研究解释自闭症儿童为什么不会物品归类

    人类的大脑识别相似事物特别敏感。大脑有能力将相似的事物归为一类，例如，猫和狗，或者椅子和书桌。在一项新的研究领域中，MIT神经科学家已经证实，大脑活动似乎控制着这项技能。

    这项研究的结果于7月27日，发表在《神经元》杂志中。这篇论文的主要作者，神经科学教授 Earl Miller 认为，这项研究的结果有助于解释为什么自闭症儿童总是全神贯注的聚焦于细节，而难以将这些细节在一个更大的领域中归类。

    Miller作为MIT学习与记忆研究所资深研究员，指出“我们认为有可能是这一系统的失衡导致了自闭症，其结果就是重视细节获取的一方远远超越了重视归类学习的一方。因此，你会拥有一个极其善于记忆细节的大脑。”

    Miller 和 博士后 Evan Antzoulatos 将他们的研究聚焦于大脑的两个区域，前额皮质和纹状体。两者对于学习而言，都是很重要的区域。而纹状体是基底神经节一部分，基底神经节是一个更大的结构。

    几年前，被证实，前额皮质能够很快的学习信息，并能够将它们学到的东西传递给基底神经节。基底神经节的作用是形成习惯，就像能够演奏乐器的能力。然而，2005年，Miller和他的同事发现，当猴子学习一些简单任务时，在整个学习过程中，他们的基底神经节在早期阶段更为活跃，接着才是前额皮质缓慢的激活。

    Miller解释道，纹状体会很快的辨认出个体的片段，而前额皮质会将他们拼装在一起。他和 Antzoulatos 推论，这样的模式在类别归类的学习中也将会一样适用。

    在这个新的神经元研究中， Antzoulatos训练猴子们将同模式的点分配到一个或者两个类别中。首先，猴子只能从每个类别中看到两个例子。这时每个类别中的数量很少，猴子们可以在不熟悉每个类别的一般特点的情况下，记住某一个是来自于哪一个类别的。而在猴子们学习了起初的两个例子后，例子的数量将会加倍。最终，这一数量很大以至于猴子们难以记住他们，而此时，猴子们的大脑开始挑选识别出每个类别的普遍特点。

    由于他们这样的做法，大脑的活动从原始的大脑区域纹状体，转向了前额皮质。前额皮质主要用于一些高级功能，例如规划和决策。

    Miller说：“归类学习的过程很原始，其实并不复杂。首先由基底神经节很快的记住例子，接着它将学到的东西传递给前额皮质。前额皮质的作用在于辨认出例子之间的共性，并提取出其本质”。

    Gregory Ashby，加州大学心理学教授，认为这个研究，是迄今为止，纹状体在归类学习中的作用的“最清晰的呈现”。他说：“在前几年，我们已经知道在归类学习中，纹状体起到了很重要的作用，但是究竟是什么作用依旧不够清晰”。

    在今后的研究中，MIT的研究者们希望能够检测他们的这个理论，即自闭症是由于纹状体和前额皮质的不平衡导致。他们初步打算通过一定方式的介入，使大脑两个区域达到平衡并观察结果，从而验证理论。

原文：
    The human brain is adept at recognizing similar items and placing them into categories — for example, dog versus cat, or chair versus table. In a new study, MIT neuroscientists have identified the brain activity that appears to control this skill.
    The findings, published in the July 27 issue of the journal Neuron, suggest a potential explanation for why autistic children focus intently on details, but often seem unable to group things into broad categories, says Earl Miller, the Picower Profess[FS:PAGE]or of Neuroscience and senior author of the paper.
    "We think what may happen in autism is the system may get out of balance … and as a result, the details overwhelm the category. Then you have a brain that's not only too good at memorizing details, it can't help but memorize the details," says Miller, a principal investigator at the Picower Institute for Learning and Memory at MIT.
    Miller and Picower postdoc Evan Antzoulatos focused their study on two brain regions, the prefrontal cortex and the striatum, which is part of a larger structure known as the basal ganglia. Both regions are known to be important for learning.
    Until a few years ago, it was believed that the prefrontal cortex learns information quickly, then sends what it learns to the basal ganglia, which helps form habits, such as the ability to play a musical instrument. However, in 2005, Miller and colleagues showed that when monkeys learn simple tasks, their basal ganglia are more active early in the process, followed by a slower activation in the prefrontal cortex.
    In other words, the striatum quickly learns the individual puzzle pieces, and the prefrontal cortex puts them together, Miller says. He and Antzoulatos theorized that the same pattern would be evident during category learning.
    For the new Neuron study, Antzoulatos trained monkeys to assign patterns of dots into one of two categories. At first, the animals would see only two examples, or "exemplars," from each category — a small enough number that they could memorize the category to which each belonged, without having to learn the general category traits. After the animals learned the first two exemplars, the number would be doubled. Eventually, the number of exemplars became so great that it was impossible to memorize them, and the monkeys' brains would start picking up on general traits that characterize each category.
    As they did so, brain activity shifted from the striatum, a more primitive brain region, to the prefrontal cortex, which is responsible for high-level functions such as planning and decision making.
    "What happens during category learning is the more primitive, faster basal ganglia can memorize the exemplars, but then it sends what it learns up to the prefrontal cortex. And the prefrontal cortex figures out what's common among all the exemplars, among all the individuals, and extracts the essence," Miller says.
    Gregory Ashby, a professor of psychology at the University of California at Santa Barbara, says the new study represents the "clearest picture yet" of the striatum's involvement in category learning. "We've known for quite a while that the striatum plays an important role in category learning, but it was not at all clear exactly what that role was," he says.
    In future studies, the MIT researchers hope to t[FS:PAGE]est their theory that autism results from an imbalance between the striatum and prefrontal cortex by interfering with the normal balance between the two brain regions and observing the results.