ARTICLES AND PAPERS ABOUT DYSLEXIA
|Effective interventions for reading disability by Williams MC, LeCluyse K, Rock-Faucheux A. .|
|Transient & Sustained Processing - A Dual subsystem Theory of Reading Disability by Solan HA, Brannan J, Ficarra A, Byne R.|
|The Effects of Varying Luminance and Wavelength on Reading Ability in Good and Poor Readers: Is there a Transient System Deficit? By Solan, HA.|
|Colour and learning disability by Howell E, Stanley G.|
|Physiological and anatomical evidence for a magnocellular defect in developmental dyslexia by Livingstone MS, Rosen GD, Drislane FW, Galaburda AM|
|A Defective Visual Pathway In Children with Reading Disability by Lehmkuhle S, Garzia R, Turner L, Hash T, Baro J.|
|Study ties dyslexia to brain flaw by S. Blakeslee (New York Times)|
|Dyslexia Article (LondonDaily Mail)|
|Drs. Solan and Brannan's report in the July 1998 Journal of the American Optometric Association|
Source: Williams MC, LeCluyse K, Rock-Faucheux A. Effective interventions for reading disability. J of the Am. Optom. Assoc. 1992; 63: 411-17.
Abstract: "A simple, readily accessible, and inexpensive intervention which produces immediate improvements in the reading comprehension abilities of reading-disabled children has been found. The intervention consists of colored overlays, or overlays which reduce the contrast of printed materials. This intervention produces reading comprehension gains in approximately 80 percent of the reading-disabled children tested."
Source: Solan HA, Brannan J, Ficarra A, Byne R. Transient & Sustained Processing - A Dual subsystem Theory of Reading Disability. J Behavioral Optom. 1994; 5:149-154.
Abstract: "In this article the author reviews the concept of interactive processing that involves two parallel, segregated visual pathways, the transient and sustained processing systems. Evidence that deficits in the transient, but not the sustained system, interfere with the reading process is examined. After tracing these pathways from the retina to the visual cortex, and beyond, special attention is given to the mechanism of the dual processing system in reading, the synchronization of these two systems, and the effects of poor timing on visual processing and reading. Two successful treatment procedures for reading-disabled are described. The importance of integrating these concepts into optometric therapeutic procedures is discussed."
p.153 "...The second study [out of the two studies done] is directly concerned with improving reading. Williams, LeCluyse, and Rock-Faucheux conducted the research with 32 normal and 38 disabled readers, ages 8 to 12 years. They demonstrated that reading achievement in disabled readers could be improved by varying wavelength, luminance, or with image blurring. As noted earlier, the rate of transient processing increases when the wavelength of light is short (blue). By placing a blue acetate transparency over the white letters on a computer monitor, they obtained statistically significant improvement (p<0.05) in reading comprehension using a reading selection that was appropriate for the child. Further, compared to the no filter condition, a blue acetate transparency placed over the print in a book was equally effective in synchronizing the transient-sustained interaction when a transient system deficit existed."
Source: Solan, HA. The Effects of Varying Luminance and Wavelength on Reading Ability in Good and Poor Readers: Is there a Transient System Deficit? Am. Opt. Assoc. meeting, New Orleans: January 1996.
Source: Howell E, Stanley G. Colour and learning disability. Clinical And Experimental Optometry 1988; 71.2:66-71.
Abstract: "The history of the use of colour in therapy for learning disability is reviewed. Relevant recent research is discussed and it is concluded that there is no convincing evidence for a retinal defect as postulated by Irlen [Helen Irlen, an educational psychologist in California that has promoted commercially the use of tinted lenses for treating "scotopic sensitivity."]. Research to separate mood and motivational effects from visual effects is recommended."
Source: Livingstone MS, Rosen GD, Drislane FW, Galaburda AM. Physiological and anatomical evidence for a magnocellular defect in developmental dyslexia. Proc Natl Acad Sci 1991; 88: 7943-7947.
Abstract: "Several behavioral studies have shown that developmental dyslexics do poorly in tests requiring rapid visual processing. In primates fast, low-contrast visual information is carried by the magnocellular subdivision of the visual pathway, and slow, high-contrast information is carried by the parvocellular division. In this study, we found that dyslexic subjects showed diminished visually evoked potentials to rapid, low-contrast stimuli but normal responses to slow or high contrast stimuli. The abnormalities in the dyslexic subjects' evoked potentials were consistent with a defect in the magnocellular pathway at the level of visual area 1 or earlier. We then compared the lateral geniculate nuclei from five dyslexic brains to five control brains and found abnormalities in the magnocellular, but not the parvocellular, layers. Studies using auditory and somatosensory tests have shown that dyslexics do poorly in these modalities only when the tests require rapid discriminations. We therefore hypothesize that many cortical systems are similarly divided into a fast and a slow subdivision and that dyslexia specifically affects the fast subdivisions."
Source: Lehmkuhle S, Garzia R, Turner L, Hash T, Baro J. A Defective Visual Pathway In Children with Reading Disability. N En J Med 1993; 328:989-96.
Abstract: "Background. The possibility that reading disability in children is associated with visual problems is in dispute. We sought to test the existence of this association by using electrophysiologic techniques to measure the processing of visual information in the magnicellular and parvicellular visual pathways of the brain.
Methods: Visual evoked potentials were measured with scalp electrodes in children 8 to 11 years old who were normal readers and in those with reading disability. The potentials were measured for targets with low (0.5 cycle per degree of visual angle) and high (4.5 cycles per degree) spatial frequency, surrounded by either a steady background or a uniform-field flickering 12 times per second. A flickering field normally reduces the amplitude and increases the latency of a transient potential evoked by a low-spatial-frequency target, which preferentially excites the magnicellular visual pathway, but has little effect on the response to a high-spatial-frequency target.
Results: With a steady background, the latencies of the early components (N1 and P1) of the visual evoked potentials were longer in the reading-disabled children than in the normal readers when the low-spatial-frequency target was used, but not when the high-spatial-frequency target was used. In normal readers, the flickering background increased the latency and reduced the amplitude of the early components, whereas in the reading-disabled children only the amplitude was affected. No differences were observed in either group with the high-spatial-frequency target.
Conclusions: The pattern of results suggests that the response of the magnicellular visual pathway is slowed in reading-disabled children, who do not, however, have a general slowing of the visual response. The possibility that there is a cause-and-effect relation between these findings and reading disability will require further study."
Source: Blakeslee S. Study Ties Dyslexia to Brain Flaw Affecting Vision and Other Senses. The New York Times National; Sept 15, 1991: P1C3, P30,C3. (Copyright of the New York Times 1991)
Article: "A new finding about dyslexia suggests that the disorder may not be a malfunction in the way people understand language but rather a brain abnormality that involves the sense of vision, and perhaps also hearing and touch.
A team of prominent brain researchers reported yesterday that studies of living dyslexic people, as well as autopsies of dyslexic brains, suggested that the basis of the condition might be a failure of the visual system's circuits to keep proper timing.
'This is the first observation that the visual system may be involved in dyslexia, and it is extremely important,' said Dr. Drake Duane, an international authority on dyslexia and learning disorders at Arizona State University. 'It reinforces the idea that the nervous systems of those who are dyslexic are atypical.'
Dyslexia, a broad term that includes a number of disorders, affecting people's ability to read, is believed to affect 4 to 5 percent of the population, or some 12 million Americans. The new finding gives theoretical support to one method of treating dyslexia, through the use of color filters in reading. If validated, it is also likely to suggest novel kinds of therapy, Dr. Duane said.
The finding could lead to methods of detecting dyslexia in infancy, and treatments could begin in very early childhood when the brain's circuitry is most capable of changing. This raises the hope that children with the abnormality might be capable of learning to read by the time they entered school.
Links to Other Problems
'I am very excited about their results,' said Dr. Paula Tallal, a professor at Rutgers Center for Molecular and Behavioral Neurosciences. She said it appeared to support the notion that early language problems, dyslexia and physical clumsiness were manifestations of the same basic brain disorder.
Most experts view dyslexia as purely a language problem, said Dr. Albert Galaburda, director of the Dyslexia Neuroanatomical Laboratory at Beth Israel Hospital in Boston and a co-author of the report. In reading, dyslexics cannot break words down to their basic sounds, and they have lasting problems with the sound system of language, he said, even if their reading problems improve over time.
The role of vision in dyslexia was ignored, Dr. Galaburda said, in large part because opthamologists could find no differences between the eyes of good readers and bad readers.
This changed, he said, with the recent finding that the visual system in humans and other primates is composed of two major pathways.
One of these pathways, the magnocellular system, is composed of large cells that carry out fast processes. The pathway is used for seeing motion, stereoscopic vision, depth perception, low contrast and locating objects in space. It probably evolved to help animals see predators move through the night.
The second pathway, the parvocellular system, is composed of smaller cells that carry out slower processes. It specializes in color, detailed forms, high contrast and stationary images. It probably evolved to help primates see brightly colored fruit while swinging through the trees in broad daylight.
Question of Timing
Experimental psychologists in the United States and Australia had developed tests suggesting that there was some sluggishness in the visual systems of dyslexics, Dr. Livingstone said. When two visual stimuli were presented in rapid succession, she said, dyslexics reported seeing only one image. Normal people saw both. When the same stimuli were presented more slowly, she said, dyslexics saw both.
In the new study, five dyslexic and seven normal people were tested, Dr. Livingstone said. They were shown a 36-rectangle checkerboard on which the squares were reversed at different speeds under conditions of high and low contrast. Contrast is the ratio of brightness between two objects.
At high contrast, when both the magno and parvo system should be responsive, the dyslexics showed a normal response to rapidly changing checkerboards, Dr. Livingstone said.
But at low contrast, when only the fast magno system should be responsive, she said, the dyslexics showed a greatly diminished response, suggesting that their magno system was sluggish.
Dr. Galaburda then performed autopsies on five dyslexic brains and five normal brains. Looking at a major visual relay situation, he found that the parvocellular systems were similar in all brains. But the magnocellular layers were more disorganized and the cell bodies appeared smaller in the dyslexic brains, he said. Overall, the magnocellular system was 27 percent smaller in this crucial area of the visual system.
Smaller cell bodies are likely to conduct impulses more slowly, Dr. Galaburda said.
In one experiment, Dr. Tallal presented children with combinations of the same high and low tone and asked children to repeat what they heard. Normal children can discriminate tones presented 8 thousands of a second apart, she said, but language-impaired children need at least 300 such milliseconds between tones to recognize a difference.
Language-impaired children have great difficulty hearing the difference between sounds like "ba" and "da," said Dr. Tallal. The "b" and "d" sounds occur in the first 4 milliseconds, followed by a 40 millisecond transition to the "ah" sounds, she said. Language-impaired children cannot process sounds in that 40 millisecond time window, she said, and thus cannot hear the difference between "ba" and "da."
But when the sounds are synthesized on a computer so that the "b" and "d" sounds are artificially lengthened, she said, the children can discriminate between "ba" and "da." Children who practice hearing lengthened sounds on computers sometimes make permanent improvements in their speech, she added.
Dr. Tallal also found that children with language and reading impairments have a defect in their sense of touch and sometimes seem clumsy. When their hands are hidden under a table and one finger is touched, she said, they can identify that finger. But if two fingers are touched in rapid succession, the children only sense a single touch, she said.
Such children must make sense of the world without perceiving vast amounts of fast-moving visual, auditory and tactile information, said Dr. Tallal. They rely instead on context, facial expressions, repetition and other strategies to know what is going on, she said and are often not identified as having a learning problem until they enter primary school and try to learn to read.
Color Light Filters Help
Based on earlier research in this area, Dr. Mary Williams of the University of New Orleans has been experimenting with colored light filters to see if the two pathways of dyslexic children can be altered to become better timed.
Dr. Williams has found that reading through blue filters helps 80 percent of the children read better, and 8 percent are helped by red filters. The filters, which are pieces of transparent colored plastic like those sometimes used in overhead projectors, cost pennies apiece, she said.
Other researchers are trying to replicate the research and are optimistic, although exactly how the filters help the problem remains a mystery.
In what may be the most hotly disputed facet of the new research, a California psychologist, Helen Irlen, has been offering colored lenses and spectacles to dyslexic adults and children since 1983. Criticized as a charlatan whose remedy is without scientific basis, Dr. Irlen said three states have tried to ban her lenses from their schools, largely at the urging of optometrists.
But Dr. Irlen, whose Irlen Institute is in Long Beach, said she had never claimed to understand the theoretical basis of using colored lenses to treat dyslexia. She said that she based her work on research with dyslexic adults who said that the words literally swayed or rippled across the page, and sometimes vanished from view. The discovery that colored lenses help hold the words in place on the page was accidental, she said.
Related Avenue of Research
In a related avenue of research, scientists have found that animals can form antibodies that destroy a protein found only in the magnocellular system. This suggests that dyslexia could be an autoimmune disease acquired before or soon after birth, Dr. Galaburda said.
Thus, abnormally processed sights and sounds might
begin to shape the infants brain and cause it to be wired up differently from the start,
he said, suggesting that intervention s to help such children should begin as early as
Source: Daily Mail (London, UK); Jan 17, 1995. (Copyright Daily Mail 1995)
Article Exert: "Dyslexia or word blindness, affects around 2.5 million in the UK, but until recently scientists have not been able to find an effective treatment, let alone a cure, for this distressing condition.
Scientists at the Applied Psychology Unit in Cambridge, (UK) however, have now proved that spectacles fitted with colored lenses can ease reading and writing difficulties.
Dyslexia is the name given to a condition which causes difficulty in reading and writing, the letters and numbers appear jumbled or reversed. Letters such as 'b' or 'd' are confused and others are transposed, meaning dyslexics read or write 'pest' for 'step', for example.
The biggest clue to childhood dyslexia is the marked difference between a child's oral and written skills. And while dyslexia has no link with low intelligence, dyslexic children often have to endure taunts and teasing for 'being slow'.
A child may put its hand up in class and answer questions correctly but its work will be a mess, and badly structured. Severe disorganization seems to be a problem for dyslexics as well. Satisfying yourself that your child isn't dyslexic is much simpler: 'If you can spell, then you aren't dyslexic,' says Michael Nation, head of psychology at the Dyslexia Institute.
Although scientists have recently isolated the gene they think causes dyslexia, there is no known cure for the condition, nor any proven treatment.
It was 10 years ago that American psychologist Helen Irlen first hit upon the idea of using coloured lenses, worn in glasses, to help to counteract the reading difficulties experienced by dyslexics.
She covered text with a variety of coloured sheets of see-through plastic to see if a particular color would make reading easier. Her findings though were largely dismissed by the medical community as 'unscientific'.
Now it appears that her theories were correct. At the end of last year, the Applied Psychology Unit published the results of a two-year study into the use of coloured lenses. According to the unit's Dr. Arnold Wilkins, their study may well be the first scientific proof that dyslexia can actually be treated although not cured.
Research has shown that people with dyslexia are more likely than others to suffer from light sensitivity. Dr. Wilkins believes these problems can be caused by strong visual stimulation, such as black writing on a white page, causing an overload in the part of the brain which deals with sight. Coloured lenses seem to help block out this interference.
The lenses work in a similar fashion to looking at the sea through Polaroid sunglasses: the 'glare' from the page is cut down so outlines of individual letters appear sharper...
Nine year old Mathew Buckley, of Humberside, was discovered to be dyslexic when he was in his second year of school. 'His writing wasn't at the same level as the rest of his class and he was struggling with his reading,' explains his mother Janet, who is slightly dyslexic herself.
The Dyslexia Institute suggested that she try coloured
lenses, so she took Matthew to an optician in Lincoln. 'His sight was fine,' she says,
'but after some basic tests the optician gave him a mint-green plastic overlay to try for
six weeks.' This overlay was put over Matthew's books see if it helped him to read letters
more clearly. As this basic trial was a success..., he was prescribed a pair of spectacles
tinted a similar colour. The results were even better.
Says Dr. Bruce Evans of the Institute of Optometry, 'It can help with good reading , but where there are education problems, these need to be addressed in different ways.'
He recommends that children with learning difficulties should first see an optometrist to determine whether there are any underlying visual problems. If the child's vision is otherwise fine, then coloured overlays are used over text first. Children use the overlays for one term before returning to an Optometrist equipped... to determine the correct colour for the lenses."