TO SEE BUT NOT TO READ - THE MAGNOCELLULAR THEORY OF DYSLEXIA

Developmental dyslexics often complain that small letters appear to bl ur and move around when they are trying to read. Anatomical, electroph ysiological, psychophysical and brain-imaging studies have all contrib uted to elucidating the functional organization of these and other vis ual confusions. They emerge not from damage to a single visual relay b ut from abnormalities of the magnocellular component of the visual sys tem, which is specialized for processing fast temporal information. Th e m-stream culminates in the posterior parietal cortex, which plays an important role in guiding visual attention. The evidence is consisten t with an increasingly sophisticated account of dyslexia that does not single out either phonological, or visual or motor deficits. Rather, temporal processing in all three systems seems to be impaired. dyslexi cs may be unable to process fast incoming sensory information adequate ly in any domain.