Phonological processing in relation to reading: an fMRI study in deaf readers

Without special education, early deprivation of auditory speech input, hinders the development of phonological representations and may alter the neural mechanisms of reading. By using fMRI during lexical and rhyming decision tasks, we compared in hearing and pre-lingually deaf subjects the neural activity in functional regions of interest (ROIs) engaged in reading. The results show in deaf readers significantly higher activation in the ROIs relevant to the grapho-phonological route, but also in the posterior medial frontal cortex (pMFC) and the right inferior frontal gyrus (IFG). These adjustments may be interpreted within the dual route model of reading as an alternative strategy, which gives priority to rule-based letter-to-sound conversion. Activation in the right IFG would account for compensation mechanisms based on phonological recoding and inner speech while activation in the posterior medial frontal cortex (pMFC) may relate to the cognitive effort called for by the alternative strategy. Our data suggest that the neural mechanisms of reading are shaped by the auditory experience of speech.