Dyslexia

Is a broad term defining a learning disability that impairs a person's fluency or accuracy in being able to read, speak, and spell. Which can manifest itself as a difficulty with phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, and/or rapid naming. Dyslexia 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. It is believed that dyslexia can affect between 5 to 10 percent of a given population although there have been no studies to indicate an accurate percentage.

There are three proposed cognitive subtypes of dyslexia: auditory, visual and attentional. Although dyslexia is not an intellectual disability, it is considered both a learning disability and a reading disability. Dyslexia and IQ are not interrelated, since reading and cognition develop independently in individuals who have dyslexia.

Accomplished adult dyslexics may be able to read with good comprehension, but they tend to read more slowly than non-dyslexics, and may perform more poorly at nonsense word reading (a measure of phonological awareness), and spelling.

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Spoken language is a universal form of man made communication. The visual notation of speech—written language is not found in all cultures and is a recent development with regard to human evolution.

There are many definitions of dyslexia but no official consensus has been reached.

The World Federation of Neurology defines dyslexia as "a disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and sociocultural opportunity".

MedlinePlus and the National Institutes of Health define dyslexia as "a reading disability resulting from the inability to process graphic symbols".

The National Institute of Neurological Disorders and Stroke gives the following definition for dyslexia:

"Dyslexia is a brain-based type of learning disability that specifically impairs a person's ability to read. These individuals typically read at levels significantly lower than expected despite having normal intelligence. Although the disorder varies from person to person, common characteristics among people with dyslexia are difficulty with spelling, phonological processing (the manipulation of sounds), and/or rapid visual-verbal responding. In adults, dyslexia usually occurs after a brain injury or in the context of dementia. It can also be inherited in some families, and recent studies have identified a number of genes that may predispose an individual to developing dyslexia".

Other published definitions are purely descriptive or embody causal theories. Varying definitions are used for dyslexia from researchers and organizations around the world; it appears that this disorder encompasses a number of reading skills, deficits and difficulties with a number of causes rather than a single condition.

Castles and Coltheart describe phonological and surface types of developmental dyslexia by analogy to classical subtypes of alexia (acquired dyslexia) which are classified according to the rate of errors in reading non-words.However, the distinction between surface and phonological dyslexia has not replaced the old empirical terminology of dysphonetic versus dyseidetic types of dyslexia. The surface/phonological distinction is only descriptive, and devoid of any aetiological assumption as to the underlying brain mechanisms (Galaburda and Cestnick 2003). Studies have, however, alluded to potential differential underlying brain mechanisms in these populations given performance differences (Cestnick et al.). The dysphonetic/dyseidetic distinction refers to two different mechanisms; one that relates to a speech discrimination deficit, and another that relates to a visual perception impairment.

Signs and Symptons

The symptoms of dyslexia vary according to the severity of the disorder as well as the age of the individual.

 Preschool-aged children

It is difficult to obtain a certain diagnosis of dyslexia before a child begins school, but many dyslexic individuals have a history of difficulties that began well before kindergarten. Children who exhibit these symptoms early in life have a higher likelihood of being diagnosed as dyslexic than other children. These symptoms include:

• delays in speech
• slow learning of new words
• not crawlingdifficulty in rhyming words, as in nursery rhymes
• low letter knowledge
• letter reversal or mirror writing (for example, "Я" instead of "R")

 Early primary school children

• Difficulty learning the alphabet or letters order
• Difficulty with associating sounds with the letters that represent them (sound-symbol correspondence)
• Difficulty identifying or generating rhyming words, or counting syllables in words (phonological awareness)
• Difficulty segmenting words into individual sounds, or blending sounds to make words (phonemic awareness)
• Difficulty with word retrieval or naming problems
• Difficulty learning to decode written words
• Difficulty distinguishing between similar sounds in words; mixing up sounds in polysyllabic words (auditory discrimination) (for example, "aminal" for animal, "bisghetti" for spaghetti)

Older primary school children

• Slow or inaccurate reading (although these individuals can read to an extent).
• Very poor spelling which has been called dysorthographia (orthographic coding)
• Difficulty reading out loud, reading words in the wrong order, skipping words and sometimes saying a word similar to another word (auditory processing disorder)
• Difficulty associating individual words with their correct meanings
• Difficulty with time keeping and concept of time when doing a certain task
• Difficulty with organization skills (working memory)
• Children with dyslexia may fail to see (and occasionally to hear) similarities and differences in letters and words, may not recognize the spacing that organizes letters into separate words, and may be unable to sound out the pronunciation of an unfamiliar word (auditory processing disorder).
• Tendencies to omit or add letters or words when writing and reading.

 Secondary school children and adults

Some people with dyslexia are able to disguise their weaknesses (even from themselves) and often do acceptably well — or better — at GCSE level (U.K. - at 16 years old). Many students reach higher education before they encounter the threshold at which they are no longer able to compensate for their learning weaknesses.

One common misconception about dyslexia is that dyslexic readers write words backwards or move letters around when reading. In fact, 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. Additionally, dyslexic people often substitute similar-looking, but unrelated, words in place of the ones intended (what/want, say/saw, help/held, run/fun, fell/fall, to/too, etc.)

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Several learning disabilities often occur with dyslexia, but it is unclear whether these learning disabilities

share underlying neurological causes with dyslexia. These disabilities include, but are not limited to:

Dysgraphia: a disorder which expresses itself primarily through writing or typing, although in some

cases it may also affect eye–hand coordination direction or sequence oriented processes such as tying

knots or carrying out a repetitive task. In dyslexia, dysgraphia is often multifactorial, due to impaired

letter writing automaticity, finger motor sequencing challenges, organizational and elaborative difficulties,

and impaired visual word form which makes it more difficult to retrieve the visual picture of words

required  for spelling.

Dysgraphia: is distinct from dyspraxia in that dyspraxia is simply related motor sequence impairment.

Dyscalculia: a neurological condition characterized by a problem with basic sense of number and

quantity and difficult retrieving rote math facts. Often people with this condition can understand very

complex  mathematical concepts and principles but have difficulty retrieving basic math facts involving

addition and subtraction.

Attention Deficit Disorder: a high degree of co-morbidity has been reported between ADD / ADHD and

dyslexia, although the contributions of dyslexia-related challenges such auditory verbal working

memory to attention issues has not been well established

Cluttering: a speech fluency disorder involving both the rate and rhythm of speech, resulting in

impaired speech intelligibility.

Speech is erratic and nonrhythmic, consisting of rapid and jerky spurts that usually

involve faulty phrasing. The personality of people with cluttering bears striking resemblance to the

personalities of those with learning disabilities.