Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Heritability of cerebro cortical asymmetry of language network regions
Poster Session A, Wednesday, September 30, 11:00 am - 1:00 pm, Wangari Maathai
Chandana Hewawasam1,2, Lachlan Strike3, Greig de Zubicaray4, Katie McMahon1,5; 1School of Clinical Sciences, Queensland University of Technology, Brisbane, Australia., 2Department of Physiology, Faculty of Medicine and Allied Health Sciences, Rajarata University of Sri Lanka, Saliyapura 50008, Sri Lanka., 3Brain and Mental Health, QIMR Berghofer, Brisbane, Australia, 4School of Psychology and Counselling, Faculty of Health, Queensland University of Technology, Brisbane, Australia., 5Herston Imaging Research Facility, Royal Brisbane and Women’s Hospital, Herston, Brisbane, Australia.
Hemispheric lateralization is a fundamental organizing principle of the human brain, with left-hemisphere dominance for core language functions. This asymmetry is thought to enhance neural communication, vocalization and neural efficiency by reducing redundant processing and freeing cortical resources for other cognitive functions. Heritability is the proportion of phenotypic variance in a trait (e.g., cortical asymmetry) that is attributable to additive genetic factors. Understanding the heritability of cortical asymmetry in language-related regions is critical for disentangling the relative contributions of genetic predispositions versus environmental and experiential factors that shape the maturation of language networks. Unlike hemispheric asymmetry, the heritability of cortical thickness (CT) and surface area (SA) laterality remains poorly understood. Our study addressed this gap by quantifying the heritability of laterality in cortical thickness and surface area within language-related regions. Participants were 388 adolescent twins (mean age = 11.35 ± 1.35 years; 48.9% female, MZ=100, DZ=94 pairs) from the Queensland Twin Adolescent Brain study. CT and SA measures were extracted from 34 bilateral language-related regions of interest (ROI) defined by the Brainnetome atlas. Hemispheric asymmetry was quantified using laterality indices [LI=100(L − R)/(L + R)], adjusted for age, sex, and handedness. Heritability of LI was estimated using a classic twin design. Associations between language skills and LI were assessed by performance on the Picture Vocabulary Test using linear mixed models. Robust hemispheric asymmetry was observed across ROIs for both CT and SA. For cortical thickness, leftward asymmetry was strongest in medial and ventral temporal regions (e.g., PhG-TL, MTG-A21c). For cortical surface area, leftward asymmetry was strongest in superior temporal cortex (STG-A22r) and extended to ventral temporal, sensorimotor, and frontal regions (e.g., ITG-A37elv, PrG-A4hf, MFG-IFJ). Covariate effects on cortical asymmetry were minimal. SA measures exhibited significant but localized sex effects in three temporal regions (STG‑A22r, STG-A41/42 and STG‑A38l). Age-related associations were weak and non-significant for both metrics. No significant handedness effects were observed. For most brain regions, unique environmental factors (e.g. idiosyncratic development) were the sole determinant of variance of LI accounting for 25 of 34 ROIs for CT and 22 of 34 ROIs for SA measures. Genetic influences were detected only in a subset of regions; [3 CT (e.g. PrG‑A6cvl, heritability = 34%; PhG‑TL, 22%; PoG‑A1/2/3ulhf, 19%) and 7 SA regions (e.g., PhG‑TL, 28%; STG‑A41/42, 25%; STG‑A38l, 20%; 3 fusiform gyrus subdivisions, ~22%; IFG‑A44op, 19%)], with heritability estimates ranging from approximately 16% to 34%. In contrast, shared environmental influences (e.g. socioeconomic status) were weak and rarely statistically significant. Associations between hemispheric laterality indices (LI) and language skills were weak with the largest effect size reaching only 0.38 (CT of anterior superior temporal sulcus - aSTS). None of the models for either CT or SA yielded statistically significant effects. Overall, these findings indicate that hemispheric asymmetry in language-related regions is robust yet shows regional variability in both direction and magnitude. Individual differences in laterality appear to be driven primarily by unique environmental factors with more limited, region-specific genetic contributions.
Topic Areas: Genetics, Language Development/Acquisition