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Poster D3, Thursday, November 9, 6:15 – 7:30 pm, Harborview and Loch Raven Ballrooms

Linking white matter integrity to syntactic category processing - an ERP and DTI study

Wan-ting Lin1, Chen-Hsiang Weng1, Min-Hsin Chen1, Wen-Yih Isaac Tseng1, Joshua Oon Soo Goh1, Chia-Lin Lee1;1National Taiwan University

This study investigated the structural basis of syntactic neural networks across the left and right hemispheres (LH, RH). We used event-related potentials (ERP) to assess structural (P600) and lexical-semantic (N400) aspects of syntactic category processing in 16 young right-handers without familial sinistrality during a grammaticality judgment task. Two-word Chinese phrases were presented word by word on a screen. ERPs were time locked to target words presented laterally to either left or right visual fields (LVF, RVF), matching or mismatching the syntactic category expectancy established by a preceding central cue (e.g., Grammatical: liǎng-dòng fáng-zi “two houses”; jí-shí bang-máng “to immediately help”. Ungrammatical: jí-shí fáng-zi “immediately house”; liǎng-dòng bang-máng “to two help”). Consistent with English findings, our results showed a left-lateralized P600 grammaticality effect with right VF presentation only and bilateral N400 grammaticality effects with both VF presentations. In the same participants, we used diffusion tensor imaging (DTI) to assess the white-matter fractional anisotropy (FA) reflecting microstructural tissue integrity of the corpus callosum (CC) and tracts found to be relevant for syntactic processing—superior longitudinal fasciculus (SLF), uncinate fasciculus (UF), semantic processing—inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), and tracts relaying dorsal syntactic and ventral semantic streams—perpendicular fasciculus (PF). Lower left-lateralized P600 effects significantly correlated with higher right ILF integrity, which was also marginally associated with higher LVF/RH P600 effects. This finding suggests that LVF/RH P600 is semantically mediated, and, consistent with the literature, that reduced language left-lateralization is due to increased RH instead of reduced LH activation. We also found important associations of the CC with lateralization of syntactic category processing. Higher integrity of anterior CC (precentral gyrus) correlated with reduced RVF/LH P600 effects, and higher integrity of posterior CC (postcentral gyrus, temporal pole, and inferior parietal lobule) correlated with a left-dominant trend (reduced LVF/RH overall grammaticality effect and larger RVF/LH N400 effect). These results underscore the importance of examining the differential roles of CC connections—excitatory or inhibitory—across callosal sub-regions. Finally, larger RVF/LH N400 grammaticality effects were associated with higher integrities of the left IFOF, supporting the semantic nature of IFOF involvement, and left PF, implicating the cross-talk between syntactic and semantic processes in the presently observed N400 effects. These findings bridge critical knowledge gaps between white-matter microstructure and temporally dynamic neural activities underlying language comprehension.

Topic Area: Grammar: Syntax

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