Hemispheric processing characteristics for lexical decisions in reading -disordered adults
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| Publicado en: | ProQuest Dissertations and Theses (1999) |
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| Acceso en liña: | Citation/Abstract Full Text - PDF |
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| Resumo: | The present study was designed to measure vocal reaction times and error responses of approximately thirty reading disabled adults to unilateral tachistoscopically presented (100 ms) single words and nonwords (monosyllabic) in a series of lexical decision tasks at two linguistic levels. The purpose of this study was two-fold. Investigation of neurolinguistic organization for lexical decision processing was examined where lexical decision vocal reaction times were measured in response to both concrete and abstract words tachistoscopically presented to the right and left visual-half fields. Hemispheric processing models were developed based on statistical analysis of the data. Levels of left and right hemisphere stimulus processing were determined while an index of interhemispheric interaction for lexical decisions was developed for the first experiment. Information relative to parafoveal stimulus processing was presented as it relates to neurolinguistic organization. The second purpose of this study was to investigate central processing strategies employed in lexical decision operations in reading disabled adults. Center foveal presentations of the lexical decision stimulus items were employed. Participants were required to perform a lexical decision vocal reaction task identical to the unilateral experiment. However, under the central condition, participants were required to read the item following a lexical decision. Specifically, two lexical decision and reading tasks were completed during the central tachistoscopic presentation of a series of concrete and abstract words, at stimulus presentation rates of 100 ms and 20 ms. Error rates and error category (semantic, structural/orthographic, phonological) were analyzed to determine the neurolinguistic processing strategies employed for foveal lexical decision processes. Information relative to those crucial strategies underlying word recognition for reading operations were presented. Interpretation of the first experimental results suggests that the hemispheric processing patterns for reading disordered adults is different from normal hemispheric processing patterns for lexical decisions. A direct access model of hemispheric processing was found for the normally reading adults, indicating that the right hemisphere was engaging in lexical processing at some level although not as efficiently as the left hemisphere. In contrast, a callosal relay model of hemisphere processing was found for the reading disordered adults indicating that the left hemisphere was responsible for executing the lexical decision task. Accuracy rate data demonstrated that lexical decisions for concrete stimuli were more accurate when presented to the right visual field. Such findings suggest that an interhemispheric signal transfer deficit may be operational in certain types of reading disorders. In addition, correlation data suggested that the interhemispheric processing time might be crucial for sight-word recognition skills, in the reading disordered population. Interpretation of the second experimental results demonstrated similar central processing strategies for the reading disordered and normally reading adults. The lexical organization of the concrete and abstract stimuli was reversed in the two rate conditions of 100 ms and 20 ms., for both groups. At the slower rate of 100 ms, concrete words were processed faster than abstract words. At the faster rate of 20 ms, abstract words were processed faster than concrete words. This study is among the first investigation to document changes in lexical processing style for various lexical categories, as a function of stimulus rate. Results supports previous investigations suggesting that concrete and abstract lexicon are separate cognitive systems. The rate of reading, however, may influence the rate of lexical access or lexical activation for various word types. Further research and clinical implication are discussed. (Abstract shortened by UMI.) |
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| ISBN: | 9780599687110 |
| Fonte: | ProQuest Dissertations & Theses Global |