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Dyslexia in Wikipedia

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Dyslexia". (Source - Retrieved 2006-09-07 14:11:39 from http://en.wikipedia.org/wiki/Dyslexia)

Introduction

Developmental Dyslexia is a condition which causes difficulty with reading and writing. It is a learning disability that is likely present from birth. Its standard definition is a difficulty in reading and writing in spite of normal development of intelligence, cognitive and sensory abilities.

The word "dyslexia" comes from the Greek words δυς- dys- ("difficulty with") and λέξις lexis ("words" or "lexicon"). It is a brain-based condition with biochemical and genetic markers$[1]$$[2]$$[3]$. People are identified as dyslexic when their reading or writing problems cannot be explained by a lack of intellectual ability, inadequate instruction, or sensory problems such as poor eyesight.

The term dyslexia is also sometimes used to refer to the the loss of reading ability following brain damage. This form of dyslexia is more often referred to as either acquired dyslexia or "Alexia". Dyslexia primarily impacts reading and writing abilities; however, other difficulties have been identified including deficits in processing spoken language$[4] as well as non-language difficulties[5]$.

Dyslexia is not limited to reversing the order of letters in reading or writing. Nor is it a visual perception deficit that involves reading letters or words backwards or upside down, as is often implied in popular culture.

Because writing systems vary across languages, the specific reading difficulties exhibited by individuals with dyslexia will also tend to vary across languages.$[6]$ However, dyslexia occurs in all societies with writing systems. It is typically marked by difficulty in the speed and efficiency with which an individual reads and writes. It can also be accompanied by other non-reading difficulties such as poor phonological awareness and short-term memory.

History

The term 'dyslexia' was coined in 1884 by R. Berlin $[7]$. He used the term to refer to a case of a young boy who had a severe impairment in learning to read and write in spite of showing typical intellectual and physical abilities in all other respects.

Several years later, W. Pringle Morgan, a British physician, published a description of a reading-specific learning disorder in a letter to the British Medical Journal. His letter described the case of a boy named Percy who, at age 14, had not yet learned to read, yet he showed normal intelligence and was generally adept at other activities typical of children of that age.


Much of the scientific research focusing on dyslexia throughout the $20th century$ focused on the idea that dyslexia stems from a visual deficit. This notion has persisted in popular culture, where it is commonly believed that dyslexia involves reading words backwards or upside-down. Nevertheless, research has failed to demonstrate that individuals with dyslexia perceive words or other visual objects differently from individuals with typical reading abilities.

A key early researcher in dyslexia was Samuel Orton. Orton coined the term strephosymbolia (meaning 'twisted signs') to describe his theory that individuals with dyslexia had difficulty associating the visual forms of words with their spoken forms $[8]$. Orton observed that reading deficits in dyslexia did not seem to stem from strictly visual deficits$[9]$. He also noted that many individuals with dyslexia were also left-handed, although this finding has been difficult to replicate and its significance continues to be hotly debated$[10]$.

In the 1970s, a new hypothesis emerged that suggested dyslexia stems from a deficit in processing the phonological form of speech. This theory suggests that reading problems in dyslexia stem from difficulty decomposing spoken words into discrete phonemes (e.g., breaking the word CAT into 'k', 'ah', and 't' sounds). As a result, affected individuals have difficulty associating these sounds with the visual letters that make up written words. Key studies of the phonological deficit hypothesis include the finding that the strongest predictor of reading success in school age children is phonological awareness$[11]$, and that phonological awareness instruction can improve reading scores in children with reading difficulties$[12]$.

Dyslexia Definitions

Dyslexia is widely accepted to be a specific learning disability. That is, dyslexia has biological traits that differentiate it from other learning disabilities. However, the specific definition of dyslexia varies somewhat across communities.

Dyslexia or Reading Disorder is defined in the Diagnostic and Statistical Manual of Mental Disorders DSM-IV as reading achievement that falls substantially below expected levels given an individual's age and education. The reading deficit should be sufficiently severe as to interfere with everyday activities requiring reading (e.g., schoolwork or employment). Finally, the reading deficit cannot be strictly due to a sensory disorder; for instance, it cannot be strictly due to vision problems that prevent an individual from seeing words on a page.

Several national and international organizations have also set out definitions of dyslexia as follows:

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 having 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 both genetic and hereditary. Dyslexia is not caused by poor vision. Dyslexia is identified following psychological and educational tests that determine language and other academic abilities, IQ and problem-solving skills, and is only identified 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 underlying 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 December 7, 2005, the government confirms that dyslexia is not a myth.

Biological Bases of Dyslexia

Developmental dyslexia appears to be the result of differences in affected individuals' neural organization for language and reading. Developmental dyslexia also appears to have a genetic component, such that it can tend to occur in multiple members of the same family. Reading difficulties in dyslexia can vary in their severity. The condition is not restricted to childhood, but can persist through adulthood. In addition, while early reports suggested dyslexia is more prevalent in boys, more recent studies have indicated it is not sex-linked, and occurs both in boys and girls with equal frequency.

Most theories focus on non-primary areas in the frontal lobe and the temporal lobe$[13]$. Studies have linked several forms of dyslexia to genetic markers$[14]$$[15]$$[16]$.

Variations and related conditions

Dyslexia is a learning disorder. Its underlying cause is believed to be a brain-based condition that influences the ability to read written language. It is identified in individuals who fail to learn to read in the absence of a verbal or nonverbal intellectual impairment, sensory deficit (e.g., a visual deficit or hearing loss), pervasive developmental deficit or a frank neurological impairment. The following conditions are sometimes confused with dyslexia because they can also lead to difficulty reading:

  • Auditory Processing Disorder is a condition that affects the ability to encode auditory information. It can lead to problems with auditory working memory and auditory sequencing.
  • Dyspraxia is a neurological condition characterized by a marked difficulty in carrying out routine tasks involving balance, fine-motor control, and kinesthetic coordination. This is most common in dyslexics who also have an attention deficit disorder.
  • Verbal Dyspraxia is a neurological condition characterized by marked difficulty in the use of speech sounds, which is the result of an immaturity in the speech production area of the brain.
  • Dysgraphia is a neurological condition characterized by distorted and incorrect handwriting.
  • Dyscalculia is a neurological condition characterized by a problem with learning fundamentals and one or more of the basic numerical skills. Often people with this condition can understand very complex mathematical concepts and principles but have difficulty processing formulas and even basic addition and subtraction.

Facts and statistics

Between 5 and 15 percent of the population can be diagnosed as suffering from various degrees of dyslexia.

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 present from birth. Most scientific criteria for dyslexia exclude cases that can be explained as arising from environmental factors such as lack of education or sensory deficits.

Current scientific theories focus on the hypothesis that dyslexia stems from a deficit in phonological awareness. This hypothesis suggests that affected individuals have difficulty analyzing the words they hear into discrete segments (such as phonemes), which in turn leads to difficulty learning spelling-sound correspondences.

Dyslexia can be substantially compensated for with proper therapy, training, and equipment.

The current consensus is that dyslexia occurs in both sexes with equal frequency. It was previously reported more frequently in males, likely due to selection factors and bias.

Although they are different conditions, dyslexia co-occurs with attention deficit disorders (ADD or ADHD) at a rate of 30-50%.

Treatment

Only traditional educational remedial techniques have any record of improving the reading ability of those identified with dyslexia $[17]$.

Remedial efforts focusing on phonological awareness training (often involving breaking words into their basic sounds and rearranging these sounds to produce different words) can improve reading skills. The earlier the phonological regimen is taken on, the better the overall result.

There is no evidence that colored lenses, any visual training, or similar proposed treatments are of any use. Anecdotal reports of success can be explained by other factors. Similarly, the belief that keeping a child active, perhaps through housework or physical exercise, will help with dyslexia is false $[18]$.

Physiology

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. Some dyslexics may show a natural dislike of reading and, in consequence, compensate by developing unique verbal communication skills, interpersonal expertise, visual-spatial abilities, 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 the 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, which seems consistent with the hypothesis that dyslexia stems from a phonological awareness deficit.

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 conditions that all affect similar and associated areas of the cortex.

Effect of Language Orthography

Some studies have concluded that speakers of languages whose orthography has a strong correspondence between letter and sound (e.g. Korean, Italian and Spanish) suffer less from effects of dyslexia than speakers of languages where the letter is less closely linked to the sound (e.g. English and French). $[19]$

In one of these studies, reported in Seymour et al.$[20]$, the word-reading accuracy of first-grade children of different European languages was measured. English children had an accuracy of just 40%, whereas among children of most other European languages accuracy was about 95%, with French and Danish children somewhere in the middle at about 75%; Danish and French are known to have an irregular pronunciation.

However, this does not mean that dyslexia is caused by orthography: instead, Ziegler et al.$[21]$ claim that the dyslexia suffered by German or Italian dyslectics is of the same kind as the one suffered by the English ones, supporting the theory that the origin of dyslexia is biological. However, dyslexia has more pronounced effects on more difficult languages.

Characteristics

Diagnosis of dyslexia is made by a qualified professional. It is typically made on an exclusionary basis—that is, dyslexia is only identified when reading difficulties cannot be explained as resulting from a more general impairment affecting sensory or neurological abilities.

Recent advances in neuroimaging and genetics could help identify children at risk of dyslexia before they learn to read, however none of these techniques are currently being used for this purpose. Currently, the only way to positively diagnose dyslexia is through behavioral testing.

The following characteristics have been adapted from R. D. Davis, 37 Common Characteristics of Dyslexia.$[22]$

General

Individuals with dyslexia:

  • Appear bright, intelligent, and articulate but are unable to read, write, or spell at an age-appropriate level.
  • Have average- to above-average intelligence, yet may have poor academic achievement; may have good oral language abilities but will perform much more poorly on similar written-language tests.
  • Might be labelled lazy, dumb, careless, immature, "not trying hard enough," or as having a "behavior problem."
  • Because dyslexia primarily affects reading while sparing other intellectual abilities, affected individuals might be categorised as not "behind enough" or "bad enough" to receive additional help in a school setting.
  • Might feel dumb and have poor self-esteem, and might be easily frustrated and emotional about school reading or testing.
  • Might try to hide their reading weaknesses with ingenious compensatory "strategies".
  • Might learn best through hands-on experience, demonstrations, experimentation, observation, and visual aids.
  • Can show talents in other areas such as art, drama, music, sports, mechanics, story-telling, sales, business, designing, building, or engineering.
  • Have related problems with inattention in a school setting; for instance they might seem to "zone out" or daydream often; get lost easily or lose track of time; and have difficulty sustaining attention.

Vision, reading, and spelling

Contrary to how it has been portrayed in the popular press, individuals with dyslexia do not perceive words backwards or upside down. In fact, visual problems are typically ruled out before a diagnosis of dyslexia can be made. Early studies of dyslexia did focus on the possibility that dyslexia is caused by visual difficulties, however very little evidence was found to support this theory. Likewise, there is little evidence that visual training provides effective treatment.$[23]$.

  • A popular theory in the 1970s suggested dyslexics may have Meares-Irlen Syndrome, a visual deficit in which the glare of the white page against black letters causes the words to shake, shiver, spin, etc. after a few minutes of reading. The proposed treatment was the use of colored plastic overlays that were thought help anchor the words to the page. This treatment has fallen out of favor as scientific studies have failed to support these claims. (See link below to asfedia).
  • Spelling errors - Because of difficulty learning letter-sound correspondences, individuals with dyslexia might tend to misspell words, or leave vowels out of words (e.g., spelling "magic" as mjc).
  • Reading - Due to dyslexics' excellent long term memory, young students tend to memorize beginning readers, but are unable to read individual words or phrases.

Writing and motor skills

Because of literacy problems, an individual with dyslexia may have difficulty with handwriting. However, slow or messy handwriting should not be confused with dyslexia.

Some studies have also reported gross motor difficulties in dyslexia, including motor skills disorder. This difficulty is indicated by clumsiness and poor coordination. The relationship between motor skills and reading difficulties is poorly understood but could be linked to the role of the cerebellum in the development of reading and motor abilities.$[24]$.

Math abilities

Dyslexia should not be confused with dyscalculia, a learning disability marked by severe difficulties with mathematics. Individuals with dyslexia can be gifted in math while having poor reading skills. However, in spite of this they might have difficulty with word problems (i.e., math problems that rely on written text rather than numbers or formulas).

Public support

In the United States, Canada, New Zealand and in the United Kingdom, some people say that there is a lack of adequate support and a general lack of interest in the learning disabilities of children in public schools. This has recently led to legal action by private parties against public schools in the United States and state schools in the United Kingdom. In English law, the recent case of Skipper v Calderdale Metropolitan Borough School (2006) EWCA Civ 238 the Court of Appeal applied Phelps v London Borough of Hillingdon (2001) 2 AC 619 as the landmark case on the failure to diagnose dyslexia (see duty of care in English law), and to hold that the appellant could pursue her claim against her school for humiliation, lost confidence, and lost self-esteem, and for loss of earnings following its failing to diagnose and treat her dyslexia despite the fact that, as Latham LJ. says at para 29:

"The extent to which her dyslexia could have been ameliorated or provided for will always remain uncertain, as will the extent to which that would have affected her performance in public examinations; the evidence that we have includes material to suggest that she, not surprisingly, reacted adversely to the break-up of her parents marriage when she was 15, in other words at a critical time in her education. Whether any improvement in her examination results would have led to her life taking a significantly different course will also be a matter for some speculation."

Some charitable organizations like the Scottish Rite Foundation have undertaken the task of testing for dyslexia and making training classes and materials available, often without cost, for teachers and students.$[25]$$[26]$$[27]$

In England and Wales, the failure of schools to diagnose and provide remedial help for dyslexia following the House of Lords decision in the case of Pamela Phelps has created an entitlement for students with dyslexia in Higher Education to receive support funded via the Disabled Students Allowance. Support can take the form of IT equipment (software and hardware) as well as personal assistance, also known as non-medical helper support. Dyslexic students will also be entitled to special provision in examinations such as additional time to allow them to read and comprehend exam questions.

The British Disability Discrimination Act also covers dyslexia.

"In some cases, people have 'coping strategies' which cease to work in certain circumstances (for example, where someone who stutters or has dyslexia is placed under stress). If it is possible that a person's ability to manage the effects of the impairment will break down so that these effects will sometimes occur, this possibility must be taken into account when assessing the effects of the impairment." — Paragraph A8, Guidance to the Definitions of Disability

Controversy

Some disagreement exists as to whether dyslexia does indeed exist as a condition, or whether it simply reflects individual differences among different readers.

"The Dyslexia Myth" is a documentary that appeared as part of the Dispatches series produced by British broadcaster Channel 4$[28]$. First aired in September 2005, it claims to expose myths and misconceptions that surround dyslexia. It argues that the common understanding of dyslexia is not only false but makes it more difficult to provide the reading help that hundreds of thousands of children desperately need. Drawing on years of intensive academic research on both sides of the Atlantic, it challenged the existence of dyslexia as a separate condition, and highlighted the many different forms of reading style.

References

  1. Cope, N, Harold D, Hill G, Moskvina V, Stevenson J, Holmans P, Owen MJ, O'Donovan MC, Williams J (April 2005). "Strong evidence that KIAA0319 on chromosome 6p is a susceptibility gene for developmental dyslexia". American Journal of Human Genetics 76 (4): 581-91. PMID 15717286.
  2. Meng, H, Smith SD, Hager K, Held M, Liu J, Olson RK, Pennington BF, DeFries JC, Gelernter J, O'Reilly-Pol T, Somlo S, Skudlarski P, Shaywitz SE, Shaywitz BA, Marchione K, Wang Y, Paramasivam M, LoTurco JJ, Page GP, Gruen JR (Nov 22 2005). "DCDC2 is associated with reading disability and modulates neuronal development in the brain". Proceedings of the National Academy of Sciences 102 (47): 17053-8. PMID 16278297.
  3. Schumacher, J, Anthoni H, Dahdouh F, Konig IR, Hillmer AM, Kluck N, Manthey M, Plume E, Warnke A, Remschmidt H, Hulsmann J, Cichon S, Lindgren CM, Propping P, Zucchelli M, Ziegler A, Peyrard-Janvid M, Schulte-Korne G, Nothen MM, Kere J (Jan 2006). "Strong genetic evidence of DCDC2 as a susceptibility gene for dyslexia". American Journal of Human Genetics 78 (1): 52-62. PMID 16385449.
  4. Stanovich, KE. (1988) Explaining the differences between the dyslexic and the garden-variety poor reader: the phonological-core variable-difference model. Journal of Learning Disabilities, 21(10):590-604.
  5. Murphy, Martin F (2004). Dyslexia, An Explanation. Flyleaf Press. ISBN 0-9539974-5-6.
  6. Katzir, T., Shaul, S., Breznitz, Z. & Wolf, M. (2004). The Universal and the unique in dyslexia: A cross-linguistic investigation of reading and reading fluency in Hebrew-and English-speaking children with reading disorders, Reading and Writing 17(7-8):739
  7. Berlin, R (1884). "Uber Dyslexie". Archiv fur Psychiatrie 15: 276-278.
  8. Orton, ST (1925). "'Word-blindness' in school children.". Archives of Neurology and Psychiatry 14: 582–615.
  9. Henry, MK (1998). "Structured, sequential, multisensory teaching: The Orton legacy". Annals of Dyslexia.
  10. Geschwind, N (1982). "Biological associations of left-handedness". Annals of Dyslexia 33: 29-40.
  11. Bradley, L, Bryant, PE (1983). "Categorizing sounds and learning to read: A Causal connection.". Nature 30 (2): 419-421.
  12. Alexander, A, Anderson, H, Heilman, P, Voeller, K, Torgesen, J (1991). "Phonological awareness training and the remediation of analytic decoding deficits in a group of severe dyslexics". Annals of Dyslexia 41: 193-206.
  13. Galaburda, AM (Apr-Jun 1994). "Developmental dyslexia and animal studies: at the interface between cognition and neurology". Cognition 50 (1-3): 133-49. PMID 8039357.
  14. Grigorenko, EL (Jan 2001). "Developmental dyslexia: an update on genes, brains, and environments". Journal of child psychology and psychiatry, and allied disciplines 42 (1): 91-125. PMID 11205626.
  15. Grigorenko, EL, Wood FB, Meyer MS, Hart LA, Speed WC, Shuster A, Pauls DL (Jan 1997). "Susceptibility loci for distinct components of developmental dyslexia on chromosomes 6 and 15". American journal of human genetics 60 (1): 27-39. PMID 8981944.
  16. Grigorenko, EL, Wood FB, Meyer MS, Pauls DL (Feb 2000). "Chromosome 6p influences on different dyslexia-related cognitive processes: further confirmation". American journal of human genetics 66 (2): 715-23. PMID 10677331.
  17. No authors listed (Nov 1998). "Learning Disabilities, Dyslexia, and Vision: A Subject Review". Pediatrics 102 (5): 1217-9. PMID 9794958.
  18. Wilsher, CR (Apr-Jun 2002). "A miracle cure? 'tonight with Trevor McDonald', ITV, 21/01/02.". Dyslexia 8 (2): 116-7. PMID 12067185.
  19. "Scientists Say Severity of Dyslexia Depends on Language", The Tech News Briefs, Los Angeles Times, March 16, 2001. Retrieved on 2006-06-06.
  20. Seymour, P. H. K., Aro, M., & Erskine, J. M. (2003). Foundation literacy acquisition in European orthographies. British Journal of Psychology, 94, 143 – 174.
  21. Johannes C. Ziegler, Conrad Perry, Anna Ma-Wyatt, Diana Ladner, and Gerd Schulte-Körne, Journal of Experimental Child Psychology 86 (2003) 169 – 193
  22. Davis, Ronald D. (1992). 37 Common Characteristics of Dyslexia. Davis Dyslexia Association International. Retrieved on June 6, 2006.
  23. Metzger, RL, Werner DB (Jun 1984). "Use of visual training for reading disabilities: a review". Pediatrics 73 (6): 824-9. PMID 6374600.
  24. Nicolson, R. and Fawcett, A. (Nov 1999). "Developmental dyslexia: the role of the cerebellum". Dyslexia: An International Journal of Research and Practice 5: 155-7.
  25. Dyslexia Workshop Topics. Alabama Scottish Rite Foundation Learning Centers. Retrieved on June 6, 2006.
  26. Scottish Rite Masonic Children's Learning Centers. Retrieved on June 6, 2006.
  27. Scottish Rite Philanthropy. The Scottish Rite Bodies of Austin. Retrieved on June 6, 2006.
  28. The Dyslexia Myth. Dispatches. Channel 4. Retrieved on June 6, 2006.

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