Children with dyslexia have trouble processing the sounds that make up words, but the underlying cause of this problem is controversial. Dyslexic children are much worse than non-dyslexic children at seeing visual signals through noise, reports a paper in the July issue of Nature Neuroscience, which may explain the origin of the reading problem.
Anne Sperling and colleagues asked dyslexic and non-dyslexic children to detect a pattern embedded in visual 'noise', which looks like the static on a television screen. Compared to the non-dyslexic children, dyslexic children needed the pattern to be much brighter before they could see it. This finding contradicts a popular idea in the field, which attributes impaired visual processing in dyslexics to defects in a subset of visual neurons known as the magnocellular pathway. The authors now separate the effect of noise from the effect of the pathway, and conclude that deficits in noise exclusion can explain those previous findings.
How might a problem with noise exclusion interfere with learning to read? The authors suggest that it may interfere with letter recognition, or that the problem of distinguishing signal from noise might extend to other senses, including the auditory system.
Anne Sperling (Georgetown University Medical Center, Washington, DC, USA)
Also available online.
(C) Nature Neuroscience press relase.
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