Neurophysiological mechanisms of reading in alexia: Development of stimuli to examine semantic integration using the N400 response

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  • In order for speech-language pathologists to improve therapy for acquired reading impairments, it is necessary to gain a better understanding of how sentences are processed during reading. Neural mechanisms underlying reading processes can be examined by using event-related potentials (ERPs). More specifically, the N400 response is an ERP component that is typically observed in response to semantically anomalous words in a sentence, and appears to be an index of semantic integration and reprocessing. The N400 response is modulated by semantic context, such that the response is smaller when the anomalous word is semantically related to the expected exemplar. Researchers have shown that individuals with alexia display different sentence processing patterns than controls. The purpose of this research project was to develop and norm stimuli for a future study that will examine the N400 response in individuals with and without alexia when reading sentences containing semantic anomalies. Eighty pairs of sentence sets were created to elicit a specific target word (the expected exemplar). An online survey was administered to 89 participants, who were asked to fill in the final word of the sentence in order to examine how well the sentence context facilitated the target word. Eighty sentences were selected based on the mean cloze probability for the expected exemplar (>0.5). The range of cloze probabilities for expected exemplars was 0.5 – 1.0, with an average of 0.86. The sentences developed in this study will be used to gain valuable information about sentence processing in both controls and those with alexia.

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    Attribution-NonCommercial-NoDerivatives 4.0 International