Differences in effective connectivity between dyslexic children and normal readers during a pseudoword reading task: an fMRI study.

PURPOSE: This fMRI study investigated phonological and lexicosemantic processing in dyslexic and in chronological age- and reading level-matched children in a pseudoword reading task.

MATERIALS AND METHODS: The effective connectivity network was compared between the three groups using a structural model including the supramarginal cortex (BA 40; BA: Brodmann area), fusiform cortex (BA 37) and inferior frontal cortex (BA 44/45) areas of the left hemisphere.

RESULTS: The results revealed differences in connectivity patterns. In dyslexic patients, in contrast with chronological age- and reading level-matched groups, no causal relationship was demonstrated between BA 40 and BA 44/45. However, a significant causal relationship was demonstrated between BA 37 and BA 44/45 both in dyslexic children and in the reading level-matched group.

CONCLUSIONS: These findings were interpreted as evidence for a phonological deficit in developmental dyslexia.