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The 5th BDA International Conference provided the opportunity for both researchers and educators to share their research findings and interests with a wide audience all committed to developing a greater understanding regarding the possible causes and problems experienced in dyslexia. On day two of the conference, several presentations concentrated on visual processing deficits in dyslexia. These stem from the suggestion that there is a mild impairment to one of the visual pathways that project from the eye to the brain. This pathway is known as the magnocellular stream and projects to areas of the brain that are important for motion.
Motion Sensitivity
Joel Talcott (University of Oxford) working with colleagues reported on findings that suggested a reduced sensitivity to motion in dyslexics and discussed how this may relate to subtypes in dyslexia. The task used in this type of research consists of presenting a number of frames containing many dots where a certain percentage of these dots are displaced between frames to give the impression of coherent motion. Research findings suggests that in dyslexia, more of the dots have to be displaced in order for coherent motion to be detected. Talcott reported that motion sensitivity deficits were more evident in dyslexics that had both poor orthographic knowledge and phonological skills.
With the theme of motion sensitivity still in mind, Mark Bradshaw (University of Surrey) discussed whether visual problems in dyslexia could be solely attributed to a magnocellular deficit. His findings suggested that the visual problems experienced by some dyslexics might arise due to a failure to integrate information between two different visual pathways rather than just a magnocellular problem.
Further support for reduced motion sensitivity in dyslexia was provided by Gary Hill (University of Wales, Bangor) who suggested that the problem lies in the ability to integrate information across successive frames rather than a magnocellular problem. He manipulated the number of frames used and asked individuals to report on two directions of motion. The results indicated that dyslexics needed longer to correctly identify two motions.
Reading
Piers Cornelissen (University of Newcastle) discussed the relationship between visual processing and word recognition and considered how visual deficits may affect reading. During reading, individuals make fixations where the reader extracts information about the written word. The ability to extract information regarding the correct position of letters at each fixation is important for reading. With this in mind, Cornelissens' research group considered the variability in the ability to process letter strings by exchanging the positions of letters in words and non-words and asking individuals to make decisions about what they had seen.
Richard Shillcock (University of Edinburgh) discussed normal word recognition and he suggested that the initial projection of a word is split between the two halves of the brain. Thus, he discussed dyslexia as a desynchronisation between the left and right hemispheres.
The use of colour filters provided an interesting presentation by Arnold Wilkins (University of Essex) who highlighted how they can help with reading, although the children he talked about were not dyslexic. He concluded by arguing that attention should be focussed on the size of text used in reading schemes, as larger text is easier to read.
The magnocellular hypothesis
The second day of the conference culminated on a high note with a well-received talk by guest keynote speaker Professor John Stein (University of Oxford). Stein outlined his theory regarding a magnocellular deficit in dyslexia and articulated on how this might impact on reading. Furthermore, he suggested that cells in this pathway are important for controlling eye movements, which are certainly important for reading. He suggested that the visual impairments sometimes reported by dyslexics regarding visual confusion of letters can be related to a mild impairment to the magnocellular pathway and speculated that a similar system may apply to the auditory domain.
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