Diffusion magnetic resonance imaging connectome featuresare predictive of functional lateralization of semanticprocessing in the anterior temporal lobes
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Philipps-Universität Marburg
Abstract
Assessment of regional language lateralization is crucial in many scenarios, but not allpopulations are suited for its evaluation via task-functional magnetic resonance imag-ing (fMRI). In this study, the utility of structural connectome features for the classifi-cation of language lateralization in the anterior temporal lobes (ATLs) wasinvestigated. Laterality indices for semantic processing in the ATL were computedfrom task-fMRI in 1038 subjects from the Human Connectome Project who werelabeled as stronger rightward lateralized (RL) or stronger leftward to bilaterally latera-lized (LL) in a data-driven approach. Data of unrelated subjects (n=432) were usedfor further analyses. Structural connectomes were generated from diffusion-MRItractography, and graph theoretical metrics (node degree, betweenness centrality)were computed. A neural network (NN) and a random forest (RF) classifier weretrained on these metrics to classify subjects as RL or LL. After classification, compari-sons of network measures were conducted via permutation testing. Degree-basedclassifiers produced significant above-chance predictions both during cross-validation(NN: AUC–ROC[CI]=0.68[0.64–0.73], accuracy[CI]=68.34%[63–73.2%]; RF:AUC–ROC[CI]=0.7[0.66–0.73], accuracy[CI]=64.81%[60.9–68.5]) and testing(NN: AUC–ROC[CI]=0.69[0.53–0.84], accuracy[CI]=68.09[53.2–80.9]; RF: AUC–ROC[CI]=0.68[0.53–0.84], accuracy[CI]=68.09[55.3–80.9]). Comparison of net-work metrics revealed small effects of increased node degree within the right poste-rior middle temporal gyrus (pMTG) in subjects with RL, while degree was decreasedin the right posterior cingulate cortex (PCC). Above-chance predictions of functionallanguage lateralization in the ATL are possible based on diffusion-MRI connectomesalone. Increased degree within the right pMTG as a right-sided homologue of aknown semantic hub, and decreased hubness of the right PCC may form a structuralbasis for rightward-lateralized semantic processing.
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