Altered hemispheric asymmetry of auditory N100m in adults with developmental dyslexia.

The current study aimed at determining whether the deviance of hemispheric asymmetry in the auditory cortex of children with dyslexia is also evident in dyslexic adults. Ten adult dyslexic subjects and 10 normally literate controls were presented with the syllable [ba:] while event-related brain activity was recorded from both hemispheres using whole-head magnetoencephalography. In control subjects, the auditory N100m source was found to be asymmetrical with a more anterior localization in the right than in the left perisylvian cortex (difference = 0.78 cm). The N100 m dipoles in dyslexic adults did not exhibit the same interhemispheric asymmetry (difference = -0.06 cm). The results indicate that reduced hemispheric laterality of perisylvian regions in dyslexia persists into adulthood.