Cerebral mechanisms involved in word reading in dyslexic children: A magnetic source imaging approach

The purpose of the present investigation was to describe spatiotemporal bra in activation profiles during word reading using magnetic source imaging (N ISI). Ten right-handed dyslexic children with severe phonological decoding problems and eight age-matched non-impaired readers were tested in two reco gnition tasks, one involving spoken and the other printed words. Dyslexic c hildren's activation profiles during the printed word recognition task cons istently featured activation of the left basal temporal cortices followed b y activation of the right temporoparietal areas (including the angular gyru s). Non-impaired readers showed predominant activation of left basal follow ed by left temporoparietal activation. In addition, we were able to rule ou t the hypothesis that hypoactivation of left temporoparietal areas in dysle xics was doe to a more general cerebral dysfunction in these areas. Rather. it seems likely that reading difficulties in developmental dyslexia are as sociated with an aberrant pattern of functional connectivity between brain areas normally involved in reading, namely ventral visual association corte x and temporoparietal areas in the left hemisphere. The interindividual con sistency of activation profiles characteristic of children with dyslexia un derlines the potential utility of this technique for examining neurophysiol ogical changes in response to specific educational intervention approaches.