Interactions Between Modal and Amodal Semantic Areas in Spoken Word Comprehension

Abstract

In neurolinguistics, the controversy about whether word semantics are stored in an amodal language-specific center or distributed in modality-specific sensory-motor systems comes from two inconsistent evidences: (i) Semantic Dementia (SD) patients who got a focal brain damage in the anterior temporal lobe (ATL) exhibit a general loss of conceptual knowledge across all word categories; (ii) fMRI examinations of semantic memory found no clues in the ATL but a broad activation in the sensory and motor regions (SMR) that represent the visual and motor features of words. To settle this dispute, the current study aims to examine the whole-range brain dynamics during word processing using (i) 2-D ERP-image analysis, (ii) independent component clustering and (iii) EEG source reconstruction methods. It was found that both ATL and SMR participated in the spoken word processing by means of recurrent interaction, and the visual and motor cortex exhibited specific activation patterns for noun and verb respectively. These results suggest a hierarchical organization of word semantics that combines amodal ATL and modal SMR to form a complete concept.