Decreased white-matter density in a left-sided fronto-temporal network in children with developmental language disorder: evidence for anatomical anomalies in a motor-language network.

The neurophysiological and neuroanatomical foundations of developmental language disorder (DLD) are still a matter of dispute. A main argument is that children with DLD show atypical anatomical asymmetries of speech-relevant brain areas, which possibly affect efficient language processing. In contrast to previous anatomical studies in DLD children, this study employed voxel based morphometry (VBM) in order to search for brain anomalies outside the classical language areas. Children with DLD (n=21) and healthy children (n=21) matched for age, sex, hand preference, and education were studied using high-resolution MRI scans. Using a new variant of the voxel-based morphometry technique (augmented VBM), the brains of children with DLD and control children were compared with respect to white matter (WM) and grey matter (GM) differences. In addition, simple hand motor tests were used to uncover possible motor impairments in DLD children. We found decreased WM volumes in a left-hemispheric network comprising the motor cortex, the dorsal premotor cortex, the ventral premotor cortex, and the planum polare on the superior temporal gyrus. In addition, DLD children exhibited motor impairments in most of the applied motor tests. These results provide strong evidence that children with DLD have anomalous anatomy in a left-sided network comprising motor and language areas. Thus, this study supports the suggestion that motor and language functions are equally impaired because the underlying anatomical underpinnings are regionally identical.