For decades, researchers have debated whether mental representations are symbolic or grounded in sensory inputs and motor programs. Certainly, aspects of mental representations are grounded. However, does the brain also contain abstract concept representations that mediate between perception and action in a flexible manner not tied to the details of sensory inputs and motor programs? Such conceptual pointers would be useful when concepts remain constant despite changes in appearance and associated actions. We evaluated whether human participants acquire such representations using fMRI. Participants completed a probabilistic concept learning task in which sensory, motor, and category variables were not perfectly coupled or entirely independent, making it possible to observe evidence for abstract representations or purely grounded representations. To assess how the learned concept structure is represented in the brain, we examined brain regions implicated in flexible cognition (e.g., pFC and parietal cortex) that are most likely to encode an abstract representation removed from sensory–motor details. We also examined sensory–motor regions that might encode grounded sensory–motor-based representations tuned for categorization. Using a cognitive model to estimate participants' category rule and multivariate pattern analysis of fMRI data, we found the left pFC and human middle temporal visual area (MT)/V5 coded for category in the absence of information coding for stimulus or response. Because category was based on the stimulus, finding an abstract representation of category was not inevitable. Our results suggest that certain brain areas support categorization behavior by constructing concept representations in a format akin to a symbol that differs from stimulus–motor codes.

几十年来，研究人员一直在争论心理表征是象征性的还是基于感觉输入和运动程序。当然，心理表征的各个方面都是有根据的。然而，大脑是否也包含抽象的概念表示，以一种灵活的方式在感知和行动之间进行调解，而不依赖于感觉输入和运动程序的细节？当概念在外观和相关动作发生变化时保持不变时，这种概念指针将很有用。我们评估了人类参与者是否使用 fMRI 获得了这种表征。参与者完成了一项概率概念学习任务，其中感觉、运动和类别变量不是完全耦合或完全独立的，因此可以观察抽象表示或纯基础表示的证据。为了评估学习到的概念结构如何在大脑中表示，我们检查了与灵活认知有关的大脑区域（例如，pFC 和顶叶皮层），这些区域最有可能编码从感觉运动细节中删除的抽象表示。我们还检查了感觉运动区域，这些区域可能编码为分类而调整的基于感觉运动的接地表征。使用认知模型估计参与者的类别规则和 fMRI 数据的多变量模式分析，我们发现左侧 pFC 和人类中间颞叶视觉区域 (MT)/V5 在没有刺激或响应信息编码的情况下进行类别编码。因为类别是基于刺激的，所以找到类别的抽象表示并非不可避免。