Laboratory for Cognitive Neurology, Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium.
Radiology Department, University Hospitals Leuven, Leuven, Belgium.
Hum Brain Mapp. 2024 Feb 1;45(2):e26603. doi: 10.1002/hbm.26603.
Reading, naming, and repetition are classical neuropsychological tasks widely used in the clinic and psycholinguistic research. While reading and repetition can be accomplished by following a direct or an indirect route, pictures can be named only by means of semantic mediation. By means of fMRI multivariate pattern analysis, we evaluated whether this well-established fundamental difference at the cognitive level is associated at the brain level with a difference in the degree to which semantic representations are activated during these tasks. Semantic similarity between words was estimated based on a word association model. Twenty subjects participated in an event-related fMRI study where the three tasks were presented in pseudo-random order. Linear discriminant analysis of fMRI patterns identified a set of regions that allow to discriminate between words at a high level of word-specificity across tasks. Representational similarity analysis was used to determine whether semantic similarity was represented in these regions and whether this depended on the task performed. The similarity between neural patterns of the left Brodmann area 45 (BA45) and of the superior portion of the left supramarginal gyrus correlated with the similarity in meaning between entities during picture naming. In both regions, no significant effects were seen for repetition or reading. The semantic similarity effect during picture naming was significantly larger than the similarity effect during the two other tasks. In contrast, several regions including left anterior superior temporal gyrus and left ventral BA44/frontal operculum, among others, coded for semantic similarity in a task-independent manner. These findings provide new evidence for the dynamic, task-dependent nature of semantic representations in the left BA45 and a more task-independent nature of the representational activation in the lateral temporal cortex and ventral BA44/frontal operculum.
阅读、命名和重复是在临床和心理语言学研究中广泛使用的经典神经心理学任务。虽然阅读和重复可以通过直接或间接的途径来完成，但图片只能通过语义中介来命名。通过 fMRI 多变量模式分析，我们评估了认知水平上这种既定的基本差异是否与在这些任务中语义表示被激活的程度差异相关。基于词联想模型来估计单词之间的语义相似性。20 名受试者参与了一项事件相关 fMRI 研究，其中三个任务以伪随机顺序呈现。fMRI 模式的线性判别分析确定了一组区域，这些区域可以在跨任务的高度单词特异性上区分单词。代表性相似性分析用于确定这些区域中是否表示了语义相似性，以及这是否取决于所执行的任务。左侧布罗德曼区 45 区（BA45）和左侧上缘回上部的神经模式之间的相似性与图片命名过程中实体之间的意义相似性相关。在这两个区域中，重复或阅读都没有观察到显著的效果。图片命名过程中的语义相似性效应明显大于其他两个任务的相似性效应。相比之下，包括左侧前上颞叶和左侧腹侧 BA44/额骨脑回等在内的几个区域以任务独立的方式编码语义相似性。这些发现为左侧 BA45 中语义表示的动态、任务依赖性提供了新的证据，并为外侧颞叶和腹侧 BA44/额骨脑回中的表示激活提供了更任务独立的性质。
