A NEUROPSYCHOLOGICAL MODEL OF DEVELOPMENT AGRAPHIA

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The primary goal of the research program is to develop and test an information processing model of children's writing. The model is derived from a model of adult writing developed from studying patients with acquired agraphia. The adult model contains specific cognitive systems that include linguistic components (necessary for generating correct spellings) and motor components (necessary for correct letter formation). Disruption of a specific component is thought to produce a specific agraphia. Evidence from preliminary studies and the literature suggest that (1) the neuropsychological abilities necessary for writing by adults may also be present in children and (2) certain types of developmental agraphia may be explained by hypothesizing disruption of these components. Therefore the specific aims of the research proposal include: (1) determining the presence or absence in normal children of the specific cognitive abilities predicted by the model, and the age when they can be evaluated; (2) determining how these abilities may be impaired in developmental disorders of spelling and writing (developmental agraphia). The hypothesized model implies a possible dissociation between the type of developmental agraphia and the type of developmental dyslexia that might be present in an individual. Therefore, an additional specific aim is to compare the type of agraphia and dyslexia present in each subject. These aims will be tested utilizing specific test paradigms, designed to isolate and test specific components hypothesized to be present in the proposed model. This approach, previously shown to be useful in studying adult writing, includes specifically varying: (1) the stimuli (asking the subject to write and read various types of words; (2) the conditions (copying or spontaneous writing), or (3) the output mode (oral spelling or writing). Other neuropsychological functions, including limb praxis, constructional ability, fine motor skills and auditory perception are related to, and possibly necessary for intact writing ability. Therefore, control tests for these functions will be administered to the subjects. It is hoped that as a result of these studies there will be a better understanding of developmental agraphia. Improved understanding of this common disorder may lead to the development of better remediation techniques for children with it.