COLLABORATIVE RESEARCH: The Cognitive Neuroscience of Category Learning

【摘要】在美国国家科学基金会的支持下，Gluck和Poldrack及其同事将进行为期三年的调查，以检验关于基底神经节和内侧颞叶在人类类别学习中的作用及其相互作用的两个假设。他们将使用功能性磁共振成像（fMRI）和对基底神经节（由于帕金森氏病）或内侧颞叶（由于缺氧或其他原因）受损的患者的研究相结合来验证这些假设。要验证的第一个假设是，基底神经节对于基于试验反馈的学习特别重要，而内侧颞叶对于没有反馈的观察学习更重要。第二个假设是，在类别学习过程中，这两个区域的参与是由正在学习的类别的结构调节的。例如，有些类别在很大程度上是由单个特征决定的；例如，大多数有喙的动物都被归类为鸟类。其他类型的分类需要跨多个特性集成信息。我们将测试内侧颞叶对于基于组合特征的学习类别至关重要的假设，而基底神经节对于基于单一特征的学习类别很重要。本课题研究的主题是分类，这是人类认知中最重要的行为之一。分类是一种认识，即各种单独的对象可以被分类成在某些方面彼此相似的更大的组。认知心理学的研究为人类如何学习新类别提供了一套复杂的模型。然而，目前对这些操作是如何在大脑中实现的知之甚少。我们目前的大部分知识来自对脑部疾病患者的研究。特别是，帕金森氏症和亨廷顿氏症患者在学习某些新类别方面存在困难，尽管他们能够学习其他类型的类别。这些疾病影响一组被称为基底神经节的深层大脑结构，它们在一些类别学习任务上的损伤表明基底神经节可能对类别学习至关重要。然而，基底神经节的确切作用尚不清楚。帕金森氏症和亨廷顿氏症患者在学习一些新类别方面受到严重损害，而内侧颞叶（包括海马体）受损后失忆症患者在类别学习方面只受到轻微损害。最初的神经成像研究表明，当正常人学习新类别时，这个区域是不活跃的，这表明它没有参与。此外，成像研究表明，在类别学习过程中，内侧颞叶和基底神经节的活动呈负相关：一个区域活动较多的个体，另一个区域的活动往往较少。这些发现表明，这两个区域可能在学习过程中相互作用，但这种相互作用的性质目前尚不清楚。这些研究具有重要的意义，无论是对类别学习的基本理解，还是对与帕金森病和阿尔茨海默病等常见疾病有关的大脑系统的理解。最重要的是，这些研究的结果将为目前仅使用行为测量的人类类别学习理论提供更强的约束。

Cognitive Neuroscience of Category LearningAbstractWith National Science Foundation support, Drs. Gluck and Poldrack and colleagues will conduct a three-year investigation to test two hypotheses about the roles of the basal ganglia and medial temporal lobe, and their interaction, in human category learning. They will test these hypotheses using a combination of functional magnetic resonance imaging (fMRI) and studies of patients with damage to either the basal ganglia (due to Parkinson's disease) or to the medial temporal lobe (due to anoxia or other causes). The first hypothesis to be tested is that the basal ganglia are particularly important for learning based on trial-by-trial feedback, whereas the medial temporal lobe is more important for observational learning in the absence of feedback. The second hypothesis is that the engagement of these two regions during category learning is modulated by the structure of the category that is being learned. For example, some categories are largely determined by single features; for example, most animals with a beak are classified as birds. Other kinds of categories require integration of information across multiple features. We will test the hypothesis that the medial temporal lobe is crucial for learning categories based on combinations of features, whereas the basal ganglia are important for learning categories based on single features.The topic studied in this project is categorization, oneof the most important acts of human cognition. Categorization is the recognition that various individual objects can be classified into larger groups that resemble each other in some way. Research in cognitive psychology has provided a set of sophisticated models for how humans learn new categories. However, little is currently known about how these operations are achieved in the brain. Most of our current knowledge comes from studies of patients with brain disorders. In particular, patients with Parkinson's and Huntington's diseases have trouble learning some kinds of new categories, though they are able to learn other kinds of categories. These diseases affect a set of deep brain structures known as the basal ganglia, and their impairment on some category learning tasks suggests that the basal ganglia may be critical for category learning. However, the exact role of the basal ganglia is unknown. Whereas patients with Parkinson's and Huntington's diseases are severely impaired at learning some new categories, patients with amnesia following damage to the medial temporal lobe (including the hippocampus) are only subtly impaired at category learning. Initial neuroimaging studies have shown that this region is deactivated when normal individuals are learning new categories, suggesting that it is not involved. Furthermore, imaging studies have shown that that activity in the medial temporal lobe and basal ganglia during category learning is negatively related: Individuals with more activity in one region tend to have less activity in the other. These findings suggest that these two regions may interact during learning, but the nature of this interaction is unclear at present.These studies have important implications, both for the basic understanding of category learning and for the understanding of the brain systems involved in such common disorders as Parkinson's and Alzheimer's diseases. Most importantly, the results of these studies will provide stronger constraints on theories of human category learning that are currently possible using behavioral measures alone.