Neuronal Pathways Associated with Phonologic-to-orthographic Mapping (spelling)

Abstract:
Spelling relies heavily on an individual's knowledge of phonologic-to-orthographic mapping. Several studies have shown that dyslexic individuals have a difficult time understanding and learning this correspondence. The current fMRI study was designed to examine the neuronal pathways responsible for phonologic-to-orthographic mapping in skilled readers. The experimental paradigm was a phonologic-to-orthographic mapping task in which subjects heard a spoken stimulus (word or non-word) followed by a visual display. This display represented the printed form of the stimuli with one letter missing. The subject indicated which of two possible letters corresponded to the missing letter. Sets of contrast maps reveal brain regions that were significantly more activated during the experimental tasks than a non-linguistic baseline task. Initial analyses indicate that this phonologic-to-orthographic mapping task strongly activated brain regions in left inferior frontal cortex, and the inferior parietal lobe. In addition there was activation in the inferior temporal lobe, an area which is known to play a critical role in the processing of both printed and spoken words and has been implicated in dyslexia. Differences between words and non-words as well as brain/behavioral relations will also be discussed.