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Sex differences in white matter tracts underlying language networks: a tractography study
Poster Session F, Friday, October 2, 2:45 - 4:45 pm, Wangari Maathai
Qingchun WANG1, Wai-Ting SIOK; 1The Hong Kong Polytechnic University, 21
Neurolinguistic research has consistently shown that males and females engage distinct functional brain networks during language processing. Recent fMRI evidence has revealed sex-specific patterns of functional connectivity among core left-hemisphere language regions, namely the inferior frontal gyrus (IFG), superior temporal gyrus (STG), and superior parietal lobule (SPL) during semantic tasks. However, since functional communication between cortical regions is fundamentally shaped by the neural architecture of underlying white matter tracts, a critical question remains: are these sex specific functional differences rooted in distinct structural connectivity profiles? Investigating this structure function relationship is essential for understanding the neuroanatomical basis of sex differences in language and may shed light on biased vulnerabilities in language disorders. In the present study, we investigated sex differences of the microstructure of the brain using both atlas-based analysis and task-based, regional tractography among three core language ROIs. Diffusion tensor imaging (DTI) data were acquired from 58 participants (28 males, all native speakers of Mandarin Chinese) who previously completed a semantic decision task during a fMRI study. Data preprocessing followed standard procedures, including eddy current correction, head motion correction, and diffusion tensor fitting mainly using MRtrix3 (Tournier et al., 2019). After preprocessing, fractional anisotropy (FA) values of major white matter tracts were extracted using the XTRACT human white matter atlas, which enables reliable automated tract segmentation. Then guided by individual peak MNI coordinates derived from the semantic task fMRI activations, ROI-based probabilistic tractography was performed to reconstruct white matter pathways linking the left IFG, STG, and SPL in each participant. Mean FA values along each tract were compared between the female group and the male group using two-sample t-tests, with appropriate multiple comparison correction. Significant sex differences were detected for both atlas-based and ROIs-based analyses. First, males exhibited significantly higher FA values than females in the left uncinate fasciculus (p < 0.001, Bonferroni-corrected), indicating greater microstructural coherence in this frontotemporal pathway. Second, ROI-based tractography revealed significantly higher FA in males than females in the white matter tract connecting the left IFG and STG (p < 0.05, uncorrected). Third, the tract linking the left IFG and SPL also showed significantly higher FA in males (p < 0.05, uncorrected). No significant group differences were observed in the STG to SPL pathway. These findings provide novel structural evidence complementing prior functional observations, demonstrating that males and females differ not only in functional connectivity dynamics during semantic processing but also in the microstructural integrity of white matter pathways linking core language regions. The left uncinate fasciculus, together with the IFG to STG and IFG to SPL tracts, may serve as key structural substrates supporting sex-specific functional language networks. The higher FA observed in males may reflect more streamlined or coherently organized fiber architecture, potentially underpinning differential neural strategies for semantic representation and top-down modulation. By integrating structural and functional perspectives, our results advance a multi-modal understanding of sex differences in the neural basis of language and may inform future investigations into the sex-biased prevalence of language disorders such as developmental dyslexia and stuttering.
Topic Areas: Meaning: Lexical Semantics,