Reading and sensorimotor fluency in dyslexia

Georgetown University, Washington DC

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Abstract

The behavioral-manifestations of developmental dyslexia are complex, including deficits in reading, motor control and early sensory processing. Although extensive behavioral research has carefully characterized these abnormalities, the specific neural mechanisms, whose dysfunction may explain the myriad behavioral manifestations of dyslexia, are still poorly understood. While many consider the core deficit in dyslexia to involve dysfunction of language mechanisms, others have emphasized the possible role of failure of sensory processing mechanisms or an overall disorder involving sensorimotor coordination evidenced by deficits in performance of speeded, bimanual movement tasks. One of the more prominent behavioral manifestations of dyslexia is impaired reading fluency, the ability to read connected text rapidly, smooth, effortlessly, and automatically. We propose a series of integrated studies combining behavioral measures with functional magnetic resonance imaging (fMRI) to investigate the relation of reading fluency to mechanisms involved in rapid naming, phonological processing, speeded motor performance and early sensory processing. Our central hypothesis posits the existence of a disorder in temporal processing in dyslexia that exhibits itself in deficits in these areas. In our previous work we have demonstrated a sensory deficit in dyslexia specific to the visual motion processing system. Using similar motor performance and to investigate the relationship of motor control abnormalities to deficits in reading fluency. A particular emphasis of the proposed research will be to identify the degree to which the systems responsible for reading, phonological processing, visual motion processing, speeded motor performance and rapid automatized name share common neural substrates. The proposed studies will provide important new information concerning the neural organization of reading in health and in disease. A deeper understanding of the processes involved when reading fails to develop normally may suggest new approaches to the diagnosis and treatment of developmental dyslexia.