Instructional treatment associated with changes in brain activation in children with dyslexia

To assess the effects of reading instruction on fMRI brain activation in children with dyslexia.

fMRI differences between dyslexic and control subjects have most often involved phonologic processing tasks. However, a growing body of research documents the role of morphologic awareness in reading and reading disability.

The authors developed tasks to probe brain activation during phoneme mapping (assigning sounds to letters) and morpheme mapping (understanding the relationship of suffixed words to their roots). Ten children with dyslexia and 11 normal readers performed these tasks during fMRI scanning. Children with dyslexia then completed 28 hours of comprehensive reading instruction. Scans were repeated on both dyslexic and control subjects using the same tasks.

Before treatment, children with dyslexia showed less activation than controls in left middle and inferior frontal gyri, right superior frontal gyrus, left middle and inferior temporal gyri, and bilateral superior parietal regions for phoneme mapping. Activation was significantly reduced for children with dyslexia on the initial morpheme mapping scan in left middle frontal gyrus, right superior parietal, and fusiform/occipital region. Treatment was associated with improved reading scores and increased brain activation during both tasks, such that quantity and pattern of activation for children with dyslexia after treatment closely resembled that of controls. The elimination of group differences at follow-up was due to both increased activation for the children with dyslexia and decreased activation for controls, presumably reflecting practice effects.

These results suggest that behavioral gains from comprehensive reading instruction are associated with changes in brain function during performance of language tasks. Furthermore, these brain changes are specific to different language processes and closely resemble patterns of neural processing characteristic of normal readers.