People who experience reading difficulty without being otherwise intellectually disabled are said to suffer from dyslexia. Studying dyslexia is very valuable for understanding intelligence and creativity. Dyslexia illustrates the power of inborn wiring of the brain in developing mental skills. At the same time it can show how inborn limitations can be overcome by using the compensatory power of the brain. Dyslexia is caused by an inability to handle linguistic information in visual form. There is also a form of dyslexia that relates to the ability to read standard analog clocks, which is a rotational positioning dyslexia, as opposed to the symetric dyslexia found with dyslexics that have reading and writing problems.
5-15% of the population can be diagnosed as suffering from various degrees of dyslexia. Its main manifestation is a difficulty in developing reading skills in elementary school children. Those difficulties result from reduced ability to link up visual symbols with sounds. In the past, dyslexia was mistakenly thought to have a motivational background. Researchers studying the brains of dyslectics have, however, found that in reading tasks dyslexics show reduced activity in the left inferior parietal cortex. Otherwise, dyslectics are known to often show higher than average intelligence. A number of bright brains are said to have suffered from varying degree of dyslexia. Those include Einstein, Edison, Alexander Graham Bell, Faraday and many others. Dyslectics may show a natural dislike of reading and, in consequence, compensate by developing unique verbal communication skills, inter-personal and leadership skills. Hence so many prominent CEOs list minor to severe dyslexia among their childhood disabilities. Those include Richard Branson (Virgin Enterprises), Henry Ford, Ted Turner (AOL - Time Warner), John Chambers (Cisco), as well as prominent statesmen: Winston Churchill, George Washington, Thomas Jefferson, John F. Kennedy and others. Perhaps for similar reasons, many dyslexics tend to take on arts (e.g. Tom Cruise or Whoopi Goldberg)
The list above indicates that those who show reading difficulties in childhood can also cope well with their deficiency later in life and become avid readers and skilled writers. Research shows that intense training in dyslectics helps them use the right part of their brain to take over the limited functionality in the left part. Even a few weeks of intense phonological training (e.g. breaking down and rearranging sounds to produce different words) can help noticeably improve reading skills. Unlike normal adults, phonological training shows increase in the activity in the right temporoparietal cortex. This part of the brain works in spatial tasks and may be the main compensatory structure in phonological training. This is the sister region of the left temporoparietal cortex responsible for visual motion processing which is underactive in many dyslexics. The earlier the phonological regimen is taken on, the better the overall result. Advanced brain scans could identify children at risk of dyslexia before they can even read.
In 1979, anatomical differences in the brain of a young dyslexic have been documented. Albert Galaburda of Harvard Medical School noticed that language centers in dyslectic brains showed microscopic flaws known as ectopias and mycrogyria. Both affect the normal six-layer structure of the cortex. An ectopia is a collection of neurons that have pushed up from lower cortical layers into the outermost one. A microgyrus is an area of cortex that includes only four layers instead of six. These flaws affect connectivity and functionality of the cortex in critical areas related to sound and visual processing. These and similar structural abnormalities may be the basis of the inevitable and hard to overcome difficulty in reading.
Several genetic regions on chromosomes 1 and 6 have been found that might be linked to dyslexia. In all likelihood, dyslexia is a conglomeration of disorders that all affect similar and associated areas of the cortex. With time, science is likely to identify and classify all individual suborders with benefits to our understanding of how low-level genetic flaws can affect the wiring of the brain and enhance or reduce a particular component of human mental capacity.
Whether today's models of dyslexia are correct or not. The main lesson of dyslexia is that minor genetic changes affecting the layering of the cortex in a minor area of the brain may impose inborn limitation on the overall intellectual function. At the same time, dyslexia shows that the brain exhibits a strong ability to compensate for its inborn or acquired limitations, and intense training can often result in miraculous turnabouts