Maturation of the Language Network: From Inter- to Intrahemispheric Connectivities

Abstract

Language development must go hand-in-hand with brain maturation. Little is known about how the brain develops to serve language processing, in particular, the processing of complex syntax, a capacity unique to humans. Behavioral reports indicate that the ability to process complex syntax is not yet adult-like by the age of seven years. Here, we apply a novel method to demonstrate that the basic neural basis of language, as revealed by low frequency fluctuation stemming from functional MRI data, differs between six-year-old children and adults in crucial aspects. Although the classical language regions are actively in place by the age of six, the functional connectivity between these regions clearly is not. In contrast to adults who show strong connectivities between frontal and temporal language regions within the left hemisphere, children's default language network is characterized by a strong functional interhemispheric connectivity, mainly between the superior temporal regions. These data indicate a functional reorganization of the neural network underlying language development towards a system that allows a close interplay between frontal and temporal regions within the left hemisphere.

Language comprehension in nonspeaking children with severe cerebral palsy: Neuroanatomical substrate?

“…30 Corresponding to what is proposed as the development of the default language network (i.e. a development from inter-to intrahemispheric connectivities 28,29 ), our findings suggest that it is conceivable that a disruption or reduction in the transcallosal connections between both hemispheres is crucial for the development of spoken language comprehension in children with BGN. Besides maturation, functional transcallosal connectivity is necessary to fully establish a sophisticated language system, integrating lexical and syntactic competence.…”

“…In our cohort, diffuse thinning of the corpus callosum, and diffuse reduction of the frontal and parietooccipital WM areas, consistently corresponded with poor spoken language comprehension, indicating the importance of inter-to intrahemispheric connectivity for language development. 28,29 In children with the BGN pattern, the involvement of WM lesions (in particular) accounted for thinning of the corpus callosum, which as said, contributed significantly to the variation in spoken language comprehension. The splenial fibres of the corpus callosum (relevant for interhemispheric connections) form dense connections between the superior and middle temporal cortices of both hemispheres and seem crucial for language development.…”

Neurophysiological preconditions of syntax acquisition

“…Adult data clearly indicate such a functional connectivity in the brain at resting state (Xiang et al, 2010) and during language processing as determined by an analysis of lowfrequency Xuctuations (Lohmann et al, 2010). A lowfrequency Xuctuation analysis of data from an fMRI study in 6-year-old children revealed no strong functional intrahemispheric connectivity between the IFG and posterior STS (Friederici, Brauer & Lohmann, 2011).…”

Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging

“…Understanding of language pathways in the human brain has significantly evolved from the classic Wernicke–Lichtheim–Geschwind model to incorporate knowledge of cortical areas other than the traditional perisylvian language areas [e.g., the role of nonlinguistic cognitive processes, especially the contribution of the attentional network, is being increasingly recognized in language models (Hagoort 2013)] and white matter pathways connecting cortical areas (Poeppel and Hickok 2004; Friederici et al. 2011; Rijntjes et al. 2012; Friederici and Gierhan 2013).…”