Tyler L K, Stamatakis E A, Bright P, Acres K, Abdallah S, Rodd J M, Moss H E
University of Cambridge, Cambridge, UK.
J Cogn Neurosci. 2004 Apr;16(3):351-62. doi: 10.1162/089892904322926692.
How objects are represented and processed in the brain is a central topic in cognitive neuroscience. Previous studies have shown that knowledge of objects is represented in a feature-based distributed neural system primarily involving occipital and temporal cortical regions. Research with nonhuman primates suggest that these features are structured in a hierarchical system with posterior neurons in the inferior temporal cortex representing simple features and anterior neurons in the perirhinal cortex representing complex conjunctions of features (Bussey & Saksida, 2002; Murray & Bussey, 1999). On this account, the perirhinal cortex plays a crucial role in object identification by integrating information from different sensory systems into more complex polymodal feature conjunctions. We tested the implications of these claims for human object processing in an event-related fMRI study in which we presented colored pictures of common objects for 19 subjects to name at two levels of specificity - basic and domain. We reasoned that domain-level naming requires access to a coarser-grained representation of objects, thus involving only posterior regions of the inferior temporal cortex. In contrast, basic-level naming requires finer-grained discrimination to differentiate between similar objects, and thus should involve anterior temporal regions, including the perirhinal cortex. We found that object processing always activated the fusiform gyrus bilaterally, irrespective of the task, whereas the perirhinal cortex was only activated when the task required finer-grained discriminations. These results suggest that the same kind of hierarchical structure, which has been proposed for object processing in the monkey temporal cortex, functions in the human.
物体在大脑中如何被表征和处理是认知神经科学的核心主题。先前的研究表明，物体的知识在一个基于特征的分布式神经系统中得到表征，该系统主要涉及枕叶和颞叶皮质区域。对非人类灵长类动物的研究表明，这些特征在一个层次系统中组织起来，颞下回后部的神经元代表简单特征，而嗅周皮质前部的神经元代表特征的复杂结合（Bussey & Saksida，2002；Murray & Bussey，1999）。据此，嗅周皮质通过将来自不同感觉系统的信息整合为更复杂的多模态特征结合，在物体识别中发挥关键作用。我们在一项事件相关功能磁共振成像研究中测试了这些观点对人类物体处理的影响，在该研究中，我们向19名受试者呈现常见物体的彩色图片，让他们在两个特异性水平——基本水平和领域水平——上进行命名。我们推断，领域水平的命名需要获取物体的更粗略表征，因此仅涉及颞下回的后部区域。相反，基本水平的命名需要更精细的辨别来区分相似物体，因此应该涉及颞叶前部区域，包括嗅周皮质。我们发现，无论任务如何，物体处理总是双侧激活梭状回，而只有当任务需要更精细的辨别时，嗅周皮质才会被激活。这些结果表明，在猴子颞叶皮质中提出的用于物体处理的那种层次结构在人类中也起作用。
