EEG source reconstruction evidence for the noun-verb neural dissociation along semantic dimensions

• Published in: Neuroscience Vol. 359; pp. 183 - 195
• Main Authors: Zhao, Bin, Dang, Jianwu, Zhang, Gaoyan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 17.09.2017
• Subjects: Acoustic Stimulation; Adult; ambiguous words; Cerebral Cortex - physiology; EEG; Electroencephalography; Evoked Potentials, Auditory; Female; Humans; Male; noun–verb dissociation; Semantics; Signal Processing, Computer-Assisted; source reconstruction; Speech Perception - physiology; Young Adult; ACC; UV; RT; EEG; ICA; MNI; sLORETA; POI; semantics; AN; ROI; PCA; CDR; fMRI; AV; source reconstruction; UN; noun–verb dissociation; ISI; PET; BA; ITI; ambiguous words
• ISSN: 0306-4522; 1873-7544; 1873-7544
• DOI: 10.1016/j.neuroscience.2017.07.019

•Noun-verb dissociation is found in the visual and motor cortices corresponding to the semantic object- or action-relatedness.•Noun-verb dissociation is neurophysiologically induced by the semantic difference instead of the grammatical classification.•Semantic processing might start early from the P1 period and repeat in the N1, P200 and N400 periods recurrently. One of the long-standing issues in neurolinguistic research is about the neural basis of word representation, concerning whether grammatical classification or semantic difference causes the neural dissociation of brain activity patterns when processing different word categories, especially nouns and verbs. To disentangle this puzzle, four orthogonalized word categories in Chinese: unambiguous nouns (UN), unambiguous verbs (UV), ambiguous words with noun-biased semantics (AN), and ambiguous words with verb-biased semantics (AV) were adopted in an auditory task for recording electroencephalographic (EEG) signals from 128 electrodes on the scalps of twenty-two subjects. With the advanced current density reconstruction (CDR) algorithm and the constraint of standardized low-resolution electromagnetic tomography, the spatiotemporal brain dynamics of word processing were explored with the results that in multiple time periods including P1 (60–90ms), N1 (100–140ms), P200 (150–250ms) and N400 (350–450ms), noun–verb dissociation over the parietal-occipital and frontal-central cortices appeared not only between the UN-UV grammatical classes but also between the grammatically identical but semantically different AN-AV pairs. The apparent semantic dissociation within one grammatical class strongly suggests that the semantic difference rather than grammatical classification could be interpreted as the origin of the noun–verb neural dissociation. Our results also revealed that semantic dissociation occurs from an early stage and repeats in multiple phases, thus supporting a functionally hierarchical word processing mechanism.