Dr. Cindy Taylor

Clinical Psychologist

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Dyslexia

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Dyslexia - the term dyslexia means "problem reading."   The prefix "dys" refers to "bad" or "faulty" implying a deficit, but not an inability to read.  Alexia is an inability to read.  In the DMS-IV, the official diagnosis for dyslexia would be "Reading disorder."  Children with dyslexia are of normal intelligence, but have trouble learning to read.  They do not perceive the word correctly, or do not process the phonetic sounds of the language in the same way as other children.  Because of this, they often take only part of the word, such as the first couple of letters, and try to come up with a word that starts with those sounds.  For example, a child asked to read the word "spell" may say "spoil."  Even though those words are not really similar to those who can read, a dyslexic child will see the similarities in the first letters, and also in the shape of the word. 

Testing for dyslexia includes evaluation of intellectual functioning and reading.  If the scores are significantly different between the individual's IQ and reading scores, the diagnosis of Reading Disorder (dyslexia) will be made.  There are many types, or classifications, of dyslexia including adquired dyslexia, developmental dyslexia, spelling or word-form dyslexia, phonological dyslexia, suface dyslexia, and deep dyslexia.

Acquired dyslexia refers to a reading disorder caused by brain damage that occurred after the individual had already learned to read.  Many different regions of the brain are involved in reading, including those responsible for comprehending speech, as well as the angular gyrus.  The association cortex is also involved in reading.

Developmental dyslexias will be seen when the child is learning to read.  There is  a genetic componenet to the developmental dyslexias and most individuals are male. These individuals are intelligent, but have great difficulty learning to read and rarely become fluent readers.    A disproportionate number of these individuals are left-handed.    One study indicated that left-handed people were 10 times more likely to have specific learning disorders.

Spelling, or word-form dyslexia is a form of acquired dyslexia in which patients are unable to recognize words, but can read them by naming the individual letters.  As you might imagine, these individuals will read slowly, with shorter words being read more quickly than longer ones.  This type of dyslexia most likely involves perceptual deficits in which the patient is unable to perceive and recognize the word as a whole.  If the case involves severe perceptual disturbance, the individuals who not be able to correctly identify some of the letters either, and therefore will not read the word correctly.  It is presumed that the region of the left hemisphere that recognizes the words is disconnected from visual input and that the brain uses a compensatory strategy involving the right hemisphere recognizing the letters and sending them to the speech areas in the left hemisphere via the corpus collosum.  Using this method, the individual can then say the letters and hearing them, pronounce the word. 

Phonological dyslexia has to do with the pholonogical rules we use for pronouncing words.  There is a connection between the letters and the sounds represented by each letter.  We have to use this skill to pronounce a new, or unfamiliar word, or to read nonwords.   The brain must decode the sounds of each letter, or letter groups, and then apply other rules, such as whether there is a "silent e" at the end of a word changing the vowel sound.  For example, try pronouncing these words:    

flid    bim    micker    reeb

You probably have not run into them before, but I bet we would read them easily and agree on the way they are pronounced.  In phonological dyslexia, the patient can read familiar words fairly well, but they have trouble with nonwords.  These individuals may also have trouble reading  function words, such as 'that' or 'you' or 'those' 'an', 'but'.  They also have difficulty with the end of words, such as when we add 's', 'ed', or 'ing' to a root word.  An example would be 'called', which might be read as 'calling' instead.  These derivational endings are referred to as bound morphemes.

Surface dyslexia is a condition similar to developmental dyslexia that also involves a visual perceptual deficit.  The individual reads phonologically, and can therefore read nonwords and words with regular spellings, although they occasionally make visual erros in reading and substitute letters, such as reading 'cart' for 'care' or 'pill' for 'pile.'  The biggest problem in surface dyslexia is reading irregularly spelled words, and we have lots of those in English.  For example, the word 'laugh' or 'caught' or 'yacht' are irregularly spelled words that are not pronounced like they look.  An individual with surface dyslexia will tend to pronounce these words as they are spelled, saying "yachet".   In surface dyslexia, the errors are made based upon the superficial aspects or visual appearance of the word, whereas in deep dyslexia, the errors relate to the deeper meaning of the word.

Deep dyslexia usually involves massive damage to the left hemisphere and most individuals also have Broca's aphasia in addition to the reading problem.  These patients are poor readers, and read words representing simple, concrete objects:  'cat', 'tree', 'dog.'  They are rarely able to read abstract words, and often make semantic substitutions.  For example, one might say 'stair' rather than 'ladder' or 'circle' rather than 'round.' 


Last Updated on Tuesday, 26 August 2014 00:06  


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