Semantic Representations in Reading

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Connectionist networks, which compute via the massively parallel cooperative and competitive interactions many simple neuron-like processing units, provide a unified framework for studying cognitive processes and their neurological implementation. The proposed research involve modeling acquired reading disorders in patients with brain damage by developing and "lesioning" a connectionist model of normal reading. Based on data from psychology and neuropsychology, the model has two routes for deriving the pronunciation of a printed word: a phonological route that maps directly from orthography to phonology by "sounding-out" the word, and a semantic route that maps indirectly via semantics by "recognizing" the meaning of the word. Preliminary connectionist implementations of each of these routes in isolation have succeeded in reproducing a limited range of normal and abnormal reading behavior. It is proposed to develop a complete dual-route model capable of addressing a much wider range of phenomena, relating to the coordination and relative contribution of each route during reading acquisition, mature skilled reading, behavior after partial damage, and recovery from damage. The model will be developed within a more neurophysiologically plausible connectionist formalism than the one used in the previous work. In addition, a major research effort will focus on developing an adequately sophisticated semantic system that overcomes the severe limitations of existing systems. High-performance computing facilities will be used to meet the extensive computational demands of training and testing the model.