to fall asleep,and also to reach non-REM sleep,which correlates with improved sleep quality.The rockers also had fewer arousals and maintained deep sleep for a longer period of time.

即使是那些已經(jīng)睡得很好的人，搖晃也縮短了他們?nèi)胨臅r間，也縮短了他們進(jìn)入非快速眼動睡眠的時間，這與睡眠質(zhì)量的提高有關(guān)。此外，搖滾樂手的清醒時間也更短，深度睡眠的時間也更長。

Curious if rocking might have any influence on memory,study subjects were also tasked with memorizing 46 random word pairs.On both their rocking and non-rocking sleepovers they were then presented with the first word and asked to recall the second after a night’s sleep.A night of rocking improved their recall threefold.

出于對搖擺是否會影響記憶的好奇，研究對象還被要求記憶46個隨機(jī)單詞對。在搖床和非搖床兩種情況下，研究人員都向他們展示了第一個單詞，并要求他們在一夜睡眠后回憶第二個單詞。一夜的搖動使他們的記憶力提高了三倍。

Finally rocking also was found to synchronize brain waves during non-REM sleep in the thalamocortical networks of the brain,a system known to be involved in both sleep and memory consolidation,the nocturnal process during which the brain processes and stores long-term memories.“What was surprising…is that we clearly showed that specific brain oscillations of non-REM sleep are synchronized and entrained by the rhythm of the bed motion,”says neuroscientist Laurence Bayer of the University of Geneva in Switzerland,who led the new study.Bayer likens the findings to our intuitive appreciation that a slowly rocking hammock can relax us and do wonders for our mood.“This is potentially a very promising avenue for future clinical research,”he notes.

最后，研究人員還發(fā)現(xiàn)，在非快速眼動睡眠期間，搖晃還能同步大腦丘腦皮質(zhì)網(wǎng)絡(luò)中的腦電波。這一系統(tǒng)被認(rèn)為同時參與了睡眠和記憶鞏固，也就是大腦處理和儲存長期記憶的夜間過程。瑞士日內(nèi)瓦大學(xué)的神經(jīng)科學(xué)家勞倫斯·拜爾領(lǐng)導(dǎo)了這項新研究，他說:“令人驚訝的是，我們清楚地表明，非快速眼動睡眠的特定腦振蕩是同步的，并被床上運動的節(jié)奏所控制。”拜耳將這一發(fā)現(xiàn)與我們直覺上的欣賞相比較，即一張慢慢搖動的吊床可以讓我們放松，并對我們的情緒產(chǎn)生奇妙的影響。“這可能是未來臨床研究的一個非常有前途的途徑。”他指出。

Previous research—and millennia of relieved parents—support the fact rocking helps coax infants to sleep.And the new findings suggest the same is true in adults.Yet it was previously unknown whether or not the same is true in other species.

先前的研究——以及幾千年來如釋重負(fù)的父母們——支持這樣一個事實:搖晃有助于哄嬰兒入睡。新的發(fā)現(xiàn)表明，同樣的道理也適用于成年人。然而，這在以前是未知的，是否同樣的情況也存在于其他物種中。

The second study found that,at least in mice,it is.Like in the human study,rocking shortened the time it took the mice to fall asleep and increased the amount of sleep time,as measured by EEG recordings.Unlike humans,however,rocking did not seem to induce deeper sleep in the rodents.The authors suspected rocking might exert its influence on sleep by stimulating the vestibular system,the sensory organs in the inner ears of mammals that control our sense of balance and spatial orientation.Using a strain of mice with impaired vestibular function,they showed this is indeed the case.Specifically,half of the mice used in the study lacked“otoliths,”small calcium carbonate–based particles that bob around two compartments of the inner ear and allow mammals to perceive vertical and horizontal acceleration.Mice without these otolithic organs showed none of benefits of rocking during sleep.“Since immemorial times we’ve rocked our babies,and often ourselves,to sleep,”says lead author on the new paper,Konstantinos Kompotis,at the University of Lausanne,also in Switzerland.“Our study provides new insights into the neurophysiological mechanisms underlying this phenomenon.”

第二項研究發(fā)現(xiàn)，至少在老鼠身上是這樣的。就像在人類研究中一樣，通過腦電圖記錄，搖晃縮短了小鼠入睡的時間，增加了睡眠時間。然而，與人類不同的是，搖晃似乎并沒有使嚙齒動物進(jìn)入深度睡眠。研究人員懷疑，搖晃可能通過刺激前庭神經(jīng)系統(tǒng)對睡眠產(chǎn)生影響。前庭神經(jīng)系統(tǒng)是哺乳動物內(nèi)耳的感覺器官，控制著我們的平衡感和空間方向感。用一種前庭功能受損的老鼠做實驗，他們發(fā)現(xiàn)事實確實如此。具體地說，研究中使用的老鼠中有一半缺乏“耳石”，這是一種以碳酸鈣為基礎(chǔ)的小顆粒，它在內(nèi)耳的兩個腔室之間來回擺動，使哺乳動物能夠感知垂直和水平加速度。沒有這些耳石器官的老鼠在睡眠時搖晃沒有任何好處。“從遠(yuǎn)古時代起，我們就一直搖著我們的嬰兒，經(jīng)常是搖著自己入睡，”這篇新論文的第一作者、同樣位于瑞士洛桑大學(xué)(University of Lausanne)的康斯坦蒂諾斯·孔波蒂斯(Konstantinos Kompotis)說。“我們的研究為這種現(xiàn)象背后的神經(jīng)生理機(jī)制提供了新的見解。”

“These findings are critically important,”adds Bryce Mander,an assistant professor of psychiatry and human behavior at the University of California,Irvine,who was not involved in these studies.“Before these papers,both the mechanisms and the functional significance of the association between vestibular-related rocking and sleep were completely unknown.”He notes the new findings open the door to testing non-invasive behavioral interventions in those with impaired sleep and memory.

“這些發(fā)現(xiàn)非常重要，”加州大學(xué)歐文分校(University of California,Irvine)精神病學(xué)和人類行為助理教授布萊斯·曼德(Bryce Mander)補(bǔ)充道。他沒有參與這些研究。在這些論文發(fā)表之前，前庭相關(guān)搖晃和睡眠之間聯(lián)系的機(jī)制和功能意義都是完全未知的。他指出，這項新發(fā)現(xiàn)為測試睡眠和記憶受損人群的非侵入性行為干預(yù)措施打開了大門。