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49085.  Thu Feb 02, 2006 1:11 pm Reply with quote


49097.  Thu Feb 02, 2006 1:57 pm Reply with quote

One form of dyslexia, primary dyslexia, appears to be hereditary. The pattern of inheritance is uncertain however, it is certainly not a straightforward Mendelian pattern but increasingly it appears that dyslexia runs in families.

Trauma dyslexia usually occurs after some type of brain trauma or injury to the area of the brain that controls reading and writing. This type of dyslexia is rarely seen in today's school-age population.

Primary dyslexia is a dysfunction of, rather than damage to, the left side of the brain (cerebral cortex) and does not change with maturity. Individuals with this type are rarely able to read above a fourth grade level and may struggle with reading, spelling, and writing as adults. Primary dyslexia is hereditary and is found more often in boys than in girls.
The difference between primary dyslexia and trauma dyslexia is that trauma dyslexia occurs after a brain trauma and primary dyslexia is a dysfunction of the brain.

Developmental dyslexia is caused by hormonal development during the early stages of foetal development. Developmental dyslexia diminishes as the child matures. This type is also more common in boys.

Problems with spatial relationships are quite common in dyslexics, as is confusion of left and right and an impairment of the ability to respond to musical rhythms.

Dyslexia is a “complex trait”.

Although there is likely to be significant involvement of genetic factors in predisposing towards dyslexia, the trait is “complex” at the genetic level because it does not display a classical Mendelian inheritance pattern which can be attributed to a single locus. There is a breakdown of the correspondence between ‘phenotype’ (i.e. how severely an individual is affected with dyslexia) and ‘genotype’ (i.e. the genetic make-up of that individual). This could be due to:

Genetic heterogeneity = different genes may be influencing the trait in different families
Reduced penetrance = some individuals with a predisposing genotype may not develop dyslexia (e.g. due to environmental or random interactions)
Phenocopy = some individuals without a predisposing genotype may nevertheless be dyslexic (again could be due to environmental/random factors)
Oligogenic inheritance = the trait might result from the simultaneous presence of predisposing genotypes at several different genes, whose interaction results in elevated risk of developing dyslexia

An added complication is the difficulty of defining exactly what the phenotype of dyslexia is, given the current debates on what consitutes the central deficit.

Pattern recognition difficulties are obviously a factor but what might not be so readily apparent is that this is not necessarily universally true and that the assigning of the term dyslexia is of questionable use in some cases, not least of all because it tends to impair our ability to differentiate between different types of reading disorder.

Children who have word recognition problems due to difficulties in storing and/or retrieving orthographic representations, and who make letter orientation errors, are probably those referred to by Willows and Terepocki (1993) as "visual dyslexies" and may also be included in groups of surface dyslexies (e.g., Manis et al., 1996). Jackson and Coltheart (2001) differentiate between visual and surface dyslexia with visual dyslexia referring specifically to cases in which there are confusions of similar appearing letters, and left-right reversals and letter-order errors.
The importance of visual pattern recognition is acknowledged by Bowers and Ishaik (2003) in their insightful discussion of the contributions of rapid automatized naming to the understanding of reading disability.

There is a suggestion that the proportion of millionaires is far higher in dyslexics than in the general population, this would make sense to me if a dyslexics ambition is necessarily diverted away from academic achievement but I can find no really solid evidence on the web so far. That there are many successful dyslexics is beyond doubt.

In addition to the thesps (eg Tom Cruise, Will Smith) there’s Thomas Edison, Bill Gates, Pablo Picasso, Richard Branson, JFK, John Lennon, Steven Spielberg and Henry Ford. This is ascribed to “picture thinking”.

“One of the problems about being dyslexic is that you don’t perform well at school and I knew I wasn’t going to pass my exams so I did other things,” said Branson. “Being dyslexic means I am good at delegation and the bigger picture.”

Lord Heseltine — the former Tory cabinet minister whose wealth was put at £203m in this year’s Sunday Times Rich List, largely from his Haymarket publishing empire — has also suffered throughout his life from dyslexia.

He recalls his first entrepreneurial steps at Shrewsbury school: “I wasn’t any good at games, so when all these very energetic fellows spent the afternoon exhausting themselves on the soccer playing fields of Shrewsbury I used to carry lemonade up the hill and sell it at a significant mark-up.”

The latest study was commissioned for a BBC2 series, Mind of a Millionaire, to be shown on Tuesday. Ivan Massow, a former Tory party adviser and businessman who made his first million at 21 and is dyslexic, said the findings chimed with his experiences.

49099.  Thu Feb 02, 2006 2:20 pm Reply with quote

IMHO - in the past, reading problems, learning problems and vision problems have often been incorrectly diagnosed as dyslexia (n.b. I have no facts to back this up, please take it as opinion).

I am suspicious of lists of "famous people" who are dyslexic, I think it is likely is that someone has once said to them that since they struggled at school they must be dyslexic - how many of the oft-quoted lists have been diagnosed by an expert in the field? - and what I am even more suspicious of is lists of long-dead people who are claimed to be dyslexic, I'd want vigorous proof before I accepted any of those as factual.

I think it is only fair in the interests of QI that we at least discuss the scientific validity of the term - I believe that it has become a buzz-word for all sorts of different problems - much to the detriment of people who suffer from true word-blindness which Garrick's poster (above) demonstrates.

49120.  Thu Feb 02, 2006 4:45 pm Reply with quote

That kid in Japan that garrick92 mentioned - isn't it just possible that he didn't learn English as well as he learned Japanese? Moving to a Japanese school at the age of six is certainly going to have affected his ability to learn to read, and this could also have been affected by his wanting to mix more with his new Japanese friends, and emulate them.

It's perfectly possible that his Japanese reading teacher was far better than his English one, so he is more able.

It also reveals that his father had reading difficulties, so that could also easily have been culturally transmitted to his son. This could easily account for 'hereditary dyslexia' too, unless they can definitely identify genes that code for the approriately 'damaged' brain areas, which I doubt.

It's still fairly wide open, as far as I can see. The investigation of the claims can't really be done scientifically because they're all individual cases, with many different effects going on at the same time that can't be ruled out.

49130.  Thu Feb 02, 2006 7:20 pm Reply with quote

Gray wrote:
I'd like to see that research.

Neuroscientist Li Hai Tan from the University of Hong Kong, China, and his colleagues speculated that dyslexia in Chinese readers might affect a different brain region. They used functional magnetic resonance imaging (fMRI) to monitor the brain activity of eight impaired and eight normal readers as they performed two language tests. Various kinds of characters were used in the experiments:

· Real characters with a single meaning.
· Homophones – characters that are pronounced the same but have different meanings.
· Fake ones that appear to be Chinese characters but are actually meaningless.

The dyslexic children performed worse, but both groups showed the same activity in their left temporoparietal cortex. Instead, children with reading difficulties showed less brain activity in another region, the left middle frontal gyrus. This area helps to coordinate shapes, pronunciation and meaning, says Tan.

Japanese is a halfway house between alphabetic languages and Chinese. Readers often have to match shapes to syllables, a different task that is likely to involve a third, as yet unidentified brain region.

Slok W. T, Perfetti C. A., Jin Z. & Tan L. H. Nature, 431. 71 - 76(2004).

Learning a regular spelling system such as Italian creates differences in brain organisation compared to learning highly irregular English. Italian has 26 rules to learn, which takes about six months; English takes longer because there are many irregularities (and several hundred rules). In Chinese 3,500 characters are needed to read the equivalent of the "Daily Mail" and about 6,000 characters to read books.

The second main difference is that in English each linguistically distinct sound, or phoneme, maps to a single letter. For example, the three phonemes in "bat" map on to three letters. If one letter is changed it makes a new word. A Chinese character maps to a whole syllable. In Putonghua, the national language of China, there are about 1,800 distinguishable syllables; each syllable can have several meanings and each meaning is typically represented by a distinct character.
How will these differences be reflected in brain organisation? Learning Chinese creates specific demands on the areas for remembering visual patterns. English readers make more use of areas for phoneme processing.

This ability to analyse syllables into phonemes is the key problem in dyslexia. Dyslexics have difficulty segmenting the word "that" into three separate sounds - so fare much worse in learning English than Chinese.

Article in the Guardian 23rd September, 2004 by Brian Butterworth and Joey Tang of the Institute of Cognitive Neuroscience at University College London.

49159.  Fri Feb 03, 2006 4:58 am Reply with quote

Thanks Flash.

I still can't see anything that directly suggests that 'Chinese dyslexia' is any different from 'Western dyslexia' though. There are a lot of fairly bold statements of fact in that second article (that's what comes of the press digesting scientific reports, unfortunately), but no explanation of why they are true (or even 'how' they are true), so I can't really make any sense of the conclusions.

For example,
children with reading difficulties showed less brain activity in another region, the left middle frontal gyrus. This area helps to coordinate shapes, pronunciation and meaning, says Tan.

reads simply like a repeated assertion of the fact that dyslexic children found reading harder. It doesn't say 'how' or 'why' it's harder, or even whether it's the same kind of hardness that Western children exhibit.

And 'how' is western script different in terms of its pictorial content from Chinese characters? They're still lines that have different sounds and 'meanings' is different contexts. How do they separate the effects of more/fewer combinations, more/fewer distinct sounds and more/fewer meanings from the differing abilities of each child - in a rather small statistical sample?

The more I read about the mapping being identified between specific abilities and specific brain areas, the less correlation there seems to be (and the more different mappings are discovered for the same ability). It's all rather confusing. But then again, it is still rather early days for understanding brain function in this kind of detail.

49264.  Fri Feb 03, 2006 1:20 pm Reply with quote

Jenny - my sister has Dyspraxia too, it mostly affects her speech and balance. It is hard to know exactly how much the Dyspraxia affects her though as she also has another D - Down syndrome. It is impossible to know which effect comes from which condition. She is in all other respects a normal if moody woman and if one more person says to me "They are very loving though" or "They are incredibly strong" I think I might have an episode.

49282.  Fri Feb 03, 2006 2:37 pm Reply with quote

Yes, that all-encompassing 'they' must be very irritating.

49284.  Fri Feb 03, 2006 2:54 pm Reply with quote

Jenny wrote:
Yes, that all-encompassing 'they' must be very irritating.

Yes, it is; and I speak as one of the 'not-they'.

Pedantic Spice
49429.  Sun Feb 05, 2006 6:12 am Reply with quote

It is a peculiar thing that, having been out of the loop for a while, and coming back to such large chunks of quotation and discussion, I can't actually get back into a discussion subject I posted!

It's not that I don't want to read it all but I just can't do it.

Sorry - dyslexia!

49657.  Tue Feb 07, 2006 10:31 am Reply with quote

Pedantic Spice - I am also dyslexic, and have the stigmatism that you described.

My dyslexia wasn't offically confirmed until two years ago. All through primary school nobody noticed it, as I was quiet and they only bothered with disruptive pupils. But then when I was 14 I decided that something really wasn't right and got myself tested. I will get extra time in my GCSEs, so that's a plus.

49661.  Tue Feb 07, 2006 10:44 am Reply with quote

Over here, there is good allowance made for dyspraxics in high school as well - particularly in allowing them to write examination papers on a computer, which makes a huge difference when your handwriting is not only appalling but very very slow.

Pedantic Spice
49765.  Wed Feb 08, 2006 4:51 am Reply with quote

Anachronism, I think it's great that you've got yourself assessed. I had to be assessed outside school as no-one realised there was a problem. I didn't find out until after GCSEs but it made a huge difference to my A-levels and degree!

Jenny, the help I got after being assessed was use of a word-processor in exams and extra time (15 mins for every hour). It's amazing what difference a bit of help makes!

I'm actually not clear on what the difference is between dyslexia and dyspraxia. The effects of dyspraxia you were describing earlier in the thread sounded very much like what I have - which I was taking as indications of dyslexia.

49796.  Wed Feb 08, 2006 11:18 am Reply with quote

As I understand it, PS, there is an overlap between the two. However, dyslexia tends to manifest more specifically in the area of words - both reading and writing. My sons have no problem with reading, writing or spelling, especially if they can use a word processor, although they do have very bad and slow handwriting. This seems to be getting better as they get older though. Where they both have problems is in organising their thinking, especially in anything that involves sequencing, and also with paying sustained attention. Both of them were very late in some physical skills - riding a bike, for example, which my younger son couldn't do until he was nine - and road skills are hard to them.

49854.  Wed Feb 08, 2006 7:17 pm Reply with quote

Do you know if dyspraxia is sex-linked at all Jenny? On a quick Google check I find nothing to suggest that but that's the result of a few minutes effort.


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