Researchers have been trying to
identify the biological basis of dyslexia since it was first identified by
Oswald Berkhan in 1881 and the term dyslexia coined in 1887 by Rudolf
Berlin. The theories of the etiology of dyslexia have and are evolving with
each new generation of dyslexia researchers, and the more recent theories of
dyslexia tend to enhance one or more of the older theories as understanding of
the nature of dyslexia evolves.
Signs and symptoms
Some early symptoms that correlate with a later diagnosis of dyslexia include delays in speech, letter reversal or mirror writing, and being easily distracted by background noise. At later ages symptoms can include a difficulty identifying or generating rhyming words, or counting syllables in words (phonological awareness), a difficulty segmenting words into individual sounds, or blending sounds to make words, a difficulty with word retrieval or naming problems, commonly very poor spelling which has been called dysorthographia , and tendencies to omit or add letters or words when writing and reading are considered classic signs. Other classic signs for teenagers and adults with dyslexia include trouble with summarizing a story, memorizing, reading aloud, and learning a foreign language. A common misconception about dyslexia is that dyslexic readers write words backwards or move letters around when reading – this only occurs in a very small population of dyslexic readers. Dyslexic people are better identified by writing that does not seem to match their level of intelligence from prior observations.
Management
Some early symptoms that correlate with a later diagnosis of dyslexia include delays in speech, letter reversal or mirror writing, and being easily distracted by background noise. At later ages symptoms can include a difficulty identifying or generating rhyming words, or counting syllables in words (phonological awareness), a difficulty segmenting words into individual sounds, or blending sounds to make words, a difficulty with word retrieval or naming problems, commonly very poor spelling which has been called dysorthographia , and tendencies to omit or add letters or words when writing and reading are considered classic signs. Other classic signs for teenagers and adults with dyslexia include trouble with summarizing a story, memorizing, reading aloud, and learning a foreign language. A common misconception about dyslexia is that dyslexic readers write words backwards or move letters around when reading – this only occurs in a very small population of dyslexic readers. Dyslexic people are better identified by writing that does not seem to match their level of intelligence from prior observations.
Management
There is no cure for dyslexia, but
dyslexic individuals can learn to read and write with educational support.
There are techniques and technical aids, which manage or even conceal symptoms
of the disorder.Removing stress and anxiety alone contributes to improving
understanding.
For dyslexia intervention with alphabet writing systems the fundamental aim is to increase a child's awareness and to relate these to reading and spelling. It has been found that training focused towards visual language and orthographic issues yields longer-lasting gains than mere oral phonological training.
There is some evidence that the use of specially tailored fonts may provide some measure of assistance for those suffering from dyslexia.Intervention early on while language areas in the brain are still developing is most successful in reducing long-term impacts of dyslexia.
For dyslexia intervention with alphabet writing systems the fundamental aim is to increase a child's awareness and to relate these to reading and spelling. It has been found that training focused towards visual language and orthographic issues yields longer-lasting gains than mere oral phonological training.
There is some evidence that the use of specially tailored fonts may provide some measure of assistance for those suffering from dyslexia.Intervention early on while language areas in the brain are still developing is most successful in reducing long-term impacts of dyslexia.
History
Dyslexia was identified by Oswald
Berkhan in 1881, but the term dyslexia was coined in 1887 by Rudolf
Berlin, who was an ophthalmologist in Stuttgart. 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.
In 1896 W. Pringle Morgan, a British physician from Seaford, East Sussex, published a description of a reading-specific learning disorder in a report to the British Medical Journal titled "Congenital Word Blindness". This described the case of a 14-year-old boy who had not yet learned to read, yet showed normal intelligence and was generally adept at other activities typical of children of that age.
In 1896 W. Pringle Morgan, a British physician from Seaford, East Sussex, published a description of a reading-specific learning disorder in a report to the British Medical Journal titled "Congenital Word Blindness". This described the case of a 14-year-old boy who had not yet learned to read, yet showed normal intelligence and was generally adept at other activities typical of children of that age.
Research
The majority of currently available
dyslexia research relates to the alphabetic writing system, and especially to
languages of European origin. However, substantial research is also available
regarding dyslexia for speakers of Arabic, Chinese, and Hebrew.
Genetic research into dyslexia has its roots in the examination of post-autopsy brains of people with dyslexia. When they observed anatomical differences in the language center in a dyslexic brain, they showed microscopic cortical malformations known as ectopias and more rarely vascular micro-malformations, and in some instances these cortical malformations appeared as a microgyrus. These studies suggested abnormal cortical development which was presumed to occur before or during the sixth month of fetal brain development
Genetic research into dyslexia has its roots in the examination of post-autopsy brains of people with dyslexia. When they observed anatomical differences in the language center in a dyslexic brain, they showed microscopic cortical malformations known as ectopias and more rarely vascular micro-malformations, and in some instances these cortical malformations appeared as a microgyrus. These studies suggested abnormal cortical development which was presumed to occur before or during the sixth month of fetal brain development
Gene-environment interaction
Research has examined gene–environment interactions in reading disability through twin studies, which estimate the proportion of variance associated with environment and the proportion associated with heritability. Studies examining the influence of environmental factors such as parental education, and teacher quality have determined that genetics have more influence-supportive environments than less optimal environments. Instead, it may just allow those genetic risk factors to account for more of the variance in outcome, because environmental risk factors that affect that outcome have been minimized.
As the environment plays a large role in learning and memory, it is likely that epigenetic modifications play an important role in reading ability. Animal models and measures of gene expression and methylation in the human periphery are used to study epigenetic processes, both of which have limitations in extrapolating to the human brain.
No comments:
Post a Comment