Native language & connectome of the brain

Investigation towards the question if the neuroanatomy of the language structural connectome is modulated by the life-long experience of speaking a specific language are presented. The current study compared the brain white matter connections of the language and speech production network in a large cohort of native speakers of two very different languages: an Indo-European morphosyntactically complex language (German) and a Semitic root-based language (Arabic).
Using high-resolution diffusion-weighted MRI and tractography-based network statistics of the language connectome, we demonstrated that German native speakers exhibited stronger connectivity in an intra-hemispheric frontal to parietal/temporal dorsal language network, known to be associated with complex syntax processing. In comparison, Arabic native speakers showed stronger connectivity in the connections between semantic language regions, including the left temporo-parietal network, and stronger inter-hemispheric connections via the posterior corpus callosum connecting bilateral superior temporal and inferior parietal regions.
The current study suggests that the structural language connectome develops and is modulated by environmental factors such as the characteristic processing demands of the native language.

  • The structural language network is modulated by the specific procesing requirements of one’s native language.
  • Native speakers of a language with complex syntax (German) show stronger connectivity in the intra-hemispheric frontal-parietal/-temporal language network.
  • Native speakers of a root-based language (Arabic) show stronger connectivity in the temporo-parietal lexical-semantic network and in inter-hemispheric connections.
 Intra- and inter-hemispheric connectivity differences in the language network. 
(A) The language-related ROIs included sub-regions in the larger language areas IFG, TL, IPL, aCC, and pCC, color-coded. The lower panels show the SMA/pre-SMA areas which are relevant in verbal language production.
(B) Group difference of the inter-hemispheric connectivity.
(C) Difference in intra-hemispheric connectivity between groups and hemispheres.
LH: left hemisphere, RH: right hemisphere. IFG: inferior frontal gyrus, TL: temporal lobe, IPL: inferior parietal lobe, CC: corpus callosum, SMA: supplementary motor area. 

This study revealed stronger structural connectivity of the syntax network in a German-speaking group compared to matched Arabic-speaking participants.
It’s suggested that this may reflect the more complex syntactic coding present in German. In contrast, the rich morphology of the Arabic language, which is involved in the lexical-semantic and phonological processes, may have led to the modulation of connections between the temporal and parietal lobes, as well as to the increased inter-hemispheric connectivity.
These results provide evidence for the modulation of the structural language network in the human brain by the demands of one’s native language. In the cognitive domain, these findings are essential for our general understanding of the interaction of environment and behavior in shaping the human brain.

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