The Cause of Dyslexia
Its normally one of the first questions asked by the parents when they learn their child is dyslexic. Maybe its just curiosity or maybe its a feeling of guilt that somehow they had caused the dyslexia but regardless of why, people want to know what causes dyslexia. Unfortunately there is no easy answer to this question because really its two questions.
What is different in the dyslexic’s brain that causes the symptoms of poor reading and spelling?
and
What causes the dyslexic’s brain to be different?
Neither question can be answered with certainty because research produces conflicting results or doesn’t explain everything.
Over the last thirty years there have been many explanations to what causes the symptoms of dyslexia. Various areas of the brain have been targeted most notably the Broca’s and Wernicke’s areas. These two parts are linked closely with our language abilities so are obvious suspects. Several different studies using a variety of techniques have found that these areas are used differently by dyslexic brains. The problem is that there is no evidence to say that this is the cause of dyslexia. The difference in brain activity might be a symptom of dyslexia and not a cause.
Over recent years the role of cerebellum has attracted the interests of neurologists. Over the last thirty years Dr Levinson, Dr Denckla and others have been showing a connection between learning problems and poor balance & coordination. The cerebellum is the area of the brain that controls coordination and balance. It also plays a role in memory, another problem area for dyslexics. As with the Broca’s and Wenicke’s area, the difference in the cerebellum may not be the cause of dyslexia but a symptom or result of a deeper problem. However the success of cerebellum based training methods such as Dore Achievement Centers suggest that the cerebellum is the key to dyslexia.
The difference between a normal cerebellum and a dyslexic’s cerebellum may be just a question of size. The clumsiness and poor coordination in a dyslexic is very similar to the way a small child moves. It may be that the cerebellum has failed to grow with the rest of the body and is underdeveloped.
Whether the cause of dyslexia is an underdeveloped cerebellum or a fault in the Broca’s area is irrelevant to the question of why the problem exists in the first place. The most likely explanation is genetics. Various genes have been highlighted as possible causes of dyslexia but the research is far from conclusive. Rather than one specific gene being the cause it is most likely that a number of genes interact, leaving a person at risk of dyslexia. It is then environment factors such as diet that may trigger the dyslexia.
The best evidence at the moment points to the cerebellum and genetics being the cause of dyslexia but in many ways the question ‘What causes Dyslexia?’ is irrelevant. What matters to a dyslexic is how they can overcome their problems. Finding the right treatment is more important than the cause.
Research:
Functional connectivity of the angular gyrus in normal reading and dyslexia
Developmental dyslexia
Memory systems in the brain and localization of a memory
Time Estimation Deficits in Developmental Dyslexia: Evidence of Cerebellar Involvement
Find Out More:
Books:
- Cerebellum
- Overcoming Dyslexia: A New and Complete Science-Based Program for Reading Problems at Any Level
- Dyslexia: Seeing Spells Achieving: Improve your spelling, reading, memory, dyslexic symptoms, in any language, by using your brain the way nature intended, through NLP and visualisation
- Surprise Treatment for Dyslexia, ADHD, Headaches and Other Conditions: It’s All About Information Management
- Reversals: A Personal Account of Victory over Dyslexia
July 8th, 2006
Dyslexia
Comments on: The Cause of Dyslexia
Chris, you seem convinced that balance and co-ordination problems are always part of dyslexia. I am not. Why? Among the people with dyslexia I know personally, few have balance/co-ordination issues. Many are superior athletes.
Don’t get me wrong — disappointing motor performance can occur in people with dyslexia. I think it is a separate issue. Bundling them together is a mistake.
Nothing about Levinson’s work is in the least scientific.
This is what Larry Silver, MD had to say about the cerebellum and learning in
Neurophysiological Approaches (a critique)
http://dyslexia.mtsu.edu/modules/articles/displayarticle.jsp?id=69
Author(s): Larry Silver M.D.
Reprinted with Permission From: International Dyslexia Association (info)
Printed Date: Spring 2001
Date Posted on this Website: October 03 2002
Cerebellar - Vestibular Dysfunction
Several investigators have suggested that the vestibular system is important in learning. They claim that there is a causal relationship between vestibular disorders and poor academic performance involving reading and written language in children with Learning Disabilities. Ayres, (1973), Frank and Levinson (1973), and Levinson (1980) suggest that such children require a specialized therapy before they can benefit from academic input. DeOuiros (1971) and Levinson (1984) suggest that evidence of a vestibular disorder is predictive of learning disabilities and that therapy can prevent these disabilities.
In recent years, Levinson has published several books on the causative role of the vestibular and vestibular-cerebellar systems in learning disabilities. He proposes the treatment of dyslexia with anti-motion sickness medication to correct the vestibular dysfunction. No research is cited in his books to support his theory or the effectiveness of his treatment. His books refer to his clinical observations and case examples. In one book (Levinson, 1984), he proposes multiple other interventions along with the anti-motion sickness medication, including many other types of medication plus special education.
The role of the vestibular system in the higher cortical functions required for academic performance is not known. Some of the symptoms generally associated with learning disabilities (faulty eye movements, poor postural coordination, poor balance, and poor spatial orientation) could be indicative of vestibular disorder. Such symptoms, however, are only indirect evidence for vestibular dysfunction. The most prominent objective sign of vestibular involvement is nystagmus (spasmodic, rapid movement of the eyeball from side to side).
The hypothesis that there is a relationship between vestibular function and the academic learning of reading and written language comes chiefly from the authors noted. Ayres used the Southern California Postrotary Nystagmus Test. In this test, the child is rotated in alighted room with eyes open, which provides both visual and vestibular stimulation. Thus, it may not be a valid test of vestibular function. Frank and Levinson, used “blurring speed” as evidence for abnormal vestibular function. This was described as the speed at which words passing across the visual field can no longer be recognized. But, because this involves the passing of stimuli across the subject’s visual field at varying speeds, it constitutes visual stimulation, not vestibular.
Consequently, none of the work of these investigators has provided conclusive evidence for vestibular dysfunction in individuals with learning disabilities. These data could possibly be interpreted as evidence of visual dysfunction. Other studies on vestibular dysfunction in children with learning disabilities have reported negative or equivocal results as well.
A study by Polatajko (1985) investigated the relationship between children’s vestibular function and academic learning using well-defined criteria for learning disabilities and exact measurements of vestibular activity. The evaluation of vestibular function consisted of examination of calibration records, search for spontaneous and gaze nystagmus, testing smooth pursuit, and vestibular and optokinetic testing. Vestibular nystagmus was induced by a rotating chair. No significant differences either in the inbsity of vestibular responsivity or in the prevalence of vestibular dysfunction were found between the normal learning children and children with learning disabilities. There was no evidence that children having low, average, or high vestibular responsivity differed significantly on measures of academic performance. There was no significant correlation between measures of vestibular function and measures of academic performance.
In summary, there is no current evidence supporting the theory of vestibular dysfunction nor supporting the proposed treatment approaches. Yet, the primary proponent of this treatment for learning disabilities remains extremely busy evaluating and treating these children.
Polatajko, H.I. (1985). A critical look at vestibular dysfunction and learning-disabled children. Dev Med Child Neurol 27:283-292
Posted by: Liz Ditz July 8th, 2006 at 6:26 pm
How about the eye and the focusing powers of the mind? I have written a concentrated fifty-page booklet on the cause and the cure of dyslexia, and a seventy-page booklet on an interactive picture-word approach to fail-safe error-free reading for beginners.
There can be no dyslexia until the child begins to learn to read. After that, the
cure is very much a reversal of the teaching method.
Posted by: Collin Corkum November 5th, 2007 at 6:12 am
As a teacher, psychologist and parent I’m very interested in this debate as I work with children everyday at high schools and primary schools who struggle with attention and or underachieving in literacy. I have worked alongside these students for 20 years. As is a common theme with people in this field I too have lived with attention, learning and output problems and the difficulties are very traceable through our family genetics.
One thing is really clear with these children and that is traditional teaching does not work for about 10% of students. My role has changed in recent years from teaching to assessment of children with attention and learning problems. I grew frustrated with Grade 7 (13 years old) students coming through to High school with reading ages of 8 year olds after being assessed and the latest literacy program trialled with little or no impact. So I began researching and trialling things to see if I could make a difference. I grew interested in the Corpus Callosum, Vestibular System and Cerebellum that all feature in research as likely culprits.I was also very interested in the development of phonics that over 90% of my students seem to consistently miss in primary school despite adequate opportunity. Research has also firmly established this is an area that effects over 80% of sutdents with Dyslexia or Reading Disorders. I noticed that the characteristics and developmental histories of these children seemed to have predictable themes. IE walked early
Posted by: Tim Feely November 28th, 2007 at 1:42 am
Can dyslexia cause my brother to get headaches? He was tested last year and is positive, he is stresses when it comes to learning. I feel as he gets headaches after along stressful day at school. Is this possible?
Posted by: Laura February 5th, 2008 at 6:46 am
After 60years of not being able to spell I NOW CAN I missed school when I was young had a bad home life took on a job which I DID NOT THINK THAT I COULD DO PASSED LAST YEAR I AM NOW A1 ASSESSOR SO IF I CAN DO IT ANY ONE CAN
Posted by: ETHEL SKINNER June 2nd, 2008 at 3:42 pm
My 10 year old daughter has albinism (with associated nystagmus) and is also aspergers (high functioning autism). She shows many many dyslexic traits and struggles at school with reading and writing (amongst other things).She is a very bright girl, but does struggle with many academic subjects. The school have done the basic dyslexia test (done on the computer) on my child. Her results suggested that she may well be dyslexic. But the school say they believe it is not dyslexia and just something to do with her poor eyesight. My daughter actually has very good vision compared to many people with albinism,she still has the reading problems, however large the print is!… and I feel that the school is simply trying to avoid adding yet another ’special need’ to Wendy’s list of problems. Does anyone have any advice or information on children who are aspergers and have nystagmus and also have dyslexia?
Posted by: Traci October 8th, 2008 at 3:55 pm
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