Laboratory for Cognitive Neurology, Department of Neurosciences, Neurology Department, and Radiology Department, University Hospitals Leuven, 3000 Leuven, Belgium, and Laboratory of Experimental Psychology, Humanities and Social Sciences Group, University of Leuven, 3000 Leuven, Belgium.
J Neurosci. 2013 Nov 20;33(47):18597-607. doi: 10.1523/JNEUROSCI.1548-13.2013.
How verbal and nonverbal visuoperceptual input connects to semantic knowledge is a core question in visual and cognitive neuroscience, with significant clinical ramifications. In an event-related functional magnetic resonance imaging (fMRI) experiment we determined how cosine similarity between fMRI response patterns to concrete words and pictures reflects semantic clustering and semantic distances between the represented entities within a single category. Semantic clustering and semantic distances between 24 animate entities were derived from a concept-feature matrix based on feature generation by >1000 subjects. In the main fMRI study, 19 human subjects performed a property verification task with written words and pictures and a low-level control task. The univariate contrast between the semantic and the control task yielded extensive bilateral occipitotemporal activation from posterior cingulate to anteromedial temporal cortex. Entities belonging to a same semantic cluster elicited more similar fMRI activity patterns in left occipitotemporal cortex. When words and pictures were analyzed separately, the effect reached significance only for words. The semantic similarity effect for words was localized to left perirhinal cortex. According to a representational similarity analysis of left perirhinal responses, semantic distances between entities correlated inversely with cosine similarities between fMRI response patterns to written words. An independent replication study in 16 novel subjects confirmed these novel findings. Semantic similarity is reflected by similarity of functional topography at a fine-grained level in left perirhinal cortex. The word specificity excludes perceptually driven confounds as an explanation and is likely to be task dependent.
言语和非言语视知觉输入如何与语义知识相关联是视觉和认知神经科学的核心问题，具有重要的临床意义。在一项事件相关功能磁共振成像（fMRI）实验中，我们确定了 fMRI 对具体单词和图片的反应模式之间的余弦相似度如何反映语义聚类以及单个类别内所代表实体之间的语义距离。基于 >1000 个主题的特征生成，从概念-特征矩阵中得出 24 个有生命实体之间的语义聚类和语义距离。在主要的 fMRI 研究中，19 名人类受试者使用书面单词和图片以及低水平控制任务执行属性验证任务。语义任务与控制任务的单变量对比产生了广泛的双侧枕颞激活，从后扣带回到前内侧颞叶皮质。属于同一语义聚类的实体在左枕颞皮质中引起更相似的 fMRI 活动模式。当分别分析单词和图片时，仅对单词达到显著效果。单词的语义相似性效应定位于左侧边缘回。根据左侧边缘回反应的代表性相似性分析，实体之间的语义距离与书面单词的 fMRI 反应模式之间的余弦相似度呈负相关。在 16 名新受试者的独立复制研究中证实了这些新发现。语义相似性反映了左侧边缘回功能拓扑在细粒度水平上的相似性。单词的特异性排除了作为解释的感知驱动混淆，并且可能依赖于任务。
