Cedar McKay
4/6/98
Professor Grobstein
Neurobiology
Dyslexia

     Choosing a topic for my research project was quite easy. Dyslexia naturally presented itself, probably  because I have a mild case myself. I thought of it as a good omen when typing the word “dyslexia” into an internet search engine, I spelled it “dsylexia”. Of course I was troubled when the computer reported zero matches, but I caught my mistake, and tried again, this time more successfully. My dyslexia is really very minor, and has not presented too much difficulty for me. I often reverse numbers, which is annoying when dealing with phone numbers, and I am a terrible speller, which may well be related to my dyslexia. However, people with severe cases are presented with a serious handicap, making reading, writing, listening and language comprehension difficult (1,2). Despite normal intelligence levels, dyslexics often feel stupid and have self-esteem problems, because of the difficulty they experience in reading and writing (1).
    Dyslexia was first described in 1896 by Pringle Morgan of Sussex, England, who described a 14 year old boy who “has always been a bright and intelligent boy, quick at games, and in no way inferior to others of his age. His great difficulty has been--and is now--his inability to learn to read.”(5) This was the first description of the disorder, which exposes the curious problem of intelligent, motivated people unable to learn basic reading skills. Dyslexia’s most diagnosable feature is a pronounced disparity between intelligence and scholastic success, particularly reading.
 Reading involves rapid association of symbols (letters and letter combinations) with the 44 phonemes ( the smallest unit of discernible sound) of the English language, which must in turn be assembled into a meaningful whole. People with dyslexia experience difficulty in assembly and dissection of words into phonemes.  Without the ability to consistently see the relationship between phonemes and letter combinations, reading is laborious and prone to errors. Though reading difficulty is the most obvious symptom, dyslexics experience other handicaps as well. The difficulty dyslexics experience in word dissection extends to listening comprehension, word decoding problems, and confusion about paired words (up down, left right, early late)(2,3,5).
     There are differences in opinion about what dyslexia actually is. One advocate web site (6) describe dyslexia as “a gift” whose symptoms arise from a unique ability to “think in pictures” It claims that there is no difference between a normal brain and a dyslexic brain, it is simply a different mode of thought. Another site (1) describes  “scientific watergate,” a conspiracy of scientists to cover up the real nature of dyslexia, to preserve the theories of the status quo, at the expense of dyslexia sufferers. It explains that dyslexia is “an inner ear problem”. This site offers “medical treatment” consisting of “a combination of inner-ear-improving medications and vitamin-type substances”. It claims 75-85% success rate.
     A more conventional explanation (5,7)  ascribes dyslexia to malfunctioning portions of the brain responsible for language and visual processing at their most basic levels. Language is processed in the brain in a hierarchical series of modules. The upper levels are responsible for semantics, syntax, and discourse. The lowest level, called the phonological module, is responsible for processing individual phonemes, breaking apart and assembling each word. Each word must be parsed into component phonemes for them to be stored in memory, retrieved, or processed. This is an unconscious process required for spoken language, which is required more intensively and more directly for reading, which requires a conscious breakdown of each word. This is why dyslexics tend to have more difficulty with reading and writing than speaking and listening, though these processes are also effected to a lesser degree. Malfunction of this phonological function in turn blocks the correct function of higher level modules associated more directly with intelligence. This is the reason why intelligent people (functioning upper level modules) may have difficulty mastering simple skills.
     With the development of functional magnetic resonance imaging (fMRI) malfunctions of specific areas of the brain can be tested directly (5,7). This non-invasive technique allows the monitoring of metabolic activity of specific areas of the brain, while the brain is actually working. Normal individuals were asked to do a variety of reading, writing, and language processing tasks while being monitored. Then these normal activities patterns were compared to that of dyslexics. Indeed, portions of the brain had different activity patterns or sizes in dyslexics, particularly the inferior frontal gyrus, which has been shown to correspond to phonological function (5).
     In addition to supporting the phonological hypothesis, fMRI studies revealed an unexpected and long discounted theory (7). For years scientist had blamed dyslexia on a visual disorder, but then in the last 30 years concluded that the malfunction lay in the language processing parts of the brain. New fMRI data suggests that visual processing may after all be involved in dyslexia. While this new evidence suggests that an image processing defect in the V5/MT portion of the brain may contribute to dyslexia, it still supports dyslexia’s roots in language processing problems. There is the possibility that both the language and visual processing problems are the result of a third, as of yet undiscovered, malfunctioning region in the brain.
     The cause of dyslexia is somewhat a mystery, though there does seem to be some genetic basis(8). Dyslexia often runs in families and tends to be more prevalent in males, but no simple inheritance scheme has been discovered. This could be explained if dyslexia were a symptom of another genetic problem, which is causative of dyslexia. For instance it has been proposed that sufferers of dyslexia have a higher than normal incidence of auto-immune diseases. Maternal antibodies may injure the developing brain during gestation(9). Some non-genetic indicators have been described as well. Cerebrovascular accidents, prematurity, and intrauterine complications are all associated with dyslexia(8).
     No success has been reported with medicinal approaches to dyslexia (except for the extravagant claims of the sellers of “a combination of inner-ear-improving medications and vitamin-type substances”) (1). However many groups report success with education oriented therapies. (3,5,6,9). These tend to focus on explicit education about and awareness of phonemes, in reading and writing. Education focused on overcoming  dyslexia works in two ways. First, if started early with phoneme awareness education and extra reading help, children tend to develop less severe cases of dyslexia. Second, students with full blown cases of dyslexia can learn to overcome and work around dyslexia by becoming “compensated dyslexics”. They learn to consciously decode each word, breaking them down to individual phonemes, a process which is unconscious for the normal reader. Though this is a route around dyslexia, it is extremely laborious and tiring. Reading just takes longer and requires great concentration.
     A clear system of diagnosis must be developed to properly help dyslexics. Now the standard way to detect dyslexics is to wait until they fall far behind classmates, then ask why. We need to develop a test which allows us to begin special education and provide extra resources to dyslexics before they fall behind. The “wait and see if they fail” system is detrimental to the progress and self-esteem of dyslexic students. Imagine falling two years behind class mates, and having difficulty reading, never knowing that it was due to a diagnosable problem. Clearly reliable tests need to be developed. Unfortunately fMRI, a potentially reliable and definitive tool for dyslexia detection is expensive and impractical as a screening device. In the mean time inexpensive paper and verbal tests designed to reveal problems with phoneme processing and language skills can be a useful substitute.
      The most important thing is educating those who are diagnosed, both to alleviate the symptoms of dyslexia, and to help provide techniques for working with and around dyslexia. Those who do not learn how to compensate for their dyslexia can end up illiterate, and dysfunctional in today’s society. Dyslexics who learn to overcome their handicaps can easily live productive and normal live, marked only by a slightly slower reading rate than non-dyslexics. We can help more dyslexics become “compensated dyslexics” by providing early detection, and a robust system of education for those identified.
 
 
 
 
 
 
 
 
 

Resources
 

1) http://www.dyslexiao nline.com/dyslexia.html#what
 From Dyslexia Online

2) http://www. ldonline.org/ld_indepth/reading/reading-4.html
 From Orton Dyslexia Society

3) http://www .ldonline.org/ld_indepth/reading/nih_report.html
 From Learning Disabilities Online

4) http://www.ldonline.o rg/ccld/ld/ldresearch.html
 From Learning Disabilities Online

5) http://www.sciam.com /1196issue/1196shaywitz.html
 From Scientific American  Dyslexia article

6) http://www.dyslexia.com/
 From Dyslexia.com an advocate site

7) http ://www.kidsource.com/kidsource/content/news/brain7_9_96.html
 From a review of an article published in Nature

8) http://www.merck.com/!!ucy831YlLucy831YlL/pubs/mmanual/html/iomhgeeg.htm
 From the Merck Manual

9) http://www.interdys.org/ articles.stm#content
 From the International Dyslexia Association
 


| Course Home Page | Back to Brain and Behavior | Back to Serendip |

Send us your comments at Serendip
© by Serendip 1994- - Last Modified: Monday, 07-Jan-2002 14:36:16 EST

This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.

Contribute Thoughts | Search Serendip for Other Papers | Serendip Home Page