Biology 202
2000 First Web Report
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Dyslexia

Elizabeth Gilbert

Imagine your childhood. Now imagine sitting in school and dreading that one moment when your elementary school teacher is going to call on you to read aloud to the class. Imagine that you dread this moment so dearly because you constantly trip over simple words and are made to feel stupid because of it. Or worse, imagine knowing that you do try your hardest but still have report cards that say that you are not living up to your full potential and need to start making an effort in school. These are just some of the thoughts and emotions that a child with dyslexia faces everyday.

Dyslexia is a language based learning disorder that is grounded in the neurobiology of the brain. The disorder interferes with the processing and comprehension of both spoken and written language. Often there are other associated symptoms such as poor spelling, writing, handwriting and occasionally arithmetic (1). People do not read or write backwards as is depicted by the media. Nor is it a disorder of laziness or lack of intelligence.

Current National Institutes of Health (NIH) studies estimate the prevalence of this disorder at 20% of school age children. This means that one in five children have the fears and emotions expressed above. It is by far the most common form of learning disability. In addition, dyslexia affects all socio-economic classes and all races equally (2) (2). It affects as many boys as girls (3). However, boys are usually spotted more quickly because they tend to exhibit externalizing behaviors such as acting out when doing poorly in school. Consequently the teacher is more likely to look for a problem in a child who is acting out in class rather than one who is quiet. Thus, boys who tend to act out more will be noticed more by the teacher.

As described above, children with the disorder often feel stupid as a result of their constant struggle in school. However, there is no correlation between intelligence and dyslexia. In fact, very intelligent people are dyslexic. For example, Einstein, arguably the one of the most intelligent people ever, was known to be dyslexic. People with dyslexia can go on to higher education and become professionals. Often, these people succeed in areas that do not require a significant number of language based tasks on a daily basis (4).

Sometimes, children can learn to work around their disability without special help. In fact, some of these people do not learn of their diagnosis until adolescence or adulthood when they suddenly start having problems keeping up with school or work. It is a disorder that can go undetected until adulthood when the person's child is diagnosed. However, it is not something that can "go-away" when discovered and treated. It cannot be cured but those with the disorder can learn to overcome it with special training and educational provisions such as untimed testing or spoken exams.

As noted above, some people find out about their disability by learning about their child’s learning problems. Dyslexia is a genetic disorder. Recently scientists located a gene on the short arm of chromosome #6 for dyslexia. Because the gene is dominant the disorder is highly heritable (1). Furthermore, studies have found that in children who are newly diagnosed, nearly 80% have a history of learning difficulties in their families. This provides strong evidence for the genetic heritability of dyslexia. Interestingly, there is also a 60% concordance with left handedness (5) Perhaps, the gene for left handedness is located near the gene for dyslexia.

Recent research by the NIH has focused on the differences in the brains of people with dyslexia and normal controls. Researchers have found that people with dyslexia use different parts of the brain when reading than controls use. While control subjects show activation in the angular gyrus area of the brain, subjects with dyslexia show little activation in this area or none at all. Furthermore, subjects with dyslexia show activation in the inferior frontal gyrus. This is an area in the front of the brain that is associated with spoken language (6) So perhaps the reason that people with dyslexia do better with spoken rather than written exams is that they are using the part of the brain that is efficient at processing spoken language.

Not only are the brains of people with dyslexia studied but also the model for sound processing. Cognitive research has focused on the phonological model of language processing. Research in this field has shown that people with dyslexia have poor phonological processing. That is, people with dyslexia do not break down the sounds of language properly or efficiently. The phonological model hypothesizes that there is a module in the brain to automatically parse language as it comes into the brain. This module also assembles the components into words before they are spoken. All of this takes place at the preconscious level so the person is unaware of it. This theory proposes that people with dyslexia have a problem in this module so that it does not function efficiently (7). The module impairs the subject's ability to segment a word into its component parts. This fits with the observation that children with dyslexia lack the ability to correctly sound out words and separate words at their syllables.

This model is useful because it explains several other aspects of dyslexia. First, it can explain why dyslexia is most often diagnosed in early school years: the child is learning to read and must first learn to understand the sounds of the language. Secondly, the model can explain why intelligence is not a factor in dyslexia. Since only one part of language processing is affected in the brain, one can see that other parts of the brain and intelligence are unaffected. That is, the ability to reason, comprehend and non-language skills are completely in tact. It also explains why people with dyslexia can learn to overcome the disability. These people learn to decode words properly. However, when taking timed tests, their decoding is still laborious and slow. Thus, they still need more time for language based tasks (7). Lastly, this model is also useful in explaining the difficulties in other languages skills that people with dyslexia face such as spelling, writing and speaking. All of these tasks require the person to be able to parse a word into its phonemes and process it correctly. Spelling is especially difficult because it requires the person remember the language structure while analyzing sounds and syllables (8).

While a person with dyslexia has a significant disability in school early diagnosis can lead to positive outcomes. Early detection and intervention can help the child learn to cope with his/her disability. Interventions that focus on phonemic awareness have been shown to be some of the most effective treatments (1). Dyslexia in not a educational death sentence. With proper interventions a child with dyslexia can achieve his/her educational aims.

Appendix: Famous People with Dyslexia(9)

Hans Christian Anderson

John Irving

Winston Churchill

George Patton

Tom Cruise

Auguste Rodin

Thomas Alva Edison

Charles Schwab

Albert Einstein

William Butler Yeats

WWW Sources

1)What is Dyslexia? , On the Bright Solutions for Dyslexia web site

2) Fact about Dyslexia , Part of the International Dyslexia Association web site.

3)What We Know About Dyslexia, On the Bright Solutions for Dyslexia web site.

4)Dyslexia Basics , On the International Dyslexia Association web site

5) What Causes Dyslexia? , Dyslexia Online Magazine

6)Dyslexia and Language Brain Areas, On the Brain Briefings web site

7)Dyslexia, Scientific American magazine article online

8)Spelling, on the International Dyslexia Association web site.

9)Selikowitz M. Dyslexia and other learning difficulties: the facts. 2nd ed. Oxford University Press: Oxford 1998.,

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