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What Is Dyslexia?

Dyslexia is a common disorder that hinders the development of reading skills.  Some researchers refer to dyslexia as a visual processing disorder that is neurological in nature.  Dyslexia is defined by the International Dyslexia Association as “… a specific learning disability that is neurological in origin.  It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities.  These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction.  Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede the growth of vocabulary and background knowledge.”  Dyslexics struggle with language acquisition skills despite having been exposed to scientific-based reading teaching methodologies.     

The visual pathway is the most important pathway involved with the acquisition of written language skills; however, when discussing visual processing ability, the actual process of seeing is not the issue.  There are two components to visual processing ability:  The first involves recognizing that words are a systematic string of individual graphemes (letters).  Each individual sequential combination represents a different word.  Therefore, students must be able to accurately track, from left-to-right, top-to-bottom, and string together the individual phonemes (sounds) to produce these words (word identification).  The second component involves the acquisition of a visual image in the “mind’s eye” based upon the text decoded (concept imagery). 

Visual processing ability is believed to be determined by the level of functioning of the angular gyrus, an area in the left hemisphere, the hemisphere that serves as the language center of the human brain for ninety percent of the human population.  The angular gyrus sits on the junction of the temporal lobe and the parietal lobe, and it translates visual input into auditory code.  It is located directly behind Wernicke’s area, the language center of the brain that is responsible for processing sound into understandable words.  The level of functioning of the angular gyrus directly impacts the recognition and recall of words. Those students who have a high level of angular gyrus activity have good visual memory. 

 Image

Figure 1.  The Angular Gyrus

 

Those who have low levels of angular gyrus activity struggle with reading, spelling, and composition due to a deficit in visual processing ability.  These students have poor visual imagery and pronounced word recognition difficulty.  Those toward the lower end of the spectrum, approximately fifteen to twenty percent of the world’s population, can be described as dyslexic with a specific visual processing difficulty.

Visual imagery and word recognition ability have no direct correlation to a student’s intelligence.  Cultural icons such as Thomas Edison and Albert Einstein had visual imagery and word recognition skills toward the lowest end of the spectrum.  In fact, Thomas Edison and Albert Einstein were both dyslexics.

 

Genetic Cause of Dyslexia

Researchers have known for quite some time that there was a genetic link between dyslexics and their families.  Anecdotally, for each dyslexic with whom I have worked, either one of their parents or one of their grandparents recalled displaying symptoms of dyslexia during their academic careers.  Researchers, however, have recently identified dyslexia and one gene in particular.

In November of 2005, Dr. Jeffrey Gruen, an associate professor at Yale School of Medicine, and his research team discovered that reading ability is influenced by a gene called DCDC2.  This gene is located on chromosome 6.  The team studied 153 families with dyslexic children and identified a altered stretch of DNA within the DCDC2 gene of the study group that correlated to a severe reading disability.     

 

Dyslexia “Red Flags”

The following list are common indicators of a language-based learning disability founded upon the visual processing of language (dyslexia):

  • Reversals of letters and words when learning to read
  • Difficulty in direction and laterality
  • Continued uncertainty of left and right handedness
  • Uneven levels in academic achievement in various testing situations
  • Persistent, unusual spelling errors
  • Difficulty with mathematical skills
  • Normal intelligence with patchy defects
  • Reading is slow and labored
  • Tendency to make wild guesses with new words
  • May skip over small words (e.g., a, an, the) while reading
  • Mixes up order of letters
  • Listening comprehension much better than reading comprehension
  • Difficulty segmenting and blending individual letter sounds and syllables
  • A tough time learning to write one’s own name
  • Difficulty with sound/symbol correspondence
  • Significant difficulty reading and spelling multisyllabic/longer words
  • Difficulty recognizing and producing rhymes
  • Confusion with letters that look alike ( b/d/p, w/m, h/n, f/t)
  • Reduced awareness of word structure (prefix, roots, and suffixes)
  • Slow rate of reading
  • Continued difficulty with spelling and written composition
  • Difficulty learning new information from text because of word reading errors
  • Trouble learning a foreign language
  • Significant difficulty writing, due to spelling and organization problems
  • Reading and spelling errors that indicate difficulty sequencing sounds ( blast vs. blats)
  • Avoids reading aloud
  • Omission of grammatical endings when reading and writing ( –s, –ed, –ing)
  • Difficulty remembering spelling of words over time

 

The aforementioned list is not all inclusive.  However, if a student demonstrates multiple indicators, parents and teachers are encouraged to pursue diagnostic testing from a qualified educational diagnostician to determine the presence of a specific language disability. 

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