Liuzzi Antonietta Gabriella, Bruffaerts Rose, Dupont Patrick, Adamczuk Katarzyna, Peeters Ronald, De Deyne Simon, Storms Gerrit, Vandenberghe Rik
Laboratory for Cognitive Neurology, Department of Neurosciences, University of Leuven, Belgium.
Radiology Department, University Hospitals Leuven, Leuven, Belgium.
Neuropsychologia. 2015 Sep;76:4-16. doi: 10.1016/j.neuropsychologia.2015.03.016. Epub 2015 Mar 18.
Left perirhinal cortex has been previously implicated in associative coding. According to a recent experiment, the similarity of perirhinal fMRI response patterns to written concrete words is higher for words which are more similar in their meaning. If left perirhinal cortex functions as an amodal semantic hub, one would predict that this semantic similarity effect would extend to the spoken modality. We conducted an event-related fMRI experiment and evaluated whether a same semantic similarity effect could be obtained for spoken as for written words. Twenty healthy subjects performed a property verification task in either the written or the spoken modality. Words corresponded to concrete animate entities for which extensive feature generation was available from more than 1000 subjects. From these feature generation data, a concept-feature matrix was derived which formed the basis of a cosine similarity matrix between the entities reflecting their similarity in meaning (called the "semantic cossimilarity matrix"). Independently, we calculated a cosine similarity matrix between the left perirhinal fMRI activity patterns evoked by the words (called the "fMRI cossimilarity matrix"). Next, the similarity was determined between the semantic cossimilarity matrix and the fMRI cossimilarity matrix. This was done for written and spoken words pooled, for written words only, for spoken words only, as well as for crossmodal pairs. Only for written words did the fMRI cossimilarity matrix correlate with the semantic cossimilarity matrix. Contrary to our prediction, we did not find any such effect for auditory word input nor did we find cross-modal effects in perirhinal cortex between written and auditory words. Our findings situate the contribution of left perirhinal cortex to word processing at the top of the visual processing pathway, rather than at an amodal stage where visual and auditory word processing pathways have already converged.
左侧嗅周皮质先前被认为与联想编码有关。根据最近的一项实验，对于意义更相似的单词，嗅周功能磁共振成像（fMRI）反应模式与书面具体单词的相似性更高。如果左侧嗅周皮质作为一个非模态语义中枢发挥作用，那么可以预测这种语义相似性效应将扩展到口语模态。我们进行了一项事件相关功能磁共振成像实验，并评估对于口语单词是否能获得与书面单词相同的语义相似性效应。20名健康受试者在书面或口语模态下执行一项属性验证任务。单词对应于具体的有生命实体，从1000多名受试者那里可获得关于这些实体的大量特征生成信息。从这些特征生成数据中，导出了一个概念-特征矩阵，该矩阵构成了反映实体意义相似性的余弦相似性矩阵（称为“语义余弦相似性矩阵”）的基础。我们独立计算了由单词诱发的左侧嗅周fMRI活动模式之间的余弦相似性矩阵（称为“fMRI余弦相似性矩阵”）。接下来，确定语义余弦相似性矩阵与fMRI余弦相似性矩阵之间的相似性。这是对汇总的书面和口语单词、仅对书面单词、仅对口语单词以及跨模态对进行的。仅对于书面单词，fMRI余弦相似性矩阵与语义余弦相似性矩阵相关。与我们的预测相反，我们在听觉单词输入中未发现任何此类效应，在嗅周皮质中也未发现书面和听觉单词之间的跨模态效应。我们的研究结果表明，左侧嗅周皮质对单词处理的贡献位于视觉处理通路的顶端，而不是在视觉和听觉单词处理通路已经汇聚的非模态阶段。
