Normal developmental changes in inferior frontal gray matter are associated with improvement in phonological processing: a longitudinal MRI analysis.

This study asked whether previously identified developmental changes in the gray matter of the left inferior frontal gyrus are associated with maturation of a linguistic skill. To test this hypothesis, we examined whether thickening of this region was correlated with developmental improvements in phonological processing but not hand motor skills in a unique longitudinal data set of 45 normally developing children (between ages 5 and 11 years) studied over a 2-year interval. We analyzed structural magnetic resonance imaging data using cortical pattern matching methods and correlated within-individual changes in cortical thickness with 2 neurocognitive scores. As predicted, gray matter thickening in the left inferior frontal cortex was associated with improving phonological processing scores but not with improving hand motor skills. By contrast, motor skill improvement was associated with thinning in the hand region of the left motor cortex, and cortical change in this region was not associated with phonological processing. This study illustrates a specific correspondence between regional gray matter thickness change and language skill change in normally developing children.