Typical and atypical language brain organization based on intrinsic connectivity and multitask functional asymmetries

Abstract

We applied a multitask multimodal hierarchical classification (MMHC) to 287 volunteers (150 left-handers) to establish different brain language hemispheric dominance patterns (LangDom). MMHC was based on inter- and intrahemispheric measures of the sentence core network (SENT_CORE): 1) task-induced asymmetries (ACTIV) while listening to, reading, and producing sentences compared to word lists; 2) resting-state degree connectivity (Rs_DC) and asymmetry; and 3) interhemispheric connectivity (Rs_mIHHC). Three LangDom were found, including two typical groups, one with higher (N=125) leftward ACTIV and Rs_DC asymmetries and lower Rs_mIHHC than the other (N=132). The third was an atypical group (ATYP, N=30, 25 left-handers), having rightward ACTIV during the 3 language tasks but high Rs_DC in both hemispheres and high Rs_mIHHC. ATYP LangDom relies on a left SENT_CORE wired for language by default with strong interhemispheric connections with their right SENT_CORE. This loose specialization was associated with 40% of dissociations, decreased anatomical asymmetries, and lower verbal memory.