A transcallosal fiber network between left and right homotopic inferior frontal regions for supporting complex linguistic processing

Inferior frontal regions in the left and right hemisphere support different aspects of language processing. In the classic model, left inferior frontal regions are mostly involved in processing based on phonological, syntactic and semantic features of language, whereas the right inferior frontal regions process paralinguistic aspects like affective prosody. Using DTI-based probabilistic fiber tracking in 20 healthy volunteers, we identify a callosal fiber network connecting left and right homotopic inferior frontal regions in the context of linguistic processing of different complexity. Anatomically, we show that the interhemispheric fibers are highly aligned and distributed along a rostral to caudal gradient in the body and genu of the corpus callosum. Functionally, our findings suggest that this transcallosal network of homotopic inferior frontal regions in the uninjured brain supports rapid integration of linguistic features of different complexity independent of emotional valence. Taking data from in-vivo neuroanatomical studies, previous DTI-based tracking studies and clinical case studies into account, we hypothesize that this role of the right inferior frontal cortex in supporting complex linguistic computations may explain patterns of right hemispheric contribution to stroke recovery as well as disorders of prosodic processing. Apart from language, inter-species differences in transcallosal connectivity and fiber density may explain differences in the ability to process complex structures between different species. . CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/079244 doi: bioRxiv preprint first posted online Oct. 4, 2016;