Dyslexia

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Dyslexia is a learning disability that manifests primarily as a difficulty with written language, particularly with reading and spelling. It is separate and distinct from reading difficulties resulting from other causes, such as a non-neurological deficiency with vision or hearing, or from poor or inadequate reading instruction.^[1] Evidence suggests that dyslexia results from differences in how the brain processes written and/or verbal language. Although dyslexia is the result of a neurological difference, it is not an intellectual disability. Dyslexia occurs at all levels of intelligence; sub-average, average, above average, and highly gifted.^[2]

Developmental reading disorder (DRD), or dyslexia, occurs when there is a problem in areas of the brain that help interpret language. It is not caused by vision problems. The disorder is a specific information processing problem that does not interfere with one’s ability to think or to understand complex ideas. Most people with DRD have normal intelligence, and many have above-average intelligence.

DRD may appear in combination with developmental writing disorder and developmental arithmetic disorder. All of these involve using symbols to convey information. These conditions may appear alone or in any combination.

DRD often runs in families.

Functional MRI (fMRI) studies have shown changes in the brains of dyslexic children and adults with phonics tutoring, along with improved performance on tests of phonemic awareness and text decoding.^{[3] [4]} Functional MRI studies have also shown changes in the brain and spelling improvement of dyslexic children taughtspelling phonetically in an orthographic manner. ^[5]

One factor that characterises the field of dyslexia treatment is the incessant flow of alternative therapeutic approaches. These controversial treatments include sensory, dietary, and movement-based approaches as well as many others. ^[6]

Learning disorders, such as DRD, tend to run in families. Affected families should make every effort to recognize existing problems early. Early intervention will provide the best possible outcome.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Identified for the first time by Oswald Berkhan in 1881, ^[1] the term ‘dyslexia’ was coined in 1887 by Rudolf Berlin, an ophthalmologist practicing in Stuttgart,Germany.^[2] 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, England 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.^[3]

During the 1890s and early 1900s, James Hinshelwood, a British ophthalmologist, published a series of articles in medical journals describing similar cases of congenital word blindness, which he defined as “a congenital defect occurring in children with otherwise normal and undamaged brains characterised by a difficulty in learning to read.” In his 1917 bookCongenital Word Blindness, Hinshelwood asserted that the primary disability was in visual memory for words and letters, and described symptoms including letter reversals, and difficulties with spelling and reading comprehension.^[4]

A key early researcher in dyslexia was Samuel T. Orton, a neurologist who worked primarily with stroke victims. In 1925 Orton met a boy who could not read and who exhibited symptoms similar to stroke victims who had lost the ability to read. Orton began studying reading difficulties and determined that there was a syndrome unrelated to brain damage that made learning to read difficult. Orton called the condition strephosymbolia (meaning ‘twisted signs’) to describe his theory that individuals with dyslexia had difficulty associating the visual forms of words with their spoken forms.^[5] Orton observed that reading deficits in dyslexia did not seem to stem from strictly visual deficits.^[6] He believed the condition was caused by the failure to establish hemispheric dominance in the brain.^[7] He also observed that the children he worked with were disproportionately left- or mixed-handed, although this finding has been difficult to replicate.^[8] Orton’s hypothesis concerning hemispheric specialization was borne out by post-mortem studies in the 1980s and 1990s establishing that the left planum temporale, a brain area associated with language processing, is physically larger than the corresponding right area in the brains of non-dyslexic subjects, but that these brain areas are symmetrical or slightly larger on the right for dyslexic subjects.^[9] FMRI imaging studies of children and young adults reported in 2003 provide further support, demonstrating that increases in age and reading level are associated with a suppression of right hemispheric activity.^{[10] [11]}

Influenced by the kinesthetic work of Helen Keller and Grace Fernald, and looking for a way to teach reading using both left and right brain functions,^[12] Orton later worked with psychologist and educator Anna Gillingham to develop an educational intervention that pioneered the use of simultaneous multisensory instruction. The Orton-Gillingham approach to remedial reading instruction is still widely used and forms the basis of many reading intervention programs. ^[13]

In contrast, Dearborn, Gates, Bennet and Blau considered a faulty guidance of the seeing mechanism to be the cause. The data collected in 1931 by Tinker and Goodenough (The J.Educ. Psych.) seemed to support this thesis. They wanted to know if a conflict between spontaneous orientation of the scanning action of the eyes from right to left and training aimed at the acquisition of an opposite direction would allow an interpretation of the facts observed in the dyslexic disorder and especially of the ability to mirror-read. To this end the authors asked four adults to read a text reflected in a mirror for ten minutes a day for a period of five months. It was confirmed that in all the subjects, the words were not perceived in their globality but required a meticulous analysis of the letters and syllables.

Moreover they also demonstrated either total or partial inversions even sometimes affecting the order of the words in a sentence. What is more, they revealed a curious impression of not just horizontal but also vertical inversions.These are errors that exist amongst dyslexics and they suffer from the aggravating circumstance inherent in all learning. What remained to be demonstrated was that there exists a preference amongst dyslexics, without sensory deficiency, or mental retardation, or any backwardness in speech or language, towards scanning with the eyes from right to left. Proof of this was provided in a work conducted under Clement Launay in 1949 (thesis G. Mahec Paris 1951). In adult subjects the reading of a series of 66 tiny lower-case letters, 5mm high, spaced 5mm apart, first from left to right and then from right to left was more easily and quickly done in the left to right direction. For former dyslexic children, a substantial number read a series of 42 letters with equal speed in both directions and some (10%) read better from right to left than from left to right. The phenomenon is clearly linked to the dynamics of sight as it disappears when the space between letters is increased, transforming the reading into spelling. This experience also explains the ability to mirror-read. This reading test can also be used to diagnose serious cases of dyslexia.

In the 1970s, a new hypothesis, based in part on Orton’s theories, emerged that dyslexia stems from a deficit inphonological processing or difficulty in recognizing that spoken words are formed by discrete phonemes (for example, that the word CAT comes from the sounds [k], [æ], and [t]). 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 isphonological awareness,^[14] and that phonological awareness instruction can improve decoding skills for children with reading difficulties.^[15]

The advent of neuroimaging techniques to study brain structure and function enhanced the research in the 1980s and 1990s. Since then, interest in the neurologically based causes has persisted. Current models of the relation between the brain and dyslexia generally focus on some form of defective or delayed brain maturation. More recently,genetic research has provided increasing evidence supporting a genetic origin of dyslexia ^[16].

Researchers are currently searching for a link between the neurological and genetic findings, and the reading disorder. There are many previous and current theories of dyslexia, but the one that has the most support from research is that, whatever the biological cause, dyslexia is a matter of reduced phonogical awareness, the ability to analyze and link the units of spoken and written languages. ^[17].

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Castles and Coltheart prove through their study that developmental dyslexia includes at least two prevalent and distinct varieties or subtypes of dyslexia. Subtypes include surface dyslexia and phonological dyslexia. Understanding these subtypes is useful in diagnosing learning patterns and developing approaches for overcoming impairments that may be visual perception impairments or speech discrimination deficits. These subtypes are based on differing patterns of underlying symptoms, as supported by a finding using large-scale data from comparative studies of reading patterns in dyslexic and normal readers ^[1]. In the study by Castles and Coltheart, 56 dyslexic boys and 56 non-dyslexic boys as a control group were tested. During the test, the boys read aloud words and non words that were presented to them. The researchers found that surface dyslexics (subjects who have poor lexical skills, or can’t make out irregular words well) had a mean difference of 14.4 words between reading regular words versus irregular words, however, the mean difference in subjects with phonological dyslexia (subjects who can’t use sub lexical skills, or can’t make out non words) was only 7.75 words which was comparable to the control group .The majority of their subjects showed signs of phonological dyslexia. Twenty-nine subjects showed that their non word reading skills were poorer than their irregular word reading skills. However, sixteen subjects showed the opposite where their irregular word reading skills were poorer than their non word reading skills and were called surface dyslexics.

Surface dyslexia is characterized by subjects who can read non words but who have trouble reading words that are irregular ^[2].Surface dyslexia is the outcome of an individual who cannot function using the lexical procedure for reading out loud. The lexical procedure includes sounding out a word though the use of a past word already known . In Castles and Coltheart’s study, the researchers matched 30 regular words with 30 irregular words and asked their surface dyslexic subjects to read the word out loud. As hypothesized in their research, the difference between the surface dyslexic subjects and control subjects was about 4.6 words which was 2.55 words higher than the difference between the phonological dyslexics to the control group. In Castles and Coltheart’s study, both control and dyslexic subjects were shown a card with a word that is irregular or that isn’t pronounced as it looks. Fifteen of the 51 dyslexics were below the confidence limit set by the control subjects on ability to read irregular words. These subjects were then called surface dyslexics .

Phonological dyslexia is characterized by subjects who can read aloud both regular and irregular words but have difficulties with non words and with connecting sounds to symbols, or with sounding out words . Phonological processing tasks predict reading accuracy and comprehension. This subtype is the most predominant form of dyslexia.In Castles and Coltheart’s study, they had 56 dyslexic boys and 56 non dyslexic boys read words and non words given to them. The majority of the boys, 55%, showed a phonological dyslexic pattern.In Castles and Coltheart’s study, dyslexic subjects and control subjects were asked to read non words listed on a card, 17 out of 51 cases of dyslexics were below the confidence limit in non word reading, which was derived by the control group of subjects their own age. These phonological dyslexics have a lower non word reading level than expected by reviewing their irregular word reading level ^[3]. Phonological dyslexia is the outcome of a subject who cannot function using the sub lexical (pronunciations are constructed from smaller orthographic components) procedure for reading out loud .In Castles and Coltheart’s study, dyslexic and control subjects read words off a note card; the researchers found that while reading irregular words, the dyslexic subjects scored comparable to the control subjects because sub lexical skills weren’t involved in this test.

Other researchers have identified a deficit related to “naming speed”, which relates to the ability of students to rapidly verbalize the names of symbols such as letters and numbers when tested ^[4]. In their study, Wolf and Bowers tested out naming speed by having their subjects name a symbol as quickly as possible when shown on a flash card. Difficulties in naming speed exist in conjunction with a phonological deficit, is characterized as double deficit dyslexia ^[4].

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Dyslexia is a learning disability. It has many underlying causes that are 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 may also be contributory or overlapping factors, or underlying cause of the dyslexic symptoms as they can 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. Many dyslexics have auditory processing problems including history of auditory reversals. Auditory processing disorder is recognized as one of the major causes of dyslexia.
• Cluttering is a speech fluency disorder involving both the rate and rhythm of speech, and resulting in impaired speech intelligibility. Speech is erratic and dysrhythmic, consisting of rapid and jerky spurts that usually involve faulty phrasing. The personality of the clutterer bears striking resemblance to the personalities of those with learning disabilities.^[1]
• Dyspraxia is a neurological condition characterized by a marked difficulty in carrying out routine tasks involving balance, fine-motor control, and kinesthetic coordination. Problems with short term memory and organization are typical of dyspraxics. This is most common in dyslexics who also have 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 disorder which expresses itself primarily during writing or typing, although in some cases it may also affect eye-hand coordination in such direction or sequence oriented processes as tying knots or carrying out a repetitive task. Dysgraphia is distinct from Dyspraxia in that the person may have the word to be written or the proper order of steps in mind clearly, but carries the sequence out in the wrong order.
• 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.
• Scotopic sensitivity syndrome, also known as Irlen Syndrome, is a term used to describe sensitivity to certain wavelengths of light which interfere with proper visual processing. See also Orthoscopics and asfedia.

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Developmental reading disorder (DRD), or dyslexia, occurs when there is a problem in areas of the brain that help interpret language. It is not caused by vision problems. The disorder is a specific information processing problem that does not interfere with one’s ability to think or to understand complex ideas. Most people with DRD have normal intelligence, and many have above-average intelligence.

DRD may appear in combination with developmental writing disorder and developmental arithmetic disorder. All of these involve using symbols to convey information. These conditions may appear alone or in any combination.

DRD often runs in families.

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In the United States, researchers estimate the prevalence of dyslexia to range from five to nine percent of school-aged children, though some have put the figure as high as 17 percent.^[1][2] Recent studies indicate that dyslexia is particularly prevalent among small business owners, with roughly 20 to 35 percent of U. S. and British entrepreneurs being affected. Researchers consider that many dyslexic entrepreneurs are successful by delegating responsibilities and excelling at verbal communication.^[3]

Dyslexia’s main manifestation is a difficulty in developing word-level 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 developmental. Most scientific criteria for dyslexia exclude cases that can be explained as arising from environmental factors such as lack of education or total sensory deficits.

Dyslexia can be substantially compensated for with proper therapy, training, and assistive technology. Many coping strategies are developed subconsciously by the individual dyslexic.

Dyslexia has many variations dependent on the cultural choice of visual notation of speech. So the nature of the notation used in different cultures creates different types of problems for their groups of dyslexics. The differences between the English text and Chinese characters is a good example.

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Specialized help (called remedial instruction) can lead to marked improvement in reading and understanding.

Reading difficulties may persist for life.

DRD may lead to:

• Problems in school, including behavior problems

• Loss of self-esteem

• Reading problems that persist into adulthood, which may affect job performance, particularly if the problem was not addressed early in life

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Because dyslexia’s most salient symptom is childhood difficulty with learning to read, the most common form of treatment is through specialized tutoring or teaching tailored to meet the particular learning characteristics of the student. Most teaching is geared to remediating specific areas of weakness, such as addressing difficulties with phonetic decoding by providing phonics-based tutoring. Some teaching is geared to specific reading skill areas, such as phonetic decoding; whereas other approaches are more comprehensive in scope, combining techniques to address basic skills along with strategies to improve comprehension and literary appreciation. Many programs are multisensory in design, meaning that instruction includes visual, auditory, and kinesthetic or tactile elements; as it is generally believed that such forms of instruction are more effective for dyslexic learners.^[1] Despite claims of some programs to be “research based”, there is very little empirical or quantitative research supporting the use of any particular approach to reading instruction as compared to another when used with dyslexic children.^[2][3]

• Alternative therapies for developmental and learning disabilities

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