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Dyslexia and Neurological Differences — The Chicken and Egg Dilemma

Chicken and eggNine-year-old Peter is one of the brightest children in his Grade 3-class. He has a wonderful vocabulary and knows everything there is to know about football. But when it comes to reading about football — or anything else — Peter has a lot of trouble. It takes him a long time to read each word, and even longer to read whole sentences. He often has to guess at how you say a word — and sometimes his guess is wrong. Reading out loud is especially stressful and embarrassing. His teacher recently told Peter’s parents she thinks he might have dyslexia.

The term dyslexia was coined from the Greek words dys, meaning ill or difficult, and lexis, meaning word. It is used to refer to persons for whom reading is simply beyond their reach. Spelling and writing, due to their close relationship with reading, are usually included.

According to popular belief dyslexia is a neurological disorder in the brain that causes information to be processed and interpreted differently, resulting in reading difficulties. Historically, the dyslexia label has been assigned to learners who are bright, even verbally articulate, but who struggle with reading; in short, learners whose high IQs mismatch their low reading scores. When children are not as bright, their reading troubles have been chalked up to their general intellectual limitations.

Research in the previous century

One could probably fill a vast library if one would put together all the research studies that attempted to prove that dyslexia is caused by a neurological dysfunction. The problem, faced by researchers in the previous century who tried to prove that dyslexia is a brain dysfunction, is that it was impossible to directly examine the living brain of a dyslexic person in order to discover whether there is an abnormality in his brain.

Known for conducting autopsies on the brains of deceased dyslexics, neurologist Albert Galaburda and his team of researchers seemed to have found a difference between dyslexic persons and non-dyslexics in the size of nerve cells in the part of the brain that helps process sounds — the left MGN, or left medial geniculate nucleus. However, as neurobiologist Margaret Livingstone at Harvard Medical School pointed out, Galaburda’s results were not conclusive because of the small numbers studied.

Because of the belief that the brain cannot change, it was historically believed —and is still believed by many — that dyslexia is incurable: “Dyslexia is like alcoholism … it can never be cured.”1

Advocacy groups, in the rush to generate public awareness for the condition of dyslexia, with the cooperation of a compliant media, have perpetuated the belief that a host of famous individuals such as Albert Einstein, Leonardo da Vinci, Thomas Edison, Walt Disney, Winston Churchill and Hans Christian Andersen were dyslexic. The folk myth — the “affliction of the geniuses” — continues to be spread despite the fact that knowledge of the definition of dyslexia and the reading of any standard biographies would immediately reveal the inaccuracy of many such claims. For example, as educational psychologist Dr Coles points out, Einstein’s reading of Kant and Darwin at age thirteen is hardly representative of individuals who are currently labelled dyslexic.

Neurological differences confirmed

By the turn of this century, the advancement in technology has made it possible for scientists to see inside the brain. As was always suspected, fMRI-scans et cetera have confirmed that there are indeed differences between the brains of dyslexic persons and good readers. Dyslexic children, for example, use nearly five times the brain area as normal children while performing a simple language task, according to a study by an interdisciplinary team of University of Washington researchers.

The UW researchers, headed by developmental neuropsychologist Virginia Berninger and neurophysicist Todd Richards, used a novel non-invasive technique called proton echo-planar spectroscopic imaging (PEPSI) to explore the metabolic brain activity of six dyslexic and seven non-dyslexic boys during oral language tasks.

The 13 boys in the study were between 8 and 13 years of age and the dyslexic and control groups were well-matched in age, IQ and head size, but not in reading skills. The controls were reading at a level above normal for their age and had a history of learning to read easily. The dyslexics had delayed reading skills and were reading well below average for their age. Their families also had a history of multi-generational dyslexia that was confirmed in a concurrent family genetics study.

The boys, fitted with earphones, were asked to perform four tasks while their brains were being imaged. Three of the tests involved pairs of words and the fourth used pairs of musical tones.

The dyslexics were using 4.6 times as much area of the brain to do the same language task as the controls. “This means their brains were working a lot harder and using more energy than the normal children,” said Richards, a professor of radiology.

While the dyslexic boys exhibited nearly five times more brain activation during a language task that asked them to interpret the sounds of words, there was no difference in the two groups during the musical tone test. This means the difference between the dyslexics and the normal children relates to auditory language and not to non-linguistic auditory function, according to Richards and Berninger.

The brain is plastic

A 1998 landmark study found that the human brain had the ability to develop new brain cells. This research challenged the prevailing theory that the human brain was a rigid system with no ability to generate new brain cells. Previously, most experts believed that humans were born with all of their brain cells, that we lose brain cells on a daily basis, and that our brains do not generate or replace the lost cells with new ones.

Many research studies followed, demonstrating the plasticity of the brain. New connections can form and the internal structure of the existing synapses can change. A person who becomes an expert in a specific domain, will have growth in the areas of the brain that are involved with their particular skill. Even if the left hemisphere of a person’s brain is severely injured (in 90% of people the left hemisphere controls the capacity to understand and generate language), the right side of the brain can take over some language functions.

In the light of brainplasticity, confirmations of brain differences between the dyslexic and the ‘normal’ reader’s brain called for more research regarding cause and effect. Which of the two — the difference in brain structure/function and the reading difficulty — is the cause and which one is the effect?

The chicken and egg dilemma

More and more research studies suggest that the popular cause-effect relationship should be reversed, i.e. that these brain differences between dyslexics and ‘normal’ readers might not be the cause, but rather the effect of the reading difficulty.

In one study, published online in the Journal of Neuroscience, researchers analysed the brains of children with dyslexia and compared them with two other groups of children: an age-matched group without dyslexia and a group of younger children who had the same reading level as the children with dyslexia. Although the children with dyslexia had less grey matter than age-matched children without dyslexia, they had the same amount of grey matter as the younger children at the same reading level.

Lead author Anthony Krafnick said this suggests that the anatomical differences reported in left-hemisphere language-processing regions of the brain appear to be a consequence of reading experience as opposed to a cause of dyslexia.

Another study’s results question the popular discrepancy model, i.e. that dyslexic learners have high IQs but low reading scores ― historically viewed as the proof of a neurological deficit.

Using brain imaging scans, neuroscientist John D E Gabrieli at the Massachusetts Institute of Technology have found that there was no difference between the way poor readers with or without dyslexia think while reading.

The study conducted by Dr Gabrieli involved 131 children, aged 7 to 16. Following a simple reading test and an IQ measure, each child was assigned to one of three groups: typical readers with typical IQs, poor readers with typical IQs, and poor readers with low IQs. During the test, researchers used functional magnetic resonance imaging (fMRI) to observe the activity in six brain regions identified as being important in connecting print and sound.

The results indicated that poor readers of all IQ levels showed significantly less brain activity in the six observed areas than typical readers. But there was no difference in the brains of the poor readers, regardless of their IQs.

The jury is still out

While the jury is still out on the cause and effect relationship, one should keep in mind that neurological differences do not equal neurological disorders and disabilities. We now also know that there are differences between the brains of people who can juggle and people who cannot juggle, between the brains of people who can play a musical instrument and people who cannot play a musical instrument. Then logically there will be differences between the brains of people who read well and people who struggle with reading!

We should also keep in mind that, when it comes to mastering skills, all instruction methods are not equal. Naturally, it will be harder for some children to learn to read and there will always be those who can read better, just as we cannot all be tennis champions. In fact, some people may even find it very hard to learn to play tennis. But by following the correct method of instruction and with sustained practice according to this method, any person will at least learn to play acceptable tennis. In the same way any child can learn to read at least acceptably if the correct method of instruction is followed and if enough practice is provided.

Let’s not underestimate the wonderful potential and capacity of the human brain. Compare the idea that dyslexia is “like alcoholism … it can never be cured” to Chafetz’s view that “the human mind can learn anything.”2 His optimism is shared by Litvak when he says that “the human brain has extensive capacities beyond those normally tapped,”3 and by Minninger and Dugan who say, “the simplest mind today controls dazzling skills, the very same skills that put the universe itself within our grasp.”4 Such conflicting views cannot exist together — either the pessimists are wrong, or Chafetz, Litvak, Minninger and Dugan and a host of others are.

 

References:

  1. Clark, M., & Gosnell, M., “Dealing with dyslexia,” Newsweek, 22 March 1982, 55-56.
  2. Chafetz, M. D., Smart for Life. How to Improve Your Brain Power at Any Age (New York: Penguin Books, 1992).
  3. Litvak, S. B., Use Your Head. How to Develop the Other 80% of Your Brain (Englewood Cliffs: Prentice-Hall, Inc., 1982).
  4. Minninger, J., & Dugan, E., Make Your Mind Work for You (New York: Pocket Books, 1988).
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