Study clears way for early identification of dyslexia

Research at The Australian National University could help identify children likely to develop dyslexia. The work, by Alison Kevan, of the Department of Psychology, could clear the way to early intervention that could help compensate for the disorder. “We wanted to see if there was a biological marker in these kids to identify those at risk,” says Kevan, a PhD candidate. “We were looking for a way to identify the problem before they started to learn to read, and, more importantly, before they failed to learn to read.”

Dyslexia tends to run in families. Children with a parent or sibling with it have a 65 per cent chance of having the disorder, too. Kevan tested children with a family history of dyslexia to see whether their visual systems differed from those of children of the same age who were not at risk of developing the disorder. She recruited both cohorts from Canberra schools and through an appeal for volunteers made through the media. The study started when the children were in kindergarten, with follow-up tests 18 months later, after they had started to learn to read. “The aim was to see if there were pre-existing differences for the at-risk children before they learned to read, and whether we could predict how well they were reading at the end of Year 1,” she says.

She looked for differences between the groups in the processing of information via two pathways that carry visual information from the eye to the visual cortex of the brain. The first pathway, the ventral stream, governs the perception of fine detail and colour. The second, the dorsal stream, involves the processing of more coarse and dynamic information – low contrast and movement. “We can design stimuli to target either pathway to see whether they have a deficit in one of them,” she says. “The findings suggest that there is something different about the visual systems in children at risk of dyslexia.

“They had difficulty seeing specific visual patterns that are processed by the dorsal stream, at the start of kindergarten, “Even more exciting is the fact that these visual measures taken at the start of kindergarten can predict how well children are reading up to 18 months later.” However, it is still unknown whether this visual impairment plays a role in reading failure or is merely a biological marker linked to a more general cognitive deficit.

Kevan plans further research to see how impairment in the dorsal pathway might contribute to reading failure. She did her BPsych (Honours) at ANU, and expects to finish her PhD in late 2008 before heading off to the United States for post-docoral work. “I really enjoy working with the kids, and hope that this research might go some way towards helping children with reading difficulties in the future.”