The goal of the proposed research is to increase our understanding of the various forms of written and oral spelling disorders that result from brain-damage. The specific issues addressed and the means used to reach the stated objective reflect important new theoretical, empirical, and computational developments in research on dysgraphia. The principal hypothesis guiding the project is that spelling involves the concerted activity of several relatively autonomous processing components: a lexical system consisting of semantic, phonological and orthographic lexicons; a procedure for converting sub-lexical phonological strings into graphemic sequences; and a set of orthographic conversion procedures for oral and written spelling. Although there is considerable evidence in support of the view of the spelling process, important questions remain. A major objective of the proposed research is to more fully chart the structure of the spelling process and how it breaks down following brain damage. Examples of the type of questions addressed in this part of the research are: What is the relationship of the semantic, phonological, and orthographic lexical components.? Does the activation of orthographic forms depend on the prior or concurrent activation of phonological forms? The other major part of the research will address more specific hypotheses regarding the nature of the representations and processing characteristics of each of the principal components of the spelling system. Examples of the issues that will be addressed are: What is the role of grammatical information in the organization of lexical-orthographic forms? Are graphemic representations linear sequences of grapheme or are they multidimensional structures which independently specify the identity of graphemes, their number, the consonant/vowel statue of individual graphemes, and graphosyllabic structure? Is the structure of graphemic representations parasitic on phonological representations? These questions will be addressed through the detailed investigation of series of dysgraphic subjects and computational modeling of two of the major components of the spelling process -- the graphemic buffer and the phonology to orthography conversion process. The results of this project should contribute significantly to our understanding of acquired disorders of writing.
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