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Children's
Reading Disability Attributed to Brain Impairment
from the National Institute of
Child Health and Human Development, August 2, 2002
Children who are poor readers appear to have a disruption in the
part of their brain involved in reading phonetically, according
to a sophisticated brain imaging study funded by the National
Institute of Child Health and Human Development (NICHD).
The study also found that
children who read poorly but who do not receive any extra help
or training eventually compensate for their disability by using
other parts of the brain as backup systems for the impaired
brain regions.
Although most of these children
eventually do learn to read, they never do so with the same
fluency as do good readers. This is probably because the
"backup" brain systems they use when reading apparently cannot
process printed information as easily as can the brain systems
primarily involved in reading. The researchers, led by
Bennett Shaywitz, M.D., of the Yale University School of
Medicine, published their results in the July "Biological
Psychiatry".
"This study shows us the physical
basis of why some children have difficulty reading," said Duane
Alexander, M.D., Director of the NICHD. "We are now in a
position to observe the brain changes that take place when poor
readers receive the training that allows them to become
proficient readers. In turn, this knowledge may allow us to
design even more effective therapies to help poor readers
overcome their disability." In the study, the researchers
used a technology known as functional magnetic resonance imaging
(fMRI), which produced computer-generated images of the brain
while the children were reading. With fMRI, the team
demonstrated differences in brain images between children with
dyslexia and non-reading impaired control children. The
disruption in the brain systems for reading was evident when the
children performed phonologic tasks, that is, tasks that
required knowing the sound structure of words. Written English
is a kind of code -- letters or combinations of letters stand
for the individual sounds within words. The reading impaired
children had difficulty with tasks that required interpretation
of this code.
Dr. Shaywitz noted that the
current study with children confirmed the researchers' earlier
finding with adults that people with dyslexia have an impairment
in the brain regions involved with reading words phonetically.
And like adults with dyslexia, they use an alternate brain
region as a backup system when reading. [The earlier study is
described at:
http://www.nichd.nih.gov/new/releases/dyslexianews.cfm.]
"The study shows some very important findings," Dr. Shaywitz
said. "First it identifies neural pathways for reading in good
readers while showing a disruption of these pathways in children
who are dyslexic (Fig 1). " Second, Dr. Shaywitz explained, the
study identifies a region for skilled reading in the the brain
area known as the left occipito-temporal region (Fig. 2). Better
readers are more likely to activate this region than are poor
readers. Third, the study shows areas of compensatory systems in
the front and the right side of the brain in dyslexic children
who are older (Fig.3).
These three images can be found at
http://www.nichd.nih.gov/new/releases/reading_disability.htm.
The researchers tested the
ability of children to rhyme nonsense words, for example, asking
them: "Do [LEAT] and [JETE] rhyme?" The children were also asked
to determine the category of real words-- "Are [CORN] and [RICE]
in the same category?" These tasks require children to use
phonology, that is, their knowledge of the sound structure of
words, which is very difficult for dyslexic readers. Shaywitz
and his collaborators used fMRI to study 144 children ranging in
age from 7 to 18 years, 70 dyslexic readers (21 girls, 49 boys)
and 74 nonimpaired readers (31 girls, 43 boys ).
"Our findings show that the
impairment in the brains of children with reading disability
persists into adulthood," said another author of the study, G.
Reid Lyon, Chief of NICHD's Child Development and Behavior
Branch. "The findings provide compelling evidence that children
with reading disabilities need to receive educational services
to help them overcome their disabilities."
Dr. Lyon added that NICHD-funded research has shown that such
services should have a firm foundation in phonological
awareness. Before most poor readers can learn to read
successfully, he said, they need to learn that spoken words can
be broken apart into smaller segments called phonemes. Next,
they usually require training in phonics- "mapping" phonemes to
the printed words on a page. Once children have mastered these
steps, they can then receive training to help them read
fluently, and to comprehend what they read.
The NICHD is part of the National
Institutes of Health, the biomedical research arm of the federal
government. The Institute sponsors research on development,
before and after birth; maternal, child, and family health;
reproductive biology and population issues; and medical
rehabilitation. NICHD publications, as well as information about
the Institute, are available from the NICHD Web site,
http://www.nichd.nih.gov,
or from the NICHD Clearinghouse, 1-800-370-2943; e-mail
NICHDClearinghouse@mail.nih.gov.
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