Dyslexia, a reading disorder, is characterized by a difficulty in
“decoding” — navigating between the visual form and sounds of a written
language. But a subset of dyslexic people, dubbed “resilient dyslexics,”
exhibit remarkably high levels of reading comprehension despite difficulties
decoding. What is the precise mechanism that allows certain individuals with
dyslexia to overcome their low decoding abilities and ultimately extract
meaning from text?
A new joint Tel Aviv University and University of California San Francisco
study identifies the brain mechanism that accounts for the discrepancy between
low decoding skills and high reading comprehension.
The research was led jointly by Dr. Smadar Patael of TAU’s Department of
Communication Disorders and Prof. Fumiko Hoeft, who is currently at the
University of California San Francisco and starts as director of the University
of Connecticut’s Brain Imaging Research Center this fall. The research was
recently published in PLOS
One.
Measuring gray matter
The research points to a larger volume of gray matter in resilient readers
in the part of the brain responsible for executive functions and working
memory. This specific region, the dorsolateral prefrontal cortex (DLPFC) of the
left hemisphere, is known as the “air traffic controller” or “conductor” of the
brain. Gray matter is the darker tissue of the brain and spinal cord,
consisting mainly of nerve cell bodies and branching dendrites.
Researchers examined 55 English-speaking children aged 10-16 with a wide
range of reading abilities. Half of these children had been diagnosed with
dyslexia. The researchers created a simple formula to calculate the difference
between the reading abilities and decoding skills of the participants. The
participants were scanned with an MRI. The researchers then compared the mapped
images of the participants’ brains with their reading skill results.
“We wanted to find whether the brain regions related to language or other
regions were responsible,” says Dr. Patael. “We found that the region in the
left frontal part of the brain known as left DLPFC was directly related to this
discrepancy. DLPFC has been shown to be important for executive functions and
cognitive controls.”
The chicken or the egg?
“We then sought to understand answer a ‘chicken or egg’ question related to
dyslexia and the slight enlargement of this brain region,” Dr. Patael
continues. “Do resilient dyslexics have distinct brain structures that allow
for better resiliency, or is their success in reading a result of compensation
strategies that actually altered the density of neurons in a specific region of
the brain?”
To answer this question, Dr. Patael, Prof. Hoeft and their colleagues
scanned 43 kindergarteners using MRI technology, and then three years later
tested the children’s reading abilities. The researchers found that the density
of neurons in the DLPFC predated mature reading ability and predicted the
discrepancy, regardless of their initial reading abilities.
“This helps us to understand the brain and cognitive mechanisms these
children utilize to enable them to do well despite their relative weakness in
decoding. It may help us think about incorporating relatively new strategies
into reading interventions,” says Prof. Hoeft.
“Much of the curriculum of kindergarten reading readiness is focused on
learning sounds of letter and phonological awareness,” concludes Dr. Patael.
“Our research findings suggest new approaches that emphasize executive
functions and working memory. If your child is entering first grade, practicing
the alphabet may not be enough. Consider activities that require working
memory, such as baking cakes and playing song and strategy games. These
activities stimulate children’s working memory and may in time foster their
ability to comprehend texts well.”
The researchers are currently further exploring the neural mechanisms of
compensation and resilience.
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