Spatiotemporal Cortical Dynamics Underlying Abstract and Concrete Word Reading

摘要

In the current study, we used whole head, anatomically constrained magnetoencephalography (aMEG) to spatiotemporally map brain responses while subjects made abstract/concrete judgments on visually presented words. Both word types evoked a similar posterior to anterior sequence of cortical recruitment involving occipital, temporal, parietal, and frontal areas from ~100–900ms post-stimulus. A prominent left temporo-frontal N400m was smaller to abstract words, while the right temporal N400m was smaller to concrete words, suggesting that differences may exist in their semantic representation. The left temporo-frontal decrease seen here for abstract words is consistent with EEG studies indicating a smaller N400 for abstract words based on a more extensive or accessible lexicosemantic network. Furthermore, in the current study, the N400m peaked at ~420ms and was followed by a large, right hemisphere, medial occipitoparietal as well as lateral parietal response to concrete words peaking at ~550ms, perhaps embodying imagistic processing. These data suggest that words may be initially understood using a left lateralized fronto-temporal verbal-linguistic system that for concrete words is supplemented after a short delay by a right parietal and medial occipital imagistic network.