DYSLEXIA- READING DISORDER

Abstract

Dyslexia is a difficulty in learning and to spell. The lack of accuracy in reading process is not due to lower intellectual or sensory impairments, social-cultural, emotional problems. Prevalence is estimated to be between 5% and 17% of school-aged children; it therefore represents a major public health issue. Dyslexia is described via way of means of the 2 essential worldwide classifications, DSMIV and ICD10, as a particular and continual studying sickness that affects the acquisition and development of the written language code (analyzing and spelling) and leading to significant handicaps in educational overall performance and/or everyday activities; it is taken under consideration while analyzing overall performance is one standard deviation below the predicted for a given age and intelligence and while those deficits cannot be defined via way of means of sensory, neurological, psychiatric, motivational or different reasons or by inadequate education. Treatment should be managed by an appropriate multidisciplinary team (a neurologist, a pediatrician, an educational psychologist, specialist instructors, speech therapists, as well as other professionals) and active participation from the school, parents, and child should be strongly encouraged. Functional Magnetic Resonance imaging (fMRI) is a method used for imaging brain function. It measures physiological signs of neural activation using a strong magnet to pinpoint blood flow. Audiologists, physiotherapists, optometrists and pharmacists can also apply for a role despite the fact that these professions do not have measures that can be used to diagnose or treat dyslexia.

Introduction

Dyslexia is a neurological disorder that is characterized by the recognition of word slowly and inaccurately. This is a learning disorder which affects your capability to read, spell, write, and speak. Kids who have this disorder are often smart and hardworking, but they have problem connecting the letters they see to the sounds those letters make.

 Most researchers working in all relevant disciplines have treated dyslexia as synonymous with the concept of reading disorder, a term generally used to describe reading (decoding) difficulties at the word level. Some of the persons in the world have some symptoms of dyslexia, such as slow reading, trouble spelling, or mixing up words. Adults can have this disorder, as well. Some people are diagnosed early in their life. Others do not notice that they have dyslexia until they get older. In 2007, the New Zealand Ministry of Education formally recognized the conditions of dyslexia for the first time.

The lack of accuracy in the reading process observed in dyslexic children is not due to lower intellectual or sensory impairments, social-cultural, emotional problems. Children with dyslexia often have normal vision and are as intelligent as their peers. But they have more difficulty in school because they take longer to read. Word processing problems can also make spelling, writing, and speech clarity difficult.

Dyslexia is defined by the two main international classifications, DSMIV and ICD10, as a specific and persistent learning disorder that affects the acquisition and development of the written language code (reading and spelling) and leading to significant handicaps in academic performance and/or daily activities life; it is taken into account when reading performance is one standard deviation below the level expected for a given age and intelligence and when these deficits cannot be explained by sensory, neurological, psychiatric, motivational or other causes or by inadequate education.

Some of the scientist defined dyslexia as being of neurobiological origin with probable genetic cause and intrinsically linked, in the vast majority of cases, to the development of oral language, particularly at the level of phonological processing.

Currently, the diagnosis of dyslexia is based on family history and clinical, psychometric, phonological awareness, language, reading and spelling tests. Looking into different resources may increase the diagnosis capacity (e.g., genes x neuro imaging).

Certain language characteristics observed in the school setting may indicate a child at risk, including:

·      Changes in the sequence of letters that form syllables and words

·      Confusion of letters opposing symmetry, such as b for d or p

·      Confusion of letters with similar sounds

·      Difficulty in understanding what is being read

·      Difficulty understanding jokes, proverbs and slang

·      Difficulties in distinguishing between similar sounds such as p-b; t, f-v; m-n

·      Difficulty in learning little songs and rhymes

·      Difficulty with fine motor skill

·      Difficulty in pronunciation of phonemes

·      Difficulty in learning foreign languages

·      Errors in the separation of words

·      Problems with laterality (right and left)

·      Omission of letters or syllables while writing

·       Reduced Vocabulary.

Developmental dyslexia (DD) and how this disorder relates to brain function are complex topics that researchers have studied since dyslexia was first described over a hundred years ago.

Areas of brain for language and reading

Brain has two hemispheres, left and right. The left hemisphere has the areas which are responsible for speech, language processing, and reading.

Frontal lobe: largest part and responsible for speech, reasoning, planning, regulating emotions, and consciousness controlling.

In the 19th century, Paul Broca was exploring areas of the brain used for language and noticed a particular part of the brain that was impaired in a man whose speech became limited after a stroke. This area received more and more attention, and today we know that Broca's area, located here in the frontal lobe, is important for the organization, production, and manipulation of language and speech. Areas of the frontal lobe are also important for silent reading proficiency

Parietal lobe: located on back in the brain and it will control sensory perceptions as well as linking spoken and written language to memory to give it meaning so we can understand what we hear and read.

Occipital lobe: found at the back of the head, is where the primary visual cortex is located. Among other types of visual perception, the visual cortex is important in the identification of letters.

Temporal lobe: located in the lower part of the brain, parallel with the ears, and is involved in verbal memory.

Wernicke's area, long known to be important in understanding language is located here. This region was identified by Carl Wernicke at about the same time and using the same methods as Broca, is critical in language processing and reading.

There is other two systems, which process language within and between lobes, are important for reading. They are left parietotemporal system and left occipitotemporal area.

Left parietotemporal system - appears to be involved in word analysis – the conscious, effortful decoding of words. This region is responsible in the process of mapping letters and written words onto their sound correspondences – letter sounds and spoken words and this area is also important for comprehending written and spoken language.

 left occipitotemporal area- involved in automatic, rapid access to whole words and is a critical area for skilled, fluent reading.

Brain imaging in dyslexia affected individual

Brain is composed of grey and white matter. Grey matter is the outer surface of brain. They are Composed of nerve cells. and white matter is inside in the deeper part of brain. It composed of connective fibers covered by myelin sheath which facilitates communication between nerves. But people with dyslexia have less grey matter in the left parietotemporal area than normal person. Less grey matter in this region may cause problems in processing the sound structure of language. And many of the dyslexia people have less white matter in the same region will reduce the ability of the regions of the brain to communicate with one another.

Neuroimaging studies of dyslexia suggest that reading difficulty is associated with differences in structure and function in the same neural circuits that are engaged by typical readers, including left-lateralized temporo-parietal, occipito-temporal, and inferior frontal cortices.

Functional Magnetic Resonance imaging (fMRI) is a method used for imaging brain function. It measures physiological signs of neural activation using a strong magnet to pinpoint blood flow. Several studies using functional imaging techniques that compared the brain activation patterns of readers with and without dyslexia show potentially important patterns of differences. We might expect that readers with reading disability would show under activation in areas where they are weaker and overactivation in other areas in order to compensate, and that is exactly what many researchers have found. Compared brain activity children with and without reading disability. The nonimpaired readers had more activation in all of the areas known to be important for reading than the children with dyslexia.

The brain of a person with dyslexia has a different distribution of metabolic activation than the brain of a person without reading problems when accomplishing the same language task. There is a failure of the left hemisphere rear brain systems to function properly during reading and many people with dyslexia often show greater activation in the lower frontal areas of the brain. This leads to the conclusion that neural systems in frontal regions may compensate for the disruption in the posterior area.

Treatment

Dyslexia is highly complex and dynamic and every case is unique. Treatment should be managed by an appropriate multidisciplinary team (a neurologist, a paediatrician, an educational psychologist, specialist instructors, speech therapists, as well as other professionals) and active participation from the school, parents, and child should be strongly encouraged. Other phonics-based auditory intervention programs incorporating articulatory training exercises based on the sensorimotor dysfunction theory of dyslexia have been proposed. Audiologists, physiotherapists, optometrists and pharmacists can also apply for a role despite the fact that these professions do not have measures that can be used to diagnose or treat dyslexia.

Reference

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·       Joseph, Noble, & Eden, 2001