With a large number of dyslexia it is not possible to prove the presence of significant structural or functional changes. On the other side, there are studies confirming that the problem is related to the temporal left hemisphere zone. Dyslexia may be genetically conditioned, but can also be acquired during life as a result of physical trauma in certain areas of the brain.
It is important to say that all the risk factors that can act during pregnancy, before, during, and immediately after delivery, can, but do not have to be, the causes of dyslexia. If symptoms of dyslexia occur in the child, it is important to examine all the anamnestic data that can give us guidelines for treatment and therapy.
Dyslexia can cause both hereditary factor and external factor. The biological cause is usually some kind of encephalopathy, or damage to the brain of different origins. From the external factors, the environment should be emphasized without emotional warmth and the way of learning the reading skills.
On theoretical basis, two general concepts of dyslexic disorders can be separated. By the first conception, dyslexia is considered as one of the possible manifestations of disorders of higher integrative abilities, which is the result of imbalance in the functioning of cerebral hemispheres. The other conception of dyslexia is defined as a milder form of dysphagic disorder.
The constitution is what we inherit with genetic code as well as what we gain in the period before and during the birth. Part of the constitution is also a tendency to dyslexia. At the end of the 1970s, two American neurologists, Norman Geschwind and Albert Galaburda, set up a theory that dyslexia, stuttering and autism may be due to a delay in the development of the left brain hemisphere. Namely, for some reason in the middle of pregnancy there is a lack of brain circulation. The cells designated for speech that should be placed in the left hemisphere are moved to the right hemisphere. This right hemisphere is less suitable for the acceptance of speech-language functions, but it is still better than the left, which due to weaker circulation at that stage of development, is completely inadequate. Thus, the right side of the brain stays for a while, and in some children it permanently dominates many activities.
As the right brain hemisphere is more linked to the synthesis functions, that is, complete images of either visual or acoustic content, word analysis or memory of the exact shape of a single letter that would be more in the left hemisphere domain becomes more and more difficult to obtain. Therefore, children with dominance of the right hemisphere have a different way of receiving, processing and storing information, i.e. have a different cognitive style.
About 4% of children who speak English are affected by specific language disorders despite adequate abilities and normal intelligence. In 98 families from the epidemiological and clinical population performed chromosome testing. Systematic quantitative analysis indicated a change in two regions: on chromosome 16 and chromosome 19. Since both the clinical and epidemiological samples showed evidence of a causal relationship to both chromosomes, these authors assume that these chromosomes constitute risk factors for speech impairment.
That the causes of dyslexia are related to the constitutional organization of brain hemispheres, but also the discrepancy between the cognitive style of children and the usual analytical method by learning the skills of reading, is also indicated by the fact that in China and Japan, children with reading and writing difficulties are less than 1%. In these languages a pictorial – letter letter is kept, in which there is no identity of writing and pronunciation, because the written word is actually a concrete artistic drawing that is remembered as a whole, that is, with the dominant part of the right brain hemisphere.
The causation of reading disorders, and just reading, is very complex. The most common causes are:
a) Physiological and neurological factors. These factors include damage or poor functional development of the corresponding centers in the cortex. Dysfunctionality of appropriate cortical structures can cause dyslexic difficulties. The role of heredity is indisputable, as analyzes of family trees have indicated the existence of similar or similar difficulties in the family.
b) Difficulties of visual and auditory perception. Visual damage is always an important problem for reading. Among the most common are short-sightedness and farsightedness. On the other hand, great difficulty can also cause light hearing. It impoverishes the dictionary, and it can lead to speech disorders.
c) Health condition and illness. Poor health conditions lead to fatigue, neglect and lack of motivation, which later reflects on poor reading performance, especially if the adoption of this skill has already begun. These poor results will quickly be compensated, as soon as the health condition is corrected, except for serious brain injuries.
d) Lack of speech development, intelligence and motivation. The importance of intelligence for the ability to master reading is much higher at the beginning of schooling than later. In close connection with intelligence, it is also a factor of motivation. However, a lesser success in reading can lead to a loss of motivation. The intelligence factor is very important for the success of the corrective work. The more intelligent the child is, the correction will be more successful.
e) Laterality. Research indicates that parts of the temporal lobe in the dyslexic are less developed in the left than in the right hemisphere, and in most people this left part of the brain is more developed than in the right hemisphere. Reporting difficulty in reading can be due to unformed lateralization of brain functions when none of the hemisphere takes up the dominant role, and the centers that should generate these functions are in some kind of interference. The connection between reading difficulties with the dominance of the arm and the eye is also noticeable. Among the bad readers there are a large number of those with dominant left eye, left-handed and ambidextrous.
f) Emotional problems. The basic problem that comes with reading in emotionally unstable children is the inability to concentrate and maintain attention.
g) School variables. There are, above all, methods of reading learning, a teacher and his expertise, as well as a maturity for learning to read
h) Social factors. The family, ie, the primary environment is the most important factor in the environment. The cultural and material status of the family as well as the educational methods that are being implemented within it are factors that influence the success of the child in reading. Too ambitious parents can affect the loss of interest and the will to work for their own child, make it unselfish and scared. On the other hand, families who do not provide adequate intellectual stimulation develop in the child indifference and poor working habits. Often there are many different factors, not just one. It should be noted that some factors are at the same time the cause and effect of disorders.