The Brain and Dyslexia

February 16, 2001
Web posted at: 11:40 AM EST (1640 GMT)

SAN FRANCISCO, California (AP) — Discovery of a deficit in key reading and
visual centers of the brain could lead to early diagnosis and treatment for a
disorder that affects about 15 percent of the population, researchers report.

A study at Georgetown University Medical Center in Washington suggests that
people with dyslexia have a much lower level of activity in the brain’s left inferior
parietal, an area that is important both in reading and in processing of visual
images.

Dr. Guinevere Eden and Dr. Thomas Zeffiro, a husband and wife team and
co-directors of the Center for the Study of Learning at Georgetown, also found
that the right inferior parietal can be taught to compensate for the weakness in
the left side of the brain through a program of intense reading training.

“These study results are further evidence that dyslexia has biological roots,” said
Eden. She and Zeffiro discussed their study Thursday at the national meeting of
the American Association for the Advancement of Science.

Dyslexia is generally diagnosed in elementary school children who have great
difficulty learning to read. The core of this difficulty, said Eden, is the inability to
link up visual symbols with sounds, an essential process in reading.

A youngster with dyslexia, for instance, could not associate the sounds in the
spoken word “cat” with the letters that make up the simple word, said Eden.

It is estimated that 5 percent to 15 percent of the population suffers from some
degree of dyslexia, she said. Some learn to compensate and eventually become
good readers, but Eden said many adults cannot read because the problem was
not identified and treated during their school years.

In their study, Eden and Zeffiro used functional magnetic resonance imaging, a
technique that, in effect, takes pictures of the brain while thinking processes are
under way.

The test involved reading and following the direction of moving dots on a screen.

In the test, they compared 20 people with dyslexia with 17 without the disorder.

Among those without the disorder, the left inferior parietal region was very
active. But for those with dyslexia, there was significantly less activity.

Eden said the findings are important because they suggest it might eventually be
possible to develop a test that would identify dyslexic children at a very early
age.

“Today we are able to diagnose dyslexia only after children have shown difficulty
in learning to read, usually around the time they’re in second or third grade,”
Zeffiro said in a statement. “If we know that the same areas of the brain used for
reading are also used to perform other types of visual tasks, then we can test
children before they reach reading age.”

Eden said it may be possible to perform such tests in children as young as four
or five.

In another study, Eden said two groups of 10 adults, all with dyslexia, received
MRI brain scans to establish their individual level of brain activity during reading
and visual activities.

Then one group was put through an intensive, eight-week program of training in
reading. The other group of 10 did not receive such training.

At the end of the period, Eden said, all 20 adults were again given brain scans
while performing reading and visual activities.

The adults who had received the training showed increased activity in the right
inferior parietal, while those without the training had no difference in the brain
scan.

“This shows that the brain, even in adults, is plastic, that it can be made to
compensate,” said Eden.

She said it is a myth that the defining characteristic of dyslexics is the tendency
to see letters reversed.

Virtually all children have this problem to some degree, but outgrow it, she said.
The reversals were long considered a primary symptom of dyslexia simply
because it takes much longer for dyslexics to overcome the problem, she said.

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