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Investigating the Role of Cortical Microstructure in Language Lateralization Using Quantitative MRI
Poster Session C, Friday, October 25, 4:30 - 6:00 pm, Great Hall 3 and 4
Xiaoyin wu1, Miaomiao Zhu2, Chu-Chung Huang1,3, Qing Cai1,2,3; 1School of Psychology and Cognitive Science, East China Normal University, China, 2Institute of Brain Science and Education Innovation, East China Normal University, China, 3NYU-ECNU Institute of Brain and Cognitive Science, New York University Shanghai, China
A striking observation in the human brain is the hemispheric asymmetry of many information-processing functions, particularly in language production. Previous studies suggest that functional lateralization may be linked to cortical myeloarchitecture and macromolecular content. However, the cortical microstructure underlying language lateralization remains unclear. We hypothesize that there are microstructural differences between atypical (right hemisphere language dominance) and typical lateralization groups. To reveal the microstructural properties of gray and white matter tissues, we used a novel and noninvasive technique, quantitative magnetic resonance imaging (qMRI), to acquire two maps, longitudinal relaxation rate (R1) and magnetization transfer saturation (MTsat). R1 pertains to myelin, lipid content, and synapses, while MTsat reflects macromolecular conditions. Seventeen left-handers participated in this study due to their higher prevalence of atypical lateralization patterns compared to right-handers. Based on an fMRI word-generation task (WGT), eight were classified as atypical lateralization, and nine were known to have left hemisphere dominance for language (typical lateralization). Using Freesurfer’s mri_vol2surf algorithm, we analyzed the R1 and MTsat values at different intracortical depths in both groups. The R1/MTsat volume was projected into surface vertices at increasing 25% steps, starting from two locations below the gray–white boundary to the pial surface. Using general linear model, we detected the differences of R1/MTsat values between the two groups at different intracortical depths. We found that in relatively superficial white matter, the R1 values in the middle and superior temporal gyrus (MTG and STG), temporal pole, and precentral gyrus of both hemispheres were significantly higher in the atypical language lateralization group compared to those in the typical group. In deep gray matter, the right-dominant group showed higher R1 values in the right hemisphere's MTG and STG than the left-dominant group, with only the STG showing similar results in the left hemisphere. In relatively superficial gray matter, the atypical group had significantly higher R1 values only in parts of the right hemisphere's MTG and medial occipital area. Additionally, we observed a marginal negative correlation between the lateralization index (LI) of the R1 values in the orbital part of the inferior frontal gyrus and the LI of WGT in the Broca region (rdeep gray matter = -0.46, p = 0.06). The LIs of the R1 values in the temporal pole at different depths were significantly negatively correlated with the LI of the fMRI task (r = -0.55 to -0.68, p < 0.05). For MTsat at different depths in gray and white matter, the differences between atypical and typical language lateralization groups in the temporal region did not resemble the R1 findings, especially in deep gray matter, with more differences observed in the middle frontal gyrus. The current findings suggest that the lipid content and synapse density in brain tissue may support functional lateralization. This study supports the idea that lateralization may have a microstructural basis, providing new evidence for the underlying neural mechanisms of language lateralization.
Topic Areas: Methods, Language Production