Glitches in the connections between certain brain areas may be at the root
of the common learning disorder dyslexia, a new study suggests.
It's estimated that up to 15% of the US population has dyslexia, which
impairs people's ability to read. While it has long been considered a
brain-based disorder, scientists have not understood exactly what the issue is.
The new findings, reported in the issue of Science, suggest the blame
lies in faulty connections between the brain's storage space for speech sounds
and the brain regions that process language.
The results were surprising, said lead researcher Bart Boets, because his
team expected to find a different problem. For more than 40 years, he said,
many scientists have thought that dyslexia involves defects in the brain's
"phonetic representations" which refers to how the basic sounds of
your native language are categorised in the brain.
But using sensitive brain imaging techniques, Boets and colleagues found
that was not the case in 23 dyslexic adults they studied. The phonetic
representations in their brains were just as "intact" as those of 22
adults with normal reading skills.
Instead, it seemed that in people with dyslexia, language-processing areas
of the brain had difficulty accessing those phonetic representations.
"A relevant metaphor might be the comparison with a computer
network," said Boets, of the Leuven Autism Research Consortium in Belgium.
"We show that the information the data on the server itself is intact, but
the connection to access this information is too slow or degraded."
And what does that all mean? It's too soon to tell, said Boets. First of
all, he said, this study used one form of brain imaging to study a small group
of adult university students.
But dyslexia normally begins in childhood. And it's possible, Boets said,
that the "intact" phonetic representations in these adults took
longer to develop and might not have been apparent when they were children.
Even if children with dyslexia have the same underlying brain issue seen in
this study, it's not clear how that could be used in managing kids' reading
According to Boets, the "most established" way to help children
with dyslexia is through instruction on the smallest sounds of speech (called
phonemes) and how each corresponds to letters.
And the good news, Boets said, is that those types of tactics should help
strengthen the brain connections that seemed to be impaired in this study.
Still, "it is not inconceivable," he added, that these results
could be used to develop more-refined therapies that try to zero in on specific
brain connections. He pointed to non-invasive magnetic stimulation of certain
brain areas as an example though that is only speculation for now.
The findings are based on functional MRI (fMRI) brain scans, which gauge
brain activity by charting changes in blood flow and oxygen. The research team used
two sophisticated analytical techniques to try to tease out what was happening
in study participants' brains as they listened to different sounds of speech
and then performed a simple test.
Studies like this one, based on fMRI, have proved useful in the "real
world", said Ben Shifrin, vice president of the International Dyslexia
Association in Baltimore.
"These fMRI studies have helped us improve interventions for
children," said Shifrin, who is also head of the Jemicy School in
Baltimore, which specializes in educating kids with language-based learning
One example, he said, is that it's now clear that the "intensity"
of the instruction more hours per day is key in children's progress.
Shifrin said it's not clear how these latest findings could be translated
into practical use. But, he added, "we know that these types of studies
can end up having direct effects in the classroom."
In general, Shifrin said, there's been a move toward more
"collaboration" between the scientists studying learning disorders
and the educators in the field.
"We need even more of that," Shifrin suggested. "For years,
it used to be that the neuroscientists were working in the lab and not talking
to educators. That's changing."
The International Dyslexia Association has more information on dyslexia.