Regional differences in the developmental trajectory of lateralization of the language network

Abstract

The timing and developmental factors underlying the establishment of language dominance are poorly understood. We investigated the degree of lateralization of traditional frontotemporal and modulatory prefrontal-cerebellar regions of the distributed language network in children (n = 57) ages 4 to 12--a critical period for language consolidation. We examined the relationship between the strength of language lateralization and neuropsychological measures and task performance. The fundamental language network is established by four with ongoing maturation of language functions as evidenced by strengthening of lateralization in the traditional frontotemporal language regions; temporal regions were strongly and consistently lateralized by age seven, while frontal regions had greater variability and were less strongly lateralized through age 10. In contrast, the modulatory prefrontal-cerebellar regions were the least strongly lateralized and degree of lateralization was not associated with age. Stronger core language skills were significantly correlated with greater right lateralization in the cerebellum.

Keywords: fMRI; language; lateralization; pediatric.

Figure 1

Distribution of categorical language dominance across age group and by region of interest. IFG = inferior frontal gyrus, WA = Wernicke's Area, CER = cerebellum, MFG = middle frontal gyrus.

Figure 2

Clustered box plots of mean LI values for region of interest (ROI) (WA = Wernicke's Area, IFG = inferior frontal gyrus, INV CER = cerebellum with inversed LI values, MFG = middle frontal gyrus), clustered by Age group. Significant main effects of ROI and age group.

Figure 3

Scatter plot of mean LI value for each participant by age for inferior frontal gyrus and Wernicke's Area (P < 0.05).

Figure 4

Axial slices of whole brain activation for ADDT task. Yellow represents the activation for all 57 children age 4 to 12 years old (FWE, P < 0.05). Blue represents activation unique to the youngest age group (P < 0.001, uncorrected). Green represents activation that is greater in the 4‐ to 6‐year‐old group and overlaps with the group map. Axial slices are in neurological convention (left is left hemisphere).