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来源：互联网 作者：佚名 更新时间：2005-11-27 07:49:18
吸毒的人经常为了得到一时的舒服而放弃美好的未来。科学家在动物体上研究了这种冲动的选择。研究者们以大鼠为实验对象，研究发现，在大鼠的大脑上有一块区域在冲动的选择上起着重要的作用。这个研究成果有助于解释人类的行为，包括那些吸毒上瘾的人。
近年来，自我控制力的生物学基础已经非常清楚了。对于动物以及人类脑部成像的研究结果表明，在大脑上有控制冲动的结构。大脑中心处的横沟就是结构之一，它也是人体验快感的结构。
英国剑桥大学的Rudolf Cardinal和他的同事们决定把横沟处作为冲动的潜在中心。他们通过化学注射的方法杀死横沟处的细胞，比较经过处理的大鼠和健康大鼠的行为。研究者给大鼠提供两个水平的选择，一个是按下按钮立刻就能得到一颗糖丸；另一个是按下按钮60秒钟之后才能得到糖丸。研究人员说：50％的正常大鼠都学会了选择能得到更多的回报的按钮，而损伤横沟的大鼠，仅有不到25％的会等着得到奖励。
神经学家John Evenden说：这个研究结果“给冲动选择的研究提供了不同的观察角度”。但是他指出，冲动可以通过很多种方式表达出来，最令人有兴趣的是看看这些大鼠在需要它们集中注意力的环境中如何选择。他还说：对于人类来说，注意力集中的缺乏更能解释冲动的原因。
Drugaddicts routinely throw away the chance of a better future for the moreimmediate satisfaction delivered by a fix. This kind of impulsive choice can bestudied in animals, and now researchers working with rats may have found abrain region that plays a key role in spur-of-the-moment decisions. The findingcould help clarify human conditions as well, including addiction.
The biologicalbasis for self-control has become clearer in recent years. Animal studies, aswell as imaging studies in people with impulsivity problems, have hinted atseveral brain structures that might help people hold their horses in hopes of alater, greater reward. The nucleus accumbens is one of these, and it‘s alsobeen shown to be critical for experiencing pleasure.
Intrigued,Rudolf Cardinal of the University of Cambridge, United Kingdom, and colleaguesdecided to zero in on the nucleus accumbens as a potential center ofimpulsiveness. They killed the cells of the nucleus accumbens by chemicalinjection in one group of rats and compared those rats’ behavior to that ofhealthy ones. The researchers offered the rats a choice of two levers. Pressingone delivered a single sugar pellet immediately, and pressing the otherdelivered four sugar pellets after a delay of up to 60 seconds. In a studypublished online today by
The findings "provide some different angles on thiswhole topic of impulsive choice," says neurologist John Evenden ofAstraZeneca in Wilmington, Delaware. But he points out that impulsivity isexpressed in many ways. It will be interesting to look at these animals insituations that call for sustained attention, he says, because lack ofconcentration is a more common manifestation of impulsivity in humans.
摘自：科学杂志在线
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