咖啡因對記憶有幫助嗎？

By Allison Aubrey

Host： Most of us know what it feels like to have a little 1）caffeine in our system. A cup of coffee wakes us up， gives us a bit of a buzz. Well， it turns out caffeinated 2）nectar does something similar for honey bees. Thats the finding of a new study published in the journal Science， as NPRs Allison Aubrey reports.

Allison Aubery： Its too early in the year to expect to see honey bees， says researcher Phil Stevenson， especially from his 3）perch at Royal 4）Botanic Gardens at Kew， just outside London.

And Stevenson says when the bees start 5）foraging for food in spring， they take long flights in search of nectar and then 6）haul it back to their 7）hives.

Now it turns out some of this nectar actually contains caffeine. Not just the nectar of coffee plants， but also 8）citrus plants—including lemons， and oranges. So Stevenson and his colleague were curious. They wanted to know if this caffeinated nectar influenced the behavior of bees. So they designed a study.

主持人：我們當中大部分人都知道，少量的咖啡因會對我們的身體產生怎樣的影響。一杯咖啡使我們清醒，讓我們精神為之一振。然而，研究結果顯示，帶有咖啡因的花蜜對蜜蜂也起到了類似作用。那是刊登在《科學》雜志的最新研究發現，請聽NPR記者阿利森·奧布里的報道。

阿利森·奧布里：研究員菲爾·史蒂文森說，現在想看到蜜蜂還為時尚早，特別是他所處的高位置——英國皇家植物園（又名邱園），就在倫敦外圍。（編者注：記者所說時間為3月。）

史蒂文森說，當蜜蜂在春天開始搜尋食物的時候，為了尋找花蜜，它們進行長途飛行，然后再把花蜜運回蜂房。

現在結果顯示有些花蜜確實含有咖啡因，不僅僅是咖啡植物的花蜜，柑橘類植物的花蜜也含有，包括檸檬和柑橘。史蒂文森和他的團隊很好奇，他們想知道含有咖啡因的花蜜是否對蜜蜂的行為有影響，于是他們開展了一個研究實驗。

Phil Stevenson： And in this study， you can train bees to associate a reward of food with a smell. Its a little bit like Pavlovs dog. When Pavlov rang the bell， the dog 9）salivated. In this case， when the bee detects the smell， it extends its 10）proboscis.

Aubery： The smell came from flowers， the proboscis is the bees long， hairy tongue used to suck up the nectar. Now， in the study， Stevenson wanted to see whether the bees would respond differently to flowers that contained a caffeine rich nectar， compared to those that had just sugary nectar.

Stevenson： We found that when they were taking sugar nectar with caffeine， they were three times better able to remember the flower 11）odor a day later than bees that were feeding on just sugar alone.

Aubery： So could this mean that a caffeinated bee has a better memory？

Stevenson： Thats exactly what the study shows. We were very surprised by it， but obviously were also very excited because it shows that bees are better able to remember a flower. And， of course， for a bee this makes it better able to locate food.

Aubery： Which is obviously a big plus in life. Now， some researchers wonder if bees simply prefer caffeinated nectar. But whether its improving their memories or making them more motivated to seek it out—its 12）intriguing that caffeine could be giving bees the same kind of buzz that people get. Abraham Palmer： Caffeine absolutely influences our behavior. It changes mood and performance in a variety of different ways.

Aubery： Thats Abraham Palmer of the University of Chicago. He says due to 13）genetic differences， our individual responses to caffeine vary. But studies show that caffeine does work on our brains reward system， and in moderate doses can help improve attention and performance on all sorts of mental and physical tasks. Some of the best studies come from the U.S. military， where caffeine has been studied as a way to keep soldiers alert.

Researcher Harris Lieberman explains he studied a group of sailors who were training to become Navy 14）SEALs. Harris Lieberman： During one portion of that training， they are substantially sleep deprived and exposed to a variety of other 15）stressors.

Aubery： Including cold temperatures and demanding physical activities. Lieberman says when he compared the sailors who consumed caffeine compared to those who had a non-caffeinated 16）placebo， he documented a range of benefits.

Lieberman： We found that in moderate doses， caffeine enhanced ability to pay attention， it enhanced 17）vigilance.

Aubery： And it seemed to improve the exhausted sailorsshort-term memories， something Lieberman was not expecting to see. Lieberman： We were somewhat surprised that caffeine had such widespread effects.

Aubery： But Lieberman says， in the absence of exhaustion， caffeine doesnt seem to help people remember any better. So he doesnt think that caffeine is much of a memory 18）booster.

Lieberman： No， I dont.

Aubery： But whether its humans or those bees， theres clearly something about caffeine that keeps us coming back for more.

菲爾·史蒂文森：在這個實驗里，你可以訓練蜜蜂對帶有某種氣味的食物作出反應，有點像巴甫洛夫的狗一樣。當巴甫洛夫搖響鈴鐺，那只狗就會分泌唾液。在這種情況下，當蜜蜂偵察到氣味，它就會伸長自己的吮吸管。

奧布里：氣味來自花朵，吮吸管是蜜蜂用于吮吸花蜜的細長而毛絨的舌頭。在實驗里，史蒂文森想知道跟那些只有甜花蜜的花朵相比，蜜蜂是否會對富含咖啡因花蜜的花朵有不同的反應。

史蒂文森：我們發現當蜜蜂吮吸帶有咖啡因的甜花蜜，一天后它們記住該花朵氣味的能力比吮吸普通甜花蜜的蜜蜂高三倍。

奧布里：那么這意味著吸了咖啡因的蜜蜂具有更好的記憶力嗎？

史蒂文森：那確實是實驗顯示的結果，我們都因此很驚訝。不過顯然我們也很興奮，因為蜜蜂能更好地記住一朵花，而且當然對于蜜蜂來說，這讓它能更好地定位食物。

奧布里：那顯然是給生活的額外饋贈。現在，有些研究者想知道蜜蜂是否只單純喜歡含咖啡因的花蜜，還是因為那能提高它們的記憶力或能激發它們的動力去找到花蜜——很想知道咖啡因對人起到醒神的作用是否也同樣作用于蜜蜂。

亞伯拉罕·帕爾默：咖啡因絕對影響著我們的行為，以各種不同的方式改變我們的情緒和表現。

奧布里：那是芝加哥大學的亞伯拉罕·帕爾默。他說因為基因不同，每個人對咖啡因的反應是不一樣的。但是多項研究表明，咖啡因對我們大腦的獎賞系統是有影響的，適度的劑量有助于在各種腦力和體力活動中集中注意力和表現更好。有些頂級的研究來自美國的部隊，他們研究發現咖啡因是能讓士兵保持警惕的一種方式。

研究員哈里斯·利伯曼解釋他研究過一群水手，他們要被訓練成海豹突擊隊。

哈里斯·利伯曼：訓練的其中一部分就是他們完全不允許睡覺，還要承受各種各樣高強度的壓力。

奧布里：利伯曼說，在天氣寒冷和要做大量體力活動的情況下，把服用了咖啡因的水手和那些只吃了不含咖啡因的安慰劑的水手相比較，他記錄了（咖啡因的）一系列好處。

利伯曼：我們發現適量的咖啡因能提高注意力，提高警覺性。

奧布里：咖啡因似乎還能改善疲憊水手的短期記憶力，那是利伯曼不曾預想看到的。

利伯曼：我們有點驚訝于咖啡因有如此廣泛的效果。奧布里：但利伯曼也說，疲憊消除后，咖啡因似乎并不能對改善人們的記憶力有任何幫助，所以他認為咖啡因并不是提高記憶力的推手。利伯曼：對，我認為不是。奧布里：但無論是對人類還是對蜜蜂，很顯然，關于咖啡因的更多東西仍值得我們繼續研究。

小鏈接

巴甫洛夫（Pavlov），又譯帕夫洛夫，俄羅斯生理學家、心理學家，在神經生理學方面，提出了著名的條件反射和信號學說，獲得1904年諾貝爾生理或醫學獎。

巴甫洛夫做了一個相當著名的實驗，他利用狗看到食物或吃東西之前會流口水的現象，在每次喂食前都先發出一些信號（一開始是搖鈴，后來還包括吹口哨、使用節拍器、敲擊音叉、開燈……等等），連續了幾次之后，他試了一次搖鈴但不喂食，發現狗雖然沒有東西可以吃，卻照樣流口水，而在重復訓練之前，狗對于“鈴聲響”是不會有反應的。他從這一點推知，狗經過了連續幾次的經驗后，將“鈴聲響”視作“進食”的信號，因此引發了“進食”會產生的流口水現象。這種現象稱為條件反射，這證明動物的行為是因為受到環境的刺激，將刺激的訊號傳到神經和大腦，神經和大腦作出反應而來。