Dyslexia refers to any reading difficulty not associated with obvious problems such as bad eyesight.More problems can include the brain being extremely or mildly jumbled. Dyslexias include the inability to name letters, to read words or sentences, or to recognize words directly even though they can be sounded out. Dyslexia is not limited to reversing the order of letters in reading or writing, as is often implied in popular culture; it may, for instance, include unexpected spelling mistakes and unusual syntax, and may be associated with dyscalculia. Most theories focus on nonprimary areas in the frontal lobe and the temporal lobe. (Galaburda, 1994; Rosenzweig, Lieman, et al., 1996;) Recent studies have linked several forms of dyslexia to genetic markers (Grigorenko, 2001; Grigorenko etal., 1997; Grigorenko, Wood, Meyer, & Pauls, 2000).
It is said to be a neurological disorder with biochemical and genetic markers. Dyslexia was originally defined as a difficulty with reading and writing that could not be explained by general intelligence. One diagnostic approach is to compare their ability in areas such as reading and writing to that which would be predicted by his or her general level of intelligence.
The term was coined in 1884 by R. Berlin. People are diagnosed as dyslexic when their reading problems cannot be explained by a lack of intellectual ability, inadequate instruction, or sensory problems such as poor eyesight.
Dyslexia International definitions.
Dyslexia is widely accepted in the international community as a learning disability. The most widely accepted theories argue that the dyslexic individual has biological traits that differentiate them from other individuals.
The World Health Organization (WHO)
A disorder manifested by difficulty learning to read, despite conventional instruction, adequate intelligence and sociocultural opportunity. It is dependent upon fundamental cognitive disabilities which are frequently of constitutional origin". ICD-10, The International Statistical Classification of Diseases and Related Health Problems, tenth revision ICIDH-2, The International Classification of Impairments, Activities, and Participation
US National Institute of Child Health and Human Development (NICHD) / International Dyslexia Association
Defines Dyslexia as a specific learning disability of neurological origin. Characterized with difficulties with accurate and/or fluent word recognition, spelling and decoding abilities.
Canadian Government
The Government of Canada's Health Portal links its description to the BC HealthGuide web site using their definition. Dyslexia is defined here with a difficulty with the alphabet, reading, writing, and spelling in spite of normal to above average intelligence, conventional teaching, and adequate sociocultural opportunity. Dyslexia is thought to be genetic and hereditary. Dyslexia is not caused by poor vision. Dyslexia is diagnosed following psychological and educational tests that determine language and other academic abilities, IQ and problem-solving skills, and is only diagnosed if the reading disability is not a result of another condition.
The British Dyslexia Association
Dyslexia is a difference in the brain area that deals with language. It affects the underlaying skills that are needed for learning to read, write and spell. Brain imaging techniques show that dyslexic people process information differently.In a report on the House of Lords Dyslexia debate which took place on Wednesday 7 December is now available the Government confirms dyslexia is not a myth.
Variations and related disorders
Dyslexia is a learning disorder. Its underlying cause may be neurological in nature, but from there, the systems involved play out into visual, language, etc. FMRI (Functional Magnetic Resonance Imaging) has been used to demonstrate differences in the dyslexic brain patterns, but much research still needs to be done to apply this information.In addition to the typical forms of dyslexia, there are numerous related disorders:
Facts and Statistics
Between 5 and 15 percent of the population can be diagnosed as suffering from various degrees of dyslexia. As previously mentioned, dyslexia can be substantially compensated for with proper therapy, training and equipment.
Most researchers agree that there is a fairly even gender balance amongst dyslexics, and that the fact that it is reported more in males is because of selection factors and bias.
Dyslexia's main manifestation is a difficulty in developing reading skills in elementary school children. Those difficulties result from reduced ability to associate visual symbols with verbal sounds. While motivational factors must also be reviewed in assessing poor performance, dyslexia is considered to be an inborn trait and rarely arises from environmental factors after the brain has matured beyond its especially plastic condition during infancy.
Physiology and Treatment
Only traditional educational remedial techniques have any record of improving the reading ability of those diagnosed with dyslexia. There is no evidence that coloured lenses, any visual training, or similar proposed treatments are of any use. Anecdotal reports of success can be explained by other factors.
Even a few weeks of intense phonological training (often involving breaking down and rearranging sounds to produce different words) can help noticeably improve reading skills. The earlier the phonological regimen is taken on, the better the overall result. Advanced brain scans could identify children at risk of dyslexia before they can even read, although it is thought that simple tests of balance could do the same. It is claimed that many of the underlying causes of dyslexia are of a genetic nature and that there are no cures, only strategies to work around the causes of a persons dyslexia, however these two claims are disputed.
It had been believed that keeping a child active, perhaps by giving them housework, or performing physical exercises, would help with dyslexia. However, this is false (Wilsher 2002 - Dyslexia, Volume 8, Number 2, April/June 2002, pp. 116-117(2)). There is no scientific evidence in support of this theory.
Researchers studying the brains of dyslexics have found that during reading tasks, dyslexics show reduced activity in the left inferior parietal cortex. It is anecdotally claimed that it is not that uncommon for dyslexics who have trained themselves to cope with their affliction, to develop uncannily efficient visual memories which aid in reading and comprehending large quantities of information much faster than is typical. Commonly dyslexics show 10 times more brain activity when reading. Sometimes, depending of the type and extent, also writing, listening and speaking. However, increased brain activity is not necessarily a sign of better processing. Conversely, some dyslexics may show a natural dislike of reading and, in consequence, compensate by developing unique verbal communication skills, inter-personal expertise, and leadership skills.
In 1979, anatomical differences in the brain of a young dyslexic were documented. Albert Galaburda of Harvard Medical School noticed that the language center in a dyslexic brain showed microscopic flaws known as ectopias and microgyria. Both affect the normal six-layer structure of the cortex. An ectopia is a collection of neurons that have pushed up from lower cortical layers into the outermost one. A microgyrus is an area of cortex that includes only four layers instead of six.
These flaws affect connectivity and functionality of the cortex in critical areas related to auditory processing and visual processing. These and similar structural abnormalities may be the basis of the inevitable and hard to overcome difficulty in reading.Another study regarding genetic regions on chromosomes 1 and 6 have been found that might be linked to dyslexia. Presenting the argument, dyslexia is a conglomeration of disorders that all affect similar and associated areas of the cortex.
Some studies have concluded that speakers of languages whose orthography has a strong correspondence between letter and sound (e.g. Korean and Italian) have a much lower incidence of dyslexia than speakers of languages where the letter is less closely linked to the sound (e.g. English and French).
Characteristics
Ronald D. Davis places forth the argument that most dyslexics will exhibit about 10 of the following traits and behaviors. These characteristics can vary from day-to-day or minute-to-minute. The most consistent thing about dyslexics is their inconsistency. Symptoms increase dramatically with confusion, time pressure, emotional stress, or poor health. This may vary according to which of the suggested underlying causes of dyslexia affect the individual dyslexic.
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