来自斯坦福大学的神经学家Brian Knutson教授（http://www-psych.stanford.edu/~knutson/,）和他的同事Camelia Kuhnen（http://www.stanford.edu/~camelia/,）发现大脑中“战争”会影响冒险决定。这一有趣的结果公布在8月31日Neuron上。
当我们在一个冒险和保守的经济投资中选择时，我们大脑中有两个部分会进行激烈的竞争。这时对大脑作一个简单的扫描就能在一个人要做出决定前的几秒钟内预测到底这个人会的选择：当大脑中欢乐打败了焦虑，就会选择去冒险。
大脑中的这两个部分中的其中一个是称为依伏神经核（nucleus accumbens）的花生状区域，这个区域由分子多巴胺填充，当我们感觉到高兴时就会被激活。并且这一区域也在药物上瘾中扮演着关键角色。另一个部分是前丘脑，这是个在焦虑，担心等坏感觉产生时会被激活的区域。而且与前一部分相对应，前丘脑在开启物理疼痛感知中作用明显。
为了具体了解情况，研究人员通过一个现金冒险游戏比较了这两个区域的相互作用。在实验当中，20名参与者可以按下电脑上的按钮选择是进行安全的投注（保证他们能获得1美元的回报），还是另两个赌注，其中一个是在一轮当中可以有一半的机会赢得10美元，但要冒25%的险失去10美元，另一个是相反的：一般机会失去10美元，四分之一的机会赢得10美元。在这个过程中，研究人员并没有告诉参与者具体的赌注，让游戏更具冒险性。但游戏结束时，参与者的大脑会用功能性磁力印象仪拍下照片。结果表明，依伏神经核在作出一个冒险决定前2秒会被激活，而当参与者选择保守投注时，下丘脑较活跃。
原文：
http://www.nature.com/news/2005/050829/full/050829-12.html
Deciding between a risky financial investment and a safe one sets two parts of the brain into competition, say researchers in California.
As centres for pleasure and anxiety battle it out, a simple brain scan of the two can actually predict what a person will chose to do a few seconds before they do it: when joy beats worry in our brain, a risky decision is made.
Studies of how the mind handles risky behaviour have highlighted a number of neural hotspots. One is a peanut-sized region of the brain called the nucleus accumbens, which is loaded with the molecule dopamine and becomes active in anticipation of pleasure. The nucleus accumbens is known to play a role in the addictive effect of drugs.
Another region, known as the anterior insula, is stimulated in anticipation of a bad sensation. This area lights up in those predicting the onset of physical pain, and in generally anxious individuals.
Neuroscientist Brian Knutson of Stanford University and his colleague Camelia Kuhnen sought to compare how these two brain regions interact by asking 20 volunteers to play an investment game for a cash reward.
Risky Business
The participants pushed a computer button to select either a safe bond, which was guaranteed to earn them $1 in any given round, or one of two stocks. One stock had a 50% chance of earning the player $10 in a single round, and a 25% chance of losing him or her $10. The other carried a 50% chance of losing $10 and a 25% chance of winning it. But the scientists did not reveal which stock was which, making it an even riskier game to play.
As the participants completed the task, a machine took snapshots using functional magnetic resonance imaging, which revealed the active parts of the brain.
The results showed that the nucleus accumbens lit up about two seconds before a risky investment was made. When the anxious anterior insula was more active, the participants stuck to the safer choice.
The results of this study, which appear in the journal Neuron, reveal a previously unknown interplay between these two brain regions.
The thing to do is to work out when and why one part of our brain outdoes the other, says Martin Paulus of the University of California, San Diego, who has studied the role of the anterior insula in decision making. "The ultimate question is: when do you listen to one circuit and not the other?" he says.
The answer might help everyone from psychologists aiming to dull anxiety in nervous patients, to marketing gurus attempting to get customers to live dangerously.
