Learning Disability Condition and Causes
What Causes Learning Disabilities?
It is believed that learning disabilities are caused by a difficulty with the nervous system that affects receiving, processing, or communicating information. Some learning disabled children are also hyperactive, easily distracted, and have a short attention span.
Dyslexia, which centers on difficulties in reading, initially confused scientists. For decades after researchers first described dyslexia, many people contended that it stemmed from a "slacker" attitude. Since dyslexics often have good intelligence and even may be gifted in some areas, it was thought that motivation could get them on the right track.
Then, almost a century later, scientists began to unearth hints that the disorder has biological causes. In 1979, a report indicated that anatomical abnormalities existed in a dyslexic patient. The left side of the brain of a 20-year-old who died accidentally depicted disorganization in the cells that control language areas. This finding caused researchers to investigate the brain's involvement in dyslexia.
Now researchers not only know that dyslexia is born of biology, but they also are getting closer to confirming the key brain areas that are affected. New insights will help pinpoint therapies and improve techniques.
Several Brain Regions May Be Responsible for Dyslexia
Many scientists have identified brain regions related to dyslexia with high-tech imaging techniques that photograph the brain in action. The tools have helped them link the disability to speech, sound processing, vision, and language brain systems. Today researchers are systematically scrutinizing large numbers of dyslexics to determine which areas of the brain are the most involved and to understand how they relate to each other and contribute to different degrees and varieties of the disability. Dyslexia's symptoms, which may include deficits in spelling, in recognizing sounds in words, in processing rapid visual information, and in saying words quickly when put on the spot, have made it difficult for researchers to tease apart the key brain regions involved.
While the areas most central to the disability are still uncertain, many researchers suspect that the brain areas that control language play a critical role. One of these areas that keeps coming up in studies is the angular gyrus (AG). Located toward the back of the brain, the AG translates the mass of words and letters we encounter in day-to-day life into language.
Some researchers believe the area, which is known to be involved in normal reading, is a key component of an overall "reading pathway" in the brain. Recent studies of a variety of reading and language tasks in dyslexic individuals showed less activity in the AG than those without the disability. Researchers suspect that this part of the brain does not function normally in dyslexics.
Some scientists speculate that dyslexics use the area inadequately and may compensate by using other brain areas, such as the inferior frontal gyrus, which is located in the front of the brain, and is associated with spoken language. For example, dyslexics who say the words they are reading under their breath may rely heavily on this area to get through a passage of text, according to one theory.
Learning Disability Researchers are Using Imaging Techniques to Treat Symptoms
Many researchers also are using imaging techniques to see if the behavioral interventions sometimes used to treat the symptoms of those with dyslexia actually modify brain activity. One group is reviewing three separate interventions thought to target either the brain system that processes written language, the speech sound processing system, or the visual system.
The results could help confirm the brain areas that are common to the many forms of the disability and lead to a fine-tuning of interventions.
Several imaging studies of reading and language skills show that the AG is involved in dyslexia. One group of researchers is currently studying how dyslexics perform Pig Latin tasks compared to normal readers. Pig Latin requires dissecting and reordering the sounds within a word.
For example, if a word begins with a consonant, the first letter is moved to the end of the word and "ay" is added. "Pig" becomes "igpay." It is a difficult test for dyslexics because it challenges their ability to sound out written words as well as their memory skills. The image above shows that activity in the AG is increased in a normal reader who performs the Pig Latin task. The researchers suspect that the activity will be lower in dyslexic readers.
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