咖啡因对记忆有帮助吗？

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：我们当中大部分人都知道，少量的咖啡因会对我们的身体产生怎样的影响。一杯咖啡使我们清醒，让我们精神为之一振。然而，研究结果显示，带有咖啡因的花蜜对蜜蜂也起到了类似作用。那是刊登在《科学》杂志的最新研究发现，请听NPR记者阿利森·奥布里的报道。

阿利森·奥布里：研究员菲尔·史蒂文森说，现在想看到蜜蜂还为时尚早，特别是他所处的高位置——英国皇家植物园（又名邱园），就在伦敦外围。（编者注：记者所说时间为3月。）

史蒂文森说，当蜜蜂在春天开始搜寻食物的时候，为了寻找花蜜，它们进行长途飞行，然后再把花蜜运回蜂房。

现在结果显示有些花蜜确实含有咖啡因，不仅仅是咖啡植物的花蜜，柑橘类植物的花蜜也含有，包括柠檬和柑橘。史蒂文森和他的团队很好奇，他们想知道含有咖啡因的花蜜是否对蜜蜂的行为有影响，于是他们开展了一个研究实验。

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.

菲尔·史蒂文森：在这个实验里，你可以训练蜜蜂对带有某种气味的食物作出反应，有点像巴甫洛夫的狗一样。当巴甫洛夫摇响铃铛，那只狗就会分泌唾液。在这种情况下，当蜜蜂侦察到气味，它就会伸长自己的吮吸管。

奥布里：气味来自花朵，吮吸管是蜜蜂用于吮吸花蜜的细长而毛绒的舌头。在实验里，史蒂文森想知道跟那些只有甜花蜜的花朵相比，蜜蜂是否会对富含咖啡因花蜜的花朵有不同的反应。

史蒂文森：我们发现当蜜蜂吮吸带有咖啡因的甜花蜜，一天后它们记住该花朵气味的能力比吮吸普通甜花蜜的蜜蜂高三倍。

奥布里：那么这意味着吸了咖啡因的蜜蜂具有更好的记忆力吗？

史蒂文森：那确实是实验显示的结果，我们都因此很惊讶。不过显然我们也很兴奋，因为蜜蜂能更好地记住一朵花，而且当然对于蜜蜂来说，这让它能更好地定位食物。

奥布里：那显然是给生活的额外馈赠。现在，有些研究者想知道蜜蜂是否只单纯喜欢含咖啡因的花蜜，还是因为那能提高它们的记忆力或能激发它们的动力去找到花蜜——很想知道咖啡因对人起到醒神的作用是否也同样作用于蜜蜂。

亚伯拉罕·帕尔默：咖啡因绝对影响着我们的行为，以各种不同的方式改变我们的情绪和表现。

奥布里：那是芝加哥大学的亚伯拉罕·帕尔默。他说因为基因不同，每个人对咖啡因的反应是不一样的。但是多项研究表明，咖啡因对我们大脑的奖赏系统是有影响的，适度的剂量有助于在各种脑力和体力活动中集中注意力和表现更好。有些顶级的研究来自美国的部队，他们研究发现咖啡因是能让士兵保持警惕的一种方式。

研究员哈里斯·利伯曼解释他研究过一群水手，他们要被训练成海豹突击队。

哈里斯·利伯曼：训练的其中一部分就是他们完全不允许睡觉，还要承受各种各样高强度的压力。

奥布里：利伯曼说，在天气寒冷和要做大量体力活动的情况下，把服用了咖啡因的水手和那些只吃了不含咖啡因的安慰剂的水手相比较，他记录了（咖啡因的）一系列好处。

利伯曼：我们发现适量的咖啡因能提高注意力，提高警觉性。

奥布里：咖啡因似乎还能改善疲惫水手的短期记忆力，那是利伯曼不曾预想看到的。

利伯曼：我们有点惊讶于咖啡因有如此广泛的效果。奥布里：但利伯曼也说，疲惫消除后，咖啡因似乎并不能对改善人们的记忆力有任何帮助，所以他认为咖啡因并不是提高记忆力的推手。利伯曼：对，我认为不是。奥布里：但无论是对人类还是对蜜蜂，很显然，关于咖啡因的更多东西仍值得我们继续研究。

小链接

巴甫洛夫（Pavlov），又译帕夫洛夫，俄罗斯生理学家、心理学家，在神经生理学方面，提出了著名的条件反射和信号学说，获得1904年诺贝尔生理或医学奖。

巴甫洛夫做了一个相当著名的实验，他利用狗看到食物或吃东西之前会流口水的现象，在每次喂食前都先发出一些信号（一开始是摇铃，后来还包括吹口哨、使用节拍器、敲击音叉、开灯……等等），连续了几次之后，他试了一次摇铃但不喂食，发现狗虽然没有东西可以吃，却照样流口水，而在重复训练之前，狗对于“铃声响”是不会有反应的。他从这一点推知，狗经过了连续几次的经验后，将“铃声响”视作“进食”的信号，因此引发了“进食”会产生的流口水现象。这种现象称为条件反射，这证明动物的行为是因为受到环境的刺激，将刺激的讯号传到神经和大脑，神经和大脑作出反应而来。