Research Projects Funded by IDA The work supported by this grant has produced two papers in Vision Research (one in press, the second submitted), one book chapter, six conference abstracts, and has contributed significantly to the fact that I was awarded the 1997 Norman-Geschwind Prize for research into the neurobiology of developmental dyslexia. Summary Reading disabled individuals find it unusually difficult to detect flickering or moving visual stimuli, consistent with impaired processing in the magnocellular visual stream. In two studies, I have tested the hypothesis that poor magnocellular function (assessed by a motion detection task) may degrade information about where letters are positioned with respect to each other. Study 1: I used a lexical decision task and a "multiple alphabetic decision task" to successfully demonstrate an explicit association between a task which taps magnocellular function (coherent motion detection) and letter position encoding. Study 2: I predicted that degraded letter position information should cause children to make reading errors which contain sounds not represented in the printed word (e.g. misreading VOCATION as VOCTION, or PERSON as PRESON). I call these orthographically inconsistent nonsense errors "letter" errors. I have shown that the likelihood of children making "letter" errors is best explained by independent contributions from motion detection (i.e. magnocellular function) and phonological awareness (assessed by a spoonerism task). This result held even when chronological age, reading ability, and IQ were controlled. |