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Grey and white matter substrates of syntactic comprehension: lesion-symptom mapping and indirect structural disconnection mapping on 130 left-hemisphere stroke survivors
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Poster C43 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Nicoletta Biondo1,2, Alexis L. Pracar1, Juliana Baldo3, Nina F. Dronkers1,4, Maria V. Ivanova1; 1University of California, Berkeley, Berkeley (CA), USA, 2Basque center on Cognition, Brain, and Language, Donostia, Spain, 3VA Northern California Health Care System, Martinez (CA), USA, 4University of California, Davis, Davis (CA), USA
The neural underpinnings of syntactic processing during sentence comprehension are far from being identified by current neurocognitive models of language comprehension. Traditionally, frontal regions (e.g., left posterior inferior frontal gyrus, IFG) were considered critical (Friederici, 2011; Hagoort, 2013). More recently, temporal regions (left posterior middle temporal gyrus, MTG), are regarded as more indispensable to syntactic comprehension (Matchin & Hickock, 2020). The processing of syntactically complex sentences is also dependent on dorsal tracts (Friederici, 2011; Hagoort, 2013; Bornkessel-Schlesewsky & Schlesewsky, 2013), while the involvement of ventral tracts (typically associated with semantic processing) is yet to be determined. Finally, syntactic processing has been investigated by using different types of non-canonical sentences interchangeably. However, sentences may be syntactically complex for different linguistic reasons. In this study, we investigated the grey and white matter substrates of syntactic comprehension in a large cohort (N = 130) of left-hemisphere stroke survivors. We analyzed the comprehension of different types of sentences (simple declaratives and non-canonical subject-extracted, object-extracted, and passive sentences) by selecting specific subtests of the CYCLE-R test (Curtiss & Yamada, 1988). Neural correlates of performance were assessed using both univariate and multivariate (Ivanova et al., 2021) lesion-symptom mapping (LSM) with lesion size, age, education, and time post-stroke as covariates. White matter disconnection severities were calculated via Indirect Structural Disconnection Mapping (Lesion Quantification Toolkit, Griffis et al., 2021). The impact of tract-level disconnection severities on the comprehension of the different sentence types was assessed through correlation analyses (Bonferroni-corrected alpha = 0.0056). Results of the LSM analyses identified the left mid to posterior MTG, and the posterior superior temporal gyrus (STG) as crucial for processing all sentence types. Non-canonical sentences also involved the left anterior MTG and STG, planum temporale and polare, and Heschl’s gyrus. Correlation analyses showed that the comprehension of all sentence types is affected by the disconnection of ventral tracts (inferior fronto-occipital fasciculus, uncinate fasciculus, inferior longitudinal fasciculus) in the left hemisphere and corpus callosum (posterior division). The processing of all non-canonical sentences was also affected by the disconnection of the middle longitudinal fasciculus. The disconnection of the dorsal tracts (arcuate fasciculus, superior longitudinal fasciculus) affected only the comprehension of subject and object-extracted sentences (not passives or declaratives). Our results show that syntactic comprehension relies on left temporal regions (Dronkers et al., 2004; Matchin et al., 2022) and underlying white matter pathways. Left frontal regions were not found to be critical, but the disconnection of fiber tracts connected to frontal areas did significantly impact syntactic comprehension, especially for non-canonical sentences (Ivanova et al., 2021; Wilson et al., 2011). The comprehension of different types of non-canonical sentences was affected by damage to slightly different regions and fiber tracts. Therefore, syntactic complexity should be better stratified in future research.
Topic Areas: Syntax and Combinatorial Semantics, Disorders: Acquired