Researchers at two universities have concluded that the condition known as dyslexia may be rooted in problems with basic sensory perception, rather than deficits in certain visual processes, as commonly thought.
The researchers, at the University of Wisconsin-Madison and the University of Southern California, said the finding not only contradicts the popular theory, but also suggests new ways of identifying people who suffer from dyslexia, and of assessing techniques used by teachers to help dyslexic students.
Anne Sperling, a USC neuroscientist and lead author of the study, said misfiring neurons make it difficult for dyslexics to differentiate between relevant visual and auditory cues from surrounding sounds and patterns -- what scientists refer to as "noise." This could be why dyslexic children find it difficult to read, she said.
"(We think) that if a child has a hard time ignoring noise, it could distort speech perception and complicate (the recognition) of sound segments, which is essential for learning how to read," Sperling said in a statement.
Sperling and colleagues studied 28 dyslexic and 27 non-dyslexic children who were asked to detect a pattern embedded in visual noise -- an array of static-like bright and dark spots. They found although dyslexic children were just as able as their peers to distinguish displays with patterns only, they struggled to isolate those same patterns when they were mixed in with the noise.
Dyslexia, a brain-based type of learning disability, affects between 5 percent and 10 percent of children in the United States. Those afflicted with the condition typically read at levels significantly lower than normal despite possessing normal intelligence. They also have difficulties with verbal skills, hand-eye coordination, concentration and memory.
At first, researchers in the 1920s suggested dyslexic children sometimes spell words backwards because they have trouble with visual perception. Recently, however, researchers have discovered that dyslexic reading problems are linked to the inability to blend phonemes -- phonetic units of sound humans use to distinguish words.
Children need to identify certain sounds that go with spoken words, because they will make it easier for them to learn how to pronounce letters, according to Mark Seidenberg, the study's co-author and a UWM psychology professor.
"For some reason (dyslexic children) are not developing knowledge of phonemes," Seidenberg said in the same statement. "This has little impact on their spoken language, but really interferes with learning to read."
J. Thomas Viall, executive director of The International Dyslexia Association was not surprised by the results of the study.
"It is a common misconception that dyslexia is a visual problem," he told United Press International. "This is nothing brand new."
Dr. Zhong-Lin Lu, also a USC neuroscientist involved in the research, said it not only proved the old hypothesis about dyslexia was incorrect, but it also created a new hypothesis.
"The (dyslexic) problem is more generic in nature and it comes down to it being a deficit in discriminating auditory stimuli," he told UPI.
The researchers are now discussing techniques teachers could use to provide better help to dyslexic children in the classroom, Lu said.
One example, Sperling said, is for teachers to "accentuate differences between sounds, showing the extremes to help (dyslexic children) build categories."
"We hope the study will help us better understand how to treat children with dyslexia and facilitate teachers (in helping children with dyslexia) as well." Lu said.
--
Katherine Torres is an intern for UPI Science News. E-mail: [email protected]
