Science & Health: Scientists search for causes of learning disorders

Students with learning disorders made up 156 of the cases of
students served by the UCLA Office of Students with Disabilities
last year.

But unlike many of the students served by the office, these
students struggle with disorders which have no known cure and
cannot be located.

Learning disorders affect a person’s ability to either
interpret what they see and hear or influence the way information
is linked to different parts of the brain.

“A learning disorder is a selective deficit in your
ability to process information,” said Dr. Alcino Silva, a
professor of neurobiology, psychiatry and psychology at the UCLA
David Geffen School of Medicine who focuses specifically on
mechanisms of learning and memory. “An individual’s
mental processes are normal except for in one area.”

According to ldonline.org, a learning disability Web site, the
most common learning disabilities are dyslexia, dyscalculia and
dysgraphia.

Dyslexia is a language-based disability which causes a person to
have trouble understanding written words, dyscalculia is a
condition where a person has difficulty solving arithmetic
problems, and dysgraphia is a condition in which a person finds it
hard to form letters or write within a defined space.

Scientists currently do not know what exactly causes learning
disabilities because most of them do not stem from a single,
specific area of the brain, but from difficulties in bringing
together information from various regions of the brain.

“The problem is that we don’t know the biological
mechanisms of learning disorders,” Silva said.

Instead of looking at biological factors, learning disabilities
are diagnosed by evaluating an individual’s intelligence,
often using IQ tests, and comparing the results with his or her
academic performance.

“We know some of the molecular and cellular biology of
learning and memory, so it follows that learning disabilities will
be associated with those areas, but how compelling is the evidence
that any one of these components is responsible for specific forms
of learning disability?” Silva said.

There have been some gains in determining specific aspects of
genetic mutation learning disabilities, but these types are
uncommon and make up only a small percentage of cases.

Learning disabilities and attention disorders, such as attention
deficit hyperactivity disorder, are not the same, but often occur
at the same time.

Melissa Del’Homme, associate director of the ADHD program
at UCLA, said about eight percent to 10 percent of the school-age
population has learning disabilities, and students with ADHD are 25
percent more likely to have a learning disorder.

Part of the reason the biological aspect of learning disorders
is unclear is due to a lack of research in the area, Silva
said.

Silva added that the study of learning disabilities does not
receive as much funding as other brain study efforts.

“For learning disorders we haven’t had a coordinated
national effort to understand why it happens,” Silva
said.

Silva said that, unlike ADHD, learning disabilities are
currently not addressed through medication.

“There haven’t been major initiatives to create
drugs for learning disabilities,” Silva said.

But Silva said companies are beginning to look at creating
cognitive enhancers, drugs or dietary supplements that work to
improve memory or other cognitive function for any individual, but
could be used to correct learning disabilities.