THE ROLE OF VISUAL EXPERTISE IN LETTER PERCEPTION

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DESCRIPTION (adapted from applicant's abstract): Behavioral, functional brain imaging (fMRI), electrophysiological (ERP) and neuropsychological experiments will investigate how letters are perceived. The project is motivated by a framework accounting for specialization for faces and letters in extrastriate cortex by a detailed analysis of the different recognition goals and the information available for the recognition of these categories. The experiments will evaluate the hypothesis that what is "special" about expert letter perception is that regularities in letter style (including orientation, case and font) is used to facilitate letter recognition (access to letter identities). In particular, we will investigate how readers may learn to use the regularity of print to facilitate letter perception at the basic level, how this ability differs from general object recognition strategies and whether it leads to specialization of letter-specific areas in visual cortex. This project has four aims: I) identify behavioral effects that are special to the way experienced readers recognize letters; II) study the basic properties of letter-selective areas in visual cortex with ERP and fMRI; III) use behavioral, fMRI and ERP measurements to investigate the hypothesis that a history of poor reading expertise in dyslexic individuals leads to abnormal specialization of the letter-specific system; IV) test predictions about lesions in areas of the visual cortex specialized for letters in individuals with acquired peripheral dyslexia (pure alexia). This research will investigate how much visual factors alone contribute to specialization for letters. This information is necessary to understand linguistic influences on reading and would extend an emerging framework interpreting category-specific effects in extrastriate cortex in terms of the recruitment through experience of processes best suited for different recognition goals. Understanding what characterizes expert letter perception is also necessary to understand disorders in which this expertise is not acquired (such as dyslexia) or is lost (such as low vision).