Exploring a common neural substrate of reading and spelling

Whether reading and spelling rely on the same orthographic representations has been a controversial issue in the neuropsychology literature. In general, associations between patterns of alexia and agraphia in neurological patients have been interpreted to support the view that reading and spelling share the same orthographic lexicon. By contrast, dissociations between reading and spelling profiles are considered as evidence for the existence of separate orthographic input and output lexicons subserving written word recognition and production. Neuroimaging research relevant to the neural substrates of orthographic processing has shown consistent association between reading and activation in the mid-lateral portions of the left fusiform gyrus (BA 37), a region that has come to be known as the "visual word form area" (VWFA). Critically, it has been shown that spelling words also activates the VWFA. These findings seem to confirm the central role of the VWFA in orthographic processing and support the view that the same orthographic representations mediate reading and spelling. Unfortunately, the available neuroimaging evidence on the relationship between reading and spelling is limited in that the relevant studies typically have involved different subject groups. The purpose of this study was to investigate whether the cortical region responsible for orthographic processing during reading is also activated during spelling in the same individuals using fMRI (functional magnetic resonance imaging). Fifteen native English speakers participated in the study and were administered reading and writing tasks designed to isolate cortical regions involved in orthographic processing during reading and writing. Results showed that the left mid fusiform gyrus corresponding to the VWFA is associated not only with orthographic processing in reading but is also recruited during the retrieval of orthographic information in spelling, suggesting that this cortical region is the common neural substrate of orthographic processing for both written language tasks. These findings are consistent with shared components cognitive models that postulate a single orthographic lexicon mediating both reading and spelling.